NASA, the European Space Agency (ESA) and contractors last week conducted an Abort To Orbit (ATO) test case for the Orion spacecraft using the Propulsion Qualification Module (PQM) module in the White Sands Test Facility (WSTF) ) in New Mexico. The White Sands team had the PQM undergo a twelve-minute sequence of engine firings to demonstrate the ability of the Orion propulsion system to cope with a stress-drop event.
In a hypothetical ATO case, Orion had to lift the slack of a below-average launch vehicle launch system (SLS) during a takeoff that was too fast to return to Earth immediately. At some point during the ascent, the safest option would be to break away from the SLS and put an end to Earth orbit to give more time to think about the situation. The test on the 5th of August was intended to check whether the drive systems from Orion are equipped for this case.
The PQM is a "battleship" version of the ESM (European Service Module) propulsion system ESM general contractor Airbus Defense and Space. The test article was delivered by Airbus to White Sands in 201
Abort To Orbit Test Case
The ESM built by ESA's Airbus DS has three engine types: twenty four RCS (attitude control system) engines for attitude control, eight aux engines for translational maneuvering and an Orion main engine (Orion Main Engine, OME) for large translational burns. The OME is a refurbished space shuttle orbital maneuvering system (OMS) deployed in pairs on the shuttle orbiters.
The PQM was delivered to the 300 area at White Sands in early 2017, minus the OME on which it was installed -Site upon arrival. The test article was then lifted to the test stand 301, which was also used during the Apollo and Shuttle programs. Similar to human-rated spacecraft from these earlier programs, ESM and PQM use hypergolic propellant. Mixed oxides of nitrogen (MON-3) are the oxidant and monomethylhydrazine (MMH) is the fuel.
(Caption: Test Bench 301 at the White Sands Test Facility in New Mexico a few hours before the start of the ATO test case on August 5. The test article is located in the building on the left, surrounded by floor equipment and facilities. The multistage stand contains a flame bucket that directs the exhaust down and to the left from this point of view.)
The PQM is a test article for the drive subsystem of the ESM; There is no equipment that tests other ESM functions such as power generation, consumption memory or thermal control. It is also more of a battleship structure than the missiles, using stronger but heavier materials for the structure and fuel tanks.
The purpose of the article is to test the engines and engines with the fuel distribution and pressurization systems. Another difference to flight modules is that the PQM has only twelve RCS engines, with one of the twelve RCS engines omitted, and all engines on the test subject are fixed in a down-firing position. The OME can be controlled on the service module and the RCS engines are arranged to allow roll, pitch and yaw control.
Two years ago, a first series of "blowdown" tests was performed before pressure control assemblies (PCA) arrived to allow active control of fuel tank pressures with helium gas. PCAs for the first ESM, Flight Model-1 (FM-1) and PQM, were delivered in the latter half of 2018. In October 2018, a two-phase test series with some OME tests was started to clear FM-1. 1 for shipment to the Kennedy Space Center in Florida.
The tests were divided into steps using unsaturated propellants in step 1 and propellant saturated in step 2 with its helium pressurized gas. "We're planning a total of thirty-eight runs and we've done thirty, we're still eight," said Mark Kirasich, NASA's Orion Program Manager, before testing White Sands, who was thirty-first overall.
(Caption: PQM ignites its translational motors during the long ATO test case on August 5. The exhaust of the firing OMS engine can be seen at the bottom of a diffuser All eight Aux engines also ran with the OMS as in an ATO Case.)
The test on August 5 was part of step 2 in which the hypergolic propellant was saturated with helium. "There is the possibility of [use] after a reasonable time on the pad, so that saturation occurs when the vehicle is standing on the pad and the gases are slowly absorbed over time. So this depends on the startup window and how fast you loaded it before the test. "Brian Anderson, NASA's PQM program test leader at White Sands.
"We are prepared and ready for an ATO. So we have enough propellant on board to run this ATO profile, and then the COPVs on one side are loaded to almost the capacity you would call before launch. The other side is a bit lower for the conditions we are in and then we will consume almost all the propellant that is available today on PQM for the Abort To Orbit.
The test of the test article for the ESM propulsion system simulated an ATO ignition profile. If manned flights begin with Artemis 2, Orion may be canceled on take-off day prior to take-off by putting it into orbit. On the first SLS launches, Orion's Solid Rocket Boosters and Core Stage and a fully charged upper stage will enter Earth orbit approximately 8 1/2 minutes after launch.
Spacecraft Launch Abort System (LAS) Discarded About three and a half minutes after launch, still in an early climb. "It probably depends on where you had a problem when you need to stop orbiting. The scenario would be if SLS has a problem at some point and you have already dropped the launch abort tower. Perhaps the safest place for the astronauts to go into orbit instead of escaping some kind of ballistic reentry. This would put them into orbit, "Jim Withrow said before the test.
He is the PQM Project Manager for the European Integration Office (EIO). at the NASA Glenn Research Center. "The mission would be finished until its final destination. This would put them in safe orbit, assess the situation and get them home.
Orion program after its cancellation and compromise rebirth at the beginning of the decade: In the event of below-average SLS performance, the Interim Cryogenic Propulsion Stage (ICPS) could also be used to close an ATO case, much like Apollo had launched on Saturn V. .)
On SLS, Orion has three abort modes: Mode 1 uses the LAS while it is still connected, Mode 2 is the ballistic, "Non-targeted demolition" and Mode 4 is an ATO. Orion was originally designed to launch with the launch vehicle of the Constellation Crew, which also had Mode 3 "Targeted Demolition Landing". On SLS, the functions of Mode 2 and Mode 4 overlap, and Mode 3 is not required.
Longest OMS engine in history
Media were invited to watch the test from the log cabin meters away from the test bench. Everyone in the area protects themselves from the test in the log cabin because of the toxic propellant gases and the high-pressure helium tanks.
WSTF is far from the nearest major population in Las Cruces, but the local winds are being monitored on personnel outside the immediate area and the staff of one of the ground station facilities of the Tracking and Data Relay Satellite Systems (TDRSS) were asked to provide protection during the test to offer because they were in front of the wind.
The helium tanks are composite-wrapped pressure vessels (COPV) that are pressurized to approximately 5000 pounds per square inch (psi) before testing begins. One of the last steps before starting the test profile was that some members of the test team left the shelter in the log cabin and secured the bottom helium systems for each good, fuel and oxidant after the tanks for the test had been pressurized one after the other.
The test profile was initialized in the afternoon, and after a lead time of five seconds, the twelve-minute detonating sequence started with the start of the RCS engines on its own and then by itself auxiliary engines. "We have about 30 seconds to get the RCS engines online, we'll heat them up, and they'll go through a kind of gas flushing process," Withrow said before the test. 19659003] "We will turn it off, we will turn on the Aux engines and they will run for about twenty seconds and then we will shut them off for about half a second," he explained. "Everything will be off in half that second, and then the OMS engine, all eight Aux engines, and two RCS Roll engines will be powered on simultaneously, about fifty seconds after the test."
The test on August 5 was the longest single spark of an OMS engine in its history. "The OMS engine runs for just over eleven minutes and thirty seconds, the Aux engines are running for the same time, and the RCS engines are running intermittently," said Withrow. After shutting down the Aux Engines and the OMS engine fired a bit RCS, and the test will be completed in about thirteen minutes. Then it will take about ten minutes for us to flush the Aux engines with nitrogen OMS engine. So the profile has expired in about twelve minutes, but the deletion is done again for about ten minutes. "
The test ran for the entire duration with the system running within the operating parameters. The team then conducts a detailed analysis of system performance and progressively certifies the propulsion system and its elements for the first-time flight with Artemis 1.
(Caption: Support equipment on test rig 301 for the hypergolic propellant used by the PQM. MMH is the fuel monomethylhydrazine and N2O4 is the oxidant nitrogen tetroxide, also called mixed oxides of nitrogen (MON-3).)  The ATO test is one of the load cases in the soil qualification series, which not only tests the engines and the fuel distribution, but also the pressurization. "One of the main objectives is the pressure control system, it has to do its job properly for these engines to ignite properly," said Withrow.
Pressure over or under pressure at the top of the fuel tanks is required to keep the engines running, and the tanks can not be completely filled to allow a little room for applying the required pressure.
"We do not have pumps that pump the propellant into the engines, but have helium in the tank. This is used to provide the power to propel the propellants to the engines themselves," said Withrow. "So you have to have some gas in the fuel tanks to apply this pressure. We fill them up, we fill these tanks like on a flight mission, except that there is only a small amount of empty space. "
" Once the engines start to ignite, the pressure control system will inject helium, but if you did not have a level, in other words, if the tanks were one hundred percent full, you could not actually provide pressure, there would be nothing, whatever pressure could provide.
Withrow added that another reason for not filling the tanks completely was thermal expansion. "If you did that with the fuel tanks and filled them up, we might have an extension," he said. "We do not want to lick these propellants."
During the test, the PCAs continuously filled the propellant tanks with helium while deflating to maintain the required idle pressure to allow the OMS and Aux engines to continue operating for 1 min.