Preparing the Mobile Launcher to be armed and ready for SLS

by Philip Sloss

The Ground Systems Development and Operations (GSDO) team at the Kennedy Space Center (KSC) in Florida is continuing construction and testing to get ready to support upcoming Exploration Mission launches. Testing at the Launch Equipment Test Facility (LETF) is in full swing delivering launch vehicle umbilicals and swing arms to the Mobile Launcher (ML).

LEFT to ML for SLS:

Construction and outfitting of systems on the ML are pointing towards multi-element verification and validation (V&V) testing next year, a major milestone that will confirm the GSE (Ground Support Equipment) is ready to receive the first SLS rocket.

A major test site for these preparations is the LETF, located in the KSC Industrial Area.

Most of the hardware that connects the SLS launch vehicles and Orion spacecraft to the Mobile Launcher is going through testing there to gather release loads data and verify the functionality of the umbilical connections and the swing arms.

“Over the past nine to ten months we’ve significantly grown the team and have really been producing most of these umbilicals,” Jeremy Parsons, GSDO Senior Project Manager for the LETF said in an interview with

“Where we’re at now is where pretty much at the apex of the ‘mountain’ of work.  So we’re at that precipice and then we’re getting ready to come down on the other side.  We’ve delivered a significant number of the umbilicals already and we have some of the hard work left.”

The team at the LETF recently finished the Core Stage Forward Skirt Umbilical (CSFSU) and Core Stage Intertank Umbilical (CSITU); the CSFSU was lifted up and attached to the ML tower in late June and testing on CSITU wrapped up shortly after that.

That umbilical is ready to be driven up the road to the ML construction site so it can be hung up on the tower.

“It will be shipped to Mobile Launcher and as of right now August 11th is the lift date,” Sam Talluto, GSDO Deputy Project Manager for the Mobile Launcher said at the time of the interview earlier this month.

“So far we’ve completed a total of fifteen of nineteen umbilicals, starting off with ten each Vehicle Support Posts, that’s eight primary support posts and two spares,” Jeff Crisafulli, GSDO Engineering Manager for the LETF added.  “That’s [also] two each Aft Skirt Electrical Umbilicals, the Orion Service Module Umbilical, and then of course the Core Stage Forward Skirt Umbilical and Core Stage Intertank Umbilical.”

“So that leaves the two TSMUs (Tail Service Mast Umbilicals), the VS (Vehicle Stabilizer), and then obviously the ICPSU (Interim Cryogenic Propulsion Stage Umbilical) and the CAA (Crew Access Arm) seal,” Parsons noted.  “The CAA seal will only be a couple of day test.  The setups will be more extensive and we’ll be able to deliver that to the VAB, so it’s not time-critical.

“Right now we have three elements that are in-flow actively testing. We just finished up our TRR, which is our Test Readiness Review for the [Liquid Oxygen] TSMU so we’re now into testing for that.  We’re well underway testing on the Vehicle Stabilizer and we just finished up our Delta Test Readiness Review to begin cryogenic operations on the ICPSU.  So we’re in the final phase of testing for that.  Those are all in the final stretch there.”

After the ICPSU completes its testing, the other tail service mast, the liquid hydrogen TSMU will start into its test flow.  The last EM-1 hardware that is planned to go through the LETF is the Crew Access Arm seal, which docks the White Room on the arm to access hatches on the Orion spacecraft.

“It’s just the seal for the white room,” Parsons continued.  “The crew access arm itself is going to be delivered directly to the Mobile Launcher.  We have that set to be delivered…probably towards the end of September directly to the Mobile Launcher.  So the seal will actually be delivered to the VAB (Vehicle Assembly Building) directly.

“That will be probably towards the end of this calendar year and it will be the last element probably out of the LETF, but we’re not putting a high schedule pressure on it at this point because we need to get the umbilicals out and this will able to follow on after that and can be installed at pretty much any point in the VAB.”

Mockups for the White Room and Orion launch abort system ogive panels will be used at the LETF for testing the seal.

Around the same time as the CSFSU was attached to the ML tower in late June, the CSITU completed testing at the LETF.  As the name implies, the CSITU will attach to the SLS Core Stage intertank; the primary function of the umbilical is to safely carry hydrogen gas venting from the hydrogen tank away from the vehicle and the tower.

The umbilical will provide other services such as environmental control, power and data to vehicle systems in the intertank.

“The LETF is a full test facility so what we tested there, we did initial tests with liquid nitrogen.  To get to a lower temperature we tested with liquid hydrogen.  The liquid nitrogen tested with the simulant of oxygen temperatures and then liquid hydrogen…obviously we tested at full hydrogen temperatures to simulate what we would actually see during launch day,” Parsons noted.

“We test electrical connectivity at the interfaces of the plate, we have sensors all up and down the plate to test temperatures, to test all sorts of things. We test primary disconnect loads, we test secondary failure modes, so we go through all of those.”

“Loads to the vehicle are our primary concern and deliverable to the program so we have multiple, six axis load cells reporting all the simulated vehicle loads,” Crisafulli added.

“One of the other large tests we did was we had to tune the hydraulic control system for that particular arm to basically make sure it swings at the right rate of speed to get itself out of the way of the launch envelope of the vehicle.  All of that was highly successful.”

Once the testing of all the “launch accessories” for EM-1 at the LETF is complete, the test facilities there will go through a maintenance period; however, they will remain ready to support any additional testing in support of the EM-1 launch campaign.  The LETF will play a similar critical role in getting ready to support the EM-2 launch, which will require testing new and modified umbilicals.

Mobile Launcher:

Construction and outfitting of the Mobile Launcher continues at the Launch Complex 39 East Park Site on the northern periphery of the Vehicle Assembly Building (VAB).

“From a structural standpoint we’re installing the steel supports for the cryo system, steel supports for the environmental control system, we have lots of piping and tubing that is going in at this time,” Cliff Lanham, GSDO Senior Project Manager for the Mobile Launcher said.

“Structural mods are [also] continuing on some of the major structural girders as well as on the tower to support launch accessories — the umbilicals.”

The launch platform and tower were originally under construction to support the Constellation program’s Ares I crew launch vehicle; after cancellation, the work was repurposed for the SLS.  Workers are also installing equipment into the base platform and the tower to support launch operations.

“From a GSE (Ground Support Equipment) installation standpoint, we have roughly a thousand items from pneumatics panels to electrical cabinets that have to go in along with cameras and those sorts of things,” Lanham explained.

“Right now we’re at just over 50% percent complete of the installation of those [overall]; of that, I would say [we’re about] 75 percent [complete] in the base and about 35 percent complete on the tower.”

Lanham provided an overview of some of the “laundry list” of the different types of commodities and services that are going onto the ML.

“From a pneumatics systems [standpoint], we’ve got gaseous oxygen, we’ve got gaseous nitrogen, we’ve got helium.  [For] cryo systems, we have [liquid] hydrogen and oxygen.

“Then some of the other systems, from an electrical standpoint, we have ground special power, hazgas (hazardous gas) leak detection, Kennedy ground control systems, launch release systems, range safety control systems, sensor / data acquisition systems, thermal systems, weather systems, handling and access, and communications systems.”

As an example of drilling down at a systems level, Lanham also outlined some of the types communications services on the ML.

“Wifi, telephones, OIS (Operational Intercommunications System), which is our operational system for the test teams to use to communicate with the LCC, the launch control center, so all those systems fall under comm.”

With outfitting work still ongoing, for now launch accessories like the umbilicals are only being structurally attached to the tower, added Talluto.

“After all the umbilicals are hung and surveyed then the tubing and piping — pneumatics, hydraulics, all that stuff — will catch up.”

(Images via NASA and L2 SLS Sections – the latter including a master LETF and ML Update Section full of images and videos from the test sites. To join L2, click here: //

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