Artemis 1 Orion returns to KSC after Plum Brook testing
Riding aboard NASA’s Super Guppy aircraft, the Orion spacecraft that will fly the Artemis 1 lunar orbit mission returned home to the Kennedy Space Center (KSC) in Florida on March 25 after four months of development testing in Ohio. The mated Crew Service Module (CSM) combo spent weeks in the thermal vacuum chamber of the Space Environments Complex at Plum Brook Station, as the civilian space agency and Orion prime contractor Lockheed Martin ran it through a series of tests.
The Glenn Research Center team monitored consoles around the clock while Orion spent almost six weeks in vacuum conditions in the chamber. The performance of the spacecraft’s systems was recorded at different thermal balance points simulating phases of flight and temperature extremes. Both the inside and the outside of the vehicle were tested at or near-vacuum conditions; technicians depressurized the crew cabin early in the test and then repressurized it while the chamber pressure remained essentially at zero.
The spacecraft came out of the tests in good shape and the data collected will help calibrate the different models that predict how it will behave in a wider set of in-space conditions. The current worldwide crisis with coronavirus disease 2019 (COVID-19) will delay the next steps, but once work can resume Lockheed Martin will complete final hardware installations and then turn Orion over to Exploration Ground Systems (EGS) for launch processing.
Back at KSC
The Super Guppy landed at Kennedy’s Launch and Landing Facility (formerly the Shuttle Landing Facility) mid-afternoon on March 25 after departing Mansfield Lahm Regional Airport in the morning.
The cargo aircraft made refueling stops at Fort Campbell, Kentucky, and Fort Benning, Georgia, on the way from Ohio to Florida. The multi-stop flight was postponed by one day due to weather.
Orion’s return home followed completion of its final major development test campaign before the Artemis 1 mission that is tentatively scheduled to launch 2021. Testing at Plum Brook wrapped up on March 9 and since then work there centered on preparing and packaging the spacecraft for its trip back to KSC.
The mounting realization of the COVID-19 worldwide pandemic affects nearly everyone and NASA re-evaluated whether or not to conduct the return trip now or leave the spacecraft in Ohio.
(Photo Caption: The Artemis 1 Orion spacecraft in the vacuum chamber at Plum Brook on March 14 following testing there. A media event was held on that day after most of the test equipment had been broken down and moved away and before the spacecraft was rotated back to horizontal and packaged for transport back to Florida.)
“In these weird extenuating circumstances we did have a lot of conversations over the weekend and on Monday and Tuesday of this week because we have support from the United States Air Force as well as the Ohio Air National Guard,” Nicole Smith, NASA’s Project Manager for Orion Testing at Plum Brook Station, said in a March 19 interview. “When we fly on the Super Guppy we stop a couple of times along the way for refueling at Air Force bases and so we had to ensure that we were able to receive support from all of the different entities that normally support us on the transportation.”
The spacecraft was designed to be assembled and tested in a vertical orientation but only fits in the Super Guppy aircraft horizontally, so work was held prior to the point where it would be rotated from vertical to horizontal to make the decision on whether to proceed or to stop. “We actually stood down with our floor operations for a few days because there does get to be a [decision] point,” Smith explained.
“The installation of the spacecraft onto the tooling that can lay it down or stand it up, that is a pretty complex maneuver to be able to lift it and do all those installations and then lay it down, so we didn’t want to do that and be told to hold here because we would have had to stand it back up to put it in a storage configuration. It’s much happier at vertical than it is in horizontal.”
On the way home the Orion retraced the trip it made last November in reverse. After being rotated to horizontal, the spacecraft was covered, connected to a portable air-conditioning unit, and then shrink-wrapped.
After being loaded on a flat-bed truck on March 21, a convoy of vehicles drove together the next day from Plum Brook Station in Sandusky, Ohio, to the airport in Mansfield. The Super Guppy arrived at the airport a few hours ahead of Orion and on March 23 the packaged spacecraft was lifted onto a special vehicle that loaded it into the Super Guppy for the flight back to Florida.
Electromagnetic interference testing wraps up Plum Brook test campaign
Smith was happy with the test campaign at Plum Brook and the results. “I think all the testing went really great and that sounds cheesy I know, but it really did,” she said.
The spacecraft arrived at Plum Brook in late November of last year and the thermal vacuum (T-Vac) portion of the testing began about a month later right around Christmas Day. The test campaign at Plum Brook Station concluded with evaluations of the spacecraft’s ability to handle different types of electromagnetic interference (EMI).
(Photo Caption: The Artemis 1 Orion spacecraft on February 21 during reconfiguring from thermal vacuum testing to electromagnetic interference (EMI) testing. The heat flux “cage” that surrounded the spacecraft during vacuum testing has already been removed.)
“We took it out [of the chamber] and spent a couple of weeks reconfiguring for the EMC (electromagnetic compatibility) test first and then EMI,” Smith noted. “The EMC test I think took a little longer than we had planned on the vehicle side.”
“They just had a lot of software scripts to run and things and I think they had like a day planned for it and they took about three days just making sure they were getting through all of it and that everything was right so that we could kick off the EMI testing.”
EMC testing first looked at whether the different spacecraft systems interfered with each other; it was followed by looking at how the spacecraft operated when subjected to external sources of EMI. “EMC is the electromagnetic compatibility and really what we do on the facility side is we provide an RF (radio frequency) quiet chamber,” Smith explained.
“So we use the thermal vacuum chamber and we put I call it RF-shielding treatments over every single thing where RF could come in or out, like any of the flanges where instrumentation would run through or we have a special personnel door that we put in there that seals very nicely so we get in and out without moving some of the big TVac doors for example.”
“We do all the shielding effectiveness checks to make sure we don’t leak RF outside where it could affect planes flying over or other people’s signals, and we don’t want to leak anything in because we want to make sure it’s a quiet space for the vehicle.”
“And then they run their systems together. Any electronic piece equipment has an electromagnetic field and if there are two things next to each other and they’re both powered up, talking to various things at the same time, that they are not going to accidentally trip themselves off or cause a computer to reboot or something like that.”
In contrast to EMC testing, the chamber was used to generate EMI to measure those effects on the spacecraft from external sources generated by amplifiers distributed around the chamber. “Anything that’s emitting some sort of an RF signal that may be very strong that we have to fly through, that’s considered a source and we’re looking at our system which could be sensitive to those signals,” Smith explained.
“We want to make sure that [for example] if we are sitting on the pad at Kennedy Space Center and the range radar is sweeping however often that we are not susceptible to the frequency and power level of that range radar signal.”
Before running the EMI tests the test equipment was calibrated with the real spacecraft now in place.
“As we moved into EMI the first thing that we had to do were loaded chamber calibration runs,” Smith explained. “In the past we’ve run those amplifiers with our chamber and our chamber had a test article in it, but it’s really hard to simulate the loading of such a complex, large spacecraft as the crew and service module so we wanted to be able to calibrate and ensure that the spacecraft was getting the correct power levels because they were reverberant and so we had to calibrate all of our sources.”
(Photo Caption: The doors of the cryo shroud are open when the Orion spacecraft was moved into the thermal vacuum chamber last December. The spacecraft was surrounded by a heat flux system to simulate in-space thermal conditions while its surroundings were at vacuum. The system allowed different parts of the spacecraft to be heated externally while the rest of the environment was chilled. The spacecraft’s own system of heaters was tested during cold stress conditions during thermal vacuum testing. Both hot and cold stress conditions were tested during the campaign.)
“There were seventy-three different sources and so that took a little while and while we were doing it we killed one of the amplifiers so we had to get a spare one pretty fast. It had already started acting weird and we’d already ordered the spare one so luckily we got it in before we really needed to use it again.”
“And then we had another spare on hand for a different amplifier and which we killed the second amplifier and we were able to use the other spare so it’s a long story,” she added. “We were running them pretty hard so those were our little test glitches that we had on our side, but we were able to pick right up and keep moving because luckily we had planned for those types of contingencies.”
“That took probably another week I would say of testing total for the EMI portion of it,” Smith noted. “You know the vehicle did really, really well, too. At the end we had a few things that we wanted to do a second investigation on and we just went back and took a look at those and we broke configuration on the night of March 9th.”
“[We’re] really, really pleased with how everything went and I think our European partner friends were really happy and Lockheed was happy and so were we and so ever since then we’ve just been packing up and trying to get it ready to go over the road to go back home to Kennedy.” The European Space Agency Service Module (ESM) was built by Airbus Defence and Space.
Thermal vacuum testing completed ahead of predicted timeline
The majority of the test time at Plum Brook was taken up by multi-week long thermal vacuum testing. Smith noted that a lot of planning went into supporting the test, both for expected needs and contingency cases.
“I would say it just took a lot of planning and a lot of contingency planning that most of which thankfully we did not have to use,” she said. “So in terms of the liquid nitrogen we worked really hard with our nitrogen supplier.”
(Photo Caption: The Artemis 1 Orion spacecraft is being broken over from its horizontal shipping orientation to its typical vertical orientation at Plum Brook in late November in preparation for testing that began shortly before Christmas. On its return trip, the spacecraft repeated these steps in reverse.)
The cryogenic fluid was used to help keep the cryo shroud area around the spacecraft in the chamber cool to simulate in-space temperature conditions. “They (the supplier) had an understanding that we were going to be needing about ten to twelve trucks a day during much of this testing,” Smith noted.
“We worked with them to bring in some temporary storage, so we had three large rotable dewars that we brought in here and plumbed up so if we had a big snowstorm and the turnpike was closed down for a day we could still keep running and keep everything safe here. So they were really good and we worked really hard with them and they were very supportive and flexible with us, which was great.”
“We had a lot of staff working around the clock and trying to balance that many people for weeks on end is always a little bit of challenge but that went really great,” Smith also noted. “And I’ll tell you we were Lysol-ing and Purell-ing everybody and everything in this facility way before COVID-19 came out because we were all here such long hours and in the control room for so many hours together that we wanted to make sure nobody caught a cold and sent it around to everybody, so we were pretty prepared I think from that perspective.”
“We have a backup generator that we have here just in case we lost power for any given period of time, a big diesel generator that could run the facility systems on so we wouldn’t lose the testing and just lots and lots of preparation and contingency planning for this. Plan for the worst, hope for the best.”
T-Vac testing ended up going faster than predicted. “The vehicle performed really, really well in thermal vacuum. We had allocated sixty-two days of T-Vac testing to be able to achieve all of the objectives that we were hoping to,” Smith said.
“We didn’t need to use it because we completed all of the thermal vac, thermal balance in forty-seven days, so it went really well. From the facility side, I was super happy with how the facility performed. It’s a fifty-year old facility, especially the thermal vac chamber and a lot of the associated systems, so for it to hang in there for forty-seven days that was the longest test we’ve ever done in that chamber.”
(Photo Caption: The packaged Orion is loaded back into the Super Guppy on March 23 for the trip back to Florida. After a one-day weather delay, the cargo aircraft landed at KSC with Orion on March 25.)
Smith noted that the thermal models had some uncertainty going into the testing, which will help calibrate them going forward. “When you perform a thermal analysis of a fairly complicated spacecraft like this one you look at the thermal properties of all the materials that are in it,” she said.
“I think it’s a very complicated thing to analyze and predict how long it will take the entire thing to get down to the level that you want [and] you know how long it will take to [thermally] balance it. This was their best estimate and they were pleased to find out that we were actually getting there faster than they had expected.”
“We were able to achieve all of the functional test objectives probably faster than they expected and that is probably a team efficiency thing,” she added. “You know all the software and [support equipment] gets checked out in an integrated software lab before it comes up here and they did a real good job with their homework before they brought the whole thing up here.”
While the external spacecraft systems operated throughout the test at vacuum, the crew cabin was also depressurized from its normal one atmosphere to not quite zero. One of the requirements for the spacecraft is that it support an emergency return to Earth if the crew cabin loses pressure, which could require operating for six days in that condition.
The spacecraft was depressurized to around one pound per square inch (psi) early in the T-Vac test. While the cryo shroud kept the test area cool, the Orion was also surrounded by a system of external heaters to simulate heating from the Sun.
The tail-to-Sun attitude that the spacecraft will typically fly in was simulated first, followed by cold and hot stress cases. “We completely repressed the cabin during the second cold stress case,” Smith noted.
“If you recall we did tail-to-Sun and then we brought it down to the first cold [test case] and then we did the hot stress and then we did a second cold and a second hot and then went to ambient. So we depressed right after tail-to-Sun and before we did the full first cold stress and then we kept it more or less depressed all the way through the first hot case and down to the second cold case where we brought it back up.
“I don’t think they had any problems at all with repressing that cabin, I think it worked great.”
COVID-19 halts Artemis 1 hardware processing
With the spacecraft back at the home of its final assembly and launch, Lockheed Martin will eventually finish its preparations for Artemis 1. For now, the spacecraft follows other parts of Orion and Space Launch System (SLS) hardware and testing into an orderly shutdown due to the impact of the COVID-19 crisis.
“NASA will temporarily suspend production and testing of Space Launch System and Orion hardware,” NASA Administrator Jim Bridenstine wrote on March 19. “The NASA and contractors teams will complete an orderly shutdown that puts all hardware in a safe condition until work can resume. Once this is complete, personnel allowed onsite will be limited to those needed to protect life and critical infrastructure.”
At a subsystem and integrated level, the spacecraft was designed to be built and tested in a vertical orientation, so before turning out the proverbial lights it will be placed back in the Final Assembly System Test (FAST) cell in the Armstrong Operations and Checkout (O&C) Building at Kennedy. Although some mission critical work at Kennedy continues with the Center at Stage 3 of the agency’s COVID-19 response framework, work on Orion is not on the critical path for Artemis 1.
The SLS Core Stage schedule for Artemis 1 is the primary critical path and Green Run testing at Stennis Space Center is on hold; Stennis at Stage 4 with all hands-on work suspended. With the Artemis 1 Orion ahead of the Core Stage, work will stop and wait for critical path SLS Green Run testing to resume.
With KSC still at Stage 3, work continues in the O&C Building on Artemis 2 Orion hardware; assembly, integration, and testing of the Crew Module and Crew Module Adapter is being performed by Lockheed Martin. In Bremen, Germany, Airbus is also continuing integration of ESM Flight Model-2 (FM-2); pre-COVID assessments had the ESM FM-2 standalone integration schedule as the critical path to Artemis 2, now with launch likely no earlier than 2023.
(Photo Caption: Prominent hardware installations in the future of the Artemis 1 Orion spacecraft have already been fit checked or fitted for earlier module-level testing. On the left, the mated Crew and Service Modules in the FAST cell in November were mated to the Spacecraft Adapter (SA) cone (left, bottom) as they will be again prior to handover to Exploration Ground Systems at KSC. On the right, both the SA cone and the solar array wings were installed on the Service Module for standalone Direct Field Acoustic Testing (DFAT) in the O&C last May. Those two sets of hardware will be connected and checked out with the spacecraft, along with the Service Module’s launch fairing panels.)
The Crew and Service Modules were mated in the FAST cell last Summer and part of the final assembly closeout work performed last year applied to both the testing at Plum Brook and configuring the vehicle for future launch processing. Once work can resume, Lockheed Martin will complete final installations including attachment of the four solar array wings to the Service Module, mating the Service Module to the Spacecraft Adapter cone, and installing the Service Module’s launch fairing panels.
Once those final installations and other closeouts are completed in the O&C Building, Lockheed Martin will turn over the spacecraft to Exploration Ground Systems for Artemis 1 launch processing. The spacecraft will be moved to the Multi-Payload Processing Facility (MPPF) at KSC for eventual loading of propellant and other fluids. The timing of those activities will likely need to be resynchronized with the SLS Core Stage schedule sometime in the future when there’s more certainty about COVID-19 recovery and Green Run progress.
Meanwhile, Plum Brook is planning on other spacecraft testing when the workforce can return. “After that, the Space Environments Complex team will be working on some Commercial Crew testing,” Smith said. “I know that we’ve got one Orion test left, which is [with] the returned Artemis 1 Crew Module. They’ll get the Crew Module back, they’ll clean it up after its flight and then they’ll send it up here and we’ll do acoustics, vibe, and some pyro shock testing on it.”