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The structure of the engine section for the Artemis III core stage was transported to KSC last December for outfitting with all of its working equipment, which will be done from now on in the Space Station Processing Facility (SSPF). The rest of the stage will continue to be assembled at MAF and then that \u201csubassembly\u201d of the other four of the five major stage elements will be transported by barge to KSC for final assembly in High Bay 2 of the VAB.<\/p>\n
\u201cThe current forecast is the end of next year to move into the high bay,\u201d Tim Burroughs, Boeing\u2019s Integrated Product Team Lead for both Core Stage-2 and Core Stage-3, said in a recent interview at MAF with NSF. \u201cObviously that depends on the readiness of the bay and the readiness of the engine section, but right now it\u2019s postured to be at the end of next year.\u201d<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2023\/12\/CS-3-Intertank-Composite-watermarked.jpg\")
<\/p>\nTwo views of the intertank for Core Stage-3 in its integration area at Michoud in October. (Credit: Philip Sloss for NSF)<\/p>\n
Outfitting or \u201cintegration\u201d of the engine section typically takes the most amount of work and time to complete and is therefore often the primary schedule driver or \u201ccritical path,\u201d but issues with completing the liquid oxygen (LOX) tank structure have pushed its production timelines and those related to it out into a similar timeframe.<\/p>\n
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\u201cFor Core Stage-3 (CS-3), the LOX tank is critical path to \u20184\/5ths\u2019 join,\u201d Burroughs said. \u201cIt\u2019s pretty much neck-and-neck with where engine section is forecast to be complete.\u201d The \u201c4\/5ths\u201d join refers to the other four major elements of the stage besides the engine section \u2014 the forward skirt, LOX tank, intertank, and liquid hydrogen (LH2) tank.<\/p>\n
The top three elements of the stage, the forward skirt, LOX tank, and intertank, are the first to be connected, with \u201cmajor join 1\u201d also frequently referred to as the \u201cforward join.\u201d Those three elements are stacked vertically in Michoud\u2019s VAB, which stands for Vertical Assembly Building at the New Orleans factory.<\/p>\n
After those three sections are joined together structurally and functionally, the forward join is rotated to horizontal and moved into the final assembly area at MAF, where the bottom of the intertank is mated to the top of the LH2 tank to begin integration of the 4\/5ths assembly.<\/p>\n
The LOX tank had been progressing toward structural completion over a year ago in 2022, but that milestone is being held up by a problem with welding the aft dome of the tank. \u201cWe don\u2019t believe there\u2019s a specific issue with the weld in and of itself,\u201d Matthew Stites, Boeing SLS Chief Engineer, said in the recent NSF interviews at MAF.<\/p>\n
\u201cIt\u2019s really the as-built condition of the gore body coming off the prior tool, the GWT (Gore Weld Tool), that we think is primarily the contributing cause to what we\u2019re seeing when that part moves to the CDWT, the circumferential dome weld tool. There\u2019s nothing specific about that weld that we think is problematic, it\u2019s really about the as-built condition of the dome, it\u2019s a little bit bigger than we were expecting it to be.\u201d<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2023\/12\/P1210772-watermarked.jpg\")
<\/p>\nCredit: Philip Sloss for NSF.<\/p>\n
(Photo Caption: The elements of the LOX tank aft dome for Core Stage-3 are seen in the dome welding tool at MAF during welding preps in October. The dome tool is used to perform circumferential, friction-stir welds to the end cap, gore body, and Y-ring.)<\/em><\/p>\n
The domes of the propellant tanks are welded together in the CDWT from a ring, a gore body, and an end cap. The GWT uses friction-stir welding to assemble a gore body from 12 gore panels and what NASA and Boeing saw was the resulting gore body was slightly out of its allowable dimensions.<\/p>\n
\u201cIt\u2019s the overall, correct, assembled dimensions,\u201d Terry Prickett, NASA SLS Stages Office Chief Engineer, said. \u201cWhen you weld these gore panels together and produce this gore body, you had a stack-up that went around, due to the tooling having some issues with it, when it produced a gore body that\u2019s dimensionally slightly out of tolerance.\u201d<\/p>\n
The problems were discovered with the first aft dome welded in the CDWT; the teams elected to set that article aside for now. \u201cWe\u2019re working the path forward on whether we can use that dome,\u201d Prickett said. \u201cFor schedule purposes, to use that dome was probably [going to require] a fair amount of testing to be done offline, and for schedule purposes we just set it aside for now and elected to build a new replacement dome.\u201d<\/p>\n
Both the Boeing and NASA teams have been going through the \u201croot cause corrective action\u201d (RCCA) process for the issues. \u201cWe went in and performed RCCA and that uncovered several things, both production-related and tooling-related, that we have corrected on that tool,\u201d Prickett noted. \u201cThe reason it\u2019s most important on this aft dome is because that\u2019s the one that\u2019s got the most critical weld on it, which is that aft dome cap, which has got the lowest margin weld that we have.\u201d<\/p>\n
Once the aft dome is completed in the dome welding tool, it will be prepared to be welded to the rest of the LOX tank, and then the tank will be prepared for the forward join (major join 1) next year. \u201c[There\u2019s] about 11 months from the time that the dome is complete [until] we should be able to go to a major join 1,\u201d Burroughs noted. \u201c[That would be] followed immediately by 4\/5ths, and then do some outfitting here and then we\u2019ll be able to ship it down, ready for the VAB about the end of the year, that\u2019s where they\u2019re kind of lining up with the engine section and being ready in the VAB.\u201d<\/p>\n
In a mid-November statement provided to NSF by public affairs, NASA\u2019s SLS program said, \u201cNASA and Boeing, the SLS core stage lead contractor, are undergoing final weld preparations and fit up operations at NASA\u2019s Michoud Assembly Facility in New Orleans for the final friction-stir weld for the aft dome of the liquid oxygen tank for the Space Launch System core stage that will support the Artemis III mission.\u201d<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2023\/12\/P1210644-watermarked.jpg\")
<\/p>\nCredit: Philip Sloss for NSF.<\/p>\n
(Photo Caption: The top three elements of the Core Stage-3 LOX tank are seen in the Vertical Assembly Center (VAC) in October. The forward dome and two barrels were welded together in the VAC over a year ago and are waiting for the aft dome to be completed to allow the full tank structure to be welded.)<\/em><\/p>\n
Work to outfit the engine section is progressing in the SSPF at Kennedy, with the goal for that to be complete in the end-of-2024 timeframe when the rest of the stage would be ready for final assembly, with the new core stage facilities in the VAB in place for the process to take place at KSC for the first time. Orbital tube welding is the focus of the work inside the engine section, while large subassemblies and equipment are being prepared for installation next year.<\/p>\n
\u201cThat\u2019s kind of the build sequence, get all of the [orbital] tube runs completed and tested, then [installing] wire harnesses is the next big scope of work,\u201d Burroughs said. \u201cTVC platforms are being built up now, so once we get through our lower thrust structure tubing, the next step will be TVC platforms, and then helium tanks are a few months away but that\u2019s after the platforms,\u201d<\/p>\n
There are four thrust vector control (TVC) platforms that hold the equipment for each of the main propulsion system (MPS) hydraulic systems and those subassemblies are first integrated outside the engine compartment before being \u201cflown\u201d inside by a crane lift. Similarly, the five large composite overwrapped pressure vessels (COPVs) that hold the in-flight supply of gaseous helium for the stage\u2019s MPS and the four RS-25 engines will be staged prior to lifting into the engine section next year.<\/p>\n
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<\/p>\n\u201c[We do] all the tube runs and then we do a bunch of [wire] harnesses, we fly in our Y-ducts, [and then] helium tanks come in after the Y-ducts, so it\u2019s probably sometime mid next year before the helium tanks go in,\u201d Burroughs said.<\/p>\n
Another milestone for engine section integration is mating the boattail, which Boeing plans to transport from Michoud to KSC next year after NASA\u2019s Pegasus barge first makes the round trip with the Artemis II core stage. \u201cOnce the barge comes back from [delivering] Core Stage-2 (CS-2), we\u2019re going to ship the Core Stage-4 (CS-4) engine section and the CS-3 boattail down,\u201d Burroughs said.<\/p>\n
That would be followed soon after by bolting the boattail to the bottom of the engine section. \u201cWe learned on Core Stage-2 we can mate [the engine section and boattail] very quickly and the advantage of the SSPF is that it\u2019s got a higher hook height [than Michoud],\u201d Burroughs noted.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2023\/12\/P1210647-watermarked.jpg\")
<\/p>\nCredit: Philip Sloss for NSF.<\/p>\n
(Photo Caption: The LH2 tank for Core Stage-3 is seen in Cell E at MAF in October. The interior, storage area of the tank is washed and cleaned in the processing cell to prepare it for installation of internal sensors. That will be preceded by the application of primer and foam to the outside of the tank.)<\/em><\/p>\n
\u201cOne of the reasons we did not mate the boattail as early as we could have on CS-2 is we could not fly in some of our big structures [at Michoud] because we ran out of hook height and ceiling, so the plan is as soon as it gets down there, we\u2019ll start staging that and immediately go to install it. That opens up additional electrical scope [that can be worked on], it prevents a lot of loose installs that [would otherwise] have to go into the boattail.\u201d<\/p>\n
\u201cOnce we go and install the boattail, then we can go [do] the full [wire] harness install.\u201d Boeing is continuing to work on the boattail while it is at MAF waiting for a ride down to KSC: \u201cWe\u2019re still parallel working boattail here, they\u2019re doing hydraulic tubing,\u201d Gregg Eldridge, NASA SLS Stages MAF Resident Management Office (RMO) Manager, said. \u201cThey\u2019re in process [working on] leak testing right now actually.\u201d<\/p>\n
The other elements of the Artemis III core stage in production at Michoud: the forward skirt, the intertank, and the LH2 tank, are progressing while troubleshooting on the LOX tank build continues. \u201cThe intertank has all [its] TPS (thermal protection system) [applied], all the external structure is complete,\u201d Burroughs said.<\/p>\n
\u201cThey\u2019re in the avionics bay installation process now, which is followed up by electrical, so we\u2019ll be two or three months of hard-core electrical, and then should be in a functional test configuration by end of first quarter next year and then go into the functional test and it\u2019ll be ready for major join 1 sometime [in the] mid next year timeframe. Forward skirt [is] clicking along, it\u2019ll be ready well before the intertank and LOX tank for stacking.\u201d<\/p>\n
LH2 tank moving ahead and the return of the \u201caft join\u201d<\/p>\n
The other propellant tank for CS-3, the LH2 tank, is now being prepared for the application of its corrosion-protective primer, followed by the insulating spray-on foam insulation (SOFI). The tank article was set aside many years ago due to welding issues at the time the tanks for the first core stage were being welded in 2016 and 2017.<\/p>\n
Following years of research, repairs of the \u201clow-ductility, low topography\u201d indications on the tank were completed in the 2021-2022 timeframe. The tank passed a second proof test earlier this year and in October was positioned in Cell E, the internal cleaning facility. Following the cleaning of its interior, the tank will move to the production cells in nearby Building 131, Cell P for primer application and Cell N for SOFI application.<\/p>\n
Burroughs noted that the third core stage will look a little different than the first two, with the omission of \u201csensor islands\u201d for development flight instrumentation (DFI) on the Artemis I and II cores. \u201cSensor islands are gone on CS-3 and beyond,\u201d he said. \u201c[Core Stage-3] has a lot fewer sensors, we took a lot of our DFI sensors away for Three.\u201d<\/p>\n
The reduction of DFI also eliminates some work required to affix wire harnesses to the skin of the tanks, and mask off the sensor island areas on the \u201cacreage\u201d of the tank for SOFI application. Since the LH2 tank is a little early in the production timeline and the LOX tank is delayed, the LH2 tank will go through the primer and SOFI cells first for this build.<\/p>\n
After the LH2 tank receives its primer and SOFI, it will be prepared for two joins now that the engine section is being completed at KSC and final assembly is also moving there. Originally, Boeing had planned core stage assembly around two vertical joins of the top and bottom halves of the vehicle, a forward join and an aft join (also referred to as \u201cmajor join 2\u201d, followed by a final major join of the two halves in a horizontal orientation.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2023\/12\/maf_20181126_p_lh2_lift_onto_aft_sim-42.resize.jpg\")
<\/p>\nCredit: NASA\/Eric Bordelon.<\/p>\n
(Photo Caption: The core stage LH2 structural test article is mated in Cell A at MAF in November 2018 to the second of two simulators. The LH2 tank for the Artemis III core stage will be stacked on top of a simulator in Cell A in an \u201caft join\u201d similar to this.)<\/em><\/p>\n
The final assembly plan was modified in 2019 to speed up completion of the first core stage build, by rearranging the sequence of joins and allowing the 4\/5ths part of the rocket to continue production in parallel with the trailing engine section. The aft join will return, with the LH2 tank being stacked on top of a simulator for the engine section that is being repurposed following structural testing that was completed before Artemis I.<\/p>\n
Adding an engine section simulator to the 4\/5ths \u201cstack\u201d allows it to be carried by the existing \u201croadway\u201d transportation tools. \u201cWe\u2019re going to go back to the original baseline, major join 1 and 2,\u201d Burroughs said. \u201cWe\u2019re going to stack the sim in Cell A on the hydrogen tank, and then we\u2019ll have the bottom half of a vehicle.\u201d<\/p>\n
\u201cThen we\u2019ll mate it to major join 1, [the] top three sections, and essentially you\u2019ll have a full core stage, less all the fun stuff inside the engine section.\u201d The simulator also allows NASA\u2019s Pegasus barge to transport the 4\/5ths assembly without any modifications.<\/p>\n
In addition to the standard production work on the core stage flight hardware, Boeing is working to construct a final assembly facility in VAB High Bay 2 at Kennedy. The final two elements of a core stage: the 4\/5ths and the engine section\/boattail, will be mated vertically in High Bay 2.<\/p>\n
\u201cThis is where we get the benefits of vertical install and build,\u201d Burroughs explained. \u201cWhen we do it horizontally you\u2019re kind of limited on any parallel work that you can do when you finish the engine section and final assembly at the same time.\u201d<\/p>\n
\u201cThe big advantage of going vertically is you do not have to finish your engine section prior to breaking over. You can go ahead and stack the top 4\/5ths on the engine section and work final assembly in parallel with [the] engine section work scope, as well as the benefit of pulling in engine section functional testing and FIFT (final integrated functional testing) and combining that, so you\u2019re looking at two to three months of overall savings from a schedule perspective.\u201d<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2023\/12\/DSC_2440-wmarked.jpg\")
<\/p>\nCredit: Julia Bergeron for NSF.<\/p>\n
(Photo Caption: One of the doors for VAB High Bay 2 is seen open during a recent NSF flyover of Kennedy Space Center. Boeing is converting the high bay into a final assembly facility for SLS core stages beginning with the third unit that will fly with the Artemis III vehicle.)<\/em><\/p>\n
The engine section was not originally designed to be mated while horizontal, so the new final assembly plan means that the CS-3 engine section can stay in a vertical orientation for the whole core stage build. When standalone integration work is completed in the SSPF, it will be moved to VAB High Bay 2, where it will be placed in one of the two production cells that will have been constructed there.<\/p>\n
The two final assembly cells Boeing is building in High Bay 2 will have additional benefits from the original stacking cell at Michoud, Cell A. \u201cIt\u2019s much more sophisticated than Cell A, so the bottom structure will be [elevated] so you can get engines installed, then there are multiple platforms around the entry points of the dry structures and then there\u2019s other platforms,\u201d Burroughs said. \u201cIt\u2019s more aligned with a Cell A plus with the wrap-around platforms and an elevator going up and down, etcetera.\u201d<\/p>\n
In addition to the time savings from not having to rotate the engine section from vertical to horizontal and then back to vertical, Boeing can also leave some of the ground support equipment access kits inside the barrel, which will also save time breaking down all the GSE and then reassembling it. \u201cThe boattail kit, that can be used,\u201d Burroughs noted.<\/p>\n
\u201cThe internal access kit that we use here at MAF will not work with the LH2 tank you have to go to the access kit that we used at Stennis and on the ML for CS1. It\u2019s a different kit because of the dome taking up a big portion of your volume [inside the engine section], but the boattail kit is essentially the same.\u201d<\/p>\n
Boeing is currently targeting completion of construction inside VAB High Bay 2 by the end of 2024, which would support delivery of the CS-3 vehicle to the facility in the same end-of-2024 timeframe. That would put completion of the Artemis III core stage somewhere in 2025. NASA is still targeting launch of Orion and SLS on the Artemis III mission for December 2025.<\/p>\n
One of the future goals is for SLS production to reach a delivery rate of two vehicles annually. To facilitate this Boeing is looking to optimize the floor space at Michoud with the new two-site production plan, including the final assembly area in Building 103 at Michoud \u2014 also called Area 47\/48.<\/p>\n
\u201cWe\u2019ve looked at that extensively, so 47\/48 was always designed to have two stages in there,\u201d Burroughs noted. \u201cIt gets very busy with ship-side support [personnel and cubicles] and pretty full, so the concept is when we get to the 4\/5ths on Core Stage-3, for example, it\u2019s not a full rocket so we can move some of our ship-side support around and we\u2019ll still be able to get a LOX tank or an LH2 tank into 47\/48 to free up other areas in the factory and eventually get to a two core stage a year type of a scenario and the footprint and all the modeling shows that\u2019s feasible with the current footprint.\u201d<\/p>\n
Core Stages for Artemis IV and beyond will support Block 1B vehicle still in development<\/p>\n
On CS-4, which will fly with the Artemis IV vehicle, the two lead elements of the previous core stage builds \u2014 the engine section and the intertank \u2014 are progressing toward structural completion. Shipment of the engine section structure to KSC is planned for early 2024, with the issues that have been encountered finishing the last welds for the Artemis III core stage having been factored into the overall production plan.<\/p>\n
\u201cIt\u2019s all maintained in a factory model that we update basically monthly on where we\u2019re at,\u201d Burroughs noted. He also noted that they are looking at other work they can do on the CS-4 engine section structure while it waits for its ride to KSC.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2023\/12\/MAF_20230915_CS2_Eng2047Install1large.CS3-CS4-Hardware.jpg\")
<\/p>\nCredit: NASA\/Michael Democker.<\/p>\n
(Photo Caption: Two of the core stage hardware elements that Boeing plans to transport to KSC soon are seen in the background of a recent picture taken in September while the RS-25 engines were being installed in the Artemis II core stage. The boattail that will attach to the bottom of the Core Stage-3 engine section is partially visible (left inset) along with the Core Stage-4 engine section structure (right inset))<\/em><\/p>\n
\u201cWe\u2019re going to try to do some external cork and other things here,\u201d Burroughs said. \u201cWe\u2019ll continue to work on it, because we have some time. Anything we can do here will buy us value in the future.\u201d<\/p>\n
\u201cWe did a fairly large scope of tooling around the thrust structure, based on sequence requirements certain components have to go in before you do your subsystem weld-ups, bleed ducts, and other things, which we\u2019re going to go ahead and install when we get to Kennedy,\u201d he added.<\/p>\n
The intertank thrust beam and panels for CS-4 are being bolted together in the structural assembly jig adjacent to its counterpart for Core Stage-3. \u201cBased on when intertank CS-3 completes [is] when you transfer the full force over to CS-4. Obviously, CS-4 has got to go get \u2018TPS-ed,\u2019 so it\u2019ll be in the processing cells for a while getting that [work] completed before it comes back for integration.\u201d<\/p>\n
The need date for CS-4 will be driven by the development and construction of the new elements for Artemis IV. This will be the first flight of the SLS Block 1B vehicle with the new Exploration Upper Stage (EUS) currently in development and a new Mobile Launcher which is being constructed at KSC to support the longer, upgraded Block 1B rocket.<\/p>\n","protected":false},"excerpt":{"rendered":"
As Boeing nears completing final assembly of NASA\u2019s second Space Launch System (SLS) core stage at the Michoud Assembly Facility (MAF) in New Orleans, the space agency\u2019s prime contractor for SLS stages is continuing production of hardware for the next two units. The core stage for Artemis II is the last one that will be […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[304,6654,6658,670,1336,7866,626,190,624],"class_list":["post-24144","post","type-post","status-publish","format-standard","hentry","category-news","tag-artemis","tag-artemis-iii","tag-artemis-iv","tag-boeing","tag-core-stage","tag-maf","tag-michoud","tag-nasa","tag-sls"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/24144"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=24144"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/24144\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=24144"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=24144"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=24144"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}