Spaceflight Insider

Mobile Launcher work moves forward with installation of umbilicals and arrival of crew access arm

Workers maneuver the Core Stage Inter-tank Umbilical onto its mounting points on the launch tower. Photo Credit: Glenn Benson / NASA

Although the maiden launch of NASA‘s Space Launch System (SLS) is still, at the earliest, more than two years away, work on the large rocket’s Mobile Launcher (ML) moves forward in support of the first flight of the agency’s next crew-rated launch vehicle.

Umbilicals and Access

Workers with NASA’s Ground Systems Development & Operations (GSDO) team recently lifted the Core Stage Inter-tank Umbilical (CSITU) arm on the ML’s tower to perform a fit check prior to its permanent installation at a later date. The CSITU, at its position 140 feet (42.67 meters) up the launch tower, is designed primarily to vent hydrogen gas that has boiled-off from the core stage’s liquid hydrogen (LH2) tank prior to launch.

The Aft Skirt Purge Umbilical seen after its testing regime at GSDO’s facility at Kennedy Space Center. Photo Credit: Curt Godwin / SpaceFlight Insider

The arm, which also provides electrical and data connections – as well as pressurized gases and conditioned air – to the core stage, will swing away from the vehicle before launch. The CSITU is the third of five new umbilical systems that will be installed on the mobile launcher.

Prior to the installation of the CSITU, GSDO had installed the Orion Service Module and Core Stage Forward Skirt umbilicals on the launch tower.

The Orion Service Module Umbilical (OSMU), situated at the 280-foot (85.34-meter) level on the launch tower, will provide coolant to the spacecraft’s service module and purge air for its systems, as well as those of the Launch Abort System (LAS).

Located 100 feet (30.48 meters) below the OSMU is the Core Stage Forward Skirt Umbilical (CSFSU). This umbilical arm will swing into place to provide conditioned air into the Core Stage Forward Skirt cavity and then swing away just prior to launch.

Installed on the Mobile Launcher’s platform are two Aft Skirt Purge Umbilicals (ASPUs). Mounted next to each of the SLS’ two solid rocket boosters (SRBs), the ASPUs remove potentially hazardous gasses and maintain a proper temperature range for the electronics in each booster’s aft skirt. The ASPUs remain connected to the vehicle from stacking in the Vehicle Assembly Building (VAB) until liftoff.

Of course, in order to launch crew to deep space destinations, astronauts must be able to board the Orion spacecraft. The Crew Access Arm, which will be mounted nearly 300 feet (91.44 meters) above the platform, will allow just that.

The arm, consisting of a truss assembly and the “White Room”, was recently shipped to Kennedy Space Center (KSC), after having been manufactured at nearby Precision Fabricating and Cleaning in Cocoa, Florida. The access arm will allow astronauts to board the Orion spacecraft as it awaits launch at KSC’s historic Pad 39B. The arm will retract before launch to allow for a clear ascent from the pad.

Prior to that, however, the arm must be installed on the launch tower. Once mounted, the ML will be rolled into the VAB for validation and fitment tests.

Though the SLS’ maiden flight – Exploration Mission 1 (EM-1) – will launch without a crew, the access arm will provide workers access to the Orion spacecraft for equipment loading and checkout.

Workers help guide the Crew Access Arm onto a work stand after it arrives at NASA's Kennedy Space Center. Photo credit: NASA / Kim Shiflett

Workers help guide the Crew Access Arm onto a work stand after it arrives at NASA’s Kennedy Space Center. Photo Credit: Kim Shiflett / NASA




Curt Godwin has been a fan of space exploration for as long as he can remember, keeping his eyes to the skies from an early age. Initially majoring in Nuclear Engineering, Curt later decided that computers would be a more interesting - and safer - career field. He's worked in education technology for more than 20 years, and has been published in industry and peer journals, and is a respected authority on wireless network engineering. Throughout this period of his life, he maintained his love for all things space and has written about his experiences at a variety of NASA events, both on his personal blog and as a freelance media representative.

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