The J-2X is a
liquid-fueled cryogenic rocket engine that was planned for use on the Ares rockets of
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, succeedi ...
's
Constellation program, and later the
Space Launch System. Built in the United States by
Aerojet Rocketdyne (formerly,
Pratt & Whitney Rocketdyne), the J-2X burns
cryogenic liquid hydrogen and
liquid oxygen propellants, with each engine producing of
thrust
Thrust is a reaction force
In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can al ...
in vacuum at a
specific impulse (''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 stages of the
Saturn rockets used during the
Apollo program, 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
Constellation program.
Originally planned for use on the
upper stages of the
Ares I and
Ares V rockets, the J-2X was later intended for use in the
Earth Departure Stage of the Block 2
Space Launch System, 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 engine.
Differences in the new engine include the removal of
beryllium, 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 and supersonic main injector based on the
RS-68, and the use of 21st-century joining techniques.
Testing
On 16 July 2007 NASA officially announced the award to
Pratt & Whitney Rocketdyne (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 at the Mississippi–Louisiana border. , it is NASA's largest rocket engine test facility. T ...
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.
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 powered
Exploration Upper Stage for SLS.
In September 2022, the components of the J-2X was put up for auction on GSA Auctions, likely confirming the cancellation of the program.
See alsoAerojet Rocketdyne J-2X Engine
* HG-3 engine
* M-1 (rocket engine)
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