SSC does what's needed for stand
By Lisa Monti
September 2013
...Need a massive rocket engine tested without disturbing the neighbors? Yeah, they
can do that at NASA’s Stennis Space Center. Need to fabricate a 7,000-pound part,
or how about miles of piping? Well, sure, they can do that, too.
...Call it a can-do attitude.
...SSC has been NASA’s premier rocket engine test facility since the 1960s Apollo
program, when the window-rattling F-1 engines that powered Saturn V were tested
here. Now the next big project on its plate is testing the RS-25 engines that will power
the core stage of NASA’s next generation Space Launch System (SLS).
...A cluster of four engines will be used to lift America’s most powerful rocket since
Saturn V, taking astronauts deeper into space than ever before.
...Testing the RS-25 engines is old hat for SSC. Those are the engines used in the
Space Shuttle, and every one was tested and certified for flight at SSC. All 15 RS-
25D engines have been at SSC since 2012.
...But the 3.5-ton RS-25 engines that will power SLS are upgraded versions with
higher thrust. They also have a new controller unit, the “brain of the engine” that
sends commands from the vehicle to the engine and data from the engine back to
the vehicle. The two way communication helps regulate thrust and the fuel mix fed to
the engine and keep tabs on its performance.
...Before the new variant of the RS-25 can be tested, welders and machinists have to
perform intricate work to get the A-1 test stand ready.
...The first task was to begin fabricating a huge steel thrust frame adapter to hold the
powerful engine in place and help measure performance. The second was to re-do
piping in the multi-story test stand to accommodate new hardware.
...NASA considered having the adapter made off site, but the Stennis shop team
figured a way to design and fabricate the adapter on site. It cost about $300,000 and
required close coordination among NASA, Lockheed Martin’s Test Operations
Contract Group and Jacobs Technology shops.
...The massive steel adapter tips the scales at 7,775 pounds and was completed in
August. It was custom made to cradle the RS-25 engines and will replace the adapter
that was used for the less-powerful J-2X. How much less powerful? The J-2X has
294,000 pounds of thrust, and the RS-25 530,000 pounds.
...NASA’s Gary Benton, in charge of the J-2X and RS-25 engine test projects, gave
the team an A plus for its design and fabrication work.
...“We have a highly skilled workforce down here. They do quality work and are very
good at what they do. They have unique skills especially when it comes to welding,”
he said.
...The thrust frame adapter is tailor-made for each type of rocket engine and it’s
attached to the test stand’s thrust measurement system. The engine is then fitted
into the adapter, which holds it in place. The adapter has to remain stable during
testing so that all aspects of the engine’s performance can be accurately measured.
...The particular grade of steel used for the adapter has to be pre-heated while being
welded so Stennis welders had to be specially trained before fabrication began.
...The welding and machining was challenging because of the scope of the project
and because the steel used for the engine mounting block was 32 inches in diameter
and 20 inches thick.
..."This is a very specific process," Benton said. "It is critical that thrust data not be
skewed or compromised during a test, so the adapter has to be precisely designed
and constructed."
...The adapter still has to undergo load testing at Lehigh University before it can be
ready for installation in A-1 in October.
...“We have to put a big load on it that simulates the amount of force the engine will
put on it,” Benton said. “We don’t have the capability here to do that heavy a load
test.” There’s still plenty of shop work to be done before the RS-25s can begin test
firings in the fall of 2014.
...J-2X testing will be finished in September and the test stand will be reconfigured for
the RS-25, Benton said.
...Benton said the Jacobs Technology crews at Stennis are building piping for the test
stand that is done in different sections that will snake through the structure. The lines
weigh hundreds of pounds.
...Since the very cold propellants create what Benton described as “an extreme
environment,” the quality of the piping has to be very high “so that we never have
anything come lose or leak.”
...The piping now being fabricated is expected to be completed and installed on the
stand by the end of the year.
...After all of the work on the stand is completed, the RS-25 engine will be installed in
May or June, Benton said, and testing will take place in the summer. “There will be
eight tests in the first series and they will vary in duration. We haven’t finalized the
test plan yet,” he said.
Underwritten in part by:
Aerospace Quarterly
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