Crew Access Arm arrives as SLS Mobile Launcher takes shape

by Chris Bergin

The huge Mobile Launcher (ML) for the Space Launch System (SLS) is gaining more of its array of appendages as it prepares to host the Exploration Mission -1 (EM-1) launch. Although this first SLS mission won’t involve astronauts, the Crew Access Arm (CAA) is making its journey on the back of a large transporter to the ML for installation.

ML Taking Shape:

The ML – designed by RS&H (base and structure), along with ASRC Aerospace Corporation (prop systems etc.) – consists of the main support structure that comprises the base, tower and facility ground support systems.

Ares 1 on ML with Roller Coaster EESIt was initially built for the Constellation Program (CxP) to host Ares I launches, with a launch specific to the “stick” design of the rocket.

However, the cancellation of the Constellation Program (CxP) resulted in the ML receiving its pink slip.

Parked up near the VAB, rumors of what would happen to the ML ranged from pulling the structure apart for scrap, through to a joke that was circulated throughout the KSC workforce claiming there was interest from Disney for turning it into a fun ride.

Ironically, Disney engineers had already worked with the KSC team on the roller coaster Emergency Egress System (EES) – a giant structure that has since been ruled out as the EES for the SLS.

The ML was brought back into focus for SLS, with the requirement to modify the structure to host the new rocket.

The launch mount was the first major element of the ML to be redesigned, changing from a mount catered for a single booster to one that could host for a vehicle with two boosters and four RS-25 engines.

Meanwhile, testing of the vast number of umbilicals that will be mated with SLS and Orion ahead of launches continues to take place at the Launch Equipment Test Facility (LETF) inside the Kennedy Space Center grounds.

Currently being tested in the Vertical Stabilizer (VS), that will – as the name suggests – keep the huge rocket stable on the pad.

Engineers recently conducted a full disconnect and retraction test with the motion simulator at the LETF.

The Motion Simulator test equipment used on the VS has also been used to impart loads into the hardware. This mimics the projected loads that will be imparted onto the VS by the SLS, as she rocks in the wind while on the pad.

At the ML site, engineers also lifted and installed a third umbilical on the ML for a fit check.

The Core Stage Inter-tank Umbilical (CSITU) was lifted up to its position on the ML by a huge crane that is residing with the ML before being lowered down ahead of final preparations for its full installation.

The CSITU has now been sent to the Vehicle Assembly Building (VAB) for instrumentation installation before the final mate with the ML in mid-December.

This umbilical is the third in a series of five new umbilicals that will be installed along the tower of the ML. Its main function is to vent excess gaseous hydrogen from the rocket’s core stage. This umbilical also will provide conditioned air, pressurized gases, and power and data connection to the core stage.

Already fully installed on the ML is the Orion Service Module Umbilical (OSMU) – which was the first umbilical to be tested at the LETF and the Core Stage Forward Skirt Umbilical, or CSFSU.

The full role of the OSMU will be to provide electrical, data, and purging processes to Orion’s Service Module.

Weighing approximately 40,000 lbs, the OSMU is 27 feet long, 17 feet wide, and 42 feet tall – including the OSMU safe house to protect it from the intense, SRB-induced launch environment.

“The OSMU is a T-0 umbilical mechanism providing GSP, Environmental Control System (ECS), GCS, BAIR, LCS, and GN2 to the Orion Service Module (SM),” noted an extensive overview presentation in L2.

The release of the OSMU will be triggered at T-0 (SRB ignition) by a signal to the release mechanism on the ground umbilical plate. At this point, the OSMU truss boom structure will tilt-up into its safe house on the ML umbilical tower. This truss boom structure (arm) will reach out toward but remain 16 feet shy of the Orion Service Module itself.

2015-07-07-163230The CSFSU is a T-0 umbilical requiring VAB access for mating of the umbilical plate to the SLS rocket.

Commodity lines for the CS FS will run through the stabilizer truss of the umbilical arm, with drape commodity lines extending from the arm to CS FS attach location.

All these umbilicals will swing away from the rocket and spacecraft just before launch, a process that will be tested in sequence in the months ahead of the first SLS launch, which is currently waiting on a new official launch date.

NASA managers are deciding between the “best case” date of December 2019 and a “risk-informed” date of Q2 (around May) 2020 for EM-1.

One of the iconic appendages for the ML will be the Crew Access Arm (CAA), which is one of the largest additions to the ML.

The CAA is so large the delivery process is happening in two phases. First, the CAA was laid on its side in order to travel from the PFC shop in Canaveral Groves where it was fabricated.

After making part of the journey to a large parking lot, the team rotated it back upright for the remaining assembly work, including the installation of two 20,000lb hinges.

The CAA will make its final trip to the ML itself by the end of this month.

A subject of government discussion is the fact this ML – as designed – will only be used for one mission.

Following the maiden flight of the SLS – in her Block 1 configuration – engineers will then go to work on a 33-month long process to reconfigure and modify the ML for the second flight of SLS in her Block 1B role.

This rocket is taller and uses a different, more powerful, Upper Stage – called the Exploration Upper Stage (EUS) – requiring a large-scale rework on the ML. Questions are being asked as to whether it would help the schedule and/or costs if NASA opted to build another ML – for Block 1B – from scratch.

NASA has previously resisted such attempts claiming it would cost several hundred million dollars to build a second ML and have as such stayed the course on the EM-1 to EM-2 modification plan for the current ML.

Images: NASA and L2 which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers.)

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

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