AR-22 Holds Ticket to Routine Space Launch Operations
July 13, 2018 - The uncompromising demands of spaceflight have long challenged efforts to reuse launch vehicles at a frequency resembling conventional aircraft, but Aerojet Rocketdyne is poised to topple that barrier with its AR-22 engine.
As part of a Defense Advanced Research Project Agency (DARPA) effort to demonstrate a spaceplane capable of rapid turnaround operations, Aerojet Rocketdyne fired an AR-22 engine an unprecedented 10 times in 240 hours. Each of the tests, conducted June 26-July 6 at NASA's Stennis Space Center in Mississippi, ran 100 second durations or longer proving the flight profile of the Phantom Express Spaceplane is feasible with daily access to space.
The Boeing-led program remains on track for flight demonstrations beginning in 2021. DARPA's ultimate goal for Phantom Express is the capability to launch, on a daily basis, payloads weighing 3,000 pounds to low Earth orbit.
Realizing that goal requires an operating tempo that had never been demonstrated on large-scale, flight-qualified rocket engines over 200,000 lbf of thrust. Enter the AR-22, a logical choice given its legacy as the main engine for NASA's now-retired fleet of space shuttles.
Achieving a single-engine turnaround time of 24 hours was quite an undertaking. Check out the "24-Hour infographic" on just what was required!
"For example, the SSME needed at least 17 hours of drying time between firings, because the moisture residue of liquid-oxygen/hydrogen combustion could cause a catastrophic failure," said Jeff Haynes, Aerojet Rocketdyne's AR-22 program manager. "On the AR-22 tests, the company was able to trim that to six hours."
"A similar philosophy also was applied to post-firing engine inspections, which on the shuttle program were detailed and intrusive. Thanks in part to data accumulated over some 1 million seconds of cumulative firing time on the basic engine design, Aerojet Rocketdyne made do with more limited inspections on the AR-22, including forgoing the shuttle-era practice of removing the turbopumps for close-up examination," Haynes said.
"In addition, the AR-22 was outfitted with significant instrumentation to flag internal conditions that strayed outside of specifications, which would have enabled managers to abort the test, if necessary," added Haynes.
Aerojet Rocketdyne's team, working around the clock in two shifts, faced an external challenge in the form of lightning strikes that caused test stand damage that had to be repaired before firings could resume. Nonetheless, the team was able to stay within its 240-hour testing envelope with 68 minutes to spare.
The AR-22 test engine featured a new controller built for the engine that will power NASA’s super-heavy-lift Space Launch System exploration rocket.
In addition, one firing was extended for 47 seconds to test a new health management system that allows the AR-22 to continue operating under certain scenarios that would have triggered a shutdown of the SSME.
"The single AR-22 rocket powering the Phantom Express is highly reliable, but the intelligent health management system called the Anomaly Command and Control Center (AC3), which is based on a million seconds of data, enhances reliability by assuming control of the engine if an anomaly occurs with the goal to meet mission success and return safely," said Mike Bradley, the AC3 architect, and Aerojet Rocketdyne’s AR-22 program Chief Engineer.
Aerojet Rocketdyne is under contract to provide two AR-22 engines for the Phantom Express program, the second of which will be used for the flight tests.
The testing in the summer of 2018 proved the AR-22 holds the ticket to routine space launch operations. Next up, is 24 hour turns with the Phantom Express Flight vehicle.