Engine section mate the last major join
Once functional testing of the engine section/boattail is complete and a “break of configuration” review is conducted to sign off on that, the assembly will have to be rotated from vertical to horizontal to support the last major join of final assembly. Additional tooling from Futuramic is being completed and is due at MAF soon.
“When we rotate this over from vertical over to horizontal that is a choreography like you wouldn’t believe, that’s a complex move,” Grow said. “It’s heavy, it’s got a weird CG (center of gravity) as far as the orientation right now.”
A fully-outfitted engine section was not intended to be rotated to horizontal by itself; originally the rotation wouldn’t have occurred until after it was mated to the LH2 tank. Part of the new tooling is a breakover fixture that will attach to the top of the engine section that is tall enough and heavy enough to help to move the center of gravity high enough to rotate the temporarily mated duo.
“They show up in the early part of July,” Ernst said of the newest Futuramic tooling. “It’s the equipment necessary to break the engine section over and then the interface to the SPMTs.” About the breakover fixture, Ernst said: “it’s really just a big box structure.”
(Photo Caption: The Core Stage-1 engine section and boattail at MAF on June 28. Scaffolding inside and outside provides access to all areas of the hardware for closeouts. The tented area in the lower right is where technicians enter and exit. The integrated assembly is now in functional testing, which will cover this stage’s role as both the first flight article and a path-finding development test article.)
The ceiling in Building 103 is too low to put that fixture on, so the first step in the sequence will be for the SPMTs to pick up the current tool the engine section/boattail is attached to and move it back into Building 110, also known as the Vertical Assembly Building (VAB) at MAF.
They will be set down in the aisle of the VAB, which has heavy-lift cranes to do the lift and breakover from vertical to horizontal. The new breakover fixture will be attached to the top of the engine section, and then after the lift and breakover to horizontal, the engine section/boattail will be put on another new transportation tool to handle it in that orientation.
The breakover fixture will be removed and the SPMTs will pick the transportation tool up and drive the engine section/boattail back to final assembly to do the final horizontal mate between the aft end of the LH2 tank and the top of the engine section.
“It’ll take about a day to rotate it over horizontally, and then it’ll take a couple of days to get it into position,” Grow explained. “You’ve got bolt holes all the way around there that you need to have lined up with the mating bolt holes on the hydrogen tank. You got hardware that’s coming in close proximity with each other and so it’s a very slow dance once we get really close.”
One installation item will be left until after shipment from MAF, the LH2 feedlines in the engine section that run from the bottom of the LH2 tank to the LH2 inlets on each of the engines. The full installation has to be done while the stage is in a vertical orientation, so that will be performed the next time the stage is vertical.
Although installation can’t be fully completed, the lines themselves are already staged inside the engine section. “They are currently in there in I’ll call it their ‘flight installed’ position and they are held in there by tools,” Grow explained. “So when we breakover [the engine section], that tooling will hold it in place so that it is ready to go and then we actually use that tooling to do the mate as well.”
Boeing will pick up with engine installations shortly after the stage is fully mated, with RS-25 engine specialists from Aerojet Rocketdyne watching closely.
(Photo Caption: Engine 2045 at MAF in late June, waiting to be the first engine installed in Core Stage-1. A couple of the transportation canisters that the engines were shipped in are in the background.)
The engines are lined up in the area next door to the stage in Final Assembly in installation order; they will be installed in sequence: Engine 2045 in position 1, Engine 2056 in position two, Engine 2058 in position three, and Engine 2060 in position four. “The engine installation sequence will be one, two, three, and four and the way that works is if you look at the back of the Core Stage it would be top-right, top-left, bottom-left, bottom-right, kind of in a counter-clockwise motion,” Andrew Rostron, RS-25 engine installation field engineer with Aerojet Rocketdyne, said.
To do this, the Core Stage will be rotated from the orientation for the engine section mate back to the current orientation the top of the stage is in, which puts the engine positions in that top-right, top-left, bottom-left, bottom-right orientation.
The handling equipment for engine installation borrows some from Shuttle, but the rest is tailored for the Core Stage. The part of the installation equipment that remains is the carrier, which physically attaches to the engine. “[It] is Hyster parts that were just converted over to the installer,” Rostron said.
(Photo Caption: A composite graphics showing the different Core Stage-1 orientations for upcoming milestones, as would be seen looking at the back end of the stage. On the left is how the stage will be oriented for engine section mate; on the right is the orientation for engine installation. The engine positions, which are also the order of installation, are numbered. The forward, four-fifts of the stage is currently in the orientation on the right, but first needs to be rolled ninety degrees counter-clockwise for the engine section mate. After that final join of stage elements is completed, the stage will be rotated back to begin engine installs.)
“Essentially the engine gets transferred to the carrier and the carrier gets picked up in another building with a higher crane and gets put on top of the installer.”
Once the carrier is attached to the engine, it will be lifted and attached to the top of a stand that lines up with the top and bottom “rows” of engines when the Core Stage is in the installation orientation. “That’s our installer,” Rostron explained. “Engines one and two are high up so there’s a spacer that comes off [the stand] for the bottom engines.”
Shuttle Orbiters in the Space Shuttle system were side-mounted and the three engines in the back were canted to help point their thrust through the center of gravity; the engines in SLS are not offset the in-line vehicle configuration. “They looked at it and I think just the floor loading and that huge, massive forklift with that Hyster and they went with this method,” Rostron said.
(Photo Caption: The tarp-covered engine carrier in the foreground and the installer stand in the background that will be used as a part of installation activities. The stand is configured to install the top engines, which is the planned sequence. The middle section is a spacer that will be removed for the bottom two engines. Boeing MAO SPMTs will drive the engine, carrier, and installer stand up to the Core Stage.)
Meanwhile, Boeing technicians will also be set up inside the engine section and boattail as each engine is driven up to the install point. As with the intertank kit, Ernst is working on the design and construction of the engine install kit to support the installs from inside.
“There’s kind of a base kit that you set up and then there’s different kits for engine locations, so it’s a modular set up,” he said. “We’re just at that point now where we’re incorporating lessons that we’re learning from the intertank in terms of the internal access kit into that, we have a little bit of time before we need it.”
Lead image credit: Aerojet Rocketdyne.