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The companies will turn over Pathfinder to NASA after they deliver it by barge from G&G\u2019s Cordova facility on the Black Warrior River to the Michoud Assembly Facility (MAF) in New Orleans, Louisiana, sometime in the next month or so.<\/p>\nA full-scale model of a Space Launch System (SLS) Core Stage, called the Core Stage Pathfinder, was recently completed at a plant in Northern Alabama, and will soon be shipped and turned over to NASA. A ceremony was held to mark the completion of construction and assembly of the gigantic steel article at G&G Steel\u2019s even more enormous facility in Cordova, Alabama.<\/p>\n
SLS Core Pathfinder:<\/p>\n
Radiance Technologies and Dynetics were contracted by NASA to build and deliver the Pathfinder; G&G Steel performed the final welding and assembly of the steel structure.<\/p>\n
The companies will turn over Pathfinder to NASA after they deliver it by barge from G&G\u2019s Cordova facility on the Black Warrior River to the Michoud Assembly Facility (MAF) in New Orleans, Louisiana, sometime in the next month or so.<\/p>\n
NASA will use Pathfinder at MAF, the Stennis Space Center (SSC) in Mississippi, and the Kennedy Space Center (KSC) in Florida to practice handling the size and weight of a fully assembled SLS Core Stage at those different locations and transportation between them before they have to start doing it with the real thing as early as next year.<\/p>\n
The Pathfinder was designed to mimic the \u201cform and fit\u201d of a real Core Stage. It has the same weight, center of gravity, size and shape as a finished, empty SLS Core Stage, which is how the rocket will be delivered by barge from MAF to Stennis and\/or KSC.<\/p>\n
The Pathfinder weighs about 228,000 pounds, is about twenty-seven and a half feet in diameter, and about 212 feet in length from the top of the forward skirt to the bottom of the engine nozzles.<\/p>\n
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\u201cThis has all the interfaces that we need at all different facilities and all different GSE (Ground Support Equipment) for transportation,\u201d Tim Flores, integration manager for the SLS Stages Element Office, said in an interview at the event.<\/p>\n
\u201cThis has the flight-like interfaces. So the pads on this Pathfinder are flight-like. [The] SRB fittings, those are the most expensive part on here, they\u2019re flight-like fittings.\u201d<\/p>\n
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In addition to things like SRB attachment fittings, the Pathfinder has or will have elements that simulate some of the larger protuberances on the outside of the stage, such as the systems tunnel and the liquid oxygen feedlines, also known as downcomers. Both the systems tunnel and the two downcomers run along most of the length of the stage.<\/p>\n
\u201c[Learning] where your clearances [are], that\u2019s a big thing and there\u2019s some places where there\u2019s just not very much clearance and knowing where those are [is important],\u201d Flores noted. \u201cSo we\u2019re trying to put everything that\u2019s going to be [on the Core Stage] on there.\u201d<\/p>\n
![\"\"](\"\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2017\/09\/2017-09-05-144729-350x262.jpg\")
Pathfinder has wire-frame simulators of the RS-25 engine nozzles at the bottom of the stage, with fins forward of that to simulate the boat tail fairings. \u201cThey made the [simulated] engines [so] there\u2019s one little piece that sticks out a little bit further and I believe that just gets the dimension of that without putting the whole fairing there,\u201d he added.<\/p>\n
After the Pathfinder gets to MAF, the remaining simulated elements that need to be added will be attached there.<\/p>\n
\u201cThere\u2019s some additional hardware that is very low fidelity that they\u2019re not going to add until it gets [to MAF] and that is the downcomers,\u201d Flores noted. \u201cThey\u2019re going to add that, but they\u2019re not going to until they get there, because it\u2019s very flimsy.<\/p>\n
Although the Pathfinder is just as large and heavy as a Core Stage, it is not structurally engineered like one. \u201cIt\u2019s just form and fit, it\u2019s not function,\u201d Flores added.<\/p>\n
For the testing that NASA has planned, the article will also keep its current flat gray primer appearance, in contrast to the foam-covered, orange and white real thing. \u201cAll we\u2019ve got on it right now is primer,\u201d Flores explained.<\/p>\n
\u201cWe\u2019re not going to paint it because it wasn\u2019t going to add anything to it other than weight and money. So we went with just primer, which should be OK [and] can handle the weather.\u201d<\/p>\n
Lift spiders:<\/p>\n
In addition to the Pathfinder, G&G Steel is completing two massive lift \u201cspiders\u201d at the Cordova facility that will also soon be delivered to NASA. One of the spiders and a lift ring were on display at the ceremony and the second spider was being completed elsewhere in the facility.<\/p>\n
![\"\"](\"\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2017\/09\/2017-09-05-143405-350x248.jpg\")
\u201cThe spiders are used in two different places,\u201d Flores explained. \u201c[They are] used at Stennis to lift and break over and also in the VAB they\u2019ll use it there. The lift ring goes in between that and the front face of the forward skirt and it\u2019s got the mechanism to be able to put a weather cover on it also.<\/p>\n
\u201cSo when you\u2019re in [the test stand at] Stennis, you\u2019re not dripping everything down inside there \u2013 it\u2019ll actually be protected. It\u2019s not out here, the weather cover. Boeing (the prime contractor for the core stage) is producing that \u2013 we don\u2019t need it for [Pathfinder].\u201d<\/p>\n
The spiders themselves are big and weigh about 45000 pounds each. \u201cIt is beefy structure,\u201d Flores said, noting that the spider is too heavy to leave bolted on the structure when it is oriented horizontally.<\/p>\n
\u201cPathfinder can\u2019t take that weight. And to tell you the truth, Core Stage can\u2019t take that weight. So when we transport it, we have to take the spider off. You just can\u2019t carry [the lift spider] around as you move around and that thing is cantilevered out there. Structurally, [a Core Stage] doesn\u2019t handle it and the Pathfinder without a doubt doesn\u2019t handle it.\u201d<\/p>\n
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Flores explained that a different piece of GSE will help support the weight of the spider, noting that \u201cwhen it goes on the front we actually have what\u2019s called a TIF, Transportation Interface Fixture, and it holds it upright.\u201d<\/p>\n
The Pathfinder and the lift spiders will be delivered to NASA on commercial barges, leaving Cordova once some final work is completed.<\/p>\n
\u201c[In] about two weeks, give or take,\u201d Sam Stephens, manager for wet structures in the SLS Stages Office, said at the event regarding the timing of the departure.<\/p>\n
\u201cThey\u2019ve still got a few more operations to do, they\u2019ve got to finish up the second spider, proof test it, [and then] they\u2019ll go on the barge. I don\u2019t know if [former Hurricane] Harvey is going to affect things. They\u2019ve got to get a barge up from New Orleans, so there\u2019s all those logistics we have to work with.\u201d<\/p>\n
Next On The Path:<\/p>\n
Once at MAF and turned over to NASA, the Pathfinder will start off outside.<\/p>\n
\u201cActually, it will be sitting in the parking lot of [Building] 303 or out on the apron,\u201d Stephens said. \u201cBecause this doesn\u2019t need to be out of the weather and it takes up a lot of real estate as you can see.\u201d<\/p>\n
![\"\"](\"\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2017\/09\/2017-09-05-144917-350x239.jpg\")
\u201cOne of the first things that we\u2019re going to do at MAF is, you see the SRB fittings that are on there, it\u2019s actually complicated to get those things pinned and get some of the hardware on that to actually run with the GSE and for the Boeing lifting capability,\u201d Flores explained.<\/p>\n
\u201cThe GSE won\u2019t quite be there when this gets there, so we\u2019re building some platforms where we can go and we can actually do the practice of changing out the hardware. The hardware is extremely heavy, hundreds of pounds in some cases, so that\u2019s one of the things that we\u2019ll do immediately.\u201d<\/p>\n
While at MAF, the Pathfinder will give NASA and Boeing a chance to practice and improve the operational sequences to deliver a completed Core Stage at the end of production.<\/p>\n
\u201cWhat we want to do over at MAF is actually run through the paces between Boeing\u2019s final assembly and then going from there over to our GSEs, Flores explained.<\/p>\n
\u201cThey are going to be assembling a Core Stage and then it will be put from their rigs over to our GSE. We want to go through those paces, so that\u2019s one of the things we\u2019re negotiating right now with Boeing to make sure that happens.<\/p>\n
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\u201cOne of the GSE systems that\u2019s called the MPTS (Multipurpose Transportation System) will connect up to the SRB fittings and then one will connect in the back and we\u2019ll pin in four places, just like the STAs (Structural Test Articles) so that connection on the Core Stage is exactly like we do on the STAs. Well, they\u2019re not simple connections. We\u2019re getting to practice right now with pinning on the back end \u2013 or we will \u2013 with the STAs and something we call the DDU (Dynamic Demonstration Unit).<\/p>\n
\u201cWe\u2019re practicing with the GSE right now with that. We\u2019ll run through those paces and make sure we understand how the different fittings fit, because we don\u2019t have anything that meets the interfaces of Core Stage other than [the Pathfinder].\u201d<\/p>\n
Robotic, motorized transporters called self-propelled modular transporters or SPMTs will pick up the MPTS that the Core Stage attaches to.<\/p>\n
Once the stage is placed and secured on the SPMTs, it can then be rolled along an approximately mile-long road route on MAF property, out from Building 103 to the dock where NASA\u2019s Pegasus barge is. The SPMTs will then be used to roll the stage with its GSE onto Pegasus, where they will be physically secured.<\/p>\n
The Pathfinder is configured so that personnel at MAF can practice this series of steps multiple times and in both directions between Final Assembly and Pegasus.<\/p>\n
Future testing:<\/p>\n
Early next year, the plan is for the SPMTs to move Pathfinder onto Pegasus and after it is secured, the barge will be taken from MAF to the relatively nearby Stennis Space Center in Mississippi. The barge will travel to the B-1\/B-2 test stand at Stennis, where the renovated and extended B-2 stand is being readied for Core Stage green run testing.<\/p>\n
![\"\"](\"\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2017\/04\/2017-04-28-111218-350x264.jpg\")
Given that Pathfinder simulates a Core Stage\u2019s form and fit, this will be an early exercise for the Pegasus barge crew making a trip with its largest, heaviest payload, and also gives them a chance to evaluate their transportation plans.<\/p>\n
As at MAF, Pathfinder will allow personnel at Stennis to practice handling operations there. Just like the real Core Stage, Pathfinder will be rolled off the barge at Stennis and lifting GSE (including one of the lift spiders) will help cranes attach to it. The article will be lifted up off the SPMTs and rotated to vertical; this \u201cbreak-over\u201d operation will be practiced multiple times.<\/p>\n
The Pathfinder will then be lifted up and into the B-2 stand where the attach fittings will be used to bolt it into the stand. The opposite sequence of removing the Pathfinder from the stand, breaking it over from vertical to horizontal, putting it back on the transportation GSE, and rolling back onto the barge will also be practiced.<\/p>\n
\u201cWe\u2019ll practice lifting it, breaking it over, and then putting it into the B-2 stand. Hopefully, we can go through that process two or three times at least,\u201d Stephens said.<\/p>\n
Unlike the real stage that has umbilical panels where all the required services can be fed into the rocket, the Pathfinder has only stickers or placards to indicate their locations.<\/p>\n
Stephens explained that this will give both Stennis and Kennedy another check on the positioning of their ground side umbilicals, noting \u201cthings that we\u2019re not attaching such as umbilicals, we just use stickers \u2013 decals positioned at the right spots so when we do position them at Kennedy or at Stennis, we can line up and go \u2018yup, we\u2019re in the right spot, it\u2019s where we expected, it\u2019s all good.’\u201d<\/p>\n
Once all the handling tests at Stennis are complete, the Pathfinder will go back onto Pegasus, which will make the much longer voyage from Stennis to KSC, giving the Pegasus crew an opportunity to practice the same trip they will take with the real Core Stage after green run testing is complete.<\/p>\n
At KSC, ground crews there will get a chance to test their handling procedures \u2013 rolling the Pathfinder on the SPMTs off the barge at the upgraded Turn Basin at Launch Complex 39 into the VAB Transfer Aisle, where crane operations can be tested.<\/p>\n
![\"\"](\"\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2017\/09\/2017-09-05-145220-350x256.jpg\")
The Pathfinder will allow lift to mate operations in the VAB to be practiced, where the stage will be lifted off the SPMTs in the Transfer Aisle, broken over to vertical, lifted up towards the top of the VAB, through the High Bay 3 diaphragm, and down towards the deck of the Mobile Launcher.<\/p>\n
In the case of Pathfinder, there won\u2019t necessarily be anything it can attach to during these practice dry-runs. \u201cIt\u2019s not set up to actually connect to the boosters,\u201d Flores explained.<\/p>\n
\u201cIf Kennedy had an opportunity to try to do something [like] connecting Pathfinder up to the boosters, we haven\u2019t talked with them about that. But we\u2019re leaving Pathfinder at Kennedy, so there will be more time for them to do some practicing and if there\u2019s opportunities like that, they can seek them out.\u201d<\/p>\n
Although the reason for Pathfinder\u2019s existence is still in front of it, there has been some thought about a final resting place when its work is complete.<\/p>\n
\u201cWe\u2019ve already been talking with the [U.S.] Space and Rocket Center (in Huntsville) about whether or not they can have it as some kind of a display,\u201d Flores noted. \u201cThey\u2019re working that, not at the [NASA] Headquarters level but at the center director level. They\u2019re making plans to do something with it [and not] let this go out to some boneyard.\u201d<\/p>\n
(Images: NASA and Philip Sloss via L2 which includes, presentations, videos, graphics and internal \u2013 interactive with actual SLS engineers \u2013 updates on the SLS and HLV, available on no other site. SLS render by L2 Artist Nathan Koga. The full gallery of Nathan\u2019s (SpaceX Dragon to MCT, SLS, Commercial Crew and more) L2 images can be *found here*))<\/p>\n
To join L2, click here: \/\/www.nasaspaceflight.com\/<\/p>\n","protected":false},"excerpt":{"rendered":"
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