Remaining “pre-ship” work
Back at MAF before the pre-ship review for Core Stage-1 starts, the outstanding tests and final outfitting need to be finished. In addition to installing the boattail fairings around the engines, the systems’ tunnel cover plates have to be installed.
“The systems tunnel covers are going on, they’re going on during FIFT, so we won’t wait for those,” Gertjejansen said. “As we close out, as we run those tests, we’re going to be doing those. Probably before we finish testing we’ll have all the covers on.”
Final thermal protection system (TPS) closeouts, where additional spray foam is applied, also need to be completed; one of those includes the seams where the systems tunnel cover plates are fastened to the tunnel base plates. “We call them ‘ramp sprays’ and they’re along the seam.”
Credit: NASA/Bill Ingalls.
(Photo Caption: NASA Administrator Jim Bridenstine (left) speaks to U.S. Congressman Randy Weber of Texas (right) on the lower access platform right next to Core Stage-1. Behind them, the uncovered systems tunnel and -Z side LOX downcomer span practically the length of the picture.)
“If our stands are still in place we’ll just walk down or the other thought is that it might be easier to drive with a scissor lift across, so we’re looking at about one night probably on third shift during rotations, stopping and taking a scissor lift and going down [the length of the tunnel].” The tunnel extends almost the full length of the stage on the -Z side, from the bottom of the forward skirt to the top of the engine section.
Other closeouts are being worked in as functional testing finishes in that area. “TPS closeouts right now are following very closely behind mechanical work, it’ll be as you put the covers on, you spray,” Gertjejansen noted.
An additional layer of TPS has already been applied to several areas of the boattail specifically for the Green Run hot-fire test. Foil tape was put on top of the layers of cork and paint to mitigate the heat damage they might see during the long test firing planned in the stand at Stennis.
“Underneath is the same kind of the thermal protection system you see on the [engine section] barrel, it’s just that we’ve covered it with the foil,” Michael Alldredge, NASA SLS TPS Team Lead, said. “The reflective foil is really just there to survive Green Run, so that we don’t burn up the stage.”
“It’ll cover a lot of the aft-facing sides if you will, because we’re worried about heat loads in the stand which are much different than during ascent because you’re not flying,” he added. The issue with the heat loads in the stand during the firing is their duration.
During a launch, the vehicle accelerates out of the dense atmosphere quickly and the heat load diminishes; during the static hot-fire test the heat load remains on the vehicle for the full eight minutes the engines are firing.
The tape is mostly installed, although obscured by the work stands around the boattail. “Actually when you go look at the engines most of that [boattail area] is taped,” Gertjejansen noted.
“There’s a little left [to put on], it’s either due to rotations or we plan to do it at Stennis because of access and things that need to come off once we go and get in the stand and do modal testing. That would still get done there.”
Credit: Philip Sloss for NSF.
(Photo Caption: Some of the silver-colored foil covering down-facing parts of the boattail can be seen in between engines one (right) and two (left). The foil is only needed for additional thermal protection during the Green Run hot-fire test because the stage and the down-facing parts of the boattail, in particular, will be exposed to a constant heat load from the firing engines for eight minutes at basically sea level. The boattail has the same cork and white Hypalon paint as the rest of the engine section barrel underneath the foil. It is hoped that the foil will reduce the amount of TPS refurbishment necessary after the hot-fire test is completed.)
Gertjejansen also explained that the closeouts on the seams of the boattail fairings will also be deferred. “Those come back off at Stennis, so we won’t be doing those closeouts here,” she said.
“We have to take them off, do some work, we’ll put them back on, do the cork right around the edge because you got where the fairing goes to the boattail. We’ll put the cork on, and then we’ll paint it and put tape on at Stennis.”
In addition to the external detailing closeout work, the horizontal access kits and other ground support equipment (GSE) needs to be removed from the stage; kits set up inside the intertank and engine section are still supporting FIFT and final shipping preps.
“Intertank access kit will start coming out after we do tank pressurization,” Gertjejansen said. “After tank pressurization, we’ve got to install a purge duct and we’ve got to do a couple of TPS closeouts and then we will take the access kit out.”
The access kit threaded through the boattail volume to support engine installs and FIFT will be disassembled piece by piece once access inside it is no longer required. “You work them all through a hole,” Gertjejansen explained.
“We have built that kit up multiple times and taken it down multiple times, so an example the intertank access kit which is very similar, we got that out in a day and a half. So we’re looking at being able to get that out almost as fast. They have practiced tearing that down, taking it down piece by piece, multiple times prior to it going in there.”
The pre-ship review is planned to coincide with the move of the stage from its current location in Area 47/48 over to the aisle of Building 110. Also known as the Vertical Assembly Building at MAF, it is a high-bay equipped with heavy cranes that will allow the stage to be transferred from the RATTs to NASA’s Multi-Purpose Transportation System (MPTS).
The plan now is to leave as little other work to do in 110 besides that crane transfer, finishing it before the move. “We’re trying to pull everything as far left as we can and get it all done in 47,” Gertjejansen said.
“So we’ve pulled a majority of that scope back to 47/48, so when I say all this final outfitting, all those covers those are trying to get on before it goes over to 110.”
“There’s very little left to do in 110. It’s taking the roll rings off and transporting it into the HIS, to the NASA transporter, and that’s all the scope because when we get over there you’re going to have the door open for a couple of days,” she added.
Credit: NASA/Bill Ingalls.
(Photo Caption: A view of Core Stage-1 from the upper platform level looking toward the front of the stage from the aft end. In the far background Boeing Director of Operations at MAF Jennifer Boland-Masterson, NASA SLS Deputy Program Manager Chris Cianciola, and Marshall Space Flight Center Director Jody Singer provides a tour of the stage to NASA Administrator and U.S. Congressman Randy Weber of Texas. The group is adjacent to the ground-side plates connected to the flight-side plates for the Core Stage Inter-Tank Umbilical (CSITU). Near the base of the platform, the gaseous oxygen and hydrogen repressurization lines run from the engine section “up” towards the top of the two propellant tanks.)
The stage is secured to the RATTs by a two-hemispheric-piece roll ring on either end; the top piece is removed to allow the cranes to be attached to the stage. After the cranes pick up the stage, the RATTs will be moved out and the MPTS moved in.
For a full Core Stage, the NASA MPTS transporter configuration includes a common Hardware Interface Structure or HIS that connects to the engine section and two forward HIS elements that connect to the forward Solid Rocket Booster (SRB) attach points on opposite sides of the intertank. Each HIS is attached to a table-shaped multipurpose carrier (MPC) that is picked up by SPMTs to move the whole transportation assembly.
Now that it is fully assembled, the stage is just under two-hundred twelve feet long and will take up most of the Building 110 aisle, perhaps even going into the footprint of the adjoining aisle of Building 114. With additional GSE attached, the door that opens to the outside has to be left open until the stage is fully transferred to the MPTS.
“We get it onto the NASA transporters and then we move it in and get the forward cover on,” Gertjejansen noted. A forward weather cover fits on top of the forward skirt for protection when the stage is outside in this pre-launch configuration.
Stennis Green Run preparations
Preparations at Stennis in the B Test Complex area to accept the Core Stage and support the beginning of the Green Run campaign are also nearing completion. Above and beyond B-2 facility readiness, Boeing is finishing up the first phase of Stage Controller work.
“It’s a couple of weeks from being complete, we’ve got it cut up into two phases,” Nappi explained. “I talked about power-up testing that we’re going to do first, that’s the Phase 1 Stage Controller.”
“That’s going to be ready about the mid part of January so that the current emulator can be disconnected and the vehicle can be hooked up. And then Phase 2 set of software with some minor modifications — there’s still some work that has to be done for hot-fire — will be available at the end of March.”
Credit: Philip Sloss for NSF.
(Photo Caption: As seen on December 10, a lift spider and the trailing crane that will both be used to breakover the stage when it gets to the B Test Complex. The lift spider is held in a Transportation Interface Fixture (TIF) that supports its 45,000-pound weight while it is being attached to the top of the forward skirt of the stage. The trailing crane will be attached to brackets on the +Z side of the engine section while the B Stand’s derrick crane is attached to the lift spider. The two cranes will lift the stage off of the NASA transporters and break it over from horizontal to vertical.)
The Stennis team will hold a review in parallel with the pre-ship review to verify they are ready to begin testing when the stage arrives. “We’ll do what we call a TRR, the Test Readiness Review, that will review once the vehicle gets here what is everything that has to be done [in] that first three weeks of modal test,” Nappi said. “It’ll probably be a day or two after the pre-ship review, which is tentatively scheduled for the 28th.”
“That’ll essentially get us into the position where we’re going to be satisfied that we’re ready to accept the Core Stage and start immediately once it gets here; and of course there is [also] the facility readiness reviews at Stennis.”
The test team is also continuing to run through simulations of different parts of the campaign. “We’ve done several actually,” Nappi said.
“We’ve done six training sessions so far, two full-up hot-fire simulations with failures so our test team is ready for when we do it for real and we’re going to do a third hot-fire training session at probably the end of January, beginning of February.”
“The facility is kind of going through the same type of operation, so we’ve actually got something planned for this Friday (December 13) where we’re going to go through and simulate a 24-hour countdown and try to find weaknesses in our approaches,” Vander added.
Credit: Philip Sloss for NSF.
(Photo Caption: A ground-level view of the B Test Stand on December 10 with the B-1 position closest (middle of the image) and the B-2 position farthest (to the right). The stand’s derrick crane and the top of the contractor trailing crane can also be seen.)
With all the new software and avionics on the stage and on the ground side, NASA and Boeing are also gearing up support groups for Green Run.
“I have a small Stage Controller group who are responsible for getting the Stage Controller connected to the vehicle, making sure that it is working properly on the test stand,” Nappi explained. “Once we start testing we expect that there’s going to be some problems with either the interface with the vehicle or potentially the Stage Controller itself, so the small group of folks are relocating from Huntsville and Florida that were part of the development of the Stage Controller. [They] will come down here and be supportive of all those tests and addressing any issues.”
“Marshall will also send engineering from our flight software group because the flight software that’s being loaded onto the flight computers is very similar to the flight software that will fly, it’s called GRAS (Green Run Application Software),” Lisa Bates, NASA SLS Stages Deputy Manager, added. “We will also bring them down here to work with Boeing to make sure that they have full support when they need things for either the vehicle or the emulator.”