SLS Upper Stage arrives at the Cape as the LETF tests its umbilicals

by Chris Bergin

A major milestone in the build-up to the maiden launch of the Space Launch System has seen the arrival of the Interim Cryogenic Propulsion Stage (ICPS) at Cape Canaveral. Meanwhile, tests are continuing on the umbilicals that will feed this Upper Stage, ahead of joining forces when mated on the Mobile Launcher.


The upper stage – which is effectively a Delta Cryogenic Second Stage (DCSS) – followed the path other DCSS’ travel, after being shipped from the United Launch Alliance (ULA) facility in Decatur, Alabama aboard the Mariner barge.

It arrived at Cape Canaveral Air Force Station (CCAFS) on Wednesday.

It is now housed at ULA’s Horizontal Integration Facility (HIF) where it will begin processing for launch at the ULA Delta Operations Center.

The eventual destination for the ICPS will be the Vehicle Assembly Building (VAB) at KSC, in preparation for mating atop the SLS stack.

The stack will be integrated while sitting on the Mobile Launcher, which will provide the lifeblood of electrical and fluid support, along with the all-important prop loading whilst at the pad.

The key hardware between the ML and the ICPS will be the umbilicals.

A vast array of connections and devices are currently being tested at the Launch Equipment Test Facility (LETF) inside the Kennedy Space Center grounds.

Weighing in at 100,000lbs, the Interim Cryogenic Propulsive Stage Umbilical (ICPSU) will be a T-0 umbilical for SLS providing “LH2 fill/drain, LO2 fill/drain, GH2 vent, GSP, ECS, GHe (gaseous helium), HGLDS, LCS, RSCS, FSS, and GN2 to the SLS Upper Stage Interim Cryogenic Propulsion Stage (ICPS).”

Mated to the vehicle in the VAB, the ICPSU will contain a ground umbilical plate that will provide the physical attachment point to the SLS vehicle.

Access to the ground umbilical plate will only be possible in the VAB, emphasizing the importance of a good VAB flow ahead of the entire stack rolling out to Pad 39B ahead of launch.

At the termination of countdown operations, a T-0 release command will be sent to the ICPSU, initiating a swing arm-style retraction of the ICPSU out of SLS’ liftoff flight path.

This release will be part of several complex instructions between the rocket, ground systems and the ML to conduct a ballet of releases and retractions as the rocket is committed to launch.

*L2 Members click here for a video overview of all the SLS umbilicals overviewed and shown in action during launch*

The ICPSU arm itself will consist of a truss boom structure terminating 10 feet from the SLS rocket, with the remaining distance covered by five (5) draped umbilicals.

The ICPSU T-0 umbilical interface is currently baselined from that of the Delta IV rocket’s 5m second stage. Thus, the swing arm umbilical is currently designed from the profile of that used by the Delta IV rocket.

In an effort to reduce cost as much as possible and use already proven hardware, the ICPSU arm will use the GOX vent arm hinge used for Space Shuttle launch operations on LC-39B.

All latchback, shock absorbers, and work platforms from the GOX vent arm at LC-39A will be used as well.

Access the ICPSU arm itself (as opposed to the plate) will be provided via the 220-foot or 240-foot level platforms of the ML umbilical tower.

These systems are undergoing real life testing at the LETF, which is providing a test run for retractions and operations.

Currently, SLS’ first mission, Exploration Mission -1 (EM-1) is an uncrewed test flight that will send Orion on a checkout flight around the Moon. The official launch date is late 2018, although this is expected to officially slip into 2019 in the next few months.

NASA managers are also conducting a politically requested study into changing the plan for EM-1 to include crew riding in Orion. That study should be complete by next month.

The ICPS will only have a short lifetime with SLS, as the program aims to move to the more powerful Exploration Upper Stage (EUS).

The official plan is to move to this stage by the second or third flight of SLS, pending the outcome of the crewed EM-1 study.

When SLS moves to the EUS, a huge amount of work will be required to change the configuration of the umblicals on the ML to match the taller Block 1B SLS rocket, with its larger EUS.

This work – per the current plan – was to be conducted during the three-year gap between EM-1 and EM-2. Even if the plan changes for EM-1, a large stand down period will be required when SLS moves to the EUS.

(Images: NASA and L2 which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers – updates on the SLS and HLV, available on no other site. Additional renders by L2 Artist Nathan Koga. The full gallery of Nathan’s (SpaceX Dragon to MCT, SLS, Commercial Crew and more) L2 images can be *found here*))

(L2 is – as it has been for over 10 years – providing full exclusive SLS and Exploration Planning coverage. To join L2, click here: //

Related Articles