The J-2X is a liquid-fueled

cryogenic rocket engine A cryogenic rocket engine is a rocket engine that uses a cryogenic fuel and oxidizer; that is, both its fuel and oxidizer are gases which have been liquefied and are stored at very low temperatures. These highly efficient engines were first fl ...

that was planned for use on the Ares rockets of

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

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 later the

Space Launch System The Space Launch System (SLS) is an American Super heavy-lift launch vehicle, super heavy-lift Expendable launch system, expendable launch vehicle used by NASA. As the primary launch vehicle of the Artemis program, Artemis Moon landing progra ...

. Built in the United States by

Aerojet Rocketdyne Aerojet Rocketdyne is a subsidiary of American Arms industry, defense company L3Harris that manufactures rocket, Hypersonic flight, hypersonic, and electric propulsive systems for space, defense, civil and commercial applications. Aerojet traces ...

(formerly,

Pratt & Whitney Rocketdyne Pratt & Whitney Rocketdyne (PWR) was an American company that designed and produced rocket engines that use liquid rocket propellants, liquid propellants. It was a division of Pratt & Whitney, a fully owned subsidiary of United Technologies Corpo ...

), the J-2X burns

cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th International Institute of Refrigeration's (IIR) International Congress of Refrigeration (held in Washington, DC in 1971) endorsed a univers ...

liquid hydrogen Liquid hydrogen () is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecule, molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point (thermodynamics), critical point of 33 Kelvins, ...

and

liquid oxygen Liquid oxygen, sometimes abbreviated as LOX or LOXygen, is a clear cyan liquid form of dioxygen . It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an application which is ongoing. Physical ...

propellants, with each engine producing of

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 ...

in vacuum at a

specific impulse Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine, such as a rocket engine, rocket using propellant or a jet engine using fuel, generates thrust. In general, this is a ratio of the ''Impulse (physics), ...

(''I''_sp) of . The engine's mass is approximately 2,470 kg (5,450 Lb), significantly heavier than its predecessors. The J-2X was intended to be based on the J-2 used on the

S-II The S-II (pronounced "S-two") was the second stage of the Saturn V rocket. It was built by North American Aviation. Using liquid hydrogen (LH2) and liquid oxygen (LOX) it had five J-2 engines in a quincunx pattern. The second stage accelerated ...

and

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. For lunar missions it was fired twice: first for Earth ...

stages of the

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 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...

rockets used during the

Apollo program The Apollo program, also known as Project Apollo, was the United States human spaceflight program led by NASA, which Moon landing, landed the first humans on the Moon in 1969. Apollo followed Project Mercury that put the first Americans in sp ...

, but as required thrust for the Ares I increased due to weight problems it became a clean-sheet design. It entered development in 2007 as part of the now-cancelled

. Originally planned for use on the

upper stage A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own Rocket engine, engines and Rocket propellant, propellant. A ''tandem'' or ''serial'' stage is mounted on top of anoth ...

s of the

Ares I Ares I was the crew launch vehicle that was being developed by NASA as part of the Constellation program. The name "Ares" refers to the Greek deity Ares, who is interpretatio graeca, identified with the Roman god Mars (mythology), Mars. Ares I w ...

and

Ares V The Ares V (formerly known as the Cargo Launch Vehicle or CaLV) was the planned cargo launch component of the cancelled NASA Constellation program, which was to have replaced the Space Shuttle after its retirement in 2011. Ares V was also plan ...

rockets, the J-2X was later intended for use in the

Earth Departure Stage The Earth Departure Stage (EDS) was the name given to the proposed second stage of the Block 2 Space Launch System. The EDS was intended to boost the rocket's payload into a parking orbit around the Earth and from there send the payload out of ...

of the Block 2

, the successor to the Constellation program. The engine is intended to be more efficient and simpler to build than its J-2 ancestor, and cost less than the

RS-25 The 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 used on the Space Launch System. Designed and manufactured in the United States by Rocketd ...

engine. Differences in the new engine include the removal of

beryllium Beryllium is a chemical element; it has Symbol (chemistry), symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with ...

, a centrifugal turbo pump versus the axial turbo pump of the J-2, different chamber and nozzle expansion ratios, a channel-walled combustion chamber versus the tube-welded chamber of the J-2, a redesign of all the electronics, a

gas generator A gas generator is a device for generating gas. A gas generator may create gas by a chemical reaction or from a solid or liquid source, when storing a pressurized gas is undesirable or impractical. The term often refers to a device that uses a ...

and supersonic main injector based on the

RS-68 The RS-68 (Rocket System-68) was a liquid-fuel rocket engine that used liquid hydrogen (LH2) and liquid oxygen (LOX) as propellants in a gas-generator cycle. It was the largest hydrogen-fueled rocket engine ever flown. Designed and manufacture ...

, and the use of 21st-century joining techniques.

Testing

On 16 July 2007 NASA officially announced the award to

(PWR) of a $1.2 billion contract "for design, development, testing and evaluation of the J-2X engine", and began construction of a new test stand for altitude testing of J-2X engines at

Stennis Space Center The John C. Stennis Space Center (SSC) is a NASA rocket testing facility in Hancock County, Mississippi, United States, on the banks of the Pearl River (Mississippi–Louisiana), Pearl River at the Mississippi–Louisiana border. , it is NASA ...

on 23 August 2007. Component testing was undertaken between December 2007 and May 2008, with nine tests of heritage J-2 engine components at SSC in preparation for the design of the J-2X engine. and on 8 September 2008 PWR announced successful testing of the initial J-2X gas generator design. The completion of a second round of successful gas generator tests was announced on 21 September 2010. Starting in 2011, the full J-2X engine, derived from heritage and new designs, has undergone hot-fire tests. * June 2011: The first hot-fire test. * November 2011: A test-firing lasting 499.97 seconds. * June 2012: A test-firing lasting 1,150 seconds, during which the J-2X was throttled up and down. * July 2012: A test-firing for 1,350 seconds ( minutes). * December 2012: Final test-firing of the powerpack assembly. *Feb 2013: Testing of engine 10002 begins on test stand A2 for 6 tests. *June 2013: Engine 10002 moved to test stand A1 for 7 further tests. *Sept 2013: Final test-firing of engine 10002. *Nov 2013: Testing of engine 10003 begins. Image:J-2X concept image June 2006.png, Concept image of the J-2X engine. Image:Test of the J-2X Engine.JPG, Test of the J-2X engine 'workhorse' gas generator. Image:NASA's J-2X Engine.jpg, Cold Flow nozzle testing for the J2X program. Image:J2-X Engine NASA test - 592563main SSC-2011-01852 946-710.jpg, The J-2X being tested at NASA's

John C. Stennis Space Center The John C. Stennis Space Center (SSC) is a NASA rocket testing facility in Hancock County, Mississippi, United States, on the banks of the Pearl River (Mississippi–Louisiana), Pearl River at the Mississippi–Louisiana border. , it is NASA ...

Hancock County, Mississippi Hancock County is the southernmost county of the U.S. state of Mississippi and is named for Founding Father John Hancock. As of the 2020 census, the population was 46,053. Its county seat is Bay St. Louis. Hancock County is part of the Gulfp ...

Program status

In October 2013, it was reported that work on the J-2X would pause following development testing in 2014, due to funding limitations, an expected delayed need for the engine's capabilities for piloted missions to Mars, and selection of the

RL10 The RL10 is a liquid-fuel cryogenic rocket engine built in the United States by Aerojet Rocketdyne that burns cryogenic liquid hydrogen and liquid oxygen propellants. Modern versions produce up to of thrust per engine in vacuum. RL10 version ...

powered

Exploration Upper Stage The Exploration Upper Stage (EUS) is a rocket stage under development for future flights of NASA’s Space Launch System (SLS). Designed for use on the SLS Block 1B and Block 2 configurations, it will replace the Interim Cryogenic Propulsion ...

for SLS. In September 2022, the components of the J-2X were put up for auction on GSA Auctions, likely confirming the cancellation of the program.

References

{{Project Constellation Rocket engines using hydrogen propellant Rocketdyne engines Space Launch System Rocket engines using the gas-generator cycle Rocket engines of the United States

Testing

Program status

See also

References