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Spaceflight (or space flight) is an application of
astronautics Astronautics (or cosmonautics) is the theory and practice of travel beyond Earth's atmosphere into outer space. Spaceflight is one of its main applications and space science its overarching field. The term ''astronautics'' (originally ''astronaut ...
to fly
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 or through
outer space Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, pred ...
, either
with With or WITH may refer to: * With, a preposition in English * Carl Johannes With (1877–1923), Danish doctor and arachnologist * With (character), a character in ''D. N. Angel'' * ''With'' (novel), a novel by Donald Harrington * ''With'' (album ...
or without humans on board. Most spaceflight is uncrewed and conducted mainly with spacecraft such as
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 radioisotope ...
s in orbit around Earth, but also includes
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 for flights beyond Earth orbit. Such spaceflight operates either by
telerobotic Telerobotics is the area of robotics concerned with the control of semi-autonomous robots from a distance, chiefly using television, wireless networks (like Wi-Fi, Bluetooth and the Deep Space Network) or tethered connections. It is a combinatio ...
or
autonomous In developmental psychology and moral, political, and bioethical philosophy, autonomy, from , ''autonomos'', from αὐτο- ''auto-'' "self" and νόμος ''nomos'', "law", hence when combined understood to mean "one who gives oneself one's ow ...
control. The more complex human spaceflight has been pursued soon after the first orbital satellites and has reached the
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
and permanent
human presence in space Human presence in space is about humanity in space, particularly about all anthropogenic presence in space and human activity in space, that is in outer space and in a broader sense also on any extraterrestrial astronomical body. Humans have ...
around Earth, particularly with the use of
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 ...
s.
Human spaceflight programs Human spaceflight programs have been conducted, started, or planned by multiple countries and companies. Until the 21st century, human spaceflight programs were sponsored exclusively by governments, through either the military or civilian space ...
include the
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 ...
, Shenzhou, the past Apollo Moon landing and the
Space Shuttle program The Space Shuttle program was the fourth human spaceflight program carried out by the U.S. National Aeronautics and Space Administration (NASA), which accomplished routine transportation for Earth-to-orbit crew and cargo from 1981 to 2011. Its ...
s, with currently the
International Space Station The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA ...
as the main destination of human spaceflight missions while China's Tiangong Space Station is under construction. Spaceflight is used for placing in Earth's orbit
communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...
s,
reconnaissance satellite A reconnaissance satellite or intelligence satellite (commonly, although unofficially, referred to as a spy satellite) is an Earth observation satellite or communications satellite deployed for military or intelligence applications. The ...
s,
Earth observation satellite An Earth observation satellite or Earth remote sensing satellite is a satellite used or designed for Earth observation (EO) from orbit, including spy satellites and similar ones intended for non-military uses such as environmental monitoring, me ...
s, but also 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 ...
such as
space observatories A space telescope or space observatory is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO-2 launched ...
and space probes, or even for
space tourism Space tourism is human space travel for recreational purposes. There are several different types of space tourism, including orbital, suborbital and lunar space tourism. During the period from 2001 to 2009, seven space tourists made eight s ...
. Spaceflight can be achieved with different types of
launch system 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, conventionally by rocket launching, which provide the initial thrust to overcome the force of gravity and propel a spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft—both when unpropelled and when under propulsion—is covered by the area of study called
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 ...
. Some spacecraft remain in space practically indefinitely, which has created the issue of space pollution in the form of
light pollution Light pollution is the presence of unwanted, inappropriate, or excessive use of artificial Visible spectrum, lighting. In a descriptive sense, the term ''light pollution'' refers to the effects of any poorly implemented lighting, during the day ...
and
space junk Space debris (also known as space junk, space pollution, space waste, space trash, or space garbage) are defunct human-made objects in space—principally in Earth orbit—which no longer serve a useful function. These include derelict spacecr ...
, which is a hazard to spaceflight. Otherwise spacecraft are terminated by
atmospheric reentry Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. There are two main types of atmospheric entry: ''uncontrolled entry'', such as the entr ...
, in which they disintegrate, or if they do not, their reentry is mostly controlled to safely reach a surface by landing or impacting, often being dumped in the oceanic
spacecraft cemetery The spacecraft cemetery, known more formally as the South Pacific Ocean(ic) Uninhabited Area, is a region in the southern Pacific Ocean east of New Zealand, where spacecraft that have reached the end of their usefulness are routinely crashed. Th ...
. As such spacecraft have been the subject of some
space traffic management Space traffic management is defined by the International Academy of Astronautics (IAA) as "the set of technical and regulatory provisions for promoting safe access into outer space, operations in outer space and return from outer space to Earth free ...
.


Terminology

There are several terms that refer to a flight into or through
outer space Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, pred ...
. A space mission refers to a spaceflight intended to achieve an objective. Objectives for space missions may include
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 ...
,
space research Space research is scientific study carried out in outer space, and by studying outer space. From the use of space technology to the observable universe, space research is a wide research field. Earth science, materials science, biology, medicine ...
, and national firsts in spaceflight. Space transport is the use of spacecraft to transport people or cargo into or through outer space. This may include
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
cargo spacecraft Cargo spacecraft are robotic spacecraft that are designed to carry cargo, possibly to support space stations' operation by transporting food, propellant and other supplies. This is different from a space probes, space probe, whose missions are to ...
flight.


History

The first theoretical proposal of space travel using
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 ...
s was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space". More well-known (though not widely outside Russia) is
Konstantin Tsiolkovsky Konstantin Eduardovich Tsiolkovsky (russian: Константи́н Эдуа́рдович Циолко́вский , , p=kənstɐnʲˈtʲin ɪdʊˈardəvʲɪtɕ tsɨɐlˈkofskʲɪj , a=Ru-Konstantin Tsiolkovsky.oga; – 19 September 1935) ...
's work, "" (''The Exploration of Cosmic Space by Means of Reaction Devices''), published in 1903. Spaceflight became an engineering possibility with the work of
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. ...
's publication in 1919 of his paper ''
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. ...
''. His application of the
de Laval nozzle A de Laval nozzle (or convergent-divergent nozzle, CD nozzle or con-di nozzle) is a tube which is pinched in the middle, making a carefully balanced, asymmetric hourglass shape. It is used to accelerate a compressible fluid to supersonic speeds ...
to
liquid fuel rocket A liquid-propellant rocket or liquid rocket utilizes a rocket engine that uses liquid propellants. Liquids are desirable because they have a reasonably high density and high specific impulse (''I''sp). This allows the volume of the propellant ta ...
s improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space; nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the
first World War 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 ...
was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's papers were highly influential internationally in his field. The world's first large-scale experimental rocket program was
Opel RAK Opel-RAK were a series of rocket vehicles produced by German automobile manufacturer Fritz von Opel, of the Opel car company, in association with others, including Max Valier, Julius Hatry, and Friedrich Wilhelm Sander. Opel RAK is generally con ...
under the leadership of
Fritz von Opel Fritz Adam Hermann von Opel (4 May 1899 – 8 April 1971) was a German rocket technology pioneer and automotive executive, nicknamed "Rocket-Fritz". He is remembered mostly for his spectacular demonstrations of rocket propulsion that earned him an ...
and
Max Valier Max Valier (9 February 1895 – 17 May 1930) was an Austrian rocketry pioneer. He was a leading figure in the world's first large-scale rocket program, Opel-RAK, and helped found the German ''Verein für Raumschiffahrt'' (VfR – "Spacefligh ...
during the late 1920s leading to the first piloted rocket cars and rocket planes, which paved the way for the Nazi era V2 program and US and Soviet activities from 1950 onwards.The Opel RAK program and the spectacular public demonstrations of ground and air vehicles drew large crowds, as well as caused global public excitement as so-called "Rocket Rumble" and had a large long-lasting impact on later spaceflight pioneers like Wernher von Braun. In the course of
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 ...
the first guided rockets, the
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 ...
were developed and employed as weapons by
Nazi Germany Nazi Germany (lit. "National Socialist State"), ' (lit. "Nazi State") for short; also ' (lit. "National Socialist Germany") (officially known as the German Reich from 1933 until 1943, and the Greater German Reich from 1943 to 1945) was ...
. At a test flight in June 1944 one such rocket reached space at an altitude of , becoming the first object in human history to do so. At the end of World War II, most of the V-2 rocket team including its head
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 ...
surrendered to the United States, and were expatriated to work on American missiles at what became the
Army Ballistic Missile Agency The Army Ballistic Missile Agency (ABMA) was formed to develop the United States Army, U.S. Army's first large ballistic missile. The agency was established at Redstone Arsenal on 1 February 1956, and commanded by Major General John Bruce Meda ...
, producing missiles such as
Juno I The Juno I was a four-stage American space launch vehicle, used to launch lightweight payloads into low Earth orbit. The launch vehicle was used between January 1958 to December 1959. The launch vehicle was a member of the Redstone launch veh ...
and
Atlas An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a region of Earth. Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geographic ...
. At that time the
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
under
Joseph Stalin Joseph Vissarionovich Stalin (born Ioseb Besarionis dze Jughashvili; – 5 March 1953) was a Georgian revolutionary and Soviet political leader who led the Soviet Union from 1924 until his death in 1953. He held power as General Secreta ...
was developing
intercontinental ballistic missile 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 to carry
nuclear weapon A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb), producing a nuclear explosion. Both bom ...
s as a counter measure to United States bomber planes. The Tsiolkovsky influenced
Sergey Korolev Sergei Pavlovich Korolev (russian: Сергей Павлович Королёв, Sergey Pavlovich Korolyov, sʲɪrˈɡʲej ˈpavləvʲɪtɕ kərɐˈlʲɵf, Ru-Sergei Pavlovich Korolev.ogg; ukr, Сергій Павлович Корольов, ...
became the chief rocket designer, derivatives of his
R-7 Semyorka The R-7 Semyorka (russian: link=no, Р-7 Семёрка), officially the GRAU index 8K71, was a Soviet missile developed during the Cold War, and the world's first intercontinental ballistic missile. The R-7 made 28 launches between 1957 and 1 ...
missiles were used to launch the world's first artificial Earth
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 radioisotope ...
,
Sputnik 1 Sputnik 1 (; see § Etymology) was the first artificial Earth satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957 as part of the Soviet space program. It sent a radio signal back to Earth for t ...
, on October 4, 1957, and later the first human to orbit the Earth,
Yuri Gagarin Yuri Alekseyevich Gagarin; Gagarin's first name is sometimes transliterated as ''Yuriy'', ''Youri'', or ''Yury''. (9 March 1934 – 27 March 1968) was a Soviet pilot and cosmonaut who became the first human to journey into outer space. Tr ...
in
Vostok 1 Vostok 1 (russian: link=no, Восток, ''East'' or '' Orient'' 1) was the first spaceflight of the Vostok programme and the first human orbital spaceflight in history. The Vostok 3KA space capsule was launched from Baikonur Cosmodrome on Apr ...
, on April 12, 1961. The first US satellite was
Explorer 1 Explorer 1 was the first satellite launched by the United States in 1958 and was part of the U.S. participation in the International Geophysical Year (IGY). The mission followed the first two satellites the previous year; the Soviet Union's ...
, launched on February 1, 1958, and the first American in orbit, became
John Glenn John Herschel Glenn Jr. (July 18, 1921 – December 8, 2016) was an American Marine Corps aviator, engineer, astronaut, businessman, and politician. He was the third American in space, and the first American to orbit the Earth, circling ...
in ''
Friendship 7 Mercury-Atlas 6 (MA-6) was the first crewed American orbital spaceflight, which took place on February 20, 1962. Piloted by astronaut John Glenn and operated by NASA as part of Project Mercury, it was the fifth human spaceflight, preceded by Sov ...
'' on February 20, 1962. As director of the
Marshall Space Flight Center The George C. Marshall Space Flight Center (MSFC), located in Redstone Arsenal, Alabama (Huntsville postal address), is the U.S. government's civilian rocketry and spacecraft propulsion research center. As the largest NASA center, MSFC's first ...
, Von Braun oversaw development of a larger class of rocket called
Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...
, which allowed the US to send the first two humans,
Neil Armstrong Neil Alden Armstrong (August 5, 1930 – August 25, 2012) was an American astronaut and aeronautical engineer who became the first person to walk on the Moon in 1969. He was also a naval aviator, test pilot, and university professor. ...
and
Buzz Aldrin Buzz Aldrin (; born Edwin Eugene Aldrin Jr.; January 20, 1930) is an American former astronaut, engineer and fighter pilot. He made three spacewalks as pilot of the 1966 Gemini 12 mission. As the Lunar Module ''Eagle'' pilot on the 1969 A ...
, to the Moon and back on
Apollo 11 Apollo 11 (July 16–24, 1969) was the American spaceflight that first landed humans on the Moon. Commander Neil Armstrong and lunar module pilot Buzz Aldrin landed the Apollo Lunar Module ''Eagle'' on July 20, 1969, at 20:17 UTC, an ...
in July 1969. At the same time, the Soviet Union secretly tried but failed to develop the
N1 rocket The N1/L3 (from , "Carrier Rocket"; Cyrillic: Н1) was a super heavy-lift launch vehicle intended to deliver payloads beyond low Earth orbit. The N1 was the Soviet counterpart to the US Saturn V and was intended to enable crewed travel to the ...
, meant to give them the capability to land humans on the Moon. Ever since spaceflight has been widely employed for placing satellites into orbit around Earth for a broad range of purposes, for sending uncrewed spacecraft exploring space beyond the Moon and having continuous crewed
human presence in space Human presence in space is about humanity in space, particularly about all anthropogenic presence in space and human activity in space, that is in outer space and in a broader sense also on any extraterrestrial astronomical body. Humans have ...
with a series of
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 ...
s, from the
salyut program The ''Salyut'' programme (russian: Салют, , meaning "salute" or "fireworks") was the first space station programme, undertaken by the Soviet Union. It involved a series of four crewed scientific research space stations and two crewed m ...
to the
International Space Station The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA ...
.


Phases


Launch

Rockets are the only means currently capable of reaching orbit or beyond. Other
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 ...
technologies have yet to be built, or remain short of orbital speeds. A
rocket launch 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 ...
for a spaceflight usually starts from a
spaceport 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 ...
(cosmodrome), which may be equipped with launch complexes and
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 ...
s for vertical rocket launches and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons.
ICBMs 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 ...
have various special launching facilities. A launch is often restricted to certain
launch window In the context of spaceflight, launch period is the collection of days and launch window is the time period on a given day during which a particular rocket must be launched in order to reach its intended target. If the rocket is not launched wit ...
s. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit. 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 ...
is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle ''Columbia'', on STS-1, weighed at takeoff.


Reaching space

The most commonly used definition of
outer space Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, pred ...
is everything beyond 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 ...
, which is above the Earth's surface. The United States sometimes defines outer space as everything beyond in altitude.
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 ...
engines are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel
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 provide forward
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 ...
that generates enough
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 ...
(change in velocity) to reach orbit. For crewed launch systems
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 are frequently fitted to allow astronauts to escape in the case of emergency.


Alternatives

Many ways to reach space other than rocket engines have been proposed. Ideas such as the
space elevator A space elevator, also referred to as a space bridge, star ladder, and orbital lift, is a proposed type of planet-to-space transportation system, often depicted in science fiction. The main component would be a cable (also called a tether) anc ...
, and
momentum exchange tether A momentum exchange tether is a kind of space tether that could theoretically be used as a launch system, or to change spacecraft orbits. Momentum exchange tethers create a controlled force on the end-masses of the system due to the pseudo-force ...
s like rotovators or
skyhooks Skyhook, sky hook or skyhooks may refer to: Fiction * 'Skyhooks' or 'Skyhooks II', parts 1 and 8 respectively of the Adventure Time Elements (miniseries), Elements miniseries. * ''Sky Hook'', a Hugo-award nominated science fiction fanzine * Sk ...
require new materials much stronger than any currently known. Electromagnetic launchers such as
launch loop A launch loop, or Lofstrom loop, is a proposed system for launching objects into orbit using a moving cable-like system situated inside a sheath attached to the Earth at two ends and suspended above the atmosphere in the middle. The design conce ...
s might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as
Reaction Engines Skylon Skylon is a series of concept designs for a reusable single-stage-to-orbit spaceplane by the British company Reaction Engines Limited (Reaction), using SABRE (rocket engine), SABRE, a combined-cycle, Air breathing engines, air-breathing rocket ...
(currently in early stage development),
scramjet A scramjet (supersonic combustion ramjet) is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully ...
powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.


Leaving orbit

Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Soviet space vehicles successfully achieved very high altitudes without going into orbit.
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 ...
considered launching
Apollo Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label=Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label= ...
missions directly into lunar trajectories but adopted the strategy of first entering a temporary
parking orbit A parking orbit is a temporary orbit used during the launch of a spacecraft. A launch vehicle boosts into the parking orbit, then coasts for a while, then fires again to enter the final desired trajectory. The alternative to a parking orbit is ''di ...
and then performing a separate burn several orbits later onto a lunar trajectory. The parking orbit approach greatly simplified Apollo mission planning in several important ways. It acted as a "time buffer" and substantially widened the allowable
launch window In the context of spaceflight, launch period is the collection of days and launch window is the time period on a given day during which a particular rocket must be launched in order to reach its intended target. If the rocket is not launched wit ...
s. The parking orbit gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it for a long journey to the Moon. Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example,
Apollo 15 Apollo 15 (July 26August 7, 1971) was the ninth crewed mission in the United States' Apollo program and the fourth to Moon landing, land on the Moon. It was the first List of Apollo missions#Alphabetical mission types, J mission, with a ...
used an unusually low parking orbit of which is not sustainable for very long due to friction with the
Earth's atmosphere 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 for ...
, but the crew would only spend three hours before reigniting the
S-IVB The S-IVB (pronounced "S-four-B") was the third stage on the Saturn V and second stage on the Saturn IB launch vehicles. Built by the Douglas Aircraft Company, it had one J-2 (rocket engine), J-2 rocket engine. For lunar missions it was fired twi ...
third stage to put them on a lunar-bound trajectory. Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory. The escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see
Oberth effect In astronautics, a powered flyby, or Oberth maneuver, is a maneuver in which a spacecraft falls into a gravitational well and then uses its engines to further accelerate as it is falling, thereby achieving additional speed. The resulting maneuve ...
and reference.Escape Velocity of Earth
Van.physics.uiuc.edu. Retrieved on 2011-10-05.
This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.


Astrodynamics

Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An
orbital maneuvering system In spaceflight, an orbital maneuver (otherwise known as a burn) is the use of propulsion systems to change the orbit of a spacecraft. For spacecraft far from Earth (for example those in orbits around the Sun) an orbital maneuver is called a ' ...
may be needed to maintain or change orbits. Non-rocket orbital propulsion methods include
solar sail Solar sails (also known as light sails and photon sails) are a method of spacecraft propulsion using radiation pressure exerted by sunlight on large mirrors. A number of spaceflight missions to test solar propulsion and navigation have been p ...
s,
magnetic sail A magnetic sail is a proposed method of spacecraft propulsion that uses a static magnetic field to deflect a plasma wind of charged particles radiated by the Sun or a Star thereby transferring momentum to accelerate or decelerate a spacecraft. ...
s, plasma-bubble magnetic systems, and using
gravitational slingshot In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing-by is the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the p ...
effects.


Transfer energy

The term "transfer energy" means the total amount of
energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...
imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a
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 ...
to an upper stage plus payload, or by an upper stage or spacecraft
kick motor An apogee kick motor (AKM) is a rocket motor that is regularly employed on artificial satellites to provide the final impulse to change the trajectory from the transfer orbit into its final (most commonly circular) orbit. For a satellite lau ...
to a
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 ...
.


Reaching space station

In order to reach towards a
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 ...
, a spacecraft would have to arrive at the same
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 ...
and approach to a very close distance (e.g. within visual contact). This is done by a set of orbital maneuvers called
space rendezvous A space rendezvous () is a set of orbital maneuvers during which two spacecraft, one of which is often a space station, arrive at the same orbit and approach to a very close distance (e.g. within visual contact). Rendezvous requires a precise ma ...
. After rendezvousing with the space station, the space vehicle then docks or berths with the station. Docking refers to joining of two separate free-flying space vehicles, while berthing refers to mating operations where an inactive vehicle is placed into the mating interface of another space vehicle by using a
robotic arm A robotic arm is a type of mechanical arm, usually programmable, with similar functions to a human arm; the arm may be the sum total of the mechanism or may be part of a more complex robot. The links of such a manipulator are connected by joints ...
.


Reentry

Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against
aerodynamic heating Aerodynamic heating is the heating of a solid body produced by its high-speed passage through air. In science and engineering, an understanding of aerodynamic heating is necessary for predicting the behaviour of meteoroids which enter the earth's ...
. The theory behind reentry was developed by
Harry Julian Allen Harry Julian Allen (April 1, 1910 – January 29, 1977), also known as Harvey Allen, was an aeronautical engineer and a Director of the NASA Ames Research Center, most noted for his "Blunt Body Theory" of atmospheric entry which permitted successf ...
. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat reaching the vehicle, and the remainder heats up the atmosphere.


Landing and recovery

The
Mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...
,
Gemini Gemini may refer to: Space * Gemini (constellation), one of the constellations of the zodiac ** Gemini in Chinese astronomy * Project Gemini, the second U.S. crewed spaceflight program * Gemini Observatory, consisting of telescopes in the Northern ...
, and
Apollo Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label=Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label= ...
capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Soviet/Russian capsules for
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 ...
make use of a big parachute and braking rockets to touch down on land.
Spaceplane A spaceplane is a vehicle that can fly and glide like an aircraft in Earth's atmosphere and maneuver like a spacecraft in outer space. To do so, spaceplanes must incorporate features of both aircraft and spacecraft. Orbital spaceplanes ten ...
s like 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 ...
land like a
glider Glider may refer to: Aircraft and transport Aircraft * Glider (aircraft), heavier-than-air aircraft primarily intended for unpowered flight ** Glider (sailplane), a rigid-winged glider aircraft with an undercarriage, used in the sport of glidin ...
. After a successful landing the spacecraft, its occupants, and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This
mid-air retrieval Mid-air retrieval is a technique used in atmospheric reentry when the reentering vehicle is incapable of a satisfactory unassisted landing. The vehicle is slowed by means of parachutes, and then a specially-equipped aircraft matches the vehicle's ...
technique was used to recover the film canisters from the
Corona Corona (from the Latin for 'crown') most commonly refers to: * Stellar corona, the outer atmosphere of the Sun or another star * Corona (beer), a Mexican beer * Corona, informal term for the coronavirus SARS-CoV-2, which causes the COVID-19 di ...
spy satellites.


Types


Uncrewed

Uncrewed spaceflight is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of crewed spaceflight, which is usually called
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 ...
. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A
robotic spacecraft A robotic spacecraft is an uncrewed spacecraft, usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather t ...
is an uncrewed spacecraft with no humans on board, that is usually under
telerobotic Telerobotics is the area of robotics concerned with the control of semi-autonomous robots from a distance, chiefly using television, wireless networks (like Wi-Fi, Bluetooth and the Deep Space Network) or tethered connections. It is a combinatio ...
control. In some cases, such as with helicopters, a spacecraft may need to act autonomously for short periods of time. A robotic spacecraft designed to make scientific research measurements is often called a
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 ...
. Uncrewed space missions use remote-controlled
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 ...
. The first uncrewed space mission was ''
Sputnik Sputnik 1 (; see § Etymology) was the first artificial Earth satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957 as part of the Soviet space program. It sent a radio signal back to Earth for t ...
'', launched October 4, 1957 to orbit the Earth. Space missions where other
animals Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage in ...
but no humans are on-board are considered uncrewed missions.


Benefits

Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as
Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never fa ...
or the vicinity of
Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...
are too hostile for human survival, given current technology. Outer planets such as
Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...
,
Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus (mythology), Uranus (Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars (mythology), Mars), grandfather ...
, and
Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times ...
are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.


Telepresence

Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.


Human

The first human spaceflight was
Vostok 1 Vostok 1 (russian: link=no, Восток, ''East'' or '' Orient'' 1) was the first spaceflight of the Vostok programme and the first human orbital spaceflight in history. The Vostok 3KA space capsule was launched from Baikonur Cosmodrome on Apr ...
on April 12, 1961, on which
cosmonaut An astronaut (from the Ancient Greek (), meaning 'star', and (), meaning 'sailor') is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally r ...
Yuri Gagarin Yuri Alekseyevich Gagarin; Gagarin's first name is sometimes transliterated as ''Yuriy'', ''Youri'', or ''Yury''. (9 March 1934 – 27 March 1968) was a Soviet pilot and cosmonaut who became the first human to journey into outer space. Tr ...
of the
USSR The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nationa ...
made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles. As of 2020, the only spacecraft regularly used for human spaceflight are
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 ...
, Shenzhou, and
Crew Dragon Dragon 2 is a class of partially reusable spacecraft developed and manufactured by American aerospace manufacturer SpaceX, primarily for flights to the International Space Station (ISS). SpaceX has also launched private missions such as Insp ...
. The U.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 ...
fleet operated from April 1981 until July 2011.
SpaceShipOne SpaceShipOne is an experimental air-launched rocket-powered aircraft with sub-orbital spaceflight capability at speeds of up to 3,000 ft/s (900 m/s, 3240 km/h), using a hybrid rocket motor. The design features a unique "feathering" a ...
has conducted two human suborbital spaceflights.


Sub-orbital

On a
sub-orbital spaceflight A sub-orbital spaceflight is a spaceflight in which the spacecraft reaches outer space, but its trajectory intersects the atmosphere or surface of the gravitating body from which it was launched, so that it will not complete one orbital re ...
the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient
specific 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), divided ...
, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours.
Pioneer 1 Pioneer 1 (also known as Able 2) was an American space probe, the first under the auspices of NASA, which was launched by a Thor-Able rocket on 11 October 1958. It was intended to orbit the Moon and make scientific measurements, but due to a g ...
was NASA's first
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 ...
intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of before reentering the Earth's atmosphere 43 hours after launch. The most generally recognized boundary of space is 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 ...
above sea level. (NASA alternatively defines an astronaut as someone who has flown more than above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004,
Civilian Space eXploration Team The Civilian Space eXploration Team, known as CSXT, is a team of around 30 civilians interested in private spaceflight. The team was created by Ky Michaelson. Having conducted multiple rocket launches in an attempt to establish altitude records ...
launched the GoFast rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004,
SpaceShipOne SpaceShipOne is an experimental air-launched rocket-powered aircraft with sub-orbital spaceflight capability at speeds of up to 3,000 ft/s (900 m/s, 3240 km/h), using a hybrid rocket motor. The design features a unique "feathering" a ...
was used for the first privately funded
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 ...
.


Point-to-point

Point-to-point, or Earth to Earth transportation, is a category of
sub-orbital spaceflight A sub-orbital spaceflight is a spaceflight in which the spacecraft reaches outer space, but its trajectory intersects the atmosphere or surface of the gravitating body from which it was launched, so that it will not complete one orbital re ...
in which a spacecraft provides rapid transport between two terrestrial locations. A conventional airline route between
London London is the capital and largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary down to the North Sea, and has been a majo ...
and
Sydney Sydney ( ) is the capital city of the state of New South Wales, and the most populous city in both Australia and Oceania. Located on Australia's east coast, the metropolis surrounds Sydney Harbour and extends about towards the Blue Mountain ...
, a flight that normally lasts over twenty hours, could be traversed in less than one hour. While no company offers this type of transportation today,
SpaceX Space Exploration Technologies Corp. (SpaceX) is an American spacecraft manufacturer, launcher, and a satellite communications corporation headquartered in Hawthorne, California. It was founded in 2002 by Elon Musk with the stated goal of ...
has revealed plans to do so as early as the 2020s using
Starship A starship, starcraft, or interstellar spacecraft is a theoretical spacecraft designed for interstellar travel, traveling between planetary systems. The term is mostly found in science fiction. Reference to a "star-ship" appears as early as 188 ...
. Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit. If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.


Orbital

A minimal
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 ...
requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal
orbital speed In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter or, if one body is much more massi ...
required for a closed orbit.


Interplanetary

Interplanetary spaceflight Interplanetary spaceflight or interplanetary travel is the crewed or uncrewed travel between stars and planets, usually within a single planetary system. In practice, spaceflights of this type are confined to travel between the planets of the ...
is flight between planets within a single
planetary system A planetary system is a set of gravitationally 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 interacti ...
. In practice, the use of the term is confined to travel between the planets of our
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
. Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's
Constellation program The Constellation program (abbreviated CxP) was a crewed spaceflight program developed by NASA, the space agency of the United States, from 2005 to 2009. The major goals of the program were "completion of the International Space Station" and a " ...
and Russia's
Kliper Kliper (Клипер, English: Clipper) was an early-2000s proposed partially- reusable crewed spacecraft concept by RSC Energia. Due to lack of funding from the ESA and RSA, the project was indefinitely postponed by 2006. Designed primarily to ...
/
Parom The ''Parom'' (''ferry'' in Russian) is a space tug that has been proposed by RKK Energia. The purpose of this vehicle is to replace most of the Progress' active components. Progress spacecraft have flown re-supply missions since 1978. Nikolai Bry ...
tandem.


Interstellar

‘’
New Horizons ''New Horizons'' is an Interplanetary spaceflight, interplanetary space probe that was launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research ...
’’ is the fifth spacecraft put on an escape trajectory leaving the
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
. ''Voyager 1'', ''Voyager 2'', ''Pioneer 10'', ''Pioneer 11'' are the earlier ones. The one farthest from the Sun is ''
Voyager 1 ''Voyager 1'' is a space probe launched by NASA on September 5, 1977, as part of the Voyager program to study the outer Solar System and interstellar space beyond the Sun's heliosphere. Launched 16 days after its twin ''Voyager 2'', ''Voya ...
'', which is more than 100 AU distant and is moving at 3.6 AU per year. In comparison,
Proxima Centauri Proxima Centauri is a small, low-mass star located away from the Sun in the southern constellation of Centaurus. Its Latin name means the 'nearest tarof Centaurus'. It was discovered in 1915 by Robert Innes and is the nearest-kno ...
, the closest star other than the Sun, is 267,000 AU distant. It will take ''Voyager 1'' over 74,000 years to reach this distance. Vehicle designs using other techniques, such as
nuclear pulse propulsion Nuclear pulse propulsion or external pulsed plasma propulsion is a hypothetical method of spacecraft propulsion that uses nuclear explosions for thrust. It originated as Project ''Orion'' with support from DARPA, after a suggestion by Stanislaw ...
are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of
time dilation In physics and relativity, time dilation is the difference in the elapsed time as measured by two clocks. It is either due to a relative velocity between them ( special relativistic "kinetic" time dilation) or to a difference in gravitational ...
, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of
propulsion Propulsion is the generation of force by any combination of pushing or pulling to modify the translational motion of an object, which is typically a rigid body (or an articulated rigid body) but may also concern a fluid. The term is derived from ...
.
Dynamic soaring Dynamic soaring is a flying technique used to gain energy by repeatedly crossing the boundary between air masses of different velocity. Such zones of wind gradient are generally found close to obstacles and close to the surface, so the technique is ...
as a way to travel across interstellar space has been proposed as well.


Intergalactic

Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered
science fiction Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel unive ...
. However, theoretically speaking, there is nothing to conclusively indicate that intergalactic travel is impossible. To date several academics have studied intergalactic travel in a serious manner.


Spacecraft

Spacecraft are vehicles capable of controlling their trajectory through space. The first 'true spacecraft' is sometimes said to be
Apollo Lunar Module The Apollo Lunar Module (LM ), originally designated the Lunar Excursion Module (LEM), was the lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program. It was the first crewed ...
, since this was the only crewed vehicle to have been designed for, and operated only in space; and is notable for its non-aerodynamic shape.


Propulsion

Spacecraft today predominantly use
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 ...
s for
propulsion Propulsion is the generation of force by any combination of pushing or pulling to modify the translational motion of an object, which is typically a rigid body (or an articulated rigid body) but may also concern a fluid. The term is derived from ...
, but other propulsion techniques such as
ion drive An ion thruster, ion drive, or ion engine is a form of electric propulsion used for spacecraft propulsion. It creates thrust by accelerating ions using electricity. An ion thruster ionizes a neutral gas by extracting some electrons out of ...
s are becoming more common, particularly for uncrewed vehicles, and this can significantly reduce the vehicle's mass and increase its
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 ...
.


Launch systems

Launch systems are used to carry a payload from Earth's surface into outer space.


Expendable

Most current spaceflight uses
multi-stage 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 ...
expendable launch systems to reach space.


Reusable

The first reusable spacecraft, 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 ...
, was air-launched on a suborbital trajectory on 19 July 1963. The first partially reusable orbital spacecraft, 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 ...
, was launched by the USA on the 20th anniversary of
Yuri Gagarin Yuri Alekseyevich Gagarin; Gagarin's first name is sometimes transliterated as ''Yuriy'', ''Youri'', or ''Yury''. (9 March 1934 – 27 March 1968) was a Soviet pilot and cosmonaut who became the first human to journey into outer space. Tr ...
's flight, on 12 April 1981. During the Shuttle era, six orbiters were built, all of which flown in the atmosphere and five of which flown in space. The ''
Enterprise Enterprise (or the archaic spelling Enterprize) may refer to: Business and economics Brands and enterprises * Enterprise GP Holdings, an energy holding company * Enterprise plc, a UK civil engineering and maintenance company * Enterprise ...
'' was used only for approach and landing tests, launching from the back of a
Boeing 747 The Boeing 747 is a large, long-range wide-body airliner designed and manufactured by Boeing Commercial Airplanes in the United States between 1968 and 2022. After introducing the 707 in October 1958, Pan Am wanted a jet times its size, t ...
and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the '' Columbia'', followed by the ''
Challenger Challenger, Challengers, or The Challengers may refer to: Entertainment Comics and manga * Challenger (character), comic book character * ''Challengers'' (manga), manga by Hinako Takanaga Film and TV * ''The Challengers'' (TV series), a 1979 ...
'', ''
Discovery Discovery may refer to: * Discovery (observation), observing or finding something unknown * Discovery (fiction), a character's learning something unknown * Discovery (law), a process in courts of law relating to evidence Discovery, The Discovery ...
'', ''
Atlantis Atlantis ( grc, Ἀτλαντὶς νῆσος, , island of Atlas (mythology), Atlas) is a fictional island mentioned in an allegory on the hubris of nations in Plato's works ''Timaeus (dialogue), Timaeus'' and ''Critias (dialogue), Critias'' ...
'', and '' Endeavour''. The ''Endeavour'' was built to replace the ''Challenger'', which was
lost Lost may refer to getting lost, or to: Geography *Lost, Aberdeenshire, a hamlet in Scotland * Lake Okeechobee Scenic Trail, or LOST, a hiking and cycling trail in Florida, US History *Abbreviation of lost work, any work which is known to have bee ...
in January 1986. The ''Columbia''
broke up A relationship breakup, breakup, or break-up is the termination of a relationship. The act is commonly termed "dumping omeone in slang when it is initiated by one partner. The term is less likely to be applied to a married couple, where a bre ...
during reentry in February 2003. The first automatic partially reusable spacecraft was the '' Buran'' (''Snowstorm''), launched by the USSR on 15 November 1988, although it made only one flight. This
spaceplane A spaceplane is a vehicle that can fly and glide like an aircraft in Earth's atmosphere and maneuver like a spacecraft in outer space. To do so, spaceplanes must incorporate features of both aircraft and spacecraft. Orbital spaceplanes ten ...
was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran. The Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the
SpaceX Dragon 2 Dragon 2 is a class of partially reusable spacecraft developed and manufactured by American aerospace manufacturer SpaceX, primarily for flights to the International Space Station (ISS). SpaceX has also launched Private spaceflight, private m ...
and
CST-100 The Boeing CST-100 Starliner
is a class of two partially
in the 2020s. The Shuttle's heavy cargo transport role is now done by commercial launch vehicles.
Scaled Composites Scaled Composites (often called simply Scaled) is an American aerospace company founded by Burt Rutan and currently owned by Northrop Grumman. It is located at the Mojave Air and Space Port in Mojave, California, United States. Founded to develo ...
SpaceShipOne SpaceShipOne is an experimental air-launched rocket-powered aircraft with sub-orbital spaceflight capability at speeds of up to 3,000 ft/s (900 m/s, 3240 km/h), using a hybrid rocket motor. The design features a unique "feathering" a ...
was a reusable
suborbital spaceplane A spaceplane is a vehicle that can fly and glide like an aircraft in Earth's atmosphere and maneuver like a spacecraft in outer space. To do so, spaceplanes must incorporate features of both aircraft and spacecraft. Orbital spaceplanes ten ...
that carried pilots
Mike Melvill Michael Winston Melvill (born November 30, 1940 in Johannesburg, South Africa) is a world-record-breaking pilot and one of the test pilots for SpaceShipOne, the experimental spaceplane developed by Scaled Composites. Melvill piloted SpaceShipO ...
and
Brian Binnie William Brian Binnie (April 26, 1953 – September 15, 2022) was a United States Navy officer and one of the test pilots for SpaceShipOne, the experimental spaceplane developed by Scaled Composites and flown from 2003 to 2004. Early life Bin ...
on consecutive flights in 2004 to win the Ansari X Prize.
The Spaceship Company The Spaceship Company (TSC) is a British/American spacecraft manufacturing company that was founded by Burt Rutan and Richard Branson in mid-2005 and was jointly owned by Virgin Group (70%) and Scaled Composites (30%) until 2012 when Virgin Gal ...
has built its successor
SpaceShipTwo The Scaled Composites Model 339 SpaceShipTwo (SS2) is an air-launched suborbital spaceplane type designed for space tourism. It is manufactured by The Spaceship Company, a California-based company owned by Virgin Galactic. SpaceShipTwo is car ...
. A fleet of SpaceShipTwos operated by
Virgin Galactic Virgin Galactic is an American spaceflight company founded by Richard Branson and his British Virgin Group retains an 11.9% stake through Virgin Investments Limited. It is headquartered in California, and operates from New Mexico. The company i ...
planned to begin reusable
private spaceflight Private spaceflight is spaceflight or the development of spaceflight technology that is conducted and paid for by an entity other than a government agency. In the early decades of the Space Age, the government space agencies of the Soviet Unio ...
carrying paying passengers (
space tourists Space tourism is human space travel for recreational purposes. There are several different types of space tourism, including orbital, suborbital and lunar space tourism. During the period from 2001 to 2009, seven space tourists made eight s ...
) in 2008, but this was delayed due to an accident in the propulsion development.
SpaceX Space Exploration Technologies Corp. (SpaceX) is an American spacecraft manufacturer, launcher, and a satellite communications corporation headquartered in Hawthorne, California. It was founded in 2002 by Elon Musk with the stated goal of ...
achieved the first vertical soft landing of a re-usable orbital rocket stage on December 21, 2015, after delivering 11 Orbcomm OG-2 commercial satellites into
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 ...
. The first Falcon 9 second flight occurred on 30 March 2017. SpaceX now routinely recovers and reuses their first stages, with the intent of reusing fairings as well.


Challenges


Space disasters

All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a
Delta II Delta II was an expendable launch system, originally designed and built by McDonnell Douglas. Delta II was part of the Delta rocket family and entered service in 1989. Delta II vehicles included the Delta 6000, and the two later Delta 7000 va ...
rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows away being broken by the blast. Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed. In 2004 the
International Association for the Advancement of Space Safety The International Association for the Advancement of Space Safety (IAASS) is a non-profit organization committed to furthering international cooperation and scientific advancement in space systems safety. Its aim is to advance the science and app ...
was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.


Weightlessness

In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes
space adaptation syndrome Space adaptation syndrome (SAS) or space sickness is a condition experienced by as many as half of all space travelers during their adaptation to weightlessness once in orbit. It is the opposite of terrestrial motion sickness since it occurs when ...
, a self-limiting nausea caused by derangement of the
vestibular system The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating movement with balance. Together with the cochlea, a part of the auditory system, it constitutes ...
. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant
deconditioning Deconditioning is adaptation of an organism to less demanding environment, or, alternatively, the decrease of physiological adaptation to normal conditions. Decondition may result from decreased physical activity, prescribed bed rest, orthopedic cas ...
of muscular and cardiovascular tissues.


Radiation

Once above the atmosphere, radiation due to the Van Allen belts,
solar radiation Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre (W/m ...
and
cosmic radiation 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 ...
issues occur and increase. Further away from the Earth,
solar flare A solar flare is an intense localized eruption of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and other solar phe ...
s can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.


Life support

In human spaceflight, the
life support system A life-support system is the combination of equipment that allows survival in an environment or situation that would not support that life in its absence. It is generally applied to systems supporting human life in situations where the outsid ...
is a group of devices that allow a human being to survive in outer space.
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 ...
often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its
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 ...
missions. The life support system may supply:
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 for ...
,
water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...
and
food Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is inge ...
. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are
life-critical A safety-critical system (SCS) or life-critical system is a system whose failure or malfunction may result in one (or more) of the following outcomes: * death or serious injury to people * loss or severe damage to equipment/property * environme ...
, and are designed and constructed using
safety engineering Safety engineering is an engineering discipline which assures that engineered systems provide acceptable levels of safety. It is strongly related to industrial engineering/systems engineering, and the subset system safety engineering. Safety en ...
techniques.


Space weather

Space weather is the concept of changing environmental conditions in
outer space Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, pred ...
. It is distinct from the concept of
weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmosphere, the ...
within a
planetary atmosphere Planetary means relating to a planet or planets. It can also refer to: ;Science * Planetary habitability, the measure of an astronomical body's potential to develop and sustain life * Planetary nebula, an astronomical object ;People * Planetary ...
, and deals with phenomena involving ambient
plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...
, magnetic fields,
radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
and other
matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic partic ...
in space (generally close to Earth but also in interplanetary, and occasionally
interstellar medium In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System." Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in
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 ...
. Geomagnetic storms due to increased solar activity can potentially blind sensors onboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for crewed spacecraft.


Environmental considerations

Exhaust pollution of rockets depends on the produced exhausts by the propellants reactions and the location of exhaustion. They mostly exhaust
greenhouse gas A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse ...
es and sometimes toxic components. Particularly at higher levels of the atmosphere the potency of exhausted gases as greenhouse gases increases considerably . Many solid rockets have chlorine in the form of
perchlorate A perchlorate is a chemical compound containing the perchlorate ion, . The majority of perchlorates are commercially produced salts. They are mainly used as oxidizers for pyrotechnic devices and to control static electricity in food packaging. Per ...
or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction. While spaceflight altogether pollutes at a fraction of other human activities, it still does pollute heavily if calculated per passenger. In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing
space debris Space debris (also known as space junk, space pollution, space waste, space trash, or space garbage) are defunct human-made objects in space—principally in Earth orbit—which no longer serve a useful function. These include derelict spacecr ...
caused by
spalling Spall are fragments of a material that are broken off a larger solid body. It can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure (as in a ball ...
of satellites and vehicles (
Kessler syndrome The Kessler syndrome (also called the Kessler effect, collisional cascading, or ablation cascade), proposed by NASA scientist Donald J. Kessler in 1978, is a scenario in which the density of objects in low Earth orbit (LEO) due to space pollut ...
). Many launched vehicles today are therefore designed to be re-entered after use.


Regulation

A wide range of issues such as
space traffic management Space traffic management is defined by the International Academy of Astronautics (IAA) as "the set of technical and regulatory provisions for promoting safe access into outer space, operations in outer space and return from outer space to Earth free ...
or liability have been issues of spaceflight regulation. Participation and representation of all humanity in spaceflight is an issue of international
space law Space law is the body of law governing space-related activities, encompassing both international and domestic agreements, rules, and principles. Parameters of space law include space exploration, liability for damage, weapons use, rescue efforts ...
ever since the first phase of space exploration. Even though some rights of non-spacefaring countries have been secured, sharing of space for all humanity is still criticized as
imperialist Imperialism is the state policy, practice, or advocacy of extending power and dominion, especially by direct territorial acquisition or by gaining political and economic control of other areas, often through employing hard power (economic and ...
and lacking, understanding spaceflight as a resource.


Applications

Current and proposed applications for spaceflight include: *
Earth observation satellite An Earth observation satellite or Earth remote sensing satellite is a satellite used or designed for Earth observation (EO) from orbit, including spy satellites and similar ones intended for non-military uses such as environmental monitoring, me ...
s such as
spy satellite A reconnaissance satellite or intelligence satellite (commonly, although unofficially, referred to as a spy satellite) is an Earth observation satellite or communications satellite deployed for military or intelligence applications. The ...
s,
weather satellite A weather satellite or meteorological satellite is a type of Earth observation satellite that is primarily used to monitor the weather and climate of the Earth. Satellites can be polar orbiting (covering the entire Earth asynchronously), or ge ...
s *
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 ...
*
Communication satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...
s *
Satellite television Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location. The signals are received via an outdoor parabolic antenna comm ...
*
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 ...
*
Space tourism Space tourism is human space travel for recreational purposes. There are several different types of space tourism, including orbital, suborbital and lunar space tourism. During the period from 2001 to 2009, seven space tourists made eight s ...
* Protecting Earth from
potentially hazardous object A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make close approaches to the Earth and is large enough to cause significant regional damage in the event of impact. They ar ...
s *
Space colonization Space colonization (also called space settlement or extraterrestrial colonization) is the use of outer space or celestial bodies other than Earth for permanent habitation or as extraterrestrial territory. The inhabitation and territori ...
Most early spaceflight development was paid for by governments. However, today major launch markets such as communication satellites and satellite television are purely commercial, though many of the launchers were originally funded by governments.
Private spaceflight Private spaceflight is spaceflight or the development of spaceflight technology that is conducted and paid for by an entity other than a government agency. In the early decades of the Space Age, the government space agencies of the Soviet Unio ...
is a rapidly developing area: space flight that is not only paid for by corporations or even private individuals, but often provided by
private spaceflight companies Private or privates may refer to: Music * "In Private", by Dusty Springfield from the 1990 album ''Reputation'' * Private (band), a Denmark-based band * Private (Ryōko Hirosue song), "Private" (Ryōko Hirosue song), from the 1999 album ''Private ...
. These companies often assert that much of the previous high cost of access to space was caused by governmental inefficiencies they can avoid. This assertion can be supported by much lower published launch costs for private space launch vehicles such as
Falcon 9 Falcon 9 is a partially reusable medium lift launch vehicle that can carry cargo and crew into Earth orbit, produced by American aerospace company SpaceX. The rocket has two stages. The first (booster) stage carries the second stage and payl ...
developed with private financing. Lower launch costs and excellent safety will be required for the applications such as space tourism and especially space colonization to become feasible for expansion.


Spacefaring

To be spacefaring is to be capable of and active in the operation of
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 ...
. It involves a knowledge of a variety of topics and development of specialised skills including:
aeronautics Aeronautics is the science or art involved with the study, design, and manufacturing of air flight–capable machines, and the techniques of operating aircraft and rockets within the atmosphere. The British Royal Aeronautical Society identifies ...
;
astronautics Astronautics (or cosmonautics) is the theory and practice of travel beyond Earth's atmosphere into outer space. Spaceflight is one of its main applications and space science its overarching field. The term ''astronautics'' (originally ''astronaut ...
; programs to train
astronaut An astronaut (from the Ancient Greek (), meaning 'star', and (), meaning 'sailor') is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally r ...
s;
space weather Space weather is a branch of space physics and aeronomy, or heliophysics, concerned with the time varying conditions within the Solar System, including the solar wind, emphasizing the space surrounding the Earth, including conditions in the ma ...
and forecasting; spacecraft operations; operation of various equipment; spacecraft design and construction; atmospheric takeoff and reentry;
orbital mechanics 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 ...
(a.k.a. astrodynamics); communications; engines and rockets; execution of evolutions such as towing,
microgravity The term micro-g environment (also μg, often referred to by the term microgravity) is more or less synonymous with the terms ''weightlessness'' and ''zero-g'', but emphasising that g-forces are never exactly zero—just very small (on the I ...
construction, and
space docking Docking and berthing of spacecraft is the joining of two space vehicles. This connection can be temporary, or partially permanent such as for space station modules. ''Docking'' specifically refers to joining of two separate free-flying space ...
; cargo handling equipment, dangerous cargos and cargo storage;
spacewalk Extravehicular activity (EVA) is any activity done by an astronaut in outer space outside a spacecraft. In the absence of a breathable atmosphere of Earth, Earthlike atmosphere, the astronaut is completely reliant on a space suit for environmen ...
ing; dealing with emergencies; survival at space and first aid; fire fighting;
life support Life support comprises the treatments and techniques performed in an emergency in order to support life after the failure of one or more vital organs. Healthcare providers and emergency medical technicians are generally certified to perform basic ...
. The degree of knowledge needed within these areas is dependent upon the nature of the work and the type of vessel employed. "Spacefaring" is analogous to
seafaring Seamanship is the art, knowledge and competence of operating a ship, boat or other craft on water. The'' Oxford Dictionary'' states that seamanship is "The skill, techniques, or practice of handling a ship or boat at sea." It involves topics a ...
. There has never been a crewed mission outside the
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
system. However, the United States, Russia, China,
European Space Agency , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (1205 ...
(ESA) countries, and a few corporations and enterprises have plans in various stages to travel to
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury (planet), Mercury. In the English language, Mars is named for the Mars (mythology), Roman god of war. Mars is a terr ...
(see
Human mission to Mars The idea of sending humans to Mars has been the subject of aerospace engineering and scientific studies since the late 1940s as part of the broader exploration of Mars. Some have also considered exploring the Martian moons of Phobos and Deimos. ...
). Spacefaring entities can be
sovereign state A sovereign state or sovereign country, is a polity, political entity represented by one central government that has supreme legitimate authority over territory. International law defines sovereign states as having a permanent population, defin ...
s, supranational entities, and private
corporation A corporation is an organization—usually a group of people or a company—authorized by the state to act as a single entity (a legal entity recognized by private and public law "born out of statute"; a legal person in legal context) and r ...
s. Spacefaring nations are those capable of independently building and launching craft into space. A growing number of private entities have become or are becoming spacefaring.


Global coordination

The
United Nations Office for Outer Space Affairs The United Nations Office for Outer Space Affairs (UNOOSA) is an office of the U.N. Secretariat that promotes and facilitates peaceful international cooperation in outer space. It works to establish or strengthen the legal and regulatory framew ...
(UNOOSA) has been the main multilateral body servicing international contact and exchange on space activity among spacefaring and non-spacefaring states.


Crewed spacefaring nations

Currently
Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
,
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 ...
, and the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
are the only crewed spacefaring
nation A nation is a community of people formed on the basis of a combination of shared features such as language, history, ethnicity, culture and/or society. A nation is thus the collective identity of a group of people understood as defined by those ...
s. Spacefaring nations listed by year of first crewed launch: #
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
(
Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
) (1961) #
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
(1961) #
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 ...
(2003)


Uncrewed spacefaring nations

The following nations or organizations have developed their own launch vehicles to launch uncrewed spacecraft into orbit either from their own territory or with foreign assistance (date of first launch in parentheses): #
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
(1957) #
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
(1958) #
France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
(1965) #
Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical re ...
(1967)★ #
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
(1967)★ #
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
(1970) #
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 ...
(1970) #
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
(1971) #
European Space Agency , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (1205 ...
(1979) #
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
(1980) #
Israel Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...
(1988) #
Ukraine Ukraine ( uk, Україна, Ukraïna, ) is a country in Eastern Europe. It is the second-largest European country after Russia, which it borders to the east and northeast. Ukraine covers approximately . Prior to the ongoing Russian inv ...
(1991)* #
Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
(1992)* #
Iran Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkmeni ...
(2009) #
North Korea North Korea, officially the Democratic People's Republic of Korea (DPRK), is a country in East Asia. It constitutes the northern half of the Korea, Korean Peninsula and shares borders with China and Russia to the north, at the Yalu River, Y ...
(2012) #
South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korea, Korean Peninsula and sharing a Korean Demilitarized Zone, land border with North Korea. Its western border is formed ...
(2013)★ #
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
(2018)★ * *Previously a major region in the Soviet Union * ★Launch vehicle fully or partially developed by another country Also several countries, such as Canada, Italy and Australia, had semi-independent spacefaring capability, launching locally-built satellites on foreign launchers. Canada had designed and built satellites (Alouette 1 and 2) in 1962 and 1965 which were orbited using US launch vehicles. Italy has designed and built several satellites, as well as pressurized modules for the
International Space Station The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA ...
. Early Italian satellites were launched using vehicles provided by NASA, first from
Wallops Flight Facility Wallops Flight Facility (WFF) is a rocket launch site on Wallops Island on the Eastern Shore of Virginia, United States, just east of the Delmarva Peninsula and approximately north-northeast of Norfolk. The facility is operated by the Goddard ...
in 1964 and then from a spaceport in Kenya (
San Marco Platform The Luigi Broglio Space Center (BSC) is an Italian-owned spaceport near Malindi, Kenya, named after its founder and Italian space pioneer Luigi Broglio. Developed in the 1960s through a partnership between the Sapienza University of Rome's Aeros ...
) between 1967 and 1988; Italy has led the development of the
Vega Vega is the brightest star in the northern constellation of Lyra. It has the Bayer designation α Lyrae, which is Latinised to Alpha Lyrae and abbreviated Alpha Lyr or α Lyr. This star is relatively close at only from the Sun, an ...
rocket programme within the European Space Agency since 1998. The
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
abandoned its independent space launch program in 1972 in favour of co-operating with the European Launcher Development Organisation (ELDO) on launch technologies until 1974. Australia abandoned its launcher program shortly after the successful launch of
WRESAT WRESAT or Weapons Research Establishment Satellite was the first Australian satellite, named after its designer. WRESAT was launched on 29 November 1967 using a modified American Redstone rocket with two upper stages known as a Sparta from the W ...
, and became the only non-European member of ELDO.


Suborbital

Considering merely launching an object beyond 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 ...
to be the minimum requirement of spacefaring,
Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...
, with 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 ...
, became the first spacefaring nation in 1944. The following nations have only achieved
suborbital spaceflight A sub-orbital spaceflight is a spaceflight in which the spacecraft reaches outer space, but its trajectory intersects the atmosphere or surface of the gravitating body from which it was launched, so that it will not complete one orbital re ...
capability by launching indigenous
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 ...
s or
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 or both into suborbital space. #
Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...
(June 20, 1944) #
East Germany East Germany, officially the German Democratic Republic (GDR; german: Deutsche Demokratische Republik, , DDR, ), was a country that existed from its creation on 7 October 1949 until its dissolution on 3 October 1990. In these years the state ...
(April 12, 1957) #
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
(September 5, 1959) #
Lebanon Lebanon ( , ar, لُبْنَان, translit=lubnān, ), officially the Republic of Lebanon () or the Lebanese Republic, is a country in Western Asia. It is located between Syria to the north and east and Israel to the south, while Cyprus li ...
(November 21, 1962) #
Switzerland ). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...
(October 27, 1967) #
Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
(April 16, 1969) #
Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
(September 21, 1976) #
Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...
(February 18, 1981) #
West Germany West Germany is the colloquial term used to indicate the Federal Republic of Germany (FRG; german: Bundesrepublik Deutschland , BRD) between its formation on 23 May 1949 and the German reunification through the accession of East Germany on 3 O ...
(March 1, 1981) #
Iraq Iraq,; ku, عێراق, translit=Êraq officially the Republic of Iraq, '; ku, کۆماری عێراق, translit=Komarî Êraq is a country in Western Asia. It is bordered by Turkey to Iraq–Turkey border, the north, Iran to Iran–Iraq ...
(June 1984) #
South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...
(June 1, 1989) #
Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...
(May 8, 1991) #
Yemen Yemen (; ar, ٱلْيَمَن, al-Yaman), officially the Republic of Yemen,, ) is a country in Western Asia. It is situated on the southern end of the Arabian Peninsula, and borders Saudi Arabia to the Saudi Arabia–Yemen border, north and ...
(May 12, 1994) #
Pakistan Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...
(April 6, 1998) #
Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...
(December 15, 1998) #
Syria Syria ( ar, سُورِيَا or سُورِيَة, translit=Sūriyā), officially the Syrian Arab Republic ( ar, الجمهورية العربية السورية, al-Jumhūrīyah al-ʻArabīyah as-Sūrīyah), is a Western Asian country loc ...
(September 1, 2000) #
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
(September 29, 2004) #
Democratic Republic of the Congo The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...
 (2007) #
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
(November 30, 2009) #
Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...
(September 27, 2018) #
Netherlands ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...
(September 19, 2020) #
Turkey Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a list of transcontinental countries, transcontinental country located mainly on the Anatolia, Anatolian Peninsula in Western Asia, with ...
(October 29, 2020)


See also

* * * * * * * * * * * * * * *
Space travel in science fiction Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually consider ...
* * * * * *


References


Further reading

* Erik Gregerson (2010): ''An Explorer's Guide to the Universe – Unmanned Space Missions'', Britannica Educational Publishing, (eBook)


External links

* Aerospace engineering at Wikiversity
Encyclopedia Astronautica

Basics of Spaceflight
* {{Authority control Astronautics