Working through almost all of the standard fortnight year-end holiday, Boeing’s final assembly team for NASA’s Space Launch System (SLS) Core Stage completed work on their first rocket with Core Stage-1 leaving the Michoud Assembly Facility (MAF) factory early on the morning of January 8.
NASA held a ceremonial event in early December to mark completion of work to install and interconnect all of the stage’s functional equipment. Boeing is the prime contractor for the Core Stage and the final assembly team spent the last month finishing integrated functional checkouts and final outfitting to prepare it for the upcoming Green Run test campaign at the Stennis Space Center in Mississippi.
Core Stage-1 was not just the first flight article to roll out of the factory, it is also the SLS Program’s first working article. As the final assembly team worked to finish their first core, they employed more improvisation, from finishing integration all horizontally during the year to a last-minute reparking idea to finish the last task in time for the rollout date.
Last-minute improvisation holds the rollout date
The last step was putting a weather cover on the front of the stage. In its flight configuration on SLS, the Core Stage’s forward skirt sits under the vehicle’s upper stage, covered by an adapter between them; during transportation and for the entire Green Run test campaign this year, the stage will be outside, and the weather cover provides shelter for the top of the rocket.
At just under 212 feet in length, the stage doesn’t fit very well in even the large Vertical Assembly Building at MAF, Building 110. “When you back it in you have eight inches on either side,” Amanda Gertjejansen, Core Stage-1 Operations Manager for Boeing, said in an interview.
Although it barely fits and the outside door can be closed, that doesn’t work for a couple of major operations there; the stage needed to be driven partially outside again and since it was backed in for those operations, that meant the weather cover would have to be attached with the front end of the stage outside.
(Photo Caption: The weather cover is installed on the front of Core Stage-1 during its rollout from the factor at MAF to the Pegasus Barge stationed at the dock. Windy conditions held up installation back in the factory until the Boeing production team decided to flip the stage around and repark the front end inside.)
“It’s on an SPMT (self-propelled mobilized transporter) actually, you’re driving it in,” she noted. “It’s like a big sail is what it looked like, really. It’s on a fixture.”
To align everything precisely and perform the operation safely, the wind needed to be light so the team improvised. “We looked at the wind and the wind was not going to work,” Gertjejansen said. “Actually I think Steve Ernst was the one who came up with the idea we just need to flip this around so we can do it in 110.”
The stage would be driven out, flipped around, and driven in front end first so it was now inside and the aft end of the vehicle was outside. As a consequence, that would move some other final work on the aft-end of the stage outside.
“Our team was doing final finishings on the aft end of the rocket, so that pushed us outside and so we were outside in JLGs (aerial lifts) and scissor lifts and everyone was like ‘oh, can you do that outside? Are you going to be able to work outside?,’ she said.
“This whole team is going to be working outside next week, so we’ve got to get used to it.” After the rocket was reparked in the Building 110 aisle, the finishing work picked up and the weather cover installation moved indoors.
“It went really smooth,” Gertjejansen said. “We flipped the rocket around, got the adapter ring removed, and installed the weather cover all within about fourteen hours.”
“That was the day before we rolled. That was the last thing we did.”
(Photo Caption: The back end of Core Stage-1 sticks out of the door of Building 110 at MAF the night before the rollout. Reparking the stage with the front end inside moved final detailing work around the engine section and boattail outside.)
Ownership of the vehicle was transferred from Boeing to NASA for the rollout, the first of many official handoffs as the stage moves first to Stennis and eventually to the Kennedy Space Center in Florida.
“NASA actually has the ownership of the stage right now, we did what’s called a DD 1149 which is a form that you sign that transfers the ownership of it,” John Shannon, Boeing’s Vice President and Program Manager for SLS, said on the day of the rollout.
“That’s the first one, and then when it is nine inches from the holddown posts (at Stennis in the B-2 Test Stand) they hand it back to Boeing, so we get it then and we do that final nine inches and put it into the holddowns and do some work setting up instrumentation for the modal test.”
Around eight in the morning on January 8, the full NASA and Boeing Core Stage team walked with the stage to celebrate its completion as it was driven out of Building 110 on the west end of the Michoud facility on the 1.3 mile trip out to the dock where NASA’s Pegasus barge was stationed to receive the stage.
Production team worked through the holidays to finish work
NASA held the “Artemis Day” event on December 9 at MAF to celebrate completing the work to install and connect all the functional elements of rocket. After being put together earlier in the year, the stage was still surrounded by scaffolding while lying horizontally in the Area 47 footprint of the Area 47/48 duplex in Building 103, where Core Stage Final Assembly takes place.
The final stretch of work on the stage was completing the Final Integrated Functional Test (FIFT), removing ground support equipment from inside and outside, and finishing final outfitting. At the time of the event, while the Boeing production team continued work to finish the FIFT and final outfitting, a pre-ship review was tentatively scheduled to be held on December 28, which would precede rollout by about a week.
The goal was to finish as close to the end of 2019 as possible, and most of the Core Stage-1 team worked through the two-week holiday for most of the NASA and contractor workforce.
(Photo Caption: The front door for the SLS Final Assembly area at MAF, Area 47/48, is opening on New Year’s Day as Boeing prepares to move the stage over to Building 110 for the final week of rollout preparations.)
The FIFT was a series of tests of the different subsystems to verify they perform together as a rocket stage to requirements and specifications. The test team typically holds a “break of configuration” review before they disconnect test equipment and move on; for this last segment of work before the stage left MAF, the build team and test teams synchronized work to proceed in parallel as much as possible.
“We did an incremental break of config,” Gertjejansen explained. “The two big things to get out to finish the rocket basically was removing that internal access kit in the engine section and one in the intertank. So we worked with [the test team] to prioritize getting the cabling out of the intertank which let us take the access kit out. And [the] same for the engine section.”
“So when they were done with the tests that were related to those cables and those access kits, they took those out and then that let us take the access kits out, which let us start rotating the vehicle so that we could finish up wherever we could get to.”
FIFT was completed just before Christmas.
“The test team managed to wrap up on the 23rd so they got to go home for Christmas,” Gertjejansen noted. “We had our whole production team here, but because we were towards the end, we didn’t need as many support people figuring out a lot of problems and looking ahead.”
“Usually we have the support team that is on the floor helping us work through immediate ‘fires’ and then we’ve got another team looking ahead a couple of weeks out, and so we didn’t need that team or those people. From a production side, we had probably about seventy-five percent of our team in.”
With work elsewhere at MAF, including the production of Core Stage-2, on hold for the holidays, Gertjejansen said about one-hundred people on her team continued to come in on three shifts around the clock through the break to get the stage ready to roll out of the factory. With inside access stands removed and some of the outside access stands moved out of the way, the team focused on completing final outfitting of the stage, which involved rotating it to provide better access to different areas around the circumference.
(Photo Caption: A comparison of the two Core Stage transporters. On the top, the Boeing Rotational Assembly and Transportation Tools (RATT) and white Manufacturing, Assembly, and Operations (MAO) Self-Propelled Modular Transporters (SPMT) hold the stage while it was moved to Building 110 on New Year’s Day. On the bottom, the NASA Multi-Purpose Transportation System (MPTS) rolls the stage out on January 8. The MPTS includes a beefier set of SPMTs to handle bigger loads and terrain that isn’t flat.)
“We started rotating Christmas Eve,” Gertjejansen noted. “We had to put on the [boattail] fairings, some Green Run sensor work — those cable routings that you saw all over when we rotated, we were able to put those on.”
“There were some access doors that had to go on, some of the final taping of that silver tape from everything that was up top. We basically rotated the rocket all the way around, flipped it upside down to work that underneath [area], putting covers on any of the ports or holes, that kind of final outfitting stuff.”
The silver foil tape on the bottom of the engine section and boattail is an additional layer of thermal protection that 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.
The team took off three shifts for Christmas. “Christmas Eve Day we were here, we took off Christmas Eve second shift. They came in Christmas night on third shift,” Gertjejansen said.
She noted there were other closeouts that needed to be finished. “We had to finish the systems tunnel covers, so we had to install all the systems tunnel covers,” she said.
“Some external TPS (thermal protection system) applications we did and there’s some ramp sprays, which we ended up doing some of that in [building] 110. And we had to tape up some of the surfaces and back out all access stands which took some time.”
(Photo Caption: The front end of Core Stage-1 sticks out of the Building 110 door as it was backed into the aisle on New Year’s Day. The stage could be moved in far enough to close the door with eight inches to spare on either end, but it had to pulled out in order for the cranes in the building to pick up the stage. The crane lift was necessary to switch from Boeing’s indoor transporters to NASA’s outdoor system.)
The team completed everything necessary and were ready to move the stage into the Building 110 aisle and hold the pre-ship review at the very end of the year. One of the last tasks while in Area 47/48 was to measure the weight and center of gravity of the stage.
“We did that New Year’s Eve,” Gertjejansen noted. “We used scales and put them under all the RATT (Rotational Assembly and Transportation Tool) pads. They put all eight of them under there and lifted the Core Stage up from the RATT, lifted the RATT feet up, and then set them back down a few times to weigh it.”
“We were ready to go on New Year’s Eve, and then the team decided to come in the next day and move,” Gertjejansen noted. “The team just didn’t want to get stuck out there. We weren’t ready until late in the afternoon, and the thought was if we leave now we can make it over there. But if something happens we’ll be stuck on New Year’s Eve night on the tarmac.”
“The actual move only took a couple of hours, but if we would have been stuck out there we would have people there on New Year’s Eve night. So there was some concern there,” she added. “But we ended up coming in the next day and it went just fine. We left here at six o’clock at night on New Year’s Eve and then we came in at 10 am on New Year’s Day.”
The stage was moved from the Final Assembly area in Building 103 a few doors down to the adjoining Building 110 and into the aisle there. “We moved the vehicle, and then we had some stuff we had to do with the door open. We wanted to get the plastic drape over the forward skirt before we closed the door because it was going to rain the next day. So [the teams] stayed until about 8 o’clock at night to finish that up and then they went home, so one long shift on New Year’s Day.”