NASA’s Space Launch System (SLS) Program, designing NASA’s next heavy lift launch vehicle intended to carry spacecraft and astronauts beyond low Earth orbit, is currently undergoing a critical design review. While this major milestone is underway, engineers recently tested the launch vehicle’s hydrogen burn-off igniters, and continue to analyze results from the QM-1 booster test fire that took place on March 11th at Orbital ATK’s test facility in Promontory, Utah. In addition, work is proceeding on the B-2 Test Stand at Stennis Space Center, which is being drastically modified to support SLS.
The design review started May 11th at NASA’s Marshall Space Flight Center in Huntsville, Alabama. According to the space agency, SLS’ boosters, stages, and engines have already completed their own reviews; Spacecraft and Payload Integration & Evolution (the SPIE Office, in charge of the Orion stage adapter, the interim cryogenic propulsion stage, and the launch vehicle stage adapter) is in the process of completing its own review. The integrated design review of SLS, according to NASA, is estimated to conclude in late July.
Engineers have also made strides in developing essential components of SLS. On May 5th, tests (nine to take place in total) of the vehicle’s hydrogen burn-off igniters began at the U.S. Army’s Redstone Test Center on Redstone Arsenal in Huntsville. SLS will have four RS-25 engines, and two five-segment solid rocket boosters. The purpose of the hydrogen burn-off igniters (the vehicle will have 12) is to rid excess hydrogen from the vehicle’s aft end, which can potentially spark an explosion.
From NASA: “Sparks fly as a hydrogen burn-off igniter test is conducted May 5 at the Redstone Test Center on Redstone Arsenal in Huntsville.” Video Credit: RTC/NASA’s Marshall Space Flight Center
According to David McDaniels, an aerospace engineer in Marshall’s Fluid Dynamics branch, “Hydrogen burn-off igniters are more like small rocket motors than an explosive. They generate enough of a propellant plume to carry the sparks at least 15 feet to the right place to burn off any excess hydrogen.” These igniters are similar to the ones used during the space shuttle era, which were highly visible in launch footage just prior to liftoff. NASA stated that the tests were being filmed by high-speed cameras to gauge measurements including how far particles were thrown, and their area of coverage.
In addition, engineers continue to inspect components of the solid rocket booster fired during the Qualification Motor-1 test fire (QM-1) in March. SLS’ boosters are being designed by Orbital ATK. In a recent AmericaSpace article, Mike Killian reported that initial findings showed the test to be an unqualified success:
“The [QM-1] test also demonstrated the booster’s ability to meet applicable ballistic performance requirements, such as thrust and pressure. Other objectives included data gathering on vital motor upgrades, such as the new internal motor insulation and liner and an improved nozzle design. ‘Current data shows the nozzle and insulation performed as expected, and ballistics performance parameters met allowable requirements,’ noted Orbital ATK in their report. ‘Additionally, the thrust vector control and avionics system provided the required command and control of the motor nozzle position.’” This week NASA further announced, “Disassembly and inspection of the booster is ongoing, but preliminary analysis of the test data shows all test objectives were successfully completed during the hot fire.”
Of course, the boosters will be subjected to further testing prior to actual flight. Killian added in his report, “A cold-temperature test, at a target of 40 degrees Fahrenheit, the low end of the propellant temperature range, is planned for QM-2 before the hardware testing to support qualification of the boosters for flight will be complete, at which point Orbital ATK will then be ready to proceed toward the first flight of SLS, an uncrewed flight to validate the entire integrated system, currently scheduled to fly on the Exploration Mission-1 (EM-1) in late-2018.” These powerhouse boosters are expected to be 20 percent more powerful than their counterparts used on the space shuttle, providing much of SLS’ thrust required to escape gravity.
While results of these tests continue to be scrutinized, the B-2 Test Stand located at the Stennis Space Center in Mississippi is undergoing modifications in order to support SLS’ core stage for future testing. NASA announced, “A major step in the modification involves repositioning and extension of the test stand’s Main Propulsion Test Article (MPTA) framework, which supports the rocket stage for testing. The framework was repositioned on the stand late last summer. Now, work has begun to add the large structural steel sections that will extend its height.” The MPTA, originally designed to support space shuttle testing, will have 100 feet added to its current height of 61 feet, and will “gain weight” in the form of a million pounds of steel.
While the integrated design review continues to take place, SLS’ engineers – coming from a variety of aerospace backgrounds and NASA space centers – continue to make progress in developing the first “beyond Earth” rocket seen since the likes of the mighty Saturn V.
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