KSC testing the VS – designed to dampen SLS swaying on a windy pad

by Chris Bergin

Engineers at the Kennedy Space Center are set to test the Vehicle Stabilizer (VS) via a motion simulator at the Launch Equipment Test Facility (LETF). The VS will have a key role during Space Launch System (SLS) pad flows, dampening out the loads on the huge structure as the monster rocket “sways” in the often-windy conditions at her coastal launch site.


NASA’s flagship Heavy Lift rocket is set to debut in 2018 in her initial Block 1 configuration.

During stacking, rollout to Pad 39B and launch, SLS will be hosted on the Mobile Launcher (ML), a huge tower and platform that provide the role of both the Fixed Service Structure (FSS) and Mobile Launch Platform (MLP) used during the Shuttle era.

2016-03-03-151331With SLS already mated to the ML, following a stacking and integration flow within the Vehicle Assembly Building (VAB), the stack will depart the building via the use of the modified Crawler Transporter, making the slow crawl to the modified “clean pad” at complex 39B.

Engineers will then complete the numerous connections between the ML and the pad electrical, hydraulic and fuelling lines.

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, which include power, communications, conditioned air, water for cooling, wash-down, and was designed with ignition over-pressure protection in mind.

Its massive tower hosts elevator and gantry systems that the pad crews – and eventually astronauts – will utilize during a launch campaign.

Its main function, however, is the array of umbilicals that will connect SLS with the ML.

Ahead of their installation into the various levels of the ML, the umbilicals are being tested in a magical area of KSC, known as the Launch Equipment Test Facility (LETF).

2015-07-07-144441A theme park for pad systems, the site has a deep heritage for testing launch-critical ground support systems and equipment, such as the Orbiter Access Arm (OAA), External Tank Gaseous Oxygen Vent Arm, External Tank vent lineTail Service Masts and umbilical systems, and Solid Rocket Booster Hold Down Posts.

It has also been involved with Cryo testing for the defunct X-33 technology demonstrator for the VentureStar program and had a role in testing Delta IV ECS umbilicals andCentaur Upper Stage rolling beam tests.

The facility allows for simulated launch vehicle events such as movement from wind, ignition and liftoff, effects of solar heating and cryogenic shrinkage. It’s equipped with a control room – allowing engineers to collate data and detect any hazardous conditions with the hardware undergoing testing.

2015-07-07-151308It also includes workshops and even its own High Bay – large enough to host the assembly of the large ground support structures.

It has already hosted test umbilical hardware for SLS, including an arm back in 2012, which had originally been planned for use with Ares 1.

However, it was the installation of the Orion Service Module Umbilical (OSMU) that was the major milestone for the new ara, with its design now set and ready to become part of an array of connections that will be vital to SLS and Orion ahead of launch.

Numerous SLS and Orion umbilicals have now made it to the LETF while others are being fabricated ahead of testing – as noted in the latest L2 LETF Status Report.

2016-03-03-160854“OSMU: The raw materials required for the next round of winch prototype fabrication and testing have been identified and purchasing is in-work. In addition, new special tooling and fixtures have been identified for this fabrication and purchasing is in-work.

“The Core Stage Forward Skirt Umbilical (CSFSU – pictured left) was loaded on a flat-bed truck at Coastal Steel and delivered to the LETF.  The LETF shop is preparing the High Bay to receive the umbilical arm.

“The Interim Cryogenic Propulsion Stage Umbilical (ICPSU) two-inch hydraulic tubing installation is 90 percent complete. The cryo flex hose platform fabrication is 100 percent complete and ready for install.”

2016-03-03-161422At the heart of the LETF is the Vehicle Motion Simulator (VMS), utilized to emulate all the movements a rocket makes as it is rolled to the launch pad, and more importantly through the first 30 milliseconds of flight.

This allows exact simulations of the force and conditions umbilicals and other launch equipment must work in to become qualified for use. Procedures and clearances can also be evaluated using the VMS.

Motion Simulator test equipment will also be used on the Vehicle Stabilizer (VS), with the simulator to be used to impart loads into the VS. This will “mimic” the projected loads that will be imparted onto the VS by the SLS, as she rocks in the wind while on the pad.

2016-03-03-162045This system has a heritage in the lessons learned during the Saturn V days when engineers literally played a tug of war and “shoved” a Saturn V back and forth inside the VAB to gather data on how the stack would behave while swaying in the wind.

The video of the “Tennis Shoe Test” – originally acquired by L2 (now uploaded to youtube for public viewing) – and overviewed by CollectSPACE.com – shows engineers pushing and pulling at the top of SA-500F with their feet and via the use of a rope.

The video – accompanied by a humorous soundtrack – also shows the Saturn V era VS, attached to the rocket via the service structure.

Thanks to modern day technology, expected loads between SLS and the ML can be accurately simulated, with the LETF adding to the database via actual testing of the hardware on the ground. This will provide the required limits that will become part of SLS’ ground rules while she’s outside of the VAB.

(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.)

(L2 is – as it has been for the past several years – providing full exclusive SLS and Exploration Planning coverage. To join L2, click here: http://www.nasaspaceflight.com/l2/)

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