Liquid oxygen in a beaker (cropped and retouched)

Liquid oxygen—abbreviated LOx, LOX or Lox in the

aerospace Aerospace is a term used to collectively refer to the atmosphere and outer space. Aerospace activity is very diverse, with a multitude of commercial, industrial and military applications. Aerospace engineering consists of aeronautics and astrona ...

submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...

and

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

industries—is the

liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...

form of

molecular oxygen There are several known allotropes of oxygen. The most familiar is molecular oxygen (O2), present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone (O3). Others are: *A ...

. It was used as the

oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...

in the first liquid-fueled rocket invented in 1926 by

Robert H. Goddard Robert Hutchings Goddard (October 5, 1882 – August 10, 1945) was an American engineer, professor, physicist, and inventor who is credited with creating and building the world's first Liquid-propellant rocket, liquid-fueled rocket. ...

, an application which has continued to the present.

Physical properties

Liquid oxygen has a pale blue color and is strongly

paramagnetic Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field. In contrast with this behavior, d ...

: it can be suspended between the poles of a powerful

horseshoe magnet A horseshoe magnet is a magnet made in the shape of a horseshoe or a U-shape and has become the most widely recognized symbol for magnets. It was invented by William Sturgeon in 1825. This type of magnet can be either a permanent magnet or a ...

. Liquid oxygen has a density of , slightly denser than liquid water, and is

cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...

with a freezing point of and a boiling point of at . Liquid oxygen has an

expansion ratio The expansion ratio of a liquefied and cryogenic substance is the volume of a given amount of that substance in liquid form compared to the volume of the same amount of substance in gaseous form, at room temperature and normal atmospheric pressur ...

of 1:861 under and , and because of this, it is used in some commercial and military aircraft as a transportable source of breathing oxygen. Because of its cryogenic nature, liquid oxygen can cause the materials it touches to become extremely brittle. Liquid oxygen is also a very powerful oxidizing agent: organic materials will burn rapidly and energetically in liquid oxygen. Further, if soaked in liquid oxygen, some materials such as coal briquettes,

carbon black Carbon black (subtypes are acetylene black, channel black, furnace black, lamp black and thermal black) is a material produced by the incomplete combustion of coal and coal tar, vegetable matter, or petroleum products, including fuel oil, fluid ...

, etc., can

detonate Detonation () is a type of combustion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations propagate supersonically through shock waves with s ...

unpredictably from sources of ignition such as flames, sparks or impact from light blows.

Petrochemical Petrochemicals (sometimes abbreviated as petchems) are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sou ...

s, including

asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...

, often exhibit this behavior. The

tetraoxygen The tetraoxygen molecule (O4), also called oxozone, is an allotrope of oxygen consisting of four oxygen atoms. History Tetraoxygen was first predicted in 1924 by Gilbert N. Lewis, who proposed it as an explanation for the failure of liquid oxyg ...

molecule (O₄) was first predicted in 1924 by

Gilbert N. Lewis Gilbert Newton Lewis (October 23 or October 25, 1875 – March 23, 1946) was an American physical chemist and a Dean of the College of Chemistry at University of California, Berkeley. Lewis was best known for his discovery of the covalent bond a ...

, who proposed it to explain why liquid oxygen defied

Curie's law For many paramagnetic materials, the magnetization of the material is directly proportional to an applied magnetic field, for sufficiently high temperatures and small fields. However, if the material is heated, this proportionality is reduced. For ...

. Modern computer simulations indicate that, although there are no stable O₄ molecules in liquid oxygen, O₂ molecules do tend to associate in pairs with antiparallel

spins The spins (as in having "the spins")Diane Marie Leiva. ''The Florida State University College of Education''Women's Voices on College Drinking: The First-Year College Experience"/ref> is an adverse reaction of intoxication that causes a state of v ...

, forming transient O₄ units.

Liquid nitrogen Liquid nitrogen—LN2—is nitrogen in a liquid state at low temperature. Liquid nitrogen has a boiling point of about . It is produced industrially by fractional distillation of liquid air. It is a colorless, low viscosity liquid that is wide ...

has a lower boiling point at −196 °C (77 K) than oxygen's −183 °C (90 K), and vessels containing liquid nitrogen can condense oxygen from air: when most of the nitrogen has evaporated from such a vessel, there is a risk that liquid oxygen remaining can react violently with organic material. Conversely, liquid nitrogen or

liquid air Liquid air is air that has been cooled to very low temperatures ( cryogenic temperatures), so that it has condensed into a pale blue mobile liquid. To thermally insulate it from room temperature, it is stored in specialized containers ( vacuum in ...

can be oxygen-enriched by letting it stand in open air; atmospheric oxygen dissolves in it, while nitrogen evaporates preferentially. The surface tension of liquid oxygen at its normal pressure boiling point is 13.2 dyn/cm.

Uses

Liquid oxygen, Bagram Airfield, Afghanistan 4

In commerce, liquid oxygen is classified as an

industrial gas Industrial gases are the gaseous materials that are manufactured for use in industry. The principal gases provided are nitrogen, oxygen, carbon dioxide, argon, hydrogen, helium and acetylene, although many other gases and mixtures are also avail ...

and is widely used for industrial and medical purposes. Liquid oxygen is obtained from the

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

found naturally in

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 ...

fractional distillation Fractional distillation is the separation of a mixture into its component parts, or fractions. Chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixture will vaporize. It uses distillation to ...

in a cryogenic air separation plant. Air forces have long recognized the strategic importance of liquid oxygen, both as an oxidizer and as a supply of gaseous oxygen for breathing in hospitals and high-altitude aircraft flights. In 1985, the USAF started a program of building its own oxygen-generation facilities at all major consumption bases.

In rocket propellant

Liquid oxygen is the most common

liquid

propellant for spacecraft rocket applications, usually in combination with

liquid hydrogen Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully li ...

kerosene Kerosene, paraffin, or lamp oil is a combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in aviation as well as households. Its name derives from el, κηρός (''keros'') meaning "wax", and was regi ...

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...

. Liquid oxygen was used in the first liquid fueled rocket. The

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 ...

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 developed ...

missile also used liquid oxygen under the name ''A-Stoff'' and ''Sauerstoff''. In the 1950s, during the

Cold War The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because the ...

both the United States' Redstone 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 ...

rockets, and the

Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...

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 ...

used liquid oxygen. Later, in the 1960s and 1970s, the ascent stages of the Apollo Saturn rockets, and the

Space Shuttle main engines The Aerojet Rocketdyne RS-25, also known as the Space Shuttle Main Engine (SSME), is a liquid-fuel cryogenic rocket engine that was used on NASA's Space Shuttle and is currently used on the Space Launch System (SLS). Designed and manufacture ...

used liquid oxygen. In 2020, many rockets used liquid oxygen: *

Chinese space program The space program of the People's Republic of China is directed by the China National Space Administration (CNSA). China's space program has overseen the development and launch of ballistic missiles, thousands of artificial satellites, mann ...

Long March 5 Long March 5 (LM-5; zh, s=长征五号 , p=Chángzhēng wǔ hào), or Changzheng 5 (CZ-5), and also by its nickname "''Pang-Wu''" (胖五, "''Fat-Five''"), is a Chinese heavy-lift launch vehicle developed by the China Academy of Launch Vehicle ...

, and its derivations

Long March 6 The Long March 6 () or Chang Zheng 6 as in pinyin, abbreviated LM 6 for export or CZ 6 within China, is a Chinese liquid-fuelled launch vehicle of the Long March family, which was developed by the China Aerospace Science and Technology Corpor ...

Long March 7 , stages = {{plainlist, * CZ-7: Two * CZ-7A: Three {{cite web, url=https://www.space.com/china-space-program-new-long-march-rockets.html, last=Jones, first=Andrew, title=China prepares to launch new rockets as part of push to boost spac ...

Indian Space Research Organisation The Indian Space Research Organisation (ISRO; ) is the national space agency of India, headquartered in Bengaluru. It operates under the Department of Space (DOS) which is directly overseen by the Prime Minister of India, while the Chairman ...

GSLV Geosynchronous Satellite Launch Vehicle (GSLV) is an expendable launch system operated by the Indian Space Research Organisation (ISRO). GSLV was used in fourteen launches from 2001 to 2021. Even though GSLV Mark III shares the name, it is an ...

JAXA The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into orb ...

(Japan):

H-IIA H-IIA (H-2A) is an active expendable launch system operated by Mitsubishi Heavy Industries (MHI) for the Japan Aerospace Exploration Agency. These liquid fuel rockets have been used to launch satellites into geostationary orbit; lunar or ...

and H3 (under development) *

Roscosmos The State Space Corporation "Roscosmos" (russian: Государственная корпорация по космической деятельности «Роскосмос»), commonly known simply as Roscosmos (russian: Роскосмос) ...

(Russia):

Soyuz-2 Soyuz-2 (GRAU index 14A14) is a modernized version of the Soviet Soyuz rocket. In its basic form, it is a three-stage launch vehicle for placing payloads into low Earth orbit. Compared to the previous versions of the Soyuz, the first-stage bo ...

and

Angara The Angara ( Buryat and mn, Ангар, ''Angar'', "Cleft"; russian: Ангара́, ''Angará'') is a major river in Siberia, which traces a course through Russia's Irkutsk Oblast and Krasnoyarsk Krai. It drains out of Lake Baikal and is ...

(under development) *

ESA , 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 ...

( EU):

Ariane 5 Ariane 5 is a European heavy-lift space launch vehicle developed and operated by Arianespace for the European Space Agency (ESA). It is launched from the Centre Spatial Guyanais (CSG) in French Guiana. It has been used to deliver payloads int ...

and

Ariane 6 Ariane 6 is a European expendable launch system currently under development since the early 2010s by ArianeGroup on behalf of the European Space Agency (ESA). It is intended to replace the Ariane 5, as part of the Ariane launch vehicle family. ...

(under development) *

Korea Aerospace Research Institute The Korea Aerospace Research Institute (KARI), established in 1989, is the aeronautics and space agency of South Korea. Its main laboratories are located in Daejeon, in the Daedeok Science Town. KARI's vision is to continue building upon indig ...

(

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 ...

KSLV-1 Naro-1 ( ko, 나로호), previously designated the Korea Space Launch Vehicle or KSLV (also KSLV-1), was South Korea's first carrier rocket, and the first South Korean launch vehicle to achieve Earth orbit. On January 30, 2013, the third Naro-1 ...

and

KSLV-II Nuri (; , meaning "world" in native Korean), also known as KSLV-II (Korean Space Launch Vehicle-II), is a three-stage launch vehicle, the second one developed by South Korea and the successor to Naro-1 (KSLV-1). Nuri is developed by Korea Aero ...

* United States **

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 ...

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 ...

Falcon Heavy Falcon Heavy is a partially reusable heavy-lift launch vehicle that is produced by SpaceX, an American aerospace manufacturer. The rocket consists of two strap-on boosters made from Falcon 9 first stages, a center core also made from a Falc ...

and ''Starship'' (under development) (liquid oxygen chilled to , 10% denser than at boiling temperature) **

United Launch Alliance United Launch Alliance (ULA), legally United Launch Alliance, LLC, is an American spacecraft launch service provider that manufactures and operates a number of rocket vehicles that are capable of launching spacecraft into orbits around Earth, a ...

Atlas V Atlas V is an expendable launch system and the fifth major version in the Atlas (rocket family), Atlas launch vehicle family. It was originally designed by Lockheed Martin, now being operated by United Launch Alliance (ULA), a joint venture be ...

Delta IV Delta IV is a group of five expendable launch systems in the Delta (rocket family), Delta rocket family introduced in the early 2000s. Originally designed by Boeing's Defense, Space and Security division for the National Security Space Launch, ...

Delta IV Heavy The Delta IV Heavy (Delta 9250H) is an Evolved Expendable Launch Vehicle, expendable heavy-lift launch vehicle, the largest type of the Delta IV family. It is the world's third highest-capacity launch vehicle in operation, behind NASA's Space L ...

Vulcan Vulcan may refer to: Mythology * Vulcan (mythology), the god of fire, volcanoes, metalworking, and the forge in Roman mythology Arts, entertainment and media Film and television * Vulcan (''Star Trek''), name of a fictional race and their home p ...

(under development) **

Northrop Grumman Northrop Grumman Corporation is an American multinational aerospace and defense technology company. With 90,000 employees and an annual revenue in excess of $30 billion, it is one of the world's largest weapons manufacturers and military techn ...

: Antares 230+ **

Blue Origin Blue Origin, LLC is an American private spaceflight, privately funded aerospace manufacturer and sub-orbital spaceflight services company headquartered in Kent, Washington. Founded in 2000 by Jeff Bezos, the founder and executive chairman of Am ...

New Shepard New Shepard is a fully reusable suborbital launch vehicle developed by Blue Origin for space tourism. The vehicle is named after Alan Shepard, the first American astronaut in space. The vehicle is capable of vertical takeoff and vertical land ...

and

New Glenn New Glenn is a heavy-lift orbital launch vehicle in development by Blue Origin. Named after NASA astronaut John Glenn, design work on the vehicle began in 2012. Illustrations of the vehicle, and the high-level specifications, were initial ...

(under development) **

Rocket Lab Rocket Lab is a public American aerospace manufacturer and launch service provider, with a New Zealand subsidiary. The company operates lightweight Electron orbital rockets, which provide dedicated launches for small satellites. Rocket Lab also ...

Electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no kn ...

Firefly Aerospace Firefly Aerospace is an American private aerospace firm based in Austin, Texas, that develops launch vehicles for commercial launches to orbit. The company completed its $75 million Series A investment round in May 2021, which was led by DADA ...

Firefly Alpha Firefly Alpha (Firefly α) is a two-stage orbital expendable launch vehicle developed by the American company Firefly Aerospace to compete in the commercial small satellite launch market. Alpha is intended to provide launch options for both ...

Virgin Orbit Virgin Orbit is a company within the Virgin Group which provides launch services for small satellites. On January 17, 2021, their ''LauncherOne'' rocket successfully reached orbit for the first time, and successfully deployed 10 cubesats. The ...

LauncherOne LauncherOne is a two-stage orbital launch vehicle developed and flown by Virgin Orbit that began operational flights in 2021, after being in development from 2007 to 2020. It is an air-launched rocket, designed to carry smallsat payloads of u ...

History

*By 1845,

Michael Faraday Michael Faraday (; 22 September 1791 – 25 August 1867) was an English scientist who contributed to the study of electromagnetism and electrochemistry. His main discoveries include the principles underlying electromagnetic inducti ...

had managed to liquefy most gases then known to exist. Six gases, however, resisted every attempt at liquefactionCryogenics
Scienceclarified.com. Retrieved on 2012-07-22. and were known at the time as "permanent gases". They were oxygen,

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

, and

nitric oxide Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its che ...

. *In 1877,

Louis Paul Cailletet Louis-Paul Cailletet (21 September 1832 – 5 January 1913) was a French physicist and inventor. Life and work Cailletet was born in Châtillon-sur-Seine, Côte-d'Or. Educated in Paris, Cailletet returned to Châtillon to manage his fathe ...

in France and

Raoul Pictet Raoul-Pierre Pictet (4 April 1846 – 27 July 1929) was a Swiss physicist. Pictet is co-credited with French scientist Louis-Paul Cailletet as the first to produce liquid oxygen in 1877. Biography Pictet was born in Geneva. He served as profes ...

in Switzerland succeeded in producing the first droplets of liquid air. *In 1883, Polish professors

Zygmunt Wróblewski Zygmunt, Zigmunt, Zigmund and spelling variations thereof are masculine given names and occasionally surnames. People so named include: Given name Medieval period * Sigismund I the Old (1467–1548), Zygmunt I Stary in Polish, King of Poland and Gr ...

and

Karol Olszewski Karol Stanisław Olszewski (29 January 1846 – 24 March 1915) was a Polish chemist, mathematician and physicist. Biography Olszewski was a graduate of Kazimierz Brodziński High School in Tarnów (I Liceum Ogólnokształcące im. Kazimierza ...

produced the first measurable quantity of liquid oxygen.

References

{{DEFAULTSORT:Liquid Oxygen Rocket oxidizers Cryogenics Oxygen Industrial gases Liquids 1883 in science

Physical properties

Uses

In rocket propellant

History

See also

References