For the IMT, the test will require more or less dedicated access to the vehicle, so no other pre-launch work can be performed until it is completed. Current projections call for the IMT somewhere around the late-August to early-September timeframe. Once complete, ground-to-vehicle connections will be re-established, the internal volumes in the vehicle will be reopened, and Orion and the secondary Cubesats will be brought to the VAB for stacking.
After the full Artemis 1 vehicle is assembled and connected to the Mobile Launcher, a broader set of tests will begin. Another IVT will be performed, bringing in the Orion spacecraft connections along with tests that Blevins noted, such as communications end-to-end tests with the Flight Termination System and SLS guidance, navigation, and control (GNC) system, the program-specific engineering tests (PSET), and a countdown sequence test.
Once all of that testing is completed and any issues raised are resolved, the focus will move to preparations to roll the vehicle out to Launch Pad 39B for the first time, likely no earlier than late-October.
Meanwhile, apart from preparations for the test sequence, teams have been working on obtaining access inside the Core Stage equipment areas (the forward skirt, intertank, and engine section) to set up umbilical connections to the Core and ICPS stages ahead of vehicle power up.
“Just two days ago on Sunday afternoon (July 11), we got access to the engine section internal area again,” John Shannon, Boeing’s Vice President and Program Manager for SLS, said in an interview with NASASpaceflight. “The access kit was installed by TOSC (Test, Operations, and Support Contractor Jacobs), and we were able to get in there again. The internal work we’re doing is working on the umbilicals, working on ground test instrumentation, [and] installing [sensors] for the [Integrated] Modal Test that they’re going to do pretty soon.”
Four umbilical plates need to be connected to the Core Stage, and another one to the ICPS, for the powered interface verification test.
(Credit: Stephen Marr for NSF/L2)
(Photo caption: The SLS ML-1 at the perimeter of LC-39B at the Kennedy Space Center in October 2020. The major swing arms that must release from the vehicle at T0 are seen here running up the length of the side of the service tower.)
Another area of ongoing work is the installation of external sensors and wiring for the modal test. The final two pieces of test article hardware for the modal test, an Orion Stage Adapter (OSA) structural test article (STA) and an Orion mass simulator, will be stacked ahead of the upcoming tests.
Those crane lifts are not on the immediate work schedule and could occur early in August.
Launch team overseeing powered testing and checkouts
When the vehicles are powered up separately or together, testing and checkouts are led by launch team console engineers in the Launch Control Center. The Artemis 1 launch team has already supervised test operations with Orion while the spacecraft was in the Multi-Payload Processing Facility (MPPF).
“Orion has been testing off and on for the last six months, seven months,” Roberta Wyrick, SLS Test Conductor with Jacobs, said in a July 7 interview. “We loaded [hypergolic propellant] on the Orion, both oxidizer and fuel. Those were extended operations, up to two weeks. We’ve done helium pressurization of those systems. We’ve powered up. So they’ve done a lot of work, and we’ve been there [on console] for all of that.”
To prepare for the upcoming integrated tests, engineers have monitored critical test and launch operations, including the Green Run test cases on the Core Stage while it was at Stennis. “It was extremely useful,” John Sterritt, Main Propulsion System Specialist with Jacobs, said in the July 7 interview.
“There was all kinds of data that we got from the Green Run testing. Not just observing it, which was great in itself, but we were shipped the data so that we could analyze it here. We held some technical interchange meetings (TIM) with the Boeing folks, with everybody coming up to speed on how the Core Stage actually performed, and we used that to update many of the Core Stage requirements for [propellant] loading and terminal count based on that data,” Sterritt added. “[There was] a lot of pencil sharpening going on, and our requirements are much more mature because of it. So that was very helpful.”
Credit: NASA/Kim Shiflett.
(Photo Caption: Artemis 1 launch team members in Firing Room 1 of the Launch Control Center during a countdown simulation on November 2, 2020. The launch team will be supervising and conducting test procedures when the vehicle is powered up during the main part of Integrated Test and Checkout (ITCO) that is expected to get underway in August.)
Sterritt also pointed out that SLS has two cryogenic stages, and that they got the opportunity to see how ULA prepared the Delta IV upper stage for launch. The ICPS is a stretched version of the Delta second stage.
“We were also fortunate enough to be able to observe some of the launches on the Cape [Canaveral] side where similar second stages were used,” Sterritt said. “We got a chance to become a little more familiar with how that stage operates as well, which was helpful.”
The extended launch team, which will include groups on console in both Firing Rooms 1 and 2 for Artemis 1, is also continuing their training with launch countdown simulations. “The great thing about all of the work that we’ve got ahead of us is it is all necessary and required, and so [simulations] fall into that same bucket of ‘necessary and required’ and they get scheduled into the work in exactly the same way that any of the processing work [would],” Jeremy Graeber, Assistant Launch Director with EGS, said in the July 7 interview.
“Whether we’re lifting [vehicle hardware], whether we’re powering up, whatever it is that needs to be done as part of the critical path [is necessary and required]. Because ultimately, the simulations that we have on the plate are required for certifying our launch team to be ready for launch. And so they get scheduled in, and just like any other item, if there was a delay or an adjustment that needed to be made, those things can get moved around.”
The final major pre-launch test for Artemis 1 will be the Wet Dress Rehearsal, a full launch countdown that runs all the way down to within a few seconds of engine ignition. “This is as high-fidelity as we can possibly get without launching,” Graeber said. “The real intention of [WDR] is to demonstrate as much launch countdown specific configurations and capabilities as possible, as it relates to performing a Wet Dress and not a launch.”
“Obviously, if we’re not launching, the sound suppression water, the HBOIs (Hydrogen Burn-Off Igniters), those types of things are not part of what we’re going to exercise [in WDR]. There will be some things that we can’t do, but we’re going to do everything that we can do. It’ll be very, very high-fidelity.”
On “launch day” of the WDR, the vehicle will be fully loaded with propellant, taken through the same launch day timelines, pressurized for flight, and isolated from ground services in the final minutes and seconds before the planned T0 time. The launch team will twice run through practically the full terminal countdown, also practicing the ability to recycle the vehicle from a last-minute hold back to the point where the team and the systems are ready to make another terminal countdown run at launching.
“We do plan to do two runs,” Wyrick said. “We’re going to go down to [T-minus] 33 seconds and stop before ALS (Autonomous Launch Sequence) starts. And we’ll recycle from there so that we can test that portion of our countdown, that we can accomplish a recycle and get ready to launch again within our expected two-hour launch window.”
“So we have one of those [recycles] planned, and then the second time around we’re going to go down to [T-minus] 9.34 seconds and go into safing.” The Ground Launch Sequencer will run the automated countdown from T-10 minutes and counting down towards liftoff, sending commands to flight and ground systems to configure them for launch, verifying that those systems execute the commands correctly and that all the system parameters are remaining within Launch Commit Criteria.
At T-33 seconds, the GLS will hand off authority of the flight vehicle to the SLS flight computers, which will start the Autonomous Launch Sequence and execute all the flight-side commands and parameter validation. The GLS continues to have authority over all the ground systems, monitors key flight parameters, and has to issue a “Go for Main Engine Start” to SLS at T-10 seconds for the vehicle to continue the countdown.
During the first run of the WDR, the countdown will be stopped just before the handoff of flight vehicle control from the GLS to the ALS. Vehicle safing will be initiated and the countdown will be recycled back to T-10 minutes.
The WDR will be the first chance to test the recycle sequence on the real rocket, but the launch team has been practicing the procedures in simulations. “We’ve practiced [the recycle sequence] a lot,” Sterritt said. “We understand the software, we understand the procedures, we understand what it takes to get the tanks vented and then [to] get the propellant re-densified and reconditioned so we’re ready for that second terminal count.”
Credit: NASA/Cory S. Huston.
(Photo Caption: The Artemis 1 Orion spacecraft arrives in the Launch Abort System Facility (LASF) with its air conditioning unit luggage in tow on July 10. The Launch Abort System (LAS) tower on the left will be stacked on top of the Orion stack which currently consists of the Crew and Service Module and the Spacecraft Adapter. After the LAS tower is attached, the ogive-shaped fairing panels will be installed, encapsulating the Crew Module.)
“We don’t really see any major obstacles through it, so we will definitely be looking to see how the timeline works out. But we got all the requirements laid out and scheduled and it certainly appears that it’ll work without any issues.”
“John makes a good point in that his team has done an amazing job working through and simulating all of those steps and those operations,” Graeber said. “Roberta and [NASA Test Director] Jeff Spaulding have done a good job pulling all the procedures together to make it happen and we actually demonstrated that recycle operation in our last launch countdown sim. So we’re going to do that more, several times I expect, before we get to Wet Dress, so when we do it for real with the vehicle at the pad it’ll be the first time we’ve done it that way but it won’t be the first time we’ve done it.”
After recycling the vehicle and ground systems to be ready to count down again for the second terminal countdown pass in the WDR, the GLS handoff will be completed and ALS will take control of the vehicle for the final seconds before T0. The SLS flight computers running ALS will start the SRB hydraulics, make sure the Core Stage RS-25 engines are ready to start, and get ready to issue start commands before cutoff is given — which will initiate an automatic safing sequence.
The launch team will be organized for Artemis 1 with the SLS Test Conductor seated next to the NASA Test Director; however, for Artemis 2, a crew will be onboard Orion for the first time, and the communications priority changes.
“Right now, the SLS Test Conductor is sitting next to Jeff Spaulding, who is the NASA Test Director for Artemis 1, but I believe for Artemis 2 the Orion Test Conductor will be sitting next to Jeff,” Wyrick said. “They have the more integral role [on Artemis 2]. Taking nothing away from the SLS Test Conductor, but [the Orion Test Conductors] are speaking with the crew, so Jeff needs to be next to them so that they can communicate and keep tabs on what’s going on with the crew.”
“[On the] Artemis 1 mission, we’re very focused on first time flying the Core Stage, first time flying with that avionics suite and those things, so having STC next to the NASA Test Director is important,” Graeber added. “Once we demonstrate that, the next mission will be Artemis 2.”
“[What’s new on Artemis 2] is a fully crewed Orion spacecraft, so again having that new part of the team and added systems as well as the crew obviously really kind of puts the focus and the emphasis on that. So as Roberta mentioned. that is something that we’ve thought about. Clearly we’ll be working to learn from everything that we do and make decisions about how that Artemis 2 team will be configured going forward.”
(Lead image credit: NASA/Glenn Benson.)
