NASA Prepares J-2X Engine for Second Set of Tests
April 25, 2012 5:41 PM
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NASA plans to test the J-2X engine throughout the rest of this year
NASA announced that its next-generation J-2X engine will begin its second round of tests starting today.
The J-2X engine is a redesign of the J-2 engine that carried astronauts to the moon during the 1960s and 1970s. It was developed by Pratt and Whitney Rocketdyne, which were
awarded a $1.2 billion NASA contract
The J-2X is the first new liquid oxygen and liquid hydrogen rocket engine made in 40 years that will be able to send humans into space again. In fact, the J-2X engine is designed to power deep space missions and will be used for
NASA's Space Launch System (SLS)
, which is a heavy-lift rocket intended for deep space missions.
Last year, NASA conducted the first round of testing on the J-2X engine, which resulted in successful test firings. In that particular round of sea-level tests, the J-2X engine was fired 10 times total for 1,040 seconds, reaching 100 percent power in just four tests. It also met a full flight-duration firing of 500 seconds in the eighth test, which proved to be quicker than any other U.S. engine.
Now, the J-2X is on to its second round of testing starting today. NASA will now simulate high-altitude conditions where there is lower atmospheric pressure. According to Tom Byrd, J-2X engine lead from NASA's Marshall Space Flight Center in Huntsville, Alabama, J-2X engines will be tested in the SLS' second stage of flight where nozzle data and overall performance will be monitored.
"We're making steady and tangible progress on our new heavy-lift rocket that will launch astronauts on journeys to destinations farther in our solar system," said Charles Bolden, NASA administrator. "As we continue test firings of the J-2X engine and a myriad of other work to open the next great chapter of exploration, we're demonstrating our commitment right now to America's continued leadership in space."
The United States' role in space has been a hot topic since
NASA retired its space shuttle fleet last year
Since that retirement, American astronauts have been forced to depend on Russian Soyuz rockets to make their way to the International Space Station (ISS), where the cost of one seat on the Russian spacecraft is expected to increase to $63 million by 2015
. The U.S. knew it had to find another way to the ISS without depending on Russia, so it jumped on the private space travel industry to fill in the gap.
SpaceX, which is expected to be the first private company to
send a spacecraft to the ISS on May 7
, stepped up with its Dragon cargo capsule in an attempt to fill the void of the space shuttle fleet.
With the U.S. back in the space race, NASA plans to test the J-2X engine throughout the rest of this year. The engine is currently on the A-2 Test Stand at NASA's Stennis Space Center in Mississippi.
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4/26/2012 11:30:32 AM
True, but the volume of H2 can be a factor. While it has a drastically higher specific impulse (a measure of its efficiency per weight) that just about every other fuel, it isn't very dense (as far as liquid propellants go). So if you can't afford the volume constraint, you might have to go with other alternatives.
As you mentioned, anything that requires cryogenics is a PITA to handle (from cost to safety).
4/26/2012 4:21:53 PM
cryogenic H2 tanks and plumbing weigh a hell of a lot more than non-cryogenic tanks and plumbing.
the extra weight penalty does take much of the specific impulse advantage of h2/lox engines.
personally i think we should concentrate on making cheap, reliable large slightly lower performance engines.
rp1/h2o2 engines seem IMO to have a lot of advantages, non cryogenic, hypergolic, non-toxic, reasonable specific impulse, cheap fuels and very reliable technology. The UK is the only country with much experience in orbital launchers using these engines - they didnt have a single failure of a h2o2/rp1 engine throughout the british space program (till it was killed in 1970).
4/26/2012 9:39:04 PM
rp1/h202 is not hypergolic.
With the current state of technology RP1/Lox is the fuel of choice for a LEO booster stage. RP1/Lox engines can achieve very high thrust, high thrust to weight ratios, and the high fuel density reduces over all size and tank weights. Although Lox is cryogenic, it's a mild cryogenic and tanks and insulation are particularly difficult to fabricate nor particularly heavy, especially for a booster stage that can take advantage of ground support equipment. High ISP is not nearly so important for a booster stage as it is for an upper stage or orbital departure stage.
For upper stages LH2/LOX is the fuel of choice because of it's high ISP. Although LH2 requires very large tanks and very aggressive tank insulation because of it's low density and boiling point only 20 degrees above absolute zero, the high ISP more than makes up for these drawbacks where weight and ISP are critical.
The appeal of H2O2 (hydrogen peroxide) was for ballistic missile systems where the missile needed to constantly sit on standby. This pushed the design tradeoffs to sacrifice performance for propellants store-able at room temperature for long periods. Thus the RP1/H2O2 engines in the UK, and the Hydrazine/Nitrogen Tetroxide engines developed in the US and USSR. Even further performance comprises were made for the submarine based missiles and the MX missile that used Solid fuel rockets, but required more stages.
The J2-X project came out of the now cancelled Constellation program. The original plan to use Space Shuttle Main Engines (SSME) as the upper stage engines for the Ares 1 and Ares V turned out not to be feasible because the SSME could not be modified to be air startable (or more accurately Re-startable) an essential requirement. A program was then started to design the J2-X, a modernized and higher thrust version of the venerable J2 engine that was used on the upper stage of the Saturn 5. However it was not possible to achieve the very high performance of the SSME. This forced the redesign of the booster stages which grew larger and larger, and in the case of the ARES I solid rocket motor which could not be made large enough to achieve the original performance forced the cannibalization and weight reduction of the Orion crew capsule. A whole cascade of design changes resulted that pushed the ARES V size and weight up to the point where the Crawler and crawler way could not support the enormous weight and were in danger of needing to be entirely replaced. Program cost kept climbing and even though the shuttle was cancelled and the ISS was planned to be splashed into the ocean in 2015 to redirect those funds to feed the monster there would still have been something like a $70 Billion shortfall in the program. Obama inherited this mess and made the only rational decision possible cancelling it after the Augustine commission report came out.
At any rate the J2-X engine project lives on.
4/29/2012 8:44:47 AM
hot decomposing h2o2 combusts with rp1.
though i agree that the two fuels when put into contact at room temperature and pressure minus a catalyst will not combust.
in a rocket engine with the appropriate catalyst the two fuels are effectively hypergolic.
the engines are very very simple and are hence very reliable and also very cheap.
the isp achievable in the sixties out of shed in coventry was ~270. i'm sure with modern manufacturing techniques this could go up a bit.
historically decision making about which fuels to use has always been about performance.
in the days of saturn v - money was no object - everything was orientated around maximum performance in the shortest time.
there is a lot of inertia in the aerospace industry. pressure to keep jobs and factories running at costs has instilled a degree of dogma into rocket design. hell congress have decided that they know more than rocket scientists and have dictated which booster technology is going to be used in SLS.
i would argure that our needs now are different.
we need acceptable performance, reliably and cheaply.
we need a rocket engine design that can be stamped out of an automated production line in a few days rather than have 50 engineers slaving away for weeks on CNC machines.
i think rp1/h2o2 has some advantages in this way.
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