With all the structural test articles (STA) of the Orion spacecraft at prime contractor Lockheed Martin’s Space Systems facility in the Denver area, work is underway to qualify the elements for the Exploration Mission-1 (EM-1) and Exploration Mission-2 (EM-2) missions to the Moon. Testing of different combinations of spacecraft hardware in support of EM-1 and EM-2 will continue into 2019.
This phase of testing will help characterize the dynamic response of the structures and verify that the design meets the required factor of safety.
The Crew Module STA is currently set up in a loads testing fixture in the Structural Test Lab at Lockheed Martin Space Systems Waterton facility in Littleton, Colorado. It was shipped from the Kennedy Space Center (KSC) in Florida on NASA’s Super Guppy cargo aircraft in late April to Buckley Air Force Base near Denver.
The Service Module STA made the same Super Guppy flight a couple of months later after the Crew Module Adapter (CMA) and European Service Module (ESM) STAs were mated at Kennedy.
“We’ve done tests on two of them so far,” Dan Qvale, Orion STA Assembly Test and Launch Operations Lead with Lockheed Martin, said during an interview with NASASpaceflight.com.
“The crew module is actually in its second test, the first one was what’s called proof pressure — we went to 150% percent of the maximum expected internal pressure on the vehicle and validated that it structurally survived. That completed [at] Kennedy before we shipped it to Denver. Now that it’s here, we’re running qualification loads testing on the crew module primary and secondary structure.
“The launch abort system has been assembled and we’re also in qualification load testing for it now, it’s having a test run. And then the service module is being set up for the next roughly one month. The spacecraft adapter cone is being installed, the outer walls on the CMA are going on, and then it will go into a modal test of just the service module. And that will begin about a month from now.”
“Everything is on the LAS essentially except for the fact that it’s [an] inert motor. No antennas, but it has fillets, ogives, it has the MATA truss assembly (Motor Adapter Truss Assembly), [and] it has the inert motor. Structurally it has got all those components — the ogives actually provide structural load path for the launch abort system as well.”
Types of tests:
The STAs will go through different types of tests in the facilities at Waterton, including modal, loads, shock, and acoustic testing.
“The tests are broken up into different types of tests and in many cases they are in multiple configurations,” Qvale explained. “A modal test is a way we take measurements of the vehicle, its dynamic response, and they use those to validate the numeric models that they’re using to simulate and obtain load data analytically.
“They need these modal tests in order to measure the stiffness of the combined joints that connect all of the pieces together. And so you tend to run them in configurations your vehicle is going to be in.
“In our case, the first one we’re going to run is the entire stacked vehicle — SM (Service Module), CM, and Launch Abort System all connected — so that’s obviously a flight configuration on the launch pad and during ascent.”
“We run a modal test on just the CM alone, which is obviously a configuration it will be on reentry. We do a modal test on just the CM and SM, which is the flight configuration it would be in during the mission. We run one on the launch abort system connected to the crew module — the LAV (Launch Abort Vehicle) they call it — because that would be the configuration you would be in if you experienced an abort event.
“So those tests are for the most part being run in order to validate models for all these different configurations that the vehicle will be in or could be in during a mission.”
The second category of tests are loads tests.
“Those very much fall into the category of one-time only [tests],” Qvale added. “What we’re trying to do is apply loads for the major events the vehicle experiences during the mission to simulate those.
“You don’t just want the vehicle to survive the maximum predicted event, you want some margin on that — some assurances that it can survive and there’s margin on top of that. And so what we do there is we try to go to 140% of what the maximum expected load is going to be. For example, right now we’re testing both the launch abort system and the crew module.”
Qvale provided a breakdown of what they are trying to qualify/validate in the loads tests for the different elements, such as the all-important – for crew safety – Launch Abort System (LAS)
“The LAS is basically getting two primary things validated, one is the ascent loads so the compression that happens on the vehicle while you’re in nominal ascent. The other is abort loads, so qualification of loads that would be applied in the event that an abort actually happens and now instead of compressive loads you have large tension loads.”
“The crew module has a whole series of nine different events that we’re trying to simulate, so those include things like main parachute extraction. (Then) we’re running LAS load cases that represent the landing of the vehicle or the ascent of the vehicle. We’ve already run cases where we simulate the jettison of the forward bay cover.
“So it’s basically case-by-case cases where we take the hydraulic jacks, connect up to the vehicle, and then we’ll apply a load that’s intended to simulate what the flight-like the loads would be plus 40%. So as long as the design doesn’t change on the vehicle, it has been qualified and there’s no need to go revisit these.”
As Qvale noted, the initial loads test on the CM articles was done at KSC. Both pressure vessels were proof tested to verify that they would hold pressure up to 140% of the maximum pressure load expected during flight. Qvale noted that the flight article, which is still at KSC being fully outfitted for the EM-1 flight, was pressurized to 140%; however, the STA was taken up to 150%.
The third type of tests are shock tests, to evaluate how well parts of the structure handle pyrotechnic events during flight.
“[A] typical first flight vehicle would get “protoqual shock tested,” Qvale explained, “which means you can’t make the shock more severe, you can’t say ‘we did it plus margin.’ It’s as severe as it ends up being. You can’t add additional explosives to make it more severe, so instead what you do is you run it twice.
“So the way that Orion is going to be ‘protoqual-ing’ the shock environment (run it twice) is by number one doing it during the EM-1 mission and number two after EM-1 is recovered, we’re going in and running it a second time. All this needs to happen before we have a manned mission.”
However, Qvale added that the program is starting shock testing on the STAs before EM-1. “We don’t want to wait until the EM-1 mission to start making sure that this will work properly,” he said, “so what the STA is doing is we are measuring the shock response on the vehicle from these events.”
“We’re going in and say we have an avionics box [that is] near a shock source. We’re putting accelerometers on it, and then we’re running the shock event and we’re measuring the response at that avionics box and we’re comparing that with the screening requirements that we gave the avionics box supplier to design and test the box too. And so this should validate that what we gave them to screen this hardware too is enveloped by the measurements that we just took.
“So it’s essentially validation of the capability of the vehicle to survive shock and the combination of these measurements that we’re doing on the STA that will be compared with screening requirements that our EM-1 hardware was bought to and then ultimately validation by running the event during the mission and then running it a second time on the EM-1 vehicle post-mission.”
The Waterton test facilities are used by Lockheed Martin on all the spacecraft they build and have been part of Orion testing since the early days of the spacecraft.
“Both the test fixturing as well as the load control and data acquisition are incredibly specialized skills, and you’re applying loads that basically take the vehicle to the limit of what it’s capable of most likely,” Qvale explained. “[It] doesn’t matter if it’s Orion or another program, you tend to have the same objective there and it’s such a specialized area that essentially the Structures Test Lab does qualification loads testing for Lockheed Martin [Space Systems], period.
“Space Systems brings them their hardware to run these sorts of tests because its impractical that you’d have this expertise on a program, even if that program had hundreds of people on it.”
At the time of the interview, Qvale noted that the Service Module was waiting for one of the next generation Global Positioning System (GPS) satellites to finish using a test facility before it could move in.
Structural test hardware for all the spacecraft elements is there to support the test campaign, with mass simulators for some of the larger moving parts, especially on the Service Module assembly.
“We got the spacecraft adapter cone at the base, we have a flight-like OMS-E nozzle, we have a structural representation of the ESM so it has mass sims (simulators) instead of avionics boxes,” Qvale explained.
“On top of the ESM we’ve got the crew module adapter, so it’s made up of — similar to the flight-like one — it has all the longeron trusses, they’re called. The forward and the aft composite walls, the composite outer walls, mass simulators for all the avionics that goes in the avionics ring.
For the four solar arrays, we don’t have any flight-like solar arrays they’re all mass simulators. And then for the SM fairings — the SAJs (Spacecraft Adapter Jettisoned panels), they’re called — they’re essentially flight like, they have the harnessing on them to run the pyro tests.”
In addition, an Orion stage adapter STA also recently hitched a ride on the Super Guppy from the Marshall Space Flight Center in Alabama to Colorado. The stage adapter connects the full spacecraft stack to the launch vehicle upper stage.
Qvale explained that the tests are mostly focused on the spacecraft structure.
“For the most part it is just the structural elements. The only electronics that we are putting on the vehicle are harnessing that’s used to get to all the pyro-mechanisms, but instead of having an avionics box that fires the pyro-mechanisms we basically take test cables, mate up to the flight-like cables, and then use test equipment to fire the pyros. The only electronics per-se, is just the harnessing on the vehicle in order to run the shock tests. Everything else is structural.
“One thing that is important is we want to have similar mass in the right locations on the vehicle to run a lot of these tests and so we have mass simulators that basically have the appropriate weight and the appropriate center of gravity so that when they get bolted onto the vehicle from a structural standpoint it looks like a flight vehicle.”
Test campaign supports EM-1 and EM-2, runs into 2019:
This round of testing in Colorado will support the two Exploration Mission test flights that first cover the major phases of flight to the Moon and back without a crew and then with a crew.
“Right now the end of the campaign is [about the] middle of 2019,” Qvale explained. “One distinction here is that some of these tests are needed before EM-1 launches, but other tests are not needed until EM-2 launches. So the ones that are happening out in the 2019 time-frame are more the tests like of the LAV — the crew module with the launch abort system. [Those tests are] trying to gather data in support of if we had either a pad or an ascent abort on EM-2.”
“We’re predicting that all the prerequisites we need to complete before EM-1 launches are going to be completed by the beginning of November 2018, and thus far if you were to look at the start of the campaign, which we typically measure as the day that the crew module got delivered to Kennedy from MAF at this point, halfway through 2017 we’re essentially on schedule for all three vehicles.
“The SM is on schedule, the launch abort system testing is on schedule and the CM is within two to three days of being on schedule.”
Different hardware combinations will go through different tests at the Lockheed Martin facilities and the ordering of the test schedule was built based on multiple factors. “In general the philosophy of how we ordered the tests, was number one we had to look at ‘do any of these tests produce data that we need soon?’,” Qvale explained.
“One of the first tests we’ll run when we build the entire vehicle up — the full stack — is an acoustic test. And similar to what I told you about the shock test, this acoustic test is intended to be similar.”
“It’s only intended to take measurements at specific locations and validate requirements that we are having [the] flight boxes screened to, so obviously it would be a really bad day to find out very late in the flow that we never designed and screened the boxes to the values that they’re going to experience. So for example [placing] a test like that early in the flow — so that we can validate [the parameters] that all this hardware for EM-1 is getting designed and built around — is a good plan.”
Qvale added that the other part that determined the flow was that it takes a lot of time to build the vehicle.
“For example, when we put the SM fairing on, that’s on the order of twenty shifts of work to get it completed. You don’t want to take them back off or you’re going to have to go back through another twenty shifts worth of labor to reinstall them. So we ordered the flow so that if we build the vehicle one time, like we will be doing this Fall, we will knock out all the tests that need the vehicle in that configuration.
“There’s an acoustic test that’s stacked, there’s a modal test that’s stacked, and then we need to disassemble the vehicle to move it from one facility that has the acoustic chamber to another facility where were going to be running the loads testing. So rather than just dismantle the vehicle, we said let’s just run the shock test for the launch abort system. Just run the test, blow the pyros, and that’s what will separate the launch abort system and now that’s how you take it apart.
“So we tried to be smart about ordering things so that we got the maximum bang for the buck every time we had to assemble the vehicle.”
There are plans to use at least some of the structural test articles after all the testing in Littleton is complete — Qvale noted plans to use the crew module STA in a water impact test at NASA’s Langley Research Center prior to the EM-2 flight. Given those future plans and the extensive testing that will be done during the test campaign, the health of the hardware will be closely monitored.
“Let’s go back to the loads test for example. The requirement may be that the vehicle needs to survive 140 percent [of] the limit load. In the case of the crew module, maybe ‘survive’ means ‘not rupture’ but it could be bent basically when you’re done.
“For our purposes that doesn’t work because we can’t destroy the vehicle — we need to use it for the next year and a half. So during these tests, they monitor the health of the vehicle and if we believe we’re bumping up on the ultimate capability and we could damage it, then we curtail things and say ‘OK, let’s put completion of this test back on the shelf.’
“We’ll revisit it in a year and say ‘were we close enough — did we get to 138 percent and that’s good enough?’ Or do we need to 140 percent and let’s put the vehicle back in there and we’ll bend things on it to verify that it doesn’t rupture.
“Thus far, every single test we’ve run has essentially gotten to the 140 percent limit load with no adverse effects. So I think we’ll get the majority of these done the first time around and hopefully we’ll end the campaign and the vehicle will have seen some extreme loading, but it will still be completely viable to go use for another mission.”
Post EM-1 tests with returning Crew Module:
As noted earlier, the crew module that flies the EM-1 mission will also take part in gathering test data.
“When we launch EM-1, the launch abort system isn’t coming back, the service module not coming back, the fairings are not coming back — the only thing we’re getting back is the crew module,” Qvale said.
The first environmental test data set collected with the EM-1 crew module will occur as it flies the uncrewed mission to lunar orbit and then returns to Earth for entry, descent, and landing.
“The reason most spacecraft go through environments testing is to verify that they work after they’re exposed to the environment, so that’s acoustics and thermal and shock,” he added. “In the case of the EM-1 mission, there’s one environment that it’s not going to experience and that’s abort.
“And so part of what we’ll be doing with this post EM-1 flight testing is not only running the second shock test but exposing the vehicle to abort-level vibration and then validating that oh, by the way, all the mechanisms you need to survive and still operate after that did in fact work.
“Part of our plan long term to validate the abort environment is we’ll still have the STA service module and the STA launch abort system and the STA service module fairings. We’re going to take all those things, assemble the vehicle with the EM-1 post-flight vehicle, and we’re going to go back and run these shock events a second time.”
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