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The stage acts as a ground-started sustainer during launch, playing the same role Orbiters did for the Space Shuttle. The multi-purpose Shuttle orbiters performed several functions beyond a launch vehicle rocket stage, but that\u2019s the only purpose for the Core Stage \u2014 there are no in-space, upper stage elements like Orbital Maneuvering System (OMS) pods, there is no payload container like a cargo bay, there are no re-entry and landing elements like delta wings, and there is no spacecraft crew module.<\/p>\n
Although redrawn around the Shuttle\u2019s liquid propellant tanks, Main Propulsion System, and RS-25 rocket engines, the stage was also reset into a bigger, inline launcher; development of new construction techniques and then putting those into practice on qualification articles and Core Stage-1 made for a bumpy first-time learning curve.<\/p>\n
Assembly of the first working engine section ended up being the biggest learning curve of the build and Boeing has deconstructed and reconstructed the work for the second one to improve the speed and the quality. \u201cWe have a new workforce here, we hired people into this facility, a lot of people transferred into this facility,\u201d Todd Nicholson, Boeing\u2019s Engine Section Integrated Product Team Lead, said, \u201cbut if you think of it as a new workforce, I call it \u2018the factory has learned.\u2019<\/p>\n
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\u201cIt has matured and the non-conforming conditions are down compared to Core Stage-1, which says you have less churn of doing red-lines to manufacturing engineering. The shop has to say \u2018engineering, we tried to build it, we encountered a problem, what do you want us to do with this problem?\u2019 So that\u2019s what I mean by less churn on that cycle of non-conforming conditions.\u201d<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2019\/09\/MAF_20190718_CS2-ES.25pct.jpg\")
<\/p>\nCredit: NASA\/Jude Guidry.<\/p>\n
(Photo Caption: The Core Stage-2 engine section in mid-July in its structural assembly jig at MAF. Following completion of structural assembly, technicians will work on the bulk of the integration phase the element\u2019s construction.)<\/em><\/p>\n
The engine section structure is a combination of welded and bolted structures, and a milestone in structural assembly was mating the welded barrel with the thrust structure the engines are mounted to. The barrel was welded together from eight panels in the Vertical Weld Center (VWC) at MAF and then an L-ring was welded to the top in the Vertical Assembly Center (VAC); that work was completed in 2017, with the VAC weld finished at the end of October, 2017.<\/p>\n
The thrust structure is bolted to the inside the barrel; the engines will be mounted to this structure on the bottom and thrust vector control (TVC) platforms (also referred to as MPS platforms) with much of the hydraulic system equipment will eventually mounted on top. The two pieces were brought together at the end of May, but several tasks performed downstream of that work sequence for the first article were brought forward for the second.<\/p>\n
\u201cSo Core Stage-2, first and foremost, we tackled more efficient ways to do the work statement,\u201d Nicholson explained.<\/p>\n
\u201cFor example, the thrust structure has an enormous amount of tubing and cabling that comes to it because that\u2019s where the engines react loads up into the vehicle. So we build the thrust structure first and then we put the barrel on top of it, right?\u201d<\/p>\n
\u201cOne of the things that we wanted to do on Core Stage-1 but we just couldn\u2019t pull it off due to timing, it was pretty much before I got on the program, was to pre-populate to the maximum extent that we could all the equipment and sub-assemblies on to that thrust structure,\u201d he continued.<\/p>\n
Vito Neal, a welding engineering with Boeing, noted that orbital tube welding started much earlier in the sequence than during integration for the first engine section.<\/p>\n
\u201cVito\u2019s right, we did some welding,\u201d Nicholson said. \u201cWe called all that \u2018pre-integrate\u2019 [work], so we pre-integrated the thrust structure prior to putting the thrust structure and the barrel together. We started putting tubing and all kinds of bracketry on it.\u201d<\/p>\n
\u201cThe cool part about that is, the most efficient part about that is, you have so much more access [when] you don\u2019t have that barrel on you,\u201d he explained. \u201cA technician doing work and needing help or to ask somebody a question, he doesn\u2019t have to come all the way out of the footprint or the barrel to go talk to the manufacturing or quality engineering.\u201d<\/p>\n
\u201cHe can pretty much just holler over the structure and say \u2018hey come here for a minute.\u2019 So [that is] just the human element of efficiency, number one.\u201d<\/p>\n
Even prior to the early integration work on thrust structure at MAF, Boeing moved up some of the structural assembly tasks for the hardware, sending the match drilling work back to the vendor.<\/p>\n
\u201cFor Core Stage-2 and on we established an initiative, we refer to it as \u2018pre-drilling\u2019 our holes,\u201d Nicholson said. \u201cWe exercised a change in the program to say why don\u2019t we drive that all the way to the fabricator of the raw part, give enough tolerance on those holes, and account for it here during the assembly process so that we\u2019re not putting a match drill operation on the mechanic and running the risk of mis-drilling it, because that\u2019s all by hand.\u201d<\/p>\n
\u201cWhereas at the fabricator you can set it up on a jig and use machinery to do those holes and they\u2019re spot on. I don\u2019t know the efficiency numbers but I\u2019ve seen the charts and Core Stage-1 to 2, it\u2019s at least two-fold better, it\u2019s astronomically better, and we expect to reap that harvest going into the future with Core Stages once we\u2019re put on contract with those.\u201d<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2019\/09\/CS2-ES-1.25pct.jpg\")
<\/p>\nCredit: NASA\/Eric Bordelon.<\/p>\n
(Photo Caption: The barrel of the Core Stage-2 engine section is lowered down over the thrust structure in the structural assembly jig for engine sections at MAF in late May. The barrel and ring on top are welded, the thrust structure is bolted, and the two pieces are bolted together in the jig.)<\/em><\/p>\n
For Core Stage-1, the thrust structure and barrel were brought together in the structural assembly jig at MAF towards the beginning of the build. At that point, the holes to hold tubing brackets were drilled.<\/p>\n
\u201cWe match-drilled them in place,\u201d Nicholson said. \u201cThat was the thought through the whole design phase of the Core Stage and you learn stuff with the first unit. We were like \u2018this is too labor intensive\u2019 which equates to time and we were having a lot of mismatched holes and so engineering came up with the clever idea that we sold to the program to drive this requirement to pre-drill these holes back at the fabricator of the piece part.\u201d<\/p>\n
\u201c[The] program did its due diligence, engineering had to build a huge trade study to go convince the program that OK it\u2019s an investment in time here but it saves you this much during assembly time and checkout,\u201d he explained. \u201cYou won\u2019t reap this harvest until months down the road.\u201d<\/p>\n
\u201cThe day we started, the day we started assembling all those pre-drilled parts everybody knew right then because our job count was exponentially higher just that one day because we all reflected back on when we did it with Core Stage-1, we said we would have a mismatched drilled hole and we would be sitting here doing a non-conformance right off the bat. [It was] an instant return on investment, an instant return on investment.\u201d<\/p>\n
\u201cThe engineers were sitting there saying \u2018See? We told you so.’\u201d<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2018\/10\/L2-banner@2x.jpg\")
For future builds, Nicholson said the vendor will deliver the thrust structure to MAF after that work: \u201cIt\u2019s part of the baseline design now, all the rest of them will be built that way.\u201d<\/p>\nHe also noted that not all the match-drilling will be done elsewhere. \u201cThere still is some match-drilling, but I\u2019m talking about primarily brackets that retain tubes and wiring and spatial geometry on a substructure. We don\u2019t see that being pre-drilled in the future, we don\u2019t see the value in that because of the intricacies of putting those parts together, they\u2019ve got to be spot-on the way you put them into position.\u201d<\/p>\n
Nicholson noted that Boeing is planning to incorporate lessons learned in future builds beyond Core Stage-2, for example with wiring. \u201cThat would be the next one we\u2019d want to tackle in advance of Core Stage-3, is to get started on the electrical wiring earlier,\u201d he said.<\/p>\n
\u201cWe had a lot of unanticipated discoveries with Core Stage-1 with our electrical work statement. We\u2019re incorporating those lessons learned within requisite engineering and that engineering is going through a release cycle right now to get those harnesses built incorporating those lessons learned.\u201d<\/p>\n
\u201cIdeally I would want to have those harnesses a couple of months ago. If you go inside [the] barrel right now we\u2019ve pre-populated those wire harness brackets to attach the wire harnesses to. I would want to in this build position go ahead and pre-install those wire harnesses to the maximum extent I could.\u201d<\/p>\n
For the second build, Nicholson said they are modifying some of the wiring to make it easier to handle: \u201cWe\u2019re incorporating lessons learned from Core Stage-1 into Core Stage-2 and one of the lessons learned was production breaks in our electrical cables.\u201d<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2019\/09\/P1080503.35pct.jpg\")
<\/p>\nCredit: Philip Sloss for NSF.<\/p>\n
(Photo Caption: The Core Stage-2 engine section barrel sitting in storage next to one of liquid oxygen (LOX) tank domes in February, 2018. The barrel is built from eight friction-stir welded panels and an L-ring on top that serves as the structural interface to the rest of the stage. The vertical weld lands for the panels can be seen here as breaks in the pre-welding primer treatment, along with the circumferential weld land for the ring at the top.)<\/em><\/p>\n
He gave a hypothetical example: \u201cWe have an electrical cable that is say seventy-five feet that runs from one side of the barrel over and up and through and all the way around to the other side of the barrel. That\u2019s a lot of labor to unfurl that cable around, put it in place, and get it just right.\u201d<\/p>\n
\u201cWell, maybe it\u2019s smarter to put a production break in there, so you have something smaller to deal with,\u201d Nicholson explained. \u201cYou can just physically handle it faster and more readily and easily.\u201d<\/p>\n
\u201cWe\u2019re implementing some of that, we\u2019re biting that off in small chunks because the more you cut the cable up into shorter lengths you have what\u2019s referred to as line loss, your current doesn\u2019t hold all the way through. So we\u2019re being very strategic about those kind of changes, but we are doing a little bit of that.\u201d<\/p>\n
In addition to efficiencies based on streamlining the work sequence, the quality of the work is improving. More work is being completed to its specification, which means less time is necessary to fix the output, fix the specifications, or both.<\/p>\n
\u201cThose three big things, incorporating total lessons learned, attacking the electrical system, and pre-integrating the thrust structure ahead of the way we did it in Core Stage-1 are gaining us leaps and bounds on efficiency,\u201d Nicholson said. \u201cOur non-conforming conditions, I don\u2019t know the number but we\u2019re light years down, ten-fold down from where they were in Core Stage-1.\u201d<\/p>\n
\u201cAnd so our expectation is that Core Stage-2 and onward obviously our efficiency will go up a curve and then eventually it\u2019ll plateau. What we don\u2019t know yet is can we forecast that plateau.\u201d<\/p>\n
\u201cOur industrial engineering team is off trying to analyze that with all the data from Core Stage-1 and current data on Core Stage-2 to try to help us understand when can we expect to say \u2018ok this is as fast as we\u2019re ever going to be able to build a rocket,’\u201d he added. \u201cHistory tells me \u2014 thirty-two years in this business, always building first-time builds, that\u2019s all I\u2019ve ever done \u2014 history tells me it\u2019ll probably be the fourth one before we really understand that, but that\u2019s just my opinion.\u201d<\/p>\n
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The engine section of the second NASA Space Launch System (SLS) Core Stage will look a lot like the first one, but prime contractor Boeing redesigned the way they are putting it together. The engine compartment, which is the bottom of the five major pieces that compose a full stage, is the most complicated piece […]<\/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":[],"class_list":["post-37904","post","type-post","status-publish","format-standard","hentry","category-news"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/37904"}],"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=37904"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/37904\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=37904"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=37904"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=37904"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}