White Sands readying OMEs for future Orion missions
Following the retirement of the Space Shuttle orbiters at the end of the program, all the hypergolic in-space maneuvering hardware was transported to White Sands for decommissioning. Each orbiter had a detachable forward RCS pod in the nose and two OMS pods on either side of the tail.
“They took the pods up to the 300 area, actually at 301 where you guys are going to be for the test,” Nick Buntain, Project Manager for Component Test Facility, said. “There’s a service building there that they set up where they could flush the pods with water to decontaminate them and then we went up and we helped them pull out the OMS engine and the thrusters off those.”
WSTF was certified at the end of the program as a maintenance facility for Shuttle maneuvering system engines, and is now refurbishing OMS engines to be Orion Main Engines for all future flights beginning with Artemis 1, a cislunar test flight which will be the first Orion mission to fly with an operating Service Module.
(Photo Caption: Technicians in a WSTF clean room surround OMS engine S/N 108. The nozzle is much larger than the rest of the engine and typically is attached separately.)
“All the OMS engines off the pods ended up here in our bonded storage, all the spares that were at Kennedy Space Center got shipped out to us and they’re stored here now,” Buntain said. The facility at White Sands has been refurbishing OMS engines for Orion.
“During Shuttle, we processed OMS engines and the subassemblies on the OMS engine, the series valve, the pneumatic pack, and various other components,” Buntain explained. “When it got repurposed for Orion, there were a few design changes.”
“We’ve added a heater onto the engine, we do a lot more non-destructive evaluation (NDE) after we disassemble the engines than we did during the Shuttle, and there’s a few more tests that we’ve added during the acceptance test portion of the engine processing.”
“The heart of the engine is really the series valve, it’s basically the valve that controls the flow of hypergolics to the injector that fires the engine,” he added. “It’s a series-redundant valve with four ball valves and a rack-and-pinion drive for opening the ball valves.”
Buntain explained that the engine has its own pneumatic pack. “Everything on the actuation pressure and purge pressure that the engine needs is all self-contained on the engine, it doesn’t come from anywhere else on the Service Module,” he said. “This high-pressure tank before flight is pressurized to around twenty-five, twenty-six hundred psi (pounds per square inch) and that’s all the pressure the engine needs for an entire mission.”
One of the overall objectives of the PQM tests is qualifying the engine for use on Orion. “Our operational envelope for OMS is larger than the Shuttle used for OMS,” Withrow explained in an earlier interview.
“We know it went through some qualification tests to get used for Shuttle and we know what those are. We are going to be operating within that original qualification envelope that Aerojet subjected that engine to, but they’re outside of the bounds of what Shuttle used, so we have some delta qual tests that we want to conduct inside a representative propulsion system for the ESM.”
(Photo Caption: OMS engine S/N 108 is prepped in the Test Stand 301 area to be installed on the PQM (not pictured) in February, 2017. White Sands is refurbishing the former Space Shuttle in-space maneuvering engines which were repurposed to be Orion’s Main Engine. S/N 108 was installed on the PQM and S/N 111 was installed on the Artemis 1 Service Module which is currently being prepared for flight in Florida.)
During a tour of the Component Test Facility prior to the test, Buntain outlined past work to support completing Orion development and current work there to prepare engines for upcoming Orion missions.
“So far we’ve processed the PQM engine, the one you’ll see firing today, that’s serial number (S/N) 108,” he noted. “The EM-1 (Exploration Mission-1) engine that’s out at KSC, that’s the first engine that we did for flight for Orion.”
“That’s also the first engine we ever processed for Shuttle when we got certified was engine serial number 111, which is also going to be the EM-1 engine.” EM-1 is now also known as Artemis 1, the S/N 111 engine was shipped to the Airbus assembly, integration, and test facility for ESMs in Bremen, Germany, minus its nozzle. Airbus installed the engine on ESM FM-1 in the Spring of last year.
S/N 117 is currently being worked on in the clean room and is currently assigned to Artemis 2. “This is the EM-2 (Exploration Mission-2) engine, it’ll be the engine for the first mission that has astronauts on it,” Buntain said.
“We’re actually disassembling that engine right now because there was some post-vibration test anomalies that occurred at JSC (Johnson Space Center) so they sent it back to us to do some failure analysis on it.” The series valve that was on the engine needs to be serviced, so it will be replaced with another unit while troubleshooting goes on with the suspect unit.
“We’re also in the process of building what they’re calling the EM-1 spare engine, which I think will become the EM-3 (Exploration Mission-3 or Artemis 3) engine if they don’t need a spare for EM-1. And then after that four, five, and six. So we have enough engines for doing that many.”
Buntain noted that while they have those three engines in process, S/N 117, 113, and 110, their flight and vehicle assignments could change between now and when they are needed. He also noted that they have hardware for about ten engines that can be used to support future flights.
“One of those became the PQM engine which obviously won’t fly, one of them has become a mass simulator out at JSC that they used prior to vibe (vibration) testing that we basically harvested a lot of flight parts off of it and sent it out there, and then we have a couple of parts engines. [NASA Glenn] had to do an assessment to try to identify which engines we wanted to use first, second, and so on down the line, and then we also basically identified two engines that we’ve decided won’t fly and those are our spare parts engines.”
PQM testing series nearing completion
Now that the ATO test case is complete, the test team is getting ready for another long test case. A Trans-Earth Injection (TEI) test case will see the Aux engines fire for an hour to test their ability to get Orion and crew from the Moon back home to Earth in a case where the Orion Main Engine is not available.
The OME provides 6000 pounds thrust, each Aux engine provides 110 pounds thrust, and the 50-pound thrust RCS engines are from ESA’s Automated Transfer Vehicle. Withrow said they are looking to run the TEI test in early September or maybe late August.
“In this case, because we’re going to be using such a large quantity of propellant for this [ATO] test, we have to get more propellant processed and ready to go to be loaded into PQM and that will take about two to three weeks,” he said. “It depends upon what we have to do to the propellant to get it ready, that’s the driver.”
(Photo Caption: PQM in the test stand at WSTF. The nozzles of the eight Aux engines can be seen at the bottom of the image; these will be fired continuously for an hour in the next test to simulate the long burn they would have to make if the main Orion engine couldn’t be used. Two of the four propellant tanks can be seen from this vantage point and parts of the black, spherical high-pressure helium COPV tanks can be seen behind them.)
“We need in that case we’re going to be loading up somewhere between five and eight hundred gallons of propellant of each commodity and getting that propellant ready to go is going to be kind of our long pole. Saturating isn’t a problem, we can saturate quickly here at this facility.”
Testing has taken longer than anticipated but overall has gone well. “Everything went really well with Step 1,” Withrow said.
“We have one more test to actually conduct with that, which is unsaturated. We want to do another priming test, you have to prime the propellant system the first time and we had an opportunity to do that when we were doing the initial blowdown testing in August of ’17.”
Withrow said they are going to purge out the RCS lines prior to repeating that test now with active pressure control available. “We want to conduct that test again in September and we’ll use unsaturated propellants for that one,” he said.
After these tests, there is some discussion about using PQM in the future. “There is some discussion for some ongoing testing for EM-3 missions,” Withrow said. “There may not be a need, we may be able to do a lot of that numerically with computers, but we’re not positive yet that that can be done. We’re still in discussions.”
Lead image credit: NASA/Rad Sinyak.