Boeing completes first NASA SLS engine section, getting ready for final Core Stage mate

by Philip Sloss

Breakover and mate

The engine section was designed for vertical integration; it was built in that orientation, and the original plan was for it to be stacked in that orientation. The stage was designed to lie horizontally during final assembly, including all its elements, but the first time the engine section would be physically tipped over in the old plan and rotated from vertical to horizontal was after the 130-foot long LH2 tank was bolted on top of it.

Credits: NASA/Steven Seipel (left), NASA/Jude Guidry (right).

(Photo Caption: The old way of doing it.  The engine section shown on the left in March mated to the boattail structure/fairing was designed to be mated vertically at MAF in this location, Cell A of Building 110. Under the original plan, the 130-foot long LH2 tank flight article similar to the qualification article shown on the right last November would have been brought into Cell A by itself stacked on top. That stacking operation would have had to wait until the functional testing being completed now. Instead, the LH2 tank was connected to the rest of the stage in late May, which allowed several further months of work before and after the connection to be accomplished on those upper four of five elements in parallel with the work to finish and test the engine section. Now the engine section and boattail have to be tipped over on their side to do that final connection with the rest of the stage horizontally over in Area 47/48.)

There’s no building at MAF tall enough to enclose a two-hundred foot tall stage and the LH2 tank is now lying horizontally as a part of the rest of the core, so the engine section has to be rotated to horizontal by itself. For the new, all-horizontal plan for final assembly, Boeing worked with Futuramic to design and fabricate one set of tools to put the front of the stage together and a second toolset is necessary for the engine section rotation or “breakover” from vertical to horizontal.

“There were four remaining tools to enable the horizontal assembly approach and two of them came in the early part of this week, Monday,” Williams said on August 14. “The last two are due in today, so that’ll complete our suite of tools for the horizontal assembly process.”

Credit: NASA/Eric Bordelon.

(Photo Caption: The engine section and boattail are slowly moved on one of the new tools through the transfer aisle in Building 110 at MAF in early April. Wire connections, orbital tube welds, and other work to fully integrate the engine section with the boattail was completed in mid-June, and subsystem checkouts were just completed in mid/late-August. The duo will now return here to the Building 110 aisle at the end of the month to be lifted and rotated from the vertical orientation shown here to horizontal. The engine section has been lifted several times before but the upcoming breakover will be a first.)

“It has about four days of operations over there where we break it over, we install a ballast system on it to allow us to break it over and transport it in that horizontal position and then we come back to 47/48 for the structural mating operations.”

Building 110, also known as the Vertical Assembly Building (VAB) at MAF, is where most Core Stage breakover operations are performed; although it’s not tall enough to stand up a completed stage unit, it has the height and the heavy-lift cranes necessary for components. Prior to their connection in late May, the cranes were used to lay down both the forward join and the LH2 tank on ground support equipment in the VAB.

The first step in the breakover is to drive the engine section boattail back to the VAB. “That engine section boattail tool that the assembly sits on right now, that big, blue, base tool, we’ll drive that tool from where it is currently parked back to 110,” Williams said.

Without the attached LH2 tank that gave the old plan’s so-called “aft join” the weight and balance that the completed engine section was designed for, the new tooling is a temporary substitute structure about ten to fifteen high. “We basically have, it’s like a truss system if you would,” Williams explained.

“It’s somewhere in the neighborhood of 8000 pounds, but it provides the ballast to enable that center of gravity of that engine section to be in the appropriate spot for us to be able to handle and manipulate the engine section to go horizontal.”

Williams explained that breakovers are a two-crane operation and the engine section is too short by itself for the VAB cranes to rotate. “This truss system serves two purposes, really,” he said. “The crane bridges were too close together and the engine section is not long enough to be manipulated by two cranes, so this truss system allows the two cranes to be used, obviously it separates the distance they [are] apart, with that extra [length].”

Credit: NASA/Jude Guidry.

(Photo Caption: Lines from two cranes are attached to the Core Stage-1 LOX tank in January at the start of its lift to mate with the intertank as a part of the forward join. For that operation, the tank was broken over from horizontal to vertical, starting with two cranes; once vertical, the second crane (in the foreground here) is disconnected. For the upcoming engine section rotation from vertical to horizontal, the process is done in reverse starting with a single crane lift, then connecting the second crane, then the breakover itself.)

Once the cranes have rotated the assembly to horizontal, it will be lowered down onto another set of modified tools. “We have a T-RATT system, the rotation and transportation tool, there’s a slight modification we’ve done to that for this extra weight and we’ll incorporate that new set of tooling into that T-RATT to allow it to hold this broken over the engine section,” Williams said.

The indoor Manufacturing, Assembly, and Operations (MAO) Self-Propelled Modular Transporters (SPMT) that Boeing uses to move tooling around MAF will then pick up and carry the horizontal engine section/boattail in its carrier back to Area 47/48, where the flange on the forward end of the engine section will be lined up with the aft flange on the LH2 tank.

“It’ll go on those T-RATTs and then traditionally how we transfer equipment, we’ll drive those SPMTs underneath that equipment and then drive it through the factory back from 110 inside the factory, we don’t have to go outside for these operations, and then come right into 47/48. [We’ll roll] from the same east part of 47/48, driving west to meet the aft end of the hydrogen tank.”

After the stage is fully joined, one of the tasks during the remainder of final assembly will be to reposition it in Area 47. “We’ll eventually move the mated portion because it’ll need those same test utilities and commodities that Terry has just used for the engine section so it’ll be on that side of the bay,” Williams explained.

Credit: NASA.

(Photo Caption: A composite of NASA 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-fifths of the stage is currently in the orientation on the right, but will 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.)

After the stage is bolted together, preparations for installing the engines will begin.  “We have to go to zero degrees for the physical mate, and once we’re mated we’ll go to what we call ‘ninety degrees up,’ and then that’s when we install the engine section horizontal platform,” Williams said.

“That’s a very complex set of tooling that goes up from the floor through the boattail, if you will, and allows the humans to access the volume to install the engines and we’ll stay in that rotation until done.  Once we’re in that rotation we’ll want to be in our final spot and install this tool, and then we won’t move the vehicle again.”

Boeing is still targeting completion of the work at MAF in December. “Yup, still holding December 10th,” Williams said.

(Lead image credit: NASA/Eric Bordelon.)

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