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A rocket (from it, rocchetto, , bobbin/spool) is a
vehicle A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), wa ...
that uses
jet propulsion Jet propulsion is the propulsion of an object in one direction, produced by ejecting a jet of fluid in the opposite direction. By Newton's third law, the moving body is propelled in the opposite direction to the jet. Reaction engines operating o ...
to
accelerate In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by the ...
without using the surrounding
air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing f ...
. A
rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordanc ...
produces thrust by
reaction Reaction may refer to a process or to a response to an action, event, or exposure: Physics and chemistry *Chemical reaction *Nuclear reaction *Reaction (physics), as defined by Newton's third law *Chain reaction (disambiguation). Biology and me ...
to exhaust expelled at high speed. Rocket engines work entirely from
propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...
carried within the vehicle; therefore a rocket can fly in the
vacuum A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often dis ...
of space. Rockets work more efficiently in a vacuum and incur a loss of thrust due to the opposing pressure of the atmosphere.
Multistage rocket A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own engines and propellant. A ''tandem'' or ''serial'' stage is mounted on top of another stage; a ''parallel'' stage i ...
s are capable of attaining
escape velocity In celestial mechanics, escape velocity or escape speed is the minimum speed needed for a free, non- propelled object to escape from the gravitational influence of a primary body, thus reaching an infinite distance from it. It is typically ...
from Earth and therefore can achieve unlimited maximum altitude. Compared with airbreathing engines, rockets are lightweight and powerful and capable of generating large
acceleration In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by the ...
s. To control their flight, rockets rely on
momentum In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
,
airfoils An airfoil (American English) or aerofoil (British English) is the cross-sectional shape of an object whose motion through a gas is capable of generating significant lift, such as a wing, a sail, or the blades of propeller, rotor, or turbine. A ...
, auxiliary reaction engines,
gimballed thrust Gimbaled thrust is the system of thrust vectoring used in most rockets, including the Space Shuttle, the Saturn V lunar rockets, and the Falcon 9. Operation In a gimbaled thrust system, the engine or just the exhaust nozzle of the rocket can be ...
, momentum wheels, deflection of the exhaust stream, propellant flow,
spin Spin or spinning most often refers to: * Spinning (textiles), the creation of yarn or thread by twisting fibers together, traditionally by hand spinning * Spin, the rotation of an object around a central axis * Spin (propaganda), an intentionally b ...
, or
gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
. Rockets for military and recreational uses date back to at least 13th-century
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
. Significant scientific, interplanetary and industrial use did not occur until the 20th century, when rocketry was the enabling technology for the
Space Age The Space Age is a period encompassing the activities related to the Space Race, space exploration, space technology, and the cultural developments influenced by these events, beginning with the Sputnik_1#Launch_and_mission, launch of Sputnik 1 ...
, including setting foot on the Moon. Rockets are now used for
fireworks Fireworks are a class of Explosive, low explosive Pyrotechnics, pyrotechnic devices used for aesthetic and entertainment purposes. They are most commonly used in fireworks displays (also called a fireworks show or pyrotechnics), combining a l ...
,
missile In military terminology, a missile is a guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously unguided rocket i ...
s and other
weapon A weapon, arm or armament is any implement or device that can be used to deter, threaten, inflict physical damage, harm, or kill. Weapons are used to increase the efficacy and efficiency of activities such as hunting, crime, law enforcement, s ...
ry,
ejection seat In aircraft, an ejection seat or ejector seat is a system designed to rescue the aircraft pilot, pilot or other aircrew, crew of an aircraft (usually military) in an emergency. In most designs, the seat is propelled out of the aircraft by an ex ...
s,
launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pad, launch pads, supported by a missile launch contro ...
s for
artificial satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisoto ...
s,
human spaceflight Human spaceflight (also referred to as manned spaceflight or crewed spaceflight) is spaceflight with a crew or passengers aboard a spacecraft, often with the spacecraft being operated directly by the onboard human crew. Spacecraft can also be ...
, and
space exploration Space exploration is the use of astronomy and space technology to explore outer space. While the exploration of space is carried out mainly by astronomers with telescopes, its physical exploration though is conducted both by robotic spacec ...
. Chemical rockets are the most common type of high power rocket, typically creating a high speed exhaust by the
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combusti ...
of
fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...
with an
oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...
. The stored propellant can be a simple pressurized gas or a single
liquid fuel Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy, usually producing kinetic energy; they also must take the shape of their container. It is the fumes of liquid fuels that are flammable ...
that disassociates in the presence of a catalyst (
monopropellant Monopropellants are propellants consisting of chemicals that release energy through exothermic chemical decomposition. The molecular bond energy of the monopropellant is released usually through use of a catalyst. This can be contrasted with biprop ...
), two liquids that spontaneously react on contact (
hypergolic propellant A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. Th ...
s), two liquids that must be ignited to react (like kerosene (RP1) and liquid oxygen, used in most
liquid-propellant rocket A liquid-propellant rocket or liquid rocket utilizes a rocket engine that uses liquid rocket propellant, liquid propellants. Liquids are desirable because they have a reasonably high density and high Specific impulse, specific impulse (''I''sp). T ...
s), a solid combination of fuel with oxidizer (
solid fuel Solid fuel refers to various forms of solid material that can be burnt to release energy, providing heat and light through the process of combustion. Solid fuels can be contrasted with liquid fuels and gaseous fuels. Common examples of solid fuels ...
), or solid fuel with liquid or gaseous oxidizer ( hybrid propellant system). Chemical rockets store a large amount of energy in an easily released form, and can be very dangerous. However, careful design, testing, construction and use minimizes risks.


History

In China,
gunpowder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). ...
-powered rockets evolved in medieval China under the
Song dynasty The Song dynasty (; ; 960–1279) was an imperial dynasty of China that began in 960 and lasted until 1279. The dynasty was founded by Emperor Taizu of Song following his usurpation of the throne of the Later Zhou. The Song conquered the rest ...
by the 13th century. They also developed an early form of
MLRS A multiple rocket launcher (MRL) or multiple launch rocket system (MLRS) is a type of rocket artillery system that contains multiple launchers which are fixed to a single platform, and shoots its rocket ordnance in a fashion similar to a voll ...
during this time. The Mongols adopted Chinese rocket technology and the invention spread via the
Mongol invasions The Mongol invasions and conquests took place during the 13th and 14th centuries, creating history's largest contiguous empire: the Mongol Empire ( 1206- 1368), which by 1300 covered large parts of Eurasia. Historians regard the Mongol devastati ...
to the Middle East and to Europe in the mid-13th century. According to Joseph Needham, the Song navy used rockets in a
military exercise A military exercise or war game is the employment of military resources in training for military operations, either exploring the effects of warfare or testing strategies without actual combat. This also serves the purpose of ensuring the com ...
dated to 1245. Internal-combustion rocket propulsion is mentioned in a reference to 1264, recording that the "ground-rat", a type of
firework Fireworks are a class of low explosive pyrotechnic devices used for aesthetic and entertainment purposes. They are most commonly used in fireworks displays (also called a fireworks show or pyrotechnics), combining a large number of devices in ...
, had frightened the Empress-Mother Gongsheng at a feast held in her honor by her son the
Emperor Lizong Emperor Lizong of Song (26 January 1205 – 16 November 1264), personal name Zhao Yun, was the 14th emperor of the Song dynasty of China and the fifth emperor of the Southern Song dynasty. He reigned from 1224 to 1264. His original name was ...
. Subsequently, rockets are included in the military treatise ''
Huolongjing The ''Huolongjing'' (; Wade-Giles: ''Huo Lung Ching''; rendered in English as ''Fire Drake Manual'' or ''Fire Dragon Manual''), also known as ''Huoqitu'' (“Firearm Illustrations”), is a Chinese military treatise compiled and edited by Jiao ...
'', also known as the Fire Drake Manual, written by the Chinese artillery officer
Jiao Yu Jiao Yu () was a Chinese military general, philosopher, and writer of the Yuan dynasty and early Ming dynasty under Zhu Yuanzhang, who founded the dynasty and became known as the Hongwu Emperor. He was entrusted by Zhu as a leading artillery ...
in the mid-14th century. This text mentions the first known
multistage rocket A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own engines and propellant. A ''tandem'' or ''serial'' stage is mounted on top of another stage; a ''parallel'' stage i ...
, the 'fire-dragon issuing from the water' (Huo long chu shui), thought to have been used by the Chinese navy.Needham, Volume 5, Part 7, 510. Medieval and early modern rockets were used militarily as
incendiary weapons Incendiary weapons, incendiary devices, incendiary munitions, or incendiary bombs are weapons designed to start fires or destroy sensitive equipment using fire (and sometimes used as anti-personnel weaponry), that use materials such as napalm, th ...
in
siege A siege is a military blockade of a city, or fortress, with the intent of conquering by attrition warfare, attrition, or a well-prepared assault. This derives from la, sedere, lit=to sit. Siege warfare is a form of constant, low-intensity con ...
s. Between 1270 and 1280, Hasan al-Rammah wrote ''al-furusiyyah wa al-manasib al-harbiyya'' (''The Book of Military Horsemanship and Ingenious War Devices''), which included 107 gunpowder recipes, 22 of them for rockets. In Europe,
Roger Bacon Roger Bacon (; la, Rogerus or ', also '' Rogerus''; ), also known by the scholastic accolade ''Doctor Mirabilis'', was a medieval English philosopher and Franciscan friar who placed considerable emphasis on the study of nature through empiri ...
mentioned firecrackers made in various parts of the world in the ''
Opus Majus The ''Opus Majus'' (Latin for "Greater Work") is the most important work of Roger Bacon. It was written in Medieval Latin, at the request of Pope Clement IV, to explain the work that Bacon had undertaken. The 878-page treatise ranges over all ...
'' of 1267. Between 1280 and 1300, the Liber Ignium gave instructions for constructing devices that are similar to firecrackers based on second hand accounts.
Konrad Kyeser Konrad Kyeser (26 August 1366 – after 1405) was a German military engineer and the author of ''Bellifortis'' (c. 1405), a book on military technology that was popular throughout the 15th century. Originally conceived for King Wenceslaus, ...
described rockets in his military treatise ''
Bellifortis ''Bellifortis'' ("Strong in War", "War Fortifications") is the first fully illustrated manual of military technology written by Konrad Kyeser and dating from the start of the 15th century. It summarises material from classical writers on milit ...
'' around 1405. The name "rocket" comes from the
Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, an ethnic group or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance language *** Regional Ita ...
''rocchetta'', meaning "bobbin" or "little spindle", given due to the similarity in shape to the bobbin or spool used to hold the thread from a spinning wheel. Leonhard Fronsperger and
Conrad Haas Conrad Haas (1509–1576) was an Austrian or Transylvanian Saxon military engineer. He was a pioneer of rocket propulsion. His designs include a three-stage rocket and a manned rocket. Haas was perhaps born in Dornbach (now part of Hernal ...
adopted the Italian term into German in the mid-16th century; "rocket" appears in English by the early 17th century. ''Artis Magnae Artilleriae pars prima'', an important early modern work on
rocket artillery Rocket artillery is artillery that uses rocket explosives as the projectile. The use of rocket artillery dates back to medieval China where devices such as fire arrows were used (albeit mostly as a psychological weapon). Fire arrows were also us ...
, by
Casimir Siemienowicz Kazimierz Siemienowicz ( la, Casimirus Siemienowicz, lt, Kazimieras Simonavičius; born 1600 – 1651) was a general of artillery, gunsmith, military engineer, and one of pioneers of rocketry. Born in the Raseiniai region of the Grand Duchy o ...
, was first printed in
Amsterdam Amsterdam ( , , , lit. ''The Dam on the River Amstel'') is the Capital of the Netherlands, capital and Municipalities of the Netherlands, most populous city of the Netherlands, with The Hague being the seat of government. It has a population ...
in 1650. The
Mysorean rockets Mysorean rockets were an Indian military weapon, the iron-cased rockets were successfully deployed for military use. The Mysorean army, under Hyder Ali and his son Tipu Sultan, used the rockets effectively against the British East India Company ...
were the first successful iron-cased rockets, developed in the late 18th century in the
Kingdom of Mysore The Kingdom of Mysore was a realm in South India, southern India, traditionally believed to have been founded in 1399 in the vicinity of the modern city of Mysore. From 1799 until 1950, it was a princely state, until 1947 in a subsidiary allia ...
(part of present-day India) under the rule of
Hyder Ali Hyder Ali ( حیدر علی, ''Haidarālī''; 1720 – 7 December 1782) was the Sultan and ''de facto'' ruler of the Kingdom of Mysore in southern India. Born as Hyder Ali, he distinguished himself as a soldier, eventually drawing the att ...
. The
Congreve rocket The Congreve rocket was a type of rocket artillery designed by British inventor Sir William Congreve in 1808. The design was based upon the rockets deployed by the Kingdom of Mysore against the East India Company during the Second, Third, an ...
was a British weapon designed and developed by
Sir William Congreve Lieutenant General Sir William Congreve, 1st Baronet (4 July 1742 – 30 April 1814) was a British military officer who improved artillery strength through gunpowder experiments. Personal life William Congreve was born in Stafford on 4 July 1 ...
in 1804. This rocket was based directly on the Mysorean rockets, used compressed powder and was fielded in the
Napoleonic Wars The Napoleonic Wars (1803–1815) were a series of major global conflicts pitting the French Empire and its allies, led by Napoleon I, against a fluctuating array of European states formed into various coalitions. It produced a period of Fren ...
. It was Congreve rockets to which
Francis Scott Key Francis Scott Key (August 1, 1779January 11, 1843) was an American lawyer, author, and amateur poet from Frederick, Maryland, who wrote the lyrics for the American national anthem "The Star-Spangled Banner". Key observed the British bombardment ...
was referring, when he wrote of the "rockets' red glare" while held captive on a British ship that was laying siege to
Fort McHenry Fort McHenry is a historical American coastal pentagonal bastion fort on Locust Point, now a neighborhood of Baltimore, Maryland. It is best known for its role in the War of 1812, when it successfully defended Baltimore Harbor from an attack b ...
in 1814. Together, the Mysorean and British innovations increased the effective range of military rockets from . The first mathematical treatment of the dynamics of rocket propulsion is due to William Moore (1813). In 1814 Congreve published a book in which he discussed the use of multiple rocket launching apparatus. In 1815 Alexander Dmitrievich Zasyadko constructed rocket-launching platforms, which allowed rockets to be fired in
salvo A salvo is the simultaneous discharge of artillery or firearms including the firing of guns either to hit a target or to perform a salute. As a tactic in warfare, the intent is to cripple an enemy in one blow and prevent them from fighting b ...
s (6 rockets at a time), and gun-laying devices.
William Hale William Hale may refer to: Academics *William Gardner Hale (1849–1928), American classical scholar and professor of Latin * William Jasper Hale (1874–1944), president of the historically black Tennessee State University * William Mathew Hale (b ...
in 1844 greatly increased the accuracy of rocket artillery.
Edward Mounier Boxer Edward Mounier Boxer (1822-1898) was an English inventor. Biography Edward M. Boxer was a colonel of the Royal Artillery. In 1855 he was appointed Superintendent of the ''Royal Laboratory'' of the Royal Arsenal at Woolwich. in 1858 he was elec ...
further improved the Congreve rocket in 1865. William Leitch first proposed the concept of using rockets to enable human spaceflight in 1861. Leitch's rocket spaceflight description was first provided in his 1861 essay "A Journey Through Space", which was later published in his book ''God's Glory in the Heavens'' (1862).
Konstantin Tsiolkovsky Konstantin Eduardovich Tsiolkovsky (russian: Константи́н Эдуа́рдович Циолко́вский , , p=kənstɐnʲˈtʲin ɪdʊˈardəvʲɪtɕ tsɨɐlˈkofskʲɪj , a=Ru-Konstantin Tsiolkovsky.oga; – 19 September 1935) ...
later (in 1903) also conceived this idea, and extensively developed a body of theory that has provided the foundation for subsequent spaceflight development. The British
Royal Flying Corps "Through Adversity to the Stars" , colors = , colours_label = , march = , mascot = , anniversaries = , decorations ...
designed a guided rocket during
World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
.
Archibald Low Archibald Montgomery Low (17 October 1888 – 13 September 1956) developed the first powered drone aircraft. He was an English consulting engineer, research physicist and inventor, and author of more than 40 books. Low has been called the "fa ...
stated "...in 1917 the Experimental Works designed an electrically steered rocket… Rocket experiments were conducted under my own patents with the help of Cdr. Brock." The patent "Improvements in Rockets" was raised in July 1918 but not published until February 1923 for security reasons. Firing and guidance controls could be either wire or wireless. The propulsion and guidance rocket eflux emerged from the deflecting cowl at the nose. In 1920, Professor
Robert Goddard Robert Hutchings Goddard (October 5, 1882 – August 10, 1945) was an American engineer, professor, physicist, and inventor who is credited with creating and building the world's first Liquid-propellant rocket, liquid-fueled rocket. ...
of
Clark University Clark University is a private research university in Worcester, Massachusetts. Founded in 1887 with a large endowment from its namesake Jonas Gilman Clark, a prominent businessman, Clark was one of the first modern research universities in the ...
published proposed improvements to rocket technology in ''
A Method of Reaching Extreme Altitudes Robert Hutchings Goddard (October 5, 1882 – August 10, 1945) was an American engineer, professor, physicist, and inventor who is credited with creating and building the world's first Liquid-propellant rocket, liquid-fueled rocket. ...
''. In 1923,
Hermann Oberth Hermann Julius Oberth (; 25 June 1894 – 28 December 1989) was an Austro-Hungarian-born German physicist and engineer. He is considered one of the founding fathers of rocketry and astronautics, along with Robert Esnault-Pelterie, Konstantin Ts ...
(1894–1989) published ''Die Rakete zu den Planetenräumen'' (''The Rocket into Planetary Space''). Modern rockets originated in 1926 when Goddard attached a
supersonic Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...
( de Laval) nozzle to a high pressure
combustion chamber A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process. Interna ...
. These nozzles turn the hot gas from the combustion chamber into a cooler,
hypersonic In aerodynamics, a hypersonic speed is one that exceeds 5 times the speed of sound, often stated as starting at speeds of Mach 5 and above. The precise Mach number at which a craft can be said to be flying at hypersonic speed varies, since in ...
, highly directed jet of gas, more than doubling the thrust and raising the engine efficiency from 2% to 64%. His use of
liquid propellant A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...
s instead of
gunpowder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). ...
greatly lowered the weight and increased the effectiveness of rockets. In 1921 the
Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...
research and development laboratory
Gas Dynamics Laboratory Gas Dynamics Laboratory (GDL) (russian: Газодинамическая лаборатория) was the first Soviet research and development laboratory to focus on rocket technology. Its activities were initially devoted to the development o ...
began developing
solid-propellant rocket A solid-propellant rocket or solid rocket is a rocket with a rocket engine that uses Rocket propellant#Solid chemical propellants, solid propellants (fuel/oxidizer). The earliest rockets were solid-fuel rockets powered by gunpowder; they were u ...
s, which resulted in the first launch in 1928, which flew for approximately 1,300 metres. These rockets were used in 1931 for the world's first successful use of rockets for jet-assisted takeoff of aircraft and became the prototypes for the
Katyusha rocket launcher The Katyusha ( rus, Катю́ша, p=kɐˈtʲuʂə, a=Ru-Катюша.ogg) is a type of rocket artillery first built and fielded by the Soviet Union in World War II. Multiple rocket launchers such as these deliver explosives to a target area ...
, which were used during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
. In 1929,
Fritz Lang Friedrich Christian Anton Lang (; December 5, 1890 – August 2, 1976), known as Fritz Lang, was an Austrian film director, screenwriter, and producer who worked in Germany and later the United States.Obituary ''Variety'', August 4, 1976, p. 6 ...
's German science fiction film ''
Woman in the Moon ''Woman in the Moon'' (German language, German ''Frau im Mond'') is a German science fiction silent film that premiered 15 October 1929 at the UFA-Palast am Zoo cinema in Berlin to an audience of 2,000. It is often considered to be one of the f ...
'' was released. It showcased the use of a
multi-stage rocket A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own engines and propellant. A ''tandem'' or ''serial'' stage is mounted on top of another stage; a ''parallel'' stage is ...
, and also pioneered the concept of a rocket
launch pad A launch pad is an above-ground facility from which a rocket-powered missile or space vehicle is vertically launched. The term ''launch pad'' can be used to describe just the central launch platform (mobile launcher platform), or the entire ...
(a rocket standing upright against a tall building before launch having been slowly rolled into place) and the rocket-launch
countdown A countdown is a sequence of backward counting to indicate the time remaining before an event is scheduled to occur. NASA commonly employs the terms "L-minus" and "T-minus" during the preparation for and anticipation of a rocket launch, and eve ...
clock."The Directors (Fritz Lang)"
Sky Arts Sky Arts (originally launched as Artsworld) is a British free-to-air television channel offering 24 hours a day of programmes dedicated to highbrow arts, including theatrical performances, movies, documentaries and music (such as opera perfor ...
. Season 1, episode 6. 2018
''
The Guardian ''The Guardian'' is a British daily newspaper. It was founded in 1821 as ''The Manchester Guardian'', and changed its name in 1959. Along with its sister papers ''The Observer'' and ''The Guardian Weekly'', ''The Guardian'' is part of the Gu ...
'' film critic Stephen Armstrong states Lang "created the rocket industry". Lang was inspired by the 1923 book ''The Rocket into Interplanetary Space'' by Hermann Oberth, who became the film's scientific adviser and later an important figure in the team that developed the V2-rocket. The film was thought to be so realistic that it was banned by the Nazis when they came to power for fear it would reveal secrets about the V-2 rockets. In 1943 production of the
V-2 rocket The V-2 (german: Vergeltungswaffe 2, lit=Retaliation Weapon 2), with the technical name ''Aggregat 4'' (A-4), was the world’s first long-range guided ballistic missile. The missile, powered by a liquid-propellant rocket engine, was developed ...
began in Germany. It was designed by the
Peenemünde Army Research Center The Peenemünde Army Research Center (german: Heeresversuchsanstalt Peenemünde, HVP) was founded in 1937 as one of five military proving grounds under the German Army Weapons Office (''Heereswaffenamt''). Several German guided missiles and ...
with
Wernher von Braun Wernher Magnus Maximilian Freiherr von Braun ( , ; 23 March 191216 June 1977) was a German and American aerospace engineer and space architect. He was a member of the Nazi Party and Allgemeine SS, as well as the leading figure in the develop ...
serving as the technical director. The V-2 became the first artificial object to travel into space by crossing the
Kármán line The Kármán line (or von Kármán line ) is an attempt to define a boundary between Earth's atmosphere and outer space, and offers a specific definition set by the Fédération aéronautique internationale (FAI), an international record-keeping ...
with the vertical launch of
MW 18014 MW 18014 was a German A-4 test rocket launched on 20 June 1944, at the Peenemünde Army Research Center in Peenemünde. It was the first man-made object to reach outer space, attaining an apogee of 176 kilometers (109.3 miles), which is well abo ...
on 20 June 1944. In parallel with the German
guided-missile In military terminology, a missile is a guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously unguided rocket i ...
programme, rockets were also used on
aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...
, either for assisting horizontal take-off (
RATO Rato is a village in the Cornillon commune in the Croix-des-Bouquets Arrondissement, Ouest department of Haiti Haiti (; ht, Ayiti ; French: ), officially the Republic of Haiti (); ) and formerly known as Hayti, is a country located o ...
), vertical take-off (
Bachem Ba 349 The Bachem Ba 349 Natter ( en, Colubrid, grass-snake) was a World War II German point-defence rocket-powered interceptor, which was to be used in a very similar way to a manned surface-to-air missile. After a vertical take-off, which eliminated ...
"Natter") or for powering them (
Me 163 The Messerschmitt Me 163 Komet is a rocket-powered interceptor aircraft primarily designed and produced by the German aircraft manufacturer Messerschmitt. It is the only operational rocket-powered fighter aircraft in history as well as ...
, see
list of World War II guided missiles of Germany During World War II, Nazi Germany developed many missile and precision-guided munition systems. These included the first cruise missile, the first short-range ballistic missile, the first guided surface-to-air missiles, and the first anti-ship mi ...
). The Allies' rocket programs were less technological, relying mostly on unguided missiles like the Soviet
Katyusha rocket The Katyusha ( rus, Катю́ша, p=kɐˈtʲuʂə, a=Ru-Катюша.ogg) is a type of rocket artillery first built and fielded by the Soviet Union in World War II. Multiple rocket launchers such as these deliver explosives to a target area ...
in the artillery role, and the American anti tank
bazooka Bazooka () is the common name for a Man-portable anti-tank systems, man-portable recoilless Anti-tank warfare, anti-tank rocket launcher weapon, widely deployed by the United States Army, especially during World War II. Also referred to as the ...
projectile. These used solid chemical propellants. The Americans captured a large number of German
rocket scientist Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecraft. It has two major and overlapping branches: aeronautical engineering and astronautical engineering. Avionics engineering is s ...
s, including Wernher von Braun, in 1945, and brought them to the United States as part of
Operation Paperclip Operation Paperclip was a secret United States intelligence program in which more than 1,600 German scientists, engineers, and technicians were taken from the former Nazi Germany to the U.S. for government employment after the end of World Wa ...
. After World War II scientists used rockets to study high-altitude conditions, by radio
telemetry Telemetry is the in situ data collection, collection of measurements or other data at remote points and their automatic data transmission, transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Gr ...
of temperature and pressure of the atmosphere, detection of
cosmic rays Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
, and further techniques; note too the
Bell X-1 The Bell X-1 (Bell Model 44) is a rocket engine–powered aircraft, designated originally as the XS-1, and was a joint National Advisory Committee for Aeronautics– U.S. Army Air Forces–U.S. Air Force supersonic research project built by Be ...
, the first crewed vehicle to break the
sound barrier The sound barrier or sonic barrier is the large increase in aerodynamic drag and other undesirable effects experienced by an aircraft or other object when it approaches the speed of sound. When aircraft first approached the speed of sound, th ...
(1947). Independently, in the Soviet Union's space program research continued under the
leadership Leadership, both as a research area and as a practical skill, encompasses the ability of an individual, group or organization to "lead", influence or guide other individuals, teams, or entire organizations. The word "leadership" often gets view ...
of the chief designer
Sergei Korolev Sergei Pavlovich Korolev (russian: Сергей Павлович Королёв, Sergey Pavlovich Korolyov, sʲɪrˈɡʲej ˈpavləvʲɪtɕ kərɐˈlʲɵf, Ru-Sergei Pavlovich Korolev.ogg; ukr, Сергій Павлович Корольов, ...
(1907–1966). During the
Cold War The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because the ...
rockets became extremely important militarily with the development of modern
intercontinental ballistic missiles An intercontinental ballistic missile (ICBM) is a ballistic missile with a range greater than , primarily designed for nuclear weapons delivery (delivering one or more thermonuclear warheads). Conventional, chemical, and biological weapons c ...
(ICBMs). The 1960s saw rapid development of rocket technology, particularly in the Soviet Union (
Vostok Vostok refers to east in Russian but may also refer to: Spaceflight * Vostok programme, Soviet human spaceflight project * Vostok (spacecraft), a type of spacecraft built by the Soviet Union * Vostok (rocket family), family of rockets derived from ...
,
Soyuz Soyuz is a transliteration of the Cyrillic text Союз ( Russian and Ukrainian, 'Union'). It can refer to any union, such as a trade union (''profsoyuz'') or the Union of Soviet Socialist Republics (Сою́з Сове́тских Социалис ...
,
Proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...
) and in the United States (e.g. the
X-15 The North American X-15 is a hypersonic rocket-powered aircraft. It was operated by the United States Air Force and the National Aeronautics and Space Administration as part of the X-plane series of experimental aircraft. The X-15 set speed ...
). Rockets came into use for
space exploration Space exploration is the use of astronomy and space technology to explore outer space. While the exploration of space is carried out mainly by astronomers with telescopes, its physical exploration though is conducted both by robotic spacec ...
. American crewed programs (
Project Mercury Project Mercury was the first human spaceflight program of the United States, running from 1958 through 1963. An early highlight of the Space Race, its goal was to put a man into Earth orbit and return him safely, ideally before the Soviet Un ...
,
Project Gemini Project Gemini () was NASA's second human spaceflight program. Conducted between projects Mercury and Apollo, Gemini started in 1961 and concluded in 1966. The Gemini spacecraft carried a two-astronaut crew. Ten Gemini crews and 16 individual ...
and later the Apollo programme) culminated in 1969 with the first crewed
landing on the Moon A Moon landing is the arrival of a spacecraft on the surface of the Moon. This includes both crewed and robotic missions. The first human-made object to touch the Moon was the Soviet Union's Luna 2, on 13 September 1959. The United S ...
– using equipment launched by the
Saturn V Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, with multistage rocket, three stages, and powered with liquid-propellant r ...
rocket.


Types

;Vehicle configurations Rocket vehicles are often constructed in the archetypal tall thin "rocket" shape that takes off vertically, but there are actually many different types of rockets including: * tiny models such as
balloon rocket A balloon rocket is a rubber balloon filled with air or other gases. Besides being simple toys, balloon rockets are a widely used as a teaching device to demonstrate basic physics. How it works To launch a simple rocket, the untied opening of an i ...
s,
water rocket A water rocket is a type of model rocket using water as its reaction mass. The water is forced out by a pressurized gas, typically compressed air. Like all rocket engines, it operates on the principle of Newton's third law of motion. Water rock ...
s,
skyrocket A skyrocket is a type of firework that uses a solid-fuel rocket to rise quickly into the sky; a bottle rocket is a small skyrocket. At the apex of its ascent, it is usual for a variety of effects (stars, bangs, crackles, etc.) to be emitted. S ...
s or small solid rockets that can be purchased at a
hobby store A hobby shop (or hobby store) sells recreational items for hobbyists. Types Modelling Classical hobby stores specialize in modelling and craft supplies and specialty magazines for model airplanes (military craft, private airplanes and airliners), ...
*
missile In military terminology, a missile is a guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously unguided rocket i ...
s * space rockets such as the enormous
Saturn V Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, with multistage rocket, three stages, and powered with liquid-propellant r ...
used for the Apollo program *
rocket car A rocket car is a land vehicle propelled by a rocket engine. A rocket dragster is a rocket car used for competing in drag racing, and this type holds the unofficial world record for the 1/4 mile. Fritz von Opel was instrumental in popularizing ...
s * rocket bike *
rocket-powered aircraft A rocket-powered aircraft or rocket plane is an aircraft that uses a rocket engine for propulsion, sometimes in addition to airbreathing jet engines. Rocket planes can achieve much higher speeds than similarly sized jet aircraft, but typicall ...
(including rocket assisted takeoff of conventional aircraft –
RATO Rato is a village in the Cornillon commune in the Croix-des-Bouquets Arrondissement, Ouest department of Haiti Haiti (; ht, Ayiti ; French: ), officially the Republic of Haiti (); ) and formerly known as Hayti, is a country located o ...
) * rocket sleds * rocket trains * rocket torpedoes * rocket-powered
jet pack A jet pack, rocket belt, or rocket pack is a device worn on the back which uses jets of gas or liquid to propel the wearer through the air. The concept has been present in science fiction for almost a century and became widespread in the 1960s. ...
s * rapid escape systems such as
ejection seat In aircraft, an ejection seat or ejector seat is a system designed to rescue the aircraft pilot, pilot or other aircrew, crew of an aircraft (usually military) in an emergency. In most designs, the seat is propelled out of the aircraft by an ex ...
s and
launch escape system A launch escape system (LES) or launch abort system (LAS) is a crew-safety system connected to a space capsule that can be used to quickly separate the capsule from its launch vehicle in case of an emergency requiring the abort of the launch, suc ...
s *
space probe A space probe is an artificial satellite that travels through space to collect scientific data. A space probe may orbit Earth; approach the Moon; travel through interplanetary space; flyby, orbit, or land or fly on other planetary bodies; or ent ...
s


Design

A rocket design can be as simple as a cardboard tube filled with
black powder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). Th ...
, but to make an efficient, accurate rocket or missile involves overcoming a number of difficult problems. The main difficulties include cooling the combustion chamber, pumping the fuel (in the case of a liquid fuel), and controlling and correcting the direction of motion.


Components

Rockets consist of a
propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...
, a place to put propellant (such as a
propellant tank A propellant tank is a container which is part of a vehicle, where propellant is stored prior to use. Propellant tanks vary in construction, and may be a fuel tank in the case of many aircraft. In rocket vehicles, propellant tanks are fairly sophis ...
), and a
nozzle A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe. A nozzle is often a pipe or tube of varying cross sectional area, a ...
. They may also have one or more
rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordanc ...
s, directional stabilization device(s) (such as
fins A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fin ...
, vernier engines or engine
gimbal A gimbal is a pivoted support that permits rotation of an object about an axis. A set of three gimbals, one mounted on the other with orthogonal pivot axes, may be used to allow an object mounted on the innermost gimbal to remain independent of ...
s for
thrust vectoring Thrust vectoring, also known as thrust vector control (TVC), is the ability of an aircraft, rocket, or other vehicle to manipulate the direction of the thrust from its engine(s) or motor(s) to control the attitude or angular velocity of the v ...
,
gyroscope A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rota ...
s) and a structure (typically
monocoque Monocoque ( ), also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word ''monocoque'' is a French term for "single shell". First used for boats, ...
) to hold these components together. Rockets intended for high speed atmospheric use also have an
aerodynamic Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
fairing such as a
nose cone A nose cone is the conically shaped forwardmost section of a rocket, guided missile or aircraft, designed to modulate oncoming airflow behaviors and minimize aerodynamic drag. Nose cones are also designed for submerged watercraft such as ...
, which usually holds the payload. As well as these components, rockets can have any number of other components, such as wings (
rocketplane A rocket-powered aircraft or rocket plane is an aircraft that uses a rocket engine for propulsion, sometimes in addition to airbreathing jet engines. Rocket planes can achieve much higher speeds than similarly sized jet aircraft, but typicall ...
s),
parachute A parachute is a device used to slow the motion of an object through an atmosphere by creating drag or, in a ram-air parachute, aerodynamic lift. A major application is to support people, for recreation or as a safety device for aviators, who ...
s, wheels (
rocket car A rocket car is a land vehicle propelled by a rocket engine. A rocket dragster is a rocket car used for competing in drag racing, and this type holds the unofficial world record for the 1/4 mile. Fritz von Opel was instrumental in popularizing ...
s), even, in a sense, a person (
rocket belt A jet pack, rocket belt, or rocket pack is a device worn on the back which uses jets of gas or liquid to propel the wearer through the air. The concept has been present in science fiction for almost a century and became widespread in the 1960s. ...
). Vehicles frequently possess navigation systems and
guidance system A guidance system is a virtual or physical device, or a group of devices implementing a controlling the movement of a ship, aircraft, missile, rocket, satellite, or any other moving object. Guidance is the process of calculating the changes in po ...
s that typically use
satellite navigation A satellite navigation or satnav system is a system that uses satellites to provide autonomous geo-spatial positioning. It allows satellite navigation devices to determine their location (longitude, latitude, and altitude/elevation) to high pr ...
and
inertial navigation system An inertial navigation system (INS) is a navigation device that uses motion sensors (accelerometers), rotation sensors ( gyroscopes) and a computer to continuously calculate by dead reckoning the position, the orientation, and the velocity (dire ...
s.


Engines

Rocket engines employ the principle of
jet propulsion Jet propulsion is the propulsion of an object in one direction, produced by ejecting a jet of fluid in the opposite direction. By Newton's third law, the moving body is propelled in the opposite direction to the jet. Reaction engines operating o ...
. The rocket engines powering rockets come in a great variety of different types; a comprehensive list can be found in the main article,
Rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordanc ...
. Most current rockets are chemically powered rockets (usually
internal combustion engines An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...
, but some employ a decomposing
monopropellant Monopropellants are propellants consisting of chemicals that release energy through exothermic chemical decomposition. The molecular bond energy of the monopropellant is released usually through use of a catalyst. This can be contrasted with biprop ...
) that emit a hot
exhaust gas Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline (petrol), diesel fuel, fuel oil, biodiesel blends, or coal. According to the type of engine, it is discharged into the atmosphere through an ...
. A rocket engine can use gas propellants,
solid propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...
,
liquid propellant A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...
, or a hybrid mixture of both solid and liquid. Some rockets use heat or pressure that is supplied from a source other than the
chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...
of propellant(s), such as
steam rocket A steam rocket (also known as a hot water rocket) is a thermal rocket that uses water held in a pressure vessel at a high temperature, such that its saturated vapor pressure is significantly greater than ambient pressure. The water is allowed to ...
s,
solar thermal rocket A solar thermal rocket is a theoretical spacecraft propulsion system that would make use of solar power to directly heat reaction mass, and therefore would not require an electrical generator, like most other forms of solar-powered propulsion do. ...
s,
nuclear thermal rocket A nuclear thermal rocket (NTR) is a type of thermal rocket where the heat from a nuclear reaction, often nuclear fission, replaces the chemical energy of the propellants in a chemical rocket. In an NTR, a working fluid, usually liquid hydro ...
engines or simple pressurized rockets such as
water rocket A water rocket is a type of model rocket using water as its reaction mass. The water is forced out by a pressurized gas, typically compressed air. Like all rocket engines, it operates on the principle of Newton's third law of motion. Water rock ...
or
cold gas thruster A cold gas thruster (or a cold gas propulsion system) is a type of rocket engine which uses the expansion of a (typically inert) pressurized gas to generate thrust. As opposed to traditional rocket engines, a cold gas thruster does not house any c ...
s. With combustive propellants a chemical reaction is initiated between the
fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...
and the
oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...
in the
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combusti ...
chamber, and the resultant hot gases accelerate out of a
rocket engine nozzle A rocket engine nozzle is a propelling nozzle (usually of the de Laval type) used in a rocket engine to expand and accelerate combustion products to high supersonic velocities. Simply: propellants pressurized by either pumps or high pressure ul ...
(or
nozzle A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe. A nozzle is often a pipe or tube of varying cross sectional area, a ...
s) at the rearward-facing end of the rocket. The
acceleration In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by the ...
of these gases through the engine exerts force ("thrust") on the combustion chamber and nozzle, propelling the vehicle (according to
Newton's Third Law Newton's laws of motion are three basic laws of classical mechanics that describe the relationship between the motion of an object and the forces acting on it. These laws can be paraphrased as follows: # A body remains at rest, or in motion ...
). This actually happens because the force (pressure times area) on the combustion chamber wall is unbalanced by the nozzle opening; this is not the case in any other direction. The shape of the nozzle also generates force by directing the exhaust gas along the axis of the rocket.


Propellant

Rocket propellant is mass that is stored, usually in some form of
propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...
tank or casing, prior to being used as the propulsive mass that is ejected from a
rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordanc ...
in the form of a
fluid In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...
jet to produce
thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...
. For chemical rockets often the propellants are a fuel such as
liquid hydrogen Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point of 33  K. However, for it to be in a fully li ...
or
kerosene Kerosene, paraffin, or lamp oil is a combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in aviation as well as households. Its name derives from el, κηρός (''keros'') meaning "wax", and was regi ...
burned with an oxidizer such as
liquid oxygen Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an applica ...
or
nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
to produce large volumes of very hot gas. The oxidiser is either kept separate and mixed in the combustion chamber, or comes premixed, as with solid rockets. Sometimes the propellant is not burned but still undergoes a chemical reaction, and can be a 'monopropellant' such as
hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...
,
nitrous oxide Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has a ...
or
hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3% ...
that can be catalytically decomposed to hot gas. Alternatively, an inert propellant can be used that can be externally heated, such as in
steam rocket A steam rocket (also known as a hot water rocket) is a thermal rocket that uses water held in a pressure vessel at a high temperature, such that its saturated vapor pressure is significantly greater than ambient pressure. The water is allowed to ...
,
solar thermal rocket A solar thermal rocket is a theoretical spacecraft propulsion system that would make use of solar power to directly heat reaction mass, and therefore would not require an electrical generator, like most other forms of solar-powered propulsion do. ...
or
nuclear thermal rocket A nuclear thermal rocket (NTR) is a type of thermal rocket where the heat from a nuclear reaction, often nuclear fission, replaces the chemical energy of the propellants in a chemical rocket. In an NTR, a working fluid, usually liquid hydro ...
s. For smaller, low performance rockets such as
attitude control thruster Spacecraft attitude control is the process of controlling the orientation of a spacecraft (vehicle/satellite) with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, et ...
s where high performance is less necessary, a pressurised fluid is used as propellant that simply escapes the spacecraft through a propelling nozzle.


Pendulum rocket fallacy

The first
liquid-fuel rocket A liquid-propellant rocket or liquid rocket utilizes a rocket engine that uses liquid rocket propellant, liquid propellants. Liquids are desirable because they have a reasonably high density and high Specific impulse, specific impulse (''I''sp). T ...
, constructed by
Robert H. Goddard Robert Hutchings Goddard (October 5, 1882 – August 10, 1945) was an American engineer, professor, physicist, and inventor who is credited with creating and building the world's first Liquid-propellant rocket, liquid-fueled rocket. ...
, differed significantly from modern rockets. The
rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordanc ...
was at the top and the fuel tank at the bottom of the rocket, based on Goddard's belief that the rocket would achieve stability by "hanging" from the engine like a
pendulum A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting, equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the ...
in flight. However, the rocket veered off course and crashed away from the
launch site A spaceport or cosmodrome is a site for launching or receiving spacecraft, by analogy to a seaport for ships or an airport for aircraft. The word ''spaceport'', and even more so ''cosmodrome'', has traditionally been used for sites capable ...
, indicating that the rocket was no more stable than one with the rocket engine at the base.


Uses

Rockets or other similar reaction devices carrying their own propellant must be used when there is no other substance (land, water, or air) or force (
gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
,
magnetism Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles ...
,
light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
) that a
vehicle A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), wa ...
may usefully employ for propulsion, such as in space. In these circumstances, it is necessary to carry all the
propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...
to be used. However, they are also useful in other situations:


Military

Some military weapons use rockets to propel
warhead A warhead is the forward section of a device that contains the explosive agent or toxic (biological, chemical, or nuclear) material that is delivered by a missile, rocket, torpedo, or bomb. Classification Types of warheads include: * Explosiv ...
s to their targets. A rocket and its payload together are generally referred to as a ''
missile In military terminology, a missile is a guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously unguided rocket i ...
'' when the weapon has a
guidance system A guidance system is a virtual or physical device, or a group of devices implementing a controlling the movement of a ship, aircraft, missile, rocket, satellite, or any other moving object. Guidance is the process of calculating the changes in po ...
(not all missiles use rocket engines, some use other engines such as jets) or as a ''
rocket A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely fr ...
'' if it is unguided. Anti-tank and anti-aircraft missiles use rocket engines to engage targets at high speed at a range of several miles, while intercontinental ballistic missiles can be used to deliver
multiple nuclear warheads Multiple may refer to: Economics *Multiple finance, a method used to analyze stock prices *Multiples of the price-to-earnings ratio *Chain stores, are also referred to as 'Multiples' * Box office multiple, the ratio of a film's total gross to th ...
from thousands of miles, and
anti-ballistic missile An anti-ballistic missile (ABM) is a surface-to-air missile designed to counter ballistic missiles (missile defense). Ballistic missiles are used to deliver nuclear weapon, nuclear, Chemical weapon, chemical, Bioagent, biological, or conventiona ...
s try to stop them. Rockets have also been tested for
reconnaissance In military operations, reconnaissance or scouting is the exploration of an area by military forces to obtain information about enemy forces, terrain, and other activities. Examples of reconnaissance include patrolling by troops (skirmisher ...
, such as the Ping-Pong rocket, which was launched to surveil enemy targets, however, recon rockets have never come into wide use in the military.


Science and research

Sounding rocket A sounding rocket or rocketsonde, sometimes called a research rocket or a suborbital rocket, is an instrument-carrying rocket designed to take measurements and perform scientific experiments during its sub-orbital flight. The rockets are used to ...
s are commonly used to carry instruments that take readings from to above the surface of the Earth. The
first images of Earth from space This is a timeline of first images of Earth from space. The initial photographs and digital images of planet Earth taken from outer space were preceded by aerial photography and continue in the form of satellite imagery. For the purpose of this ...
were obtained from a
V-2 The V-2 (german: Vergeltungswaffe 2, lit=Retaliation Weapon 2), with the technical name ''Aggregat 4'' (A-4), was the world’s first long-range guided ballistic missile. The missile, powered by a liquid-propellant rocket engine, was develope ...
rocket in 1946 ( flight #13). Rocket engines are also used to propel rocket sleds along a rail at extremely high speed. The world record for this is Mach 8.5.


Spaceflight

Larger rockets are normally launched from a
launch pad A launch pad is an above-ground facility from which a rocket-powered missile or space vehicle is vertically launched. The term ''launch pad'' can be used to describe just the central launch platform (mobile launcher platform), or the entire ...
that provides stable support until a few seconds after ignition. Due to their high exhaust velocity——rockets are particularly useful when very high speeds are required, such as orbital speed at approximately . Spacecraft delivered into orbital trajectories become
artificial satellites A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...
, which are used for many commercial purposes. Indeed, rockets remain the only way to launch
spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...
into orbit and beyond. They are also used to rapidly accelerate spacecraft when they change orbits or de-orbit for
landing Landing is the last part of a flight, where a flying animal, aircraft, or spacecraft returns to the ground. When the flying object returns to water, the process is called alighting, although it is commonly called "landing", "touchdown" or ...
. Also, a rocket may be used to soften a hard parachute landing immediately before touchdown (see
retrorocket A retrorocket (short for ''retrograde rocket'') is a rocket engine providing thrust opposing the motion of a vehicle, thereby causing it to decelerate. They have mostly been used in spacecraft, with more limited use in short-runway aircraft land ...
).


Rescue

Rockets were used to propel a line to a stricken ship so that a
Breeches buoy A breeches buoy is a rope-based rescue device used to extract people from wrecked vessels, or to transfer people from one place to another in situations of danger. The device resembles a round emergency personal flotation device with a leg harn ...
can be used to
rescue Rescue comprises responsive operations that usually involve the saving of life, or the urgent treatment of injuries after an accident or a dangerous situation. Tools used might include search and rescue dogs, mounted search and rescue ho ...
those on board. Rockets are also used to launch emergency flares. Some crewed rockets, notably the
Saturn V Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, with multistage rocket, three stages, and powered with liquid-propellant r ...
and
Soyuz Soyuz is a transliteration of the Cyrillic text Союз ( Russian and Ukrainian, 'Union'). It can refer to any union, such as a trade union (''profsoyuz'') or the Union of Soviet Socialist Republics (Сою́з Сове́тских Социалис ...
, have
launch escape system A launch escape system (LES) or launch abort system (LAS) is a crew-safety system connected to a space capsule that can be used to quickly separate the capsule from its launch vehicle in case of an emergency requiring the abort of the launch, suc ...
s. This is a small, usually solid rocket that is capable of pulling the crewed capsule away from the main vehicle towards safety at a moments notice. These types of systems have been operated several times, both in testing and in flight, and operated correctly each time. This was the case when the Safety Assurance System (Soviet nomenclature) successfully pulled away the L3 capsule during three of the four failed launches of the Soviet moon rocket, N1 vehicles 3L, 5L and 7L. In all three cases the capsule, albeit uncrewed, was saved from destruction. Only the three aforementioned N1 rockets had functional Safety Assurance Systems. The outstanding vehicle, 6L, had dummy upper stages and therefore no escape system giving the N1 booster a 100% success rate for egress from a failed launch. A successful escape of a crewed capsule occurred when
Soyuz T-10 Soyuz T-10 was the fifth expedition to the Salyut 7 space station. It entered a darkened and empty station because of the loss of Soyuz T-10a. It was visited by the sixth and seventh expeditions. During the course of the cosmonauts stay, thr ...
, on a mission to the
Salyut 7 Salyut 7 (russian: Салют-7; en, Salute 7) (a.k.a. DOS-6, short for Durable Orbital Station) was a space station in low Earth orbit from April 1982 to February 1991. It was first crewed in May 1982 with two crew via Soyuz T-5, and last vi ...
space station A space station is a spacecraft capable of supporting a human crew in orbit for an extended period of time, and is therefore a type of space habitat. It lacks major propulsion or landing systems. An orbital station or an orbital space station i ...
, exploded on the pad. Solid rocket propelled
ejection seat In aircraft, an ejection seat or ejector seat is a system designed to rescue the aircraft pilot, pilot or other aircrew, crew of an aircraft (usually military) in an emergency. In most designs, the seat is propelled out of the aircraft by an ex ...
s are used in many military aircraft to propel crew away to safety from a vehicle when flight control is lost.


Hobby, sport, and entertainment

A model rocket is a small rocket designed to reach low altitudes (e.g., for model) and be recovered by a variety of means. According to the United States
National Association of Rocketry The National Association of Rocketry (NAR) is a non-profit tax-exempt scientific organization dedicated to consumer safety, youth education, and the advancement of technology in the hobby of sport rocketry in the United States. Founded in 1957, t ...
(nar) Safety Code, model rockets are constructed of paper, wood, plastic and other lightweight materials. The code also provides guidelines for motor use, launch site selection, launch methods, launcher placement, recovery system design and deployment and more. Since the early 1960s, a copy of the Model Rocket Safety Code has been provided with most model rocket kits and motors. Despite its inherent association with extremely flammable substances and objects with a pointed tip traveling at high speeds, model rocketry historically has proven to be a very safe hobby and has been credited as a significant source of inspiration for children who eventually become
scientist A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an Branches of science, area of the natural sciences. In classical antiquity, there was no real ancient analog of a modern scientist. Instead, ...
s and
engineer Engineers, as practitioners of engineering, are professionals who invent, design, analyze, build and test machines, complex systems, structures, gadgets and materials to fulfill functional objectives and requirements while considering the l ...
s. Hobbyists build and fly a wide variety of model rockets. Many companies produce model rocket kits and parts but due to their inherent simplicity some hobbyists have been known to make rockets out of almost anything. Rockets are also used in some types of consumer and professional
fireworks Fireworks are a class of Explosive, low explosive Pyrotechnics, pyrotechnic devices used for aesthetic and entertainment purposes. They are most commonly used in fireworks displays (also called a fireworks show or pyrotechnics), combining a l ...
. A
water rocket A water rocket is a type of model rocket using water as its reaction mass. The water is forced out by a pressurized gas, typically compressed air. Like all rocket engines, it operates on the principle of Newton's third law of motion. Water rock ...
is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is usually a used plastic soft drink bottle. The water is forced out by a pressurized gas, typically compressed air. It is an example of Newton's third law of motion. The scale of amateur rocketry can range from a small rocket launched in one's own backyard to a rocket that reached space. Amateur rocketry is split into three categories according to total engine
impulse Impulse or Impulsive may refer to: Science * Impulse (physics), in mechanics, the change of momentum of an object; the integral of a force with respect to time * Impulse noise (disambiguation) * Specific impulse, the change in momentum per uni ...
: low-power, mid-power, and high-power.
Hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3% ...
rockets are used to power
jet packs Jet Packs is a sci-fi themed aerial carousel attraction in Tomorrowland in Shanghai Disneyland, and opened along with the rest of the park on June 16, 2016. Ride experience Similar to other aerial carousels, such as the Astro Orbiter The ...
, and have been used to power
cars A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarded as t ...
and a rocket car holds the all time (albeit unofficial)
drag racing Drag racing is a type of motor racing in which automobiles or motorcycles compete, usually two at a time, to be first to cross a set finish line. The race follows a short, straight course from a standing start over a measured distance, most c ...
record.
Corpulent Stump Corpulent Stump is a rocket designed and built by Richard Brown at Rocket Store and is the most powerful non commercial rocket ever launched on an Aerotech Consumer Aerospace, Aerotech engine in the United Kingdom. The rocket weighs 50 kg and ...
is the most powerful non-commercial rocket ever launched on an Aerotech engine in the United Kingdom.


Flight

Launches for
orbital spaceflight An orbital spaceflight (or orbital flight) is a spaceflight in which a spacecraft is placed on a trajectory where it could remain in space for at least one orbit. To do this around the Earth, it must be on a free trajectory which has an altit ...
s, or into
interplanetary space Interplanetary may refer to: *Interplanetary space, the space between the planets of the Solar System *Interplanetary spaceflight, travel between planets *The interplanetary medium, the material that exists in interplanetary space *The InterPlanet ...
, are usually from a fixed location on the ground, but would also be possible from an aircraft or ship. Rocket launch technologies include the entire set of systems needed to successfully launch a vehicle, not just the vehicle itself, but also the firing control systems, mission control center,
launch pad A launch pad is an above-ground facility from which a rocket-powered missile or space vehicle is vertically launched. The term ''launch pad'' can be used to describe just the central launch platform (mobile launcher platform), or the entire ...
,
ground station A ground station, Earth station, or Earth terminal is a terrestrial radio station designed for extraplanetary telecommunication with spacecraft (constituting part of the ground segment of the spacecraft system), or reception of radio waves fro ...
s, and
tracking station A ground station, Earth station, or Earth terminal is a terrestrial radio station designed for extraplanetary telecommunication with spacecraft (constituting part of the ground segment of the spacecraft system), or reception of radio waves fro ...
s needed for a successful launch or recovery or both. These are often collectively referred to as the "
ground segment A ground segment consists of all the ground-based elements of a space system used by operators and support personnel, as opposed to the space segment and user segment. The ground segment enables management of a spacecraft, and distribution of p ...
". Orbital
launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pad, launch pads, supported by a missile launch contro ...
s commonly take off vertically, and then begin to progressively lean over, usually following a
gravity turn In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the strong ...
trajectory. Once above the majority of the atmosphere, the vehicle then angles the rocket jet, pointing it largely horizontally but somewhat downwards, which permits the vehicle to gain and then maintain altitude while increasing horizontal speed. As the speed grows, the vehicle will become more and more horizontal until at orbital speed, the engine will cut off. All current vehicles ''stage'', that is, jettison hardware on the way to orbit. Although vehicles have been proposed which would be able to reach orbit without staging, none have ever been constructed, and, if powered only by rockets, the exponentially increasing fuel requirements of such a vehicle would make its useful payload tiny or nonexistent. Most current and historical launch vehicles "expend" their jettisoned hardware, typically by allowing it to crash into the ocean, but some have recovered and reused jettisoned hardware, either by parachute or by propulsive landing. When launching a spacecraft to orbit, a "" is a guided, powered turn during ascent phase that causes a rocket's flight path to deviate from a "straight" path. A dogleg is necessary if the desired launch azimuth, to reach a desired orbital inclination, would take the
ground track A ground track or ground trace is the path on the surface of a planet directly below an aircraft's or satellite's trajectory. In the case of satellites, it is also known as a suborbital track, and is the vertical projection of the satellite's or ...
over land (or over a populated area, e.g. Russia usually does launch over land, but over unpopulated areas), or if the rocket is trying to reach an orbital plane that does not reach the
latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...
of the launch site. Doglegs are undesirable due to extra onboard fuel required, causing heavier load, and a reduction of vehicle performance.


Noise

Rocket exhaust generates a significant amount of acoustic energy. As the
supersonic Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...
exhaust collides with the ambient air,
shock wave In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a med ...
s are formed. The
sound intensity Sound intensity, also known as acoustic intensity, is defined as the power carried by sound waves per unit area in a direction perpendicular to that area. The SI unit of intensity, which includes sound intensity, is the watt per square meter (W/m2 ...
from these shock waves depends on the size of the rocket as well as the exhaust velocity. The sound intensity of large, high performance rockets could potentially kill at close range. The
Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program na ...
generated 180 dB of noise around its base. To combat this, NASA developed a sound suppression system which can flow water at rates up to 900,000 gallons per minute (57 m3/s) onto the launch pad. The water reduces the noise level from 180 dB down to 142 dB (the design requirement is 145 dB). Without the sound suppression system, acoustic waves would reflect off of the launch pad towards the rocket, vibrating the sensitive payload and crew. These acoustic waves can be so severe as to damage or destroy the rocket. Noise is generally most intense when a rocket is close to the ground, since the noise from the engines radiates up away from the jet, as well as reflecting off the ground. This noise can be reduced somewhat by flame trenches with roofs, by water injection around the jet and by deflecting the jet at an angle. For crewed rockets various methods are used to reduce the sound intensity for the passengers, and typically the placement of the astronauts far away from the rocket engines helps significantly. For the passengers and crew, when a vehicle goes
supersonic Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...
the sound cuts off as the sound waves are no longer able to keep up with the vehicle.


Physics


Operation

The
effect Effect may refer to: * A result or change of something ** List of effects ** Cause and effect, an idiom describing causality Pharmacy and pharmacology * Drug effect, a change resulting from the administration of a drug ** Therapeutic effect, a ...
of the combustion of propellant in the rocket engine is to increase the internal energy of the resulting gases, utilizing the stored chemical energy in the fuel. As the internal energy increases, pressure increases, and a nozzle is used to convert this energy into a directed kinetic energy. This produces thrust against the ambient environment to which these gases are released. The ideal direction of motion of the exhaust is in the direction so as to cause thrust. At the top end of the combustion chamber the hot, energetic gas fluid cannot move forward, and so, it pushes upward against the top of the rocket engine's
combustion chamber A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process. Interna ...
. As the combustion gases approach the exit of the combustion chamber, they increase in speed. The effect of the convergent part of the rocket engine nozzle on the high pressure fluid of combustion gases, is to cause the gases to accelerate to high speed. The higher the speed of the gases, the lower the pressure of the gas (
Bernoulli's principle In fluid dynamics, Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in static pressure or a decrease in the fluid's potential energy. The principle is named after the Swiss mathematici ...
or
conservation of energy In physics and chemistry, the law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be ''conserved'' over time. This law, first proposed and tested by Émilie du Châtelet, means th ...
) acting on that part of the combustion chamber. In a properly designed engine, the flow will reach Mach 1 at the throat of the nozzle. At which point the speed of the flow increases. Beyond the throat of the nozzle, a bell shaped expansion part of the engine allows the gases that are expanding to push against that part of the rocket engine. Thus, the bell part of the nozzle gives additional thrust. Simply expressed, for every action there is an equal and opposite reaction, according to
Newton's third law Newton's laws of motion are three basic laws of classical mechanics that describe the relationship between the motion of an object and the forces acting on it. These laws can be paraphrased as follows: # A body remains at rest, or in motion ...
with the result that the exiting gases produce the reaction of a force on the rocket causing it to accelerate the rocket. In a closed chamber, the pressures are equal in each direction and no acceleration occurs. If an opening is provided in the bottom of the chamber then the pressure is no longer acting on the missing section. This opening permits the exhaust to escape. The remaining pressures give a resultant thrust on the side opposite the opening, and these pressures are what push the rocket along. The shape of the nozzle is important. Consider a balloon propelled by air coming out of a tapering nozzle. In such a case the combination of air pressure and viscous friction is such that the nozzle does not push the balloon but is ''pulled'' by it. Using a convergent/divergent nozzle gives more force since the exhaust also presses on it as it expands outwards, roughly doubling the total force. If propellant gas is continuously added to the chamber then these pressures can be maintained for as long as propellant remains. Note that in the case of liquid propellant engines, the pumps moving the propellant into the combustion chamber must maintain a pressure larger than the combustion chamber – typically on the order of 100 atmospheres. As a side effect, these pressures on the rocket also act on the exhaust in the opposite direction and accelerate this exhaust to very high speeds (according to
Newton's Third Law Newton's laws of motion are three basic laws of classical mechanics that describe the relationship between the motion of an object and the forces acting on it. These laws can be paraphrased as follows: # A body remains at rest, or in motion ...
). From the principle of
conservation of momentum In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
the speed of the exhaust of a rocket determines how much momentum increase is created for a given amount of propellant. This is called the rocket's ''
specific impulse Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse i ...
''. Because a rocket, propellant and exhaust in flight, without any external perturbations, may be considered as a closed system, the total momentum is always constant. Therefore, the faster the net speed of the exhaust in one direction, the greater the speed of the rocket can achieve in the opposite direction. This is especially true since the rocket body's mass is typically far lower than the final total exhaust mass.


Forces on a rocket in flight

The general study of the
force In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...
s on a rocket is part of the field of
ballistics Ballistics is the field of mechanics concerned with the launching, flight behaviour and impact effects of projectiles, especially ranged weapon munitions such as bullets, unguided bombs, rockets or the like; the science or art of designing and a ...
. Spacecraft are further studied in the subfield of
astrodynamics Orbital mechanics or astrodynamics is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft. The motion of these objects is usually calculated from Newton's laws of ...
. Flying rockets are primarily affected by the following: *
Thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...
from the engine(s) *
Gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
from
celestial bodies An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often us ...
* Drag if moving in atmosphere *
Lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Paternoster lift, a type of lift using a continuous chain of cars which do not stop ** Patient lift, or Hoyer lift, mobil ...
; usually relatively small effect except for
rocket-powered aircraft A rocket-powered aircraft or rocket plane is an aircraft that uses a rocket engine for propulsion, sometimes in addition to airbreathing jet engines. Rocket planes can achieve much higher speeds than similarly sized jet aircraft, but typicall ...
In addition, the inertia and centrifugal pseudo-force can be significant due to the path of the rocket around the center of a celestial body; when high enough speeds in the right direction and altitude are achieved a stable
orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...
or
escape velocity In celestial mechanics, escape velocity or escape speed is the minimum speed needed for a free, non- propelled object to escape from the gravitational influence of a primary body, thus reaching an infinite distance from it. It is typically ...
is obtained. These forces, with a stabilizing tail (the ''
empennage The empennage ( or ), also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow.Crane, Dale: ''Dictionary of Aeronautical Terms, third ed ...
'') present will, unless deliberate control efforts are made, naturally cause the vehicle to follow a roughly parabolic trajectory termed a
gravity turn In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the strong ...
, and this trajectory is often used at least during the initial part of a launch. (This is true even if the rocket engine is mounted at the nose.) Vehicles can thus maintain low or even zero
angle of attack In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is m ...
, which minimizes transverse
stress Stress may refer to: Science and medicine * Stress (biology), an organism's response to a stressor such as an environmental condition * Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...
on the
launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pad, launch pads, supported by a missile launch contro ...
, permitting a weaker, and hence lighter, launch vehicle.


Drag

Drag is a force opposite to the direction of the rocket's motion relative to any air it is moving through. This slows the speed of the vehicle and produces structural loads. The deceleration forces for fast-moving rockets are calculated using the
drag equation In fluid dynamics, the drag equation is a formula used to calculate the force of drag experienced by an object due to movement through a fully enclosing fluid. The equation is: F_\, =\, \tfrac12\, \rho\, u^2\, c_\, A where *F_ is the drag force ...
. Drag can be minimised by an aerodynamic
nose cone A nose cone is the conically shaped forwardmost section of a rocket, guided missile or aircraft, designed to modulate oncoming airflow behaviors and minimize aerodynamic drag. Nose cones are also designed for submerged watercraft such as ...
and by using a shape with a high
ballistic coefficient In ballistics, the ballistic coefficient (BC, ''C'') of a body is a measure of its ability to overcome air resistance in flight. It is inversely proportional to the negative acceleration: a high number indicates a low negative acceleration—the d ...
(the "classic" rocket shape—long and thin), and by keeping the rocket's
angle of attack In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is m ...
as low as possible. During a launch, as the vehicle speed increases, and the atmosphere thins, there is a point of maximum aerodynamic drag called max Q. This determines the minimum aerodynamic strength of the vehicle, as the rocket must avoid
buckling In structural engineering, buckling is the sudden change in shape (deformation) of a structural component under load, such as the bowing of a column under compression or the wrinkling of a plate under shear. If a structure is subjected to a gr ...
under these forces.


Net thrust

A typical rocket engine can handle a significant fraction of its own mass in propellant each second, with the propellant leaving the nozzle at several kilometres per second. This means that the
thrust-to-weight ratio Thrust-to-weight ratio is a dimensionless ratio of thrust to weight of a rocket, jet engine, propeller engine, or a vehicle propelled by such an engine that is an indicator of the performance of the engine or vehicle. The instantaneous thrust-to-w ...
of a rocket engine, and often the entire vehicle can be very high, in extreme cases over 100. This compares with other jet propulsion engines that can exceed 5 for some of the better engines. It can be shown that the net thrust of a rocket is: where: The effective exhaust velocity v_ is more or less the speed the exhaust leaves the vehicle, and in the vacuum of space, the effective exhaust velocity is often equal to the actual average exhaust speed along the thrust axis. However, the effective exhaust velocity allows for various losses, and notably, is reduced when operated within an atmosphere. The rate of propellant flow through a rocket engine is often deliberately varied over a flight, to provide a way to control the thrust and thus the airspeed of the vehicle. This, for example, allows minimization of aerodynamic losses and can limit the increase of ''g''-forces due to the reduction in propellant load.


Total impulse

Impulse is defined as a force acting on an object over time, which in the absence of opposing forces (gravity and aerodynamic drag), changes the
momentum In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
(integral of mass and velocity) of the object. As such, it is the best performance class (payload mass and terminal velocity capability) indicator of a rocket, rather than takeoff thrust, mass, or "power". The total impulse of a rocket (stage) burning its propellant is: When there is fixed thrust, this is simply: The total impulse of a multi-stage rocket is the sum of the impulses of the individual stages.


Specific impulse

As can be seen from the thrust equation, the effective speed of the exhaust controls the amount of thrust produced from a particular quantity of fuel burnt per second. An equivalent measure, the net impulse per weight unit of propellant expelled, is called
specific Impulse Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse i ...
, I_, and this is one of the most important figures that describes a rocket's performance. It is defined such that it is related to the effective exhaust velocity by: where: Thus, the greater the specific impulse, the greater the net thrust and performance of the engine. I_ is determined by measurement while testing the engine. In practice the effective exhaust velocities of rockets varies but can be extremely high, ~4500 m/s, about 15 times the sea level speed of sound in air.


Delta-v (rocket equation)

The
delta-v Delta-''v'' (more known as "change in velocity"), symbolized as ∆''v'' and pronounced ''delta-vee'', as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as ...
capacity of a rocket is the theoretical total change in velocity that a rocket can achieve without any external interference (without air drag or gravity or other forces). When v_e is constant, the delta-v that a rocket vehicle can provide can be calculated from the
Tsiolkovsky rocket equation Konstantin Eduardovich Tsiolkovsky (russian: Константи́н Эдуа́рдович Циолко́вский , , p=kənstɐnʲˈtʲin ɪdʊˈardəvʲɪtɕ tsɨɐlˈkofskʲɪj , a=Ru-Konstantin Tsiolkovsky.oga; – 19 September 1935) ...
: :\Delta v\ = v_e \ln \frac where: When launched from the Earth practical delta-vs for a single rockets carrying payloads can be a few km/s. Some theoretical designs have rockets with delta-vs over 9 km/s. The required delta-v can also be calculated for a particular manoeuvre; for example the delta-v to launch from the surface of the Earth to
low Earth orbit A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...
is about 9.7 km/s, which leaves the vehicle with a sideways speed of about 7.8 km/s at an altitude of around 200 km. In this manoeuvre about 1.9 km/s is lost in
air drag In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding ...
,
gravity drag In astrodynamics and rocketry, gravity loss is a measure of the loss in the net performance of a rocket while it is thrusting in a gravitational field. In other words, it is the cost of having to hold the rocket up in a gravity field. Gravity lo ...
and gaining altitude. The ratio \frac is sometimes called the ''mass ratio''.


Mass ratios

Almost all of a launch vehicle's mass consists of propellant. Mass ratio is, for any 'burn', the ratio between the rocket's initial mass and its final mass. Everything else being equal, a high mass ratio is desirable for good performance, since it indicates that the rocket is lightweight and hence performs better, for essentially the same reasons that low weight is desirable in sports cars. Rockets as a group have the highest
thrust-to-weight ratio Thrust-to-weight ratio is a dimensionless ratio of thrust to weight of a rocket, jet engine, propeller engine, or a vehicle propelled by such an engine that is an indicator of the performance of the engine or vehicle. The instantaneous thrust-to-w ...
of any type of engine; and this helps vehicles achieve high
mass ratio In aerospace engineering, mass ratio is a measure of the efficiency of a rocket. It describes how much more massive the vehicle is with propellant than without; that is, the ratio of the rocket's ''wet mass'' (vehicle plus contents plus propellan ...
s, which improves the performance of flights. The higher the ratio, the less engine mass is needed to be carried. This permits the carrying of even more propellant, enormously improving the delta-v. Alternatively, some rockets such as for rescue scenarios or racing carry relatively little propellant and payload and thus need only a lightweight structure and instead achieve high accelerations. For example, the Soyuz escape system can produce 20 ''g''. Achievable mass ratios are highly dependent on many factors such as propellant type, the design of engine the vehicle uses, structural safety margins and construction techniques. The highest mass ratios are generally achieved with liquid rockets, and these types are usually used for
orbital launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pads, supported by a launch control center and syste ...
s, a situation which calls for a high delta-v. Liquid propellants generally have densities similar to water (with the notable exceptions of
liquid hydrogen Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point of 33  K. However, for it to be in a fully li ...
and
liquid methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...
), and these types are able to use lightweight, low pressure tanks and typically run high-performance
turbopumps A turbopump is a propellant pump with two main components: a rotodynamic pump and a driving gas turbine, usually both mounted on the same shaft, or sometimes geared together. They were initially developed in Germany in the early 1940s. The purpo ...
to force the propellant into the combustion chamber. Some notable mass fractions are found in the following table (some aircraft are included for comparison purposes):


Staging

Thus far, the required velocity (delta-v) to achieve orbit has been unattained by any single rocket because the
propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...
, tankage, structure, guidance, valves and engines and so on, take a particular minimum percentage of take-off mass that is too great for the propellant it carries to achieve that delta-v carrying reasonable payloads. Since
Single-stage-to-orbit A single-stage-to-orbit (SSTO) vehicle reaches orbit from the surface of a body using only propellants and fluids and without expending tanks, engines, or other major hardware. The term usually, but not exclusively, refers to reusable vehicles ...
has so far not been achievable, orbital rockets always have more than one stage. For example, the first stage of the Saturn V, carrying the weight of the upper stages, was able to achieve a
mass ratio In aerospace engineering, mass ratio is a measure of the efficiency of a rocket. It describes how much more massive the vehicle is with propellant than without; that is, the ratio of the rocket's ''wet mass'' (vehicle plus contents plus propellan ...
of about 10, and achieved a specific impulse of 263 seconds. This gives a delta-v of around 5.9 km/s whereas around 9.4 km/s delta-v is needed to achieve orbit with all losses allowed for. This problem is frequently solved by
staging Staging may refer to: Computing * Staging (cloud computing), a process used to assemble, test, and review a new solution before it is moved into production and the existing solution is decommissioned * Staging (data), intermediately storing data ...
—the rocket sheds excess weight (usually empty tankage and associated engines) during launch. Staging is either ''serial'' where the rockets light after the previous stage has fallen away, or ''parallel'', where rockets are burning together and then detach when they burn out. The maximum speeds that can be achieved with staging is theoretically limited only by the speed of light. However the payload that can be carried goes down geometrically with each extra stage needed, while the additional delta-v for each stage is simply additive.


Acceleration and thrust-to-weight ratio

From Newton's second law, the acceleration, a, of a vehicle is simply: where is the instantaneous mass of the vehicle and F_n is the net force acting on the rocket (mostly thrust, but air drag and other forces can play a part). As the remaining propellant decreases, rocket vehicles become lighter and their acceleration tends to increase until the propellant is exhausted. This means that much of the speed change occurs towards the end of the burn when the vehicle is much lighter. However, the thrust can be throttled to offset or vary this if needed. Discontinuities in acceleration also occur when stages burn out, often starting at a lower acceleration with each new stage firing. Peak accelerations can be increased by designing the vehicle with a reduced mass, usually achieved by a reduction in the fuel load and tankage and associated structures, but obviously this reduces range, delta-v and burn time. Still, for some applications that rockets are used for, a high peak acceleration applied for just a short time is highly desirable. The minimal mass of vehicle consists of a rocket engine with minimal fuel and structure to carry it. In that case the
thrust-to-weight ratio Thrust-to-weight ratio is a dimensionless ratio of thrust to weight of a rocket, jet engine, propeller engine, or a vehicle propelled by such an engine that is an indicator of the performance of the engine or vehicle. The instantaneous thrust-to-w ...
of the rocket engine limits the maximum acceleration that can be designed. It turns out that rocket engines generally have truly excellent thrust to weight ratios (137 for the
NK-33 The NK-33 and NK-43 are rocket engines designed and built in the late 1960s and early 1970s by the Kuznetsov Design Bureau. The NK designation is derived from the initials of chief designer Nikolay Kuznetsov. The NK-33 was among the most powerf ...
engine; some solid rockets are over 1000), and nearly all really high-g vehicles employ or have employed rockets. The high accelerations that rockets naturally possess means that rocket vehicles are often capable of
vertical takeoff Takeoff is the phase of flight in which an aerospace vehicle leaves the ground and becomes airborne. For aircraft traveling vertically, this is known as liftoff. For aircraft that take off horizontally, this usually involves starting with a t ...
, and in some cases, with suitable guidance and control of the engines, also vertical landing. For these operations to be done it is necessary for a vehicle's engines to provide more than the local
gravitational acceleration In physics, gravitational acceleration is the acceleration of an object in free fall within a vacuum (and thus without experiencing drag). This is the steady gain in speed caused exclusively by the force of gravitational attraction. All bodies ...
.


Energy


Energy efficiency

The energy density of a typical rocket propellant is often around one-third that of conventional hydrocarbon fuels; the bulk of the mass is (often relatively inexpensive) oxidizer. Nevertheless, at take-off the rocket has a great deal of energy in the fuel and oxidizer stored within the vehicle. It is of course desirable that as much of the energy of the propellant end up as
kinetic Kinetic (Ancient Greek: κίνησις “kinesis”, movement or to move) may refer to: * Kinetic theory of gases, Kinetic theory, describing a gas as particles in random motion * Kinetic energy, the energy of an object that it possesses due to i ...
or
potential energy In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors. Common types of potential energy include the gravitational potentia ...
of the body of the rocket as possible. Energy from the fuel is lost in air drag and
gravity drag In astrodynamics and rocketry, gravity loss is a measure of the loss in the net performance of a rocket while it is thrusting in a gravitational field. In other words, it is the cost of having to hold the rocket up in a gravity field. Gravity lo ...
and is used for the rocket to gain altitude and speed. However, much of the lost energy ends up in the exhaust. In a chemical propulsion device, the engine efficiency is simply the ratio of the kinetic power of the exhaust gases and the power available from the chemical reaction: 100% efficiency within the engine (engine efficiency \eta_c = 100\%) would mean that all the heat energy of the combustion products is converted into kinetic energy of the jet. This is not possible, but the near-adiabatic high expansion ratio nozzles that can be used with rockets come surprisingly close: when the nozzle expands the gas, the gas is cooled and accelerated, and an energy efficiency of up to 70% can be achieved. Most of the rest is heat energy in the exhaust that is not recovered. The high efficiency is a consequence of the fact that rocket combustion can be performed at very high temperatures and the gas is finally released at much lower temperatures, and so giving good Carnot efficiency. However, engine efficiency is not the whole story. In common with the other jet-based engines, but particularly in rockets due to their high and typically fixed exhaust speeds, rocket vehicles are extremely inefficient at low speeds irrespective of the engine efficiency. The problem is that at low speeds, the exhaust carries away a huge amount of
kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...
rearward. This phenomenon is termed
propulsive efficiency In aerospace engineering, concerning aircraft, rocket and spacecraft design, overall propulsion system efficiency \eta is the efficiency with which the energy contained in a vehicle's fuel is converted into kinetic energy of the vehicle, to accelera ...
(\eta_p). However, as speeds rise, the resultant exhaust speed goes down, and the overall vehicle energetic efficiency rises, reaching a peak of around 100% of the engine efficiency when the vehicle is travelling exactly at the same speed that the exhaust is emitted. In this case the exhaust would ideally stop dead in space behind the moving vehicle, taking away zero energy, and from conservation of energy, all the energy would end up in the vehicle. The efficiency then drops off again at even higher speeds as the exhaust ends up traveling forwards – trailing behind the vehicle. From these principles it can be shown that the propulsive efficiency \eta_p for a rocket moving at speed u with an exhaust velocity c is: And the overall (instantaneous) energy efficiency \eta is: For example, from the equation, with an \eta_c of 0.7, a rocket flying at Mach 0.85 (which most aircraft cruise at) with an exhaust velocity of Mach 10, would have a predicted overall energy efficiency of 5.9%, whereas a conventional, modern, air-breathing jet engine achieves closer to 35% efficiency. Thus a rocket would need about 6x more energy; and allowing for the specific energy of rocket propellant being around one third that of conventional air fuel, roughly 18x more mass of propellant would need to be carried for the same journey. This is why rockets are rarely if ever used for general aviation. Since the energy ultimately comes from fuel, these considerations mean that rockets are mainly useful when a very high speed is required, such as
ICBM An intercontinental ballistic missile (ICBM) is a ballistic missile with a range greater than , primarily designed for nuclear weapons delivery (delivering one or more thermonuclear warheads). Conventional, chemical, and biological weapons c ...
s or
orbital launch An orbital spaceflight (or orbital flight) is a spaceflight in which a spacecraft is placed on a trajectory where it could remain in space for at least one orbit. To do this around the Earth, it must be on a free trajectory which has an altit ...
. For example,
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...
's
Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program na ...
fired its engines for around 8.5 minutes, consuming 1,000 tonnes of solid propellant (containing 16% aluminium) and an additional 2,000,000 litres of liquid propellant (106,261 kg of
liquid hydrogen Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point of 33  K. However, for it to be in a fully li ...
fuel) to lift the 100,000 kg vehicle (including the 25,000 kg payload) to an altitude of 111 km and an orbital
velocity Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity is a ...
of 30,000 km/h. At this altitude and velocity, the vehicle had a kinetic energy of about 3 TJ and a potential energy of roughly 200 GJ. Given the initial energy of 20 TJ, the Space Shuttle was about 16% energy efficient at launching the orbiter. Thus jet engines, with a better match between speed and jet exhaust speed (such as
turbofans The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the ''turbo'' portion refers to a gas turbine engine which achieves mechani ...
—in spite of their worse \eta_c)—dominate for subsonic and supersonic atmospheric use, while rockets work best at hypersonic speeds. On the other hand, rockets serve in many short-range ''relatively'' low speed military applications where their low-speed inefficiency is outweighed by their extremely high thrust and hence high accelerations.


Oberth effect

One subtle feature of rockets relates to energy. A rocket stage, while carrying a given load, is capable of giving a particular
delta-v Delta-''v'' (more known as "change in velocity"), symbolized as ∆''v'' and pronounced ''delta-vee'', as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as ...
. This delta-v means that the speed increases (or decreases) by a particular amount, independent of the initial speed. However, because
kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...
is a square law on speed, this means that the faster the rocket is travelling before the burn the more
orbital energy In the gravitational two-body problem, the specific orbital energy \varepsilon (or vis-viva energy) of two orbiting bodies is the constant sum of their mutual potential energy (\varepsilon_p) and their total kinetic energy (\varepsilon_k), divid ...
it gains or loses. This fact is used in interplanetary travel. It means that the amount of delta-v to reach other planets, over and above that to reach escape velocity can be much less if the delta-v is applied when the rocket is travelling at high speeds, close to the Earth or other planetary surface; whereas waiting until the rocket has slowed at altitude multiplies up the effort required to achieve the desired trajectory.


Safety, reliability and accidents

The reliability of rockets, as for all physical systems, is dependent on the quality of engineering design and construction. Because of the enormous chemical energy in
rocket propellant Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propuls ...
s (greater energy by weight than explosives, but lower than
gasoline Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...
), consequences of accidents can be severe. Most space missions have some problems. In 1986, following the Space Shuttle ''Challenger'' disaster, American physicist
Richard Feynman Richard Phillips Feynman (; May 11, 1918 – February 15, 1988) was an American theoretical physicist, known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, the physics of the superflu ...
, having served on the
Rogers Commission The Rogers Commission Report was written by a Presidential Commission charged with investigating the Space Shuttle ''Challenger'' disaster during its 10th mission, STS-51-L. The report, released and submitted to President Ronald Reagan on Jun ...
, estimated that the chance of an unsafe condition for a launch of the Shuttle was very roughly 1%; more recently the historical per person-flight risk in orbital spaceflight has been calculated to be around 2% or 4%. In May 2003 the astronaut office made clear its position on the need and feasibility of improving crew safety for future NASA crewed missions indicating their "consensus that an order of magnitude reduction in the risk of human life during ascent, compared to the
Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program na ...
, is both achievable with current technology and consistent with NASA's focus on steadily improving rocket reliability".


Costs and economics

The costs of rockets can be roughly divided into propellant costs, the costs of obtaining and/or producing the 'dry mass' of the rocket, and the costs of any required support equipment and facilities."A Rocket a Day Keeps the High Costs Away"
by John Walker. September 27, 1993.
Most of the takeoff mass of a rocket is normally propellant. However propellant is seldom more than a few times more expensive than gasoline per kilogram (as of 2009 gasoline was about or less), and although substantial amounts are needed, for all but the very cheapest rockets, it turns out that the propellant costs are usually comparatively small, although not completely negligible. With liquid oxygen costing and liquid hydrogen , the
Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program na ...
in 2009 had a liquid propellant expense of approximately $1.4 million for each launch that cost $450 million from other expenses (with 40% of the mass of propellants used by it being liquids in the external fuel tank, 60% solids in the SRBs). Even though a rocket's non-propellant, dry mass is often only between 5–20% of total mass, nevertheless this cost dominates. For hardware with the performance used in orbital
launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pad, launch pads, supported by a missile launch contro ...
s, expenses of $2000–$10,000+ per kilogram of
dry weight Vehicle weight is a measurement of wheeled motor vehicles; either an actual measured weight of the vehicle under defined conditions or a gross weight rating for its weight carrying capacity. Curb or kerb weight Curb weight (U.S. English) or kerb ...
are common, primarily from engineering, fabrication, and testing; raw materials amount to typically around 2% of total expense.Regis, Ed (1990), ''Great Mambo Chicken And The Transhuman Condition: Science Slightly Over The Edge'', Basic Books,
Excerpt online
/ref> U.S. Air Force Research Report No. AU-ARI-93-8: LEO On The Cheap. Retrieved April 29, 2011. For most rockets except reusable ones (shuttle engines) the engines need not function more than a few minutes, which simplifies design. Extreme performance requirements for rockets reaching orbit correlate with high cost, including intensive quality control to ensure reliability despite the limited
safety factor In engineering, a factor of safety (FoS), also known as (and used interchangeably with) safety factor (SF), expresses how much stronger a system is than it needs to be for an intended load. Safety factors are often calculated using detailed analy ...
s allowable for weight reasons. Components produced in small numbers if not individually machined can prevent amortization of R&D and facility costs over mass production to the degree seen in more pedestrian manufacturing. Amongst liquid-fueled rockets, complexity can be influenced by how much hardware must be lightweight, like pressure-fed engines can have two orders of magnitude lesser part count than pump-fed engines but lead to more weight by needing greater tank pressure, most often used in just small maneuvering thrusters as a consequence. To change the preceding factors for orbital launch vehicles, proposed methods have included mass-producing simple rockets in large quantities or on large scale, or developing reusable rockets meant to fly very frequently to amortize their up-front expense over many payloads, or reducing rocket performance requirements by constructing a
non-rocket spacelaunch Non-rocket spacelaunch refers to theoretical concepts for launch into space where much of the speed and altitude needed to achieve orbit is provided by a propulsion technique that is not subject to the limits of the rocket equation. Although al ...
system for part of the velocity to orbit (or all of it but with most methods involving some rocket use). The costs of support equipment, range costs and launch pads generally scale up with the size of the rocket, but vary less with launch rate, and so may be considered to be approximately a fixed cost. Rockets in applications other than launch to orbit (such as military rockets and
rocket-assisted take off JATO (acronym for jet-assisted take-off) is a type of assisted take-off for helping overloaded aircraft into the air by providing additional thrust in the form of small rockets. The term ''JATO'' is used interchangeably with the (more specific ...
), commonly not needing comparable performance and sometimes mass-produced, are often relatively inexpensive.


2010s emerging private competition

Since the early 2010s, new private options for obtaining spaceflight services emerged, bringing substantial price pressure into the existing market.


See also

Lists *
Chronology of Pakistan's rocket tests The Suparco's spaceflight missions and tests were the sounding rocket launches of the Space Research Commission (SUPARCO) that were aimed for developing high-altitude rockets for Pakistan's space programme. The exploration programme provides op ...
*
Lists of rockets There are several different types of rockets. The following articles contain lists of rockets by type: * List of missiles * List of orbital launch systems * List of sounding rockets * List of military rockets * List of rocket stages See also * C ...
*
Timeline of rocket and missile technology This article gives a concise timeline of rocket and missile technology. 11th century-13th century * 11th century AD - The first documented record of what appears to be gunpowder and the fire arrow, an early form of rocketry, appears in the Chi ...
General rocketry * * * * * Rocket propulsion * * * * Recreational rocketry * * * * Weaponry * * * * * Rockets for research * * Miscellaneous * * * * *


Notes


External links

Governing agencies
FAA Office of Commercial Space Transportation

National Aeronautics and Space Administration (NASA)

National Association of Rocketry (US)

Tripoli Rocketry Association

Asoc. Coheteria Experimental y Modelista de Argentina

United Kingdom Rocketry Association

IMR – German/Austrian/Swiss Rocketry Association

Canadian Association of Rocketry

Indian Space Research Organisation
Information sites *
Encyclopedia Astronautica The ''Encyclopedia Astronautica'' is a reference web site on space travel. A comprehensive catalog of vehicles, technology, astronauts, and flights, it includes information from most countries that have had an active rocket research program, f ...

Rocket and Missile Alphabetical Index


* Gunter's Space Page
Complete Rocket and Missile Lists



Relativity Calculator – Learn Tsiolkovsky's rocket equations

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