All or nothing breakover operation
The move to two-shift, round-the-clock operations is necessary because once they start the breakover process the lift team either has to fully complete it or fully back out of it.
(Photo Caption: Two different views of the quad pods supporting the weight of the Core Stage-1 engine section during the latter stages of its standalone integration this year. The left image shows them holding up the engine section in March in Area 51 where it was assembled and outfitted. The right image shows the quad pods supporting the engine section mated to the boattail in Cell A of Building 110 where they were bolted together in late March. The quad pod struts are tied into brackets bolted into the engine section’s structural SRB ring. Separate from the aft SRB attach fittings that are also integrated with the structure, the brackets will be used to pin the engine section to Boeing and NASA transportation tools while it is horizontal.)
As more and more equipment was added inside the engine section during integration, four “quad pods” were bolted into brackets around the lower SRB ring to support the growing weight. The engine section has a reinforcing structural ring in the barrel where the aft SRB attach points are also located.
While the engine section is in its current vertical orientation, Dillard said “the only thing it will sit safely on is the quad pods.” The brackets are also used during the breakover and to secure the engine section once it is horizontal, so the quad pods will have to be removed.
“We don’t have a ‘safe harbor’ if something doesn’t fit right when we get it hanging,” Dillard explained. “Say we pull all the quad pods off and go to put the bracket on and [it didn’t fit] — we can’t just go set it down, now we have to reinstall the quad pods, we only have this dolly to put it back on, so everything has to be undone to get back to where it’s at now and a safe harbor.”
“That’s why we’re going on two shifts to do it continuously. We told them if everything goes right it’s probably [complete at about] the eighteen, twenty-ish hour mark; [but] if we have an issue, you’ve got probably that much [work] on the backside of that to get it back to [vertical].”
(Photo Caption: The engine section/boattail are lifted out of Cell A in late March after they were initially bolted together. Much of this same configuration will be used for the first part of the breakover, with the crane connected to the yellow I-beam spreader bar as seen here. Instead of the lift brackets seen here attached to the top of the engine section, the I-beam will be connected to the breakover fixture, which will be positioned on the top of the engine section in the same relative orientation, parallel to how the I-beam is seen here.)
Picking up with the sequence, Dillard said: “The next morning we’ll come back, half of us will be on first, half of us will be on second and we’ll lift it. The four quad pods come off with the secondary crane, the two aft brackets will be installed, then that secondary tail crane will grab that big spreader beam out there and we’ll break it over.”
The second crane will attach to the +Z side of the engine section where the two tail service mast umbilical plates are. Both remaining pieces of the stage, the “four-fifths” and the engine section/boattail, will be oriented with the LOX feedlines at the twelve o’clock and six o’clock positions, so the second crane will raise the bottom-heavy engine compartment from the brackets bolted on the SRB ring to the outside of the two umbilical plates.
Another specialized tool for the horizontal engine section
Boeing modified one of its Core Stage Rotational Assembly and Transportation Tools (RATT) for the unique application of securing and transporting the engine section by itself while it’s horizontal.
(Photo Caption: Parts of the modified Core Stage RATT can be seen to the left of the engine section/boattail on the transportation tool as they were spotted in the Building 110 aisle on September 3. The semicircular upper roll ring can be seen just behind the RATT with the lower roll ring attached. In between the RATT hardware and the engine section and tools the two tripod jack stands are visible where the technicians and personnel are located. In the background, the Core Stage-2 LH2 tank hangs in the Vertical Assembly Center. After the engine section work is completed and it clears the aisle, the aft dome will be brought in to complete major welding for the second Core Stage.)
“The RATT originally was never meant to be used as a single tool, it was always a system with two RATTs,” Dillard noted. “There’s a full roll ring segment and there are actually more struts that have been fashioned.”
“The rotation capability of that RATT that the engine section/boattail article will go on is no more. We took that ACME-shaft that had the rotation capability out and created a new sub-frame to install it to then hold the struts that will balance that article out.”
In addition to the roll ring, which will connect to the same brackets around the SRB structural ring on the engine section barrel, Dillard noted: “we’re also tied on the aft where the boattail connects to the engine section where the join is.”
With the hardware now hanging from the two cranes horizontally, Dillard explained that one of the MAO SPMTs will pick up the modified Core Stage RATT and position it underneath instead of the cranes positioning the hardware over the RATT. “The reason being our SPMTs have much more fidelity and granularity to do minute adjustments than our 110 overhead cranes do,” he said.
“The RATT is actually pre-staged out there in Cell B. Once we get it broke over, we’ll drive [the engine section] over to where we want it, where we think it wants to be, on the cranes and then we’ll drive that RATT under it and we’ll fine-tune that RATT to match the article as its hanging.”
“We’ve learned over time it’s easier and faster to do that and use that SPMT to adjust things than to do crane movements a hundred and ninety feet in the air,” he added. “Safer for us, safer for the articles, all the way around.”
(Photo Caption: The rest of Core Stage-1 in Final Assembly on August 2. There are different types of RATTs; a “standard” Core Stage RATT is attached to the very front of the stage on the forward skirt seen on the far right here. After the engine section is mated to the aft end, those two RATTs will support the stage for the remaining moves and rotations of the final assembly sequence.)
The roll rings on the Core Stage RATTs are divided into semicircles, with the upper half detachable. The brackets on the -Z side of the engine section SRB ring match to similar bracket fittings on the roll rings, with pins securing the rings to the hardware. With the engine section/boattail now on its side, the heavy breakover fixture would now be hanging off the side without being braced, so jack stands will be placed under the fixture to keep the cantilevered load off of the engine section flange.
“So second shift rolls in, it’s broke over, now we start pinning it to the RATT,” Dillard said. “There’s some big blue jack stands out in 110. They’re about twelve, fourteen foot tall, they’re pretty huge.”
“Once we get it pinned to the lower roll ring segment, four pins, we’ll put those two jack stands on, that’s what’s going to hold the weight of that breakover fixture,” he added. “Then there are struts that are on the RATT that come up and interface with their article. Then we offload the weight from the two [crane] hooks, disconnect, now it’s safe.”
Summarizing, Dillard said: “Once we pin it, put the jack stands under the forward fixture, assemble the struts on the RATT, slack the cranes off, that’s probably about the next eight-ish hours, so we’re about the twenty-hour mark now if everything goes great, all the engineering works, then we can de-rig the cranes and that’ll be the stop of the breakover and install.”
The engine section/boattail with the breakover fixture still attached would now be supported by part of the RATT and the jack stands at that point, but still not quite ready to roll. “We have to finish building the RATT structure, so forward fixture would come off the next day, everybody would roll back onto first shift where we’ve got a full crew,” Dillard said. “The aft [lifting] brackets will be removed.”
“The upper roll ring pins to the same positions, interfaces to the same spots, that’ll be buttoned up. Forward fixture comes off, upper roll ring goes on, all the torquing happens and then hopefully we’re ready to move.”
The article would be ready to move, but Boeing is using high-resolution imaging of the mating surfaces to assist with the final mating. The flanges that will come into contact for the mate and other surfaces that will be mated later are “white-light scanned” and virtually brought together to check on their alignment before the physical mate.
“They’ve already shot it twice in the vertical orientation,” Dillard noted. “Once we break it over, we want to give them enough time to shoot it over here in the horizontal to see if anything deflected or anything moved before we go try and mate it.”
The rest of the stage was going to be rotated to the orientation for the mate and Ernst explained that the LH2 tank aft flange area was also going to be scanned again at that point. “In the engine section integration orientation we’re going to be white-light scanning the entire aft dome, focus on the flanges and the specific holes we’ll be monitoring during mate,” he said. “Correspondingly, we’ll be doing the same thing on the engine section once we have it broken over.”
(Photo Caption: Core Stage-1 elements on August 27. The top of the stage on the left was oriented to support installation of the aft systems tunnel segment. The engine section/boattail was still surrounded by scaffolding at this point; before that could be disconnected all the testing equipment and cabling had to be broken down first.)
“We want to know what [the engine section] looks like in the horizontal and what the hydrogen tank side does and that’ll all get loaded into our live PhotoG system that our supplier will be running for us and as we bring the two together we’ll be monitoring those locations so we know we have it lined up.”
A second SPMT will be brought in for the roll back to the final assembly area, also called Area 47/48. The rest of the stage was mated in Area 48 and is still there for this final mate.
“We’ll use two SPMTs for the travel from 110 over to Area 48, I call it 47 and a half-ish because it’s kind of in the middle of the two,” Dillard said. “It’s going to look quite precarious but we’ve run through the stress analysis on multiple different levels, single SPMT, dual SPMT under the RATTs.”
“It’s a speed-sensitive move so we’ve had to restrict our travel speed to no more than ten feet per minute because of the cg offset, what the tooling has been built to handle, and the g-loads/transportation loads.”
The floors of the different buildings at MAF are not flat and heavy-weight loads can move around a little, which is an important consideration when mating hardware with small tolerances for alignment. “You’re on coffee grounds down here, the floors float, right?” Dillard explained. “We’re in Louisiana.”
“That’s one of the issues we have to deal with all the time. We end up taking laser shots after we break something over and put it on RATTs. When we’re engaged under it, we’ll have them shoot it, then we’ll set the jacks on the RATTs, we’ll come out from under it, have them shoot it again.
“So our RATT bases from when we’re engaged to them to when they’re static and we’re not there, the floor will actually raise up and change elevation on them,” he added. “You’ve got to account for that delta.”
Those “floor deviations” keep the moves slow. “There’s spots that [deviate] five to six inches within thirty-five to forty feet, so when you have a forty-foot wheel base you eat that up,” Dillard explained. “Your floor deviation can overcome the allowed stroke, depending on that wheel base because the SPMTs, as good as they are, only have ten inches of stroke.”
(Photo Caption: Stairs are positioned next to the access door on the -Z side of the engine section on September 3 in the Building 110 aisle. There was still a dozen or so tasks for the engine section team to complete before the element was turned over to the lift team to do the breakover.)
“Ten inches sounds like a lot, but I have to start out in the center line of that stroke at nominal, so really I only have five on the top and five on the bottom.” (“Fixing” the floors is considered even more problematic since it would suspend critical operations within the Core Stage assembly and production process.)
Another factor keeping the speed limit for moves low is that much of the tooling being used to pull off the horizontal final assembly plan was designed and built in the last few months and is being used in many cases for the first or second time. “We take it easy with all of them, especially with the newer tools,” Dillard said.
Referring to the transportation tool that the engine section/boattail has been on since April, Dillard said: “This is a new tool. It works great but that’s the second time we’ve moved it from when we loaded it. We’re still hesitant to say ‘hey this is great, let’s go!’ so we take it easy.”
The drive back over to the final assembly area will slow down even more as the engine section moves up close to the LH2 tank. “Once we get over there about fifteen feet away we’ll then stop, pull one SPMT out, rotate a single one under it because we can’t get close enough with two sticking out the front of the RATT because of the interface,” Dillard said.
“We’ll have a collision with the PRS (Passive Roller Stand) that’s over there, so we had to rotate to one. We’ll slowly drive it in with one.”
Lead image credit: NASA