All hail the Super Crawler – CT-2 put through its paces ahead of SLS

by Chris Bergin

One of the unsung workhorses of the space program, the Crawler Transporter, is ready for its own transition back to exploration – with CT-2 testing out its array of modifications in preparation for carrying the Space Launch System (SLS). Its growth into a “Super Crawler” is part of a 20 year extension of its lifetime that ranges back to 1963.

CT-2 – The Super Crawler:

After fabrication of the giant machine’s parts begin in Ohio in 1963, assembly of the first crawler-transporter was completed on Merritt Island the following year.

The CT’s were built in response to the huge effort to put a US astronaut on the surface of the Moon by the end of the 1960s, with the first Saturn V rocket transported to the pad by the CT was the “Facilities Checkout Vehicle” AS-500F, ahead of the unmanned Apollo 4 mission, with the CT transporting the Saturn Vs for all of the Moon missions.

The final Saturn to be transported to Complex 39 was the Saturn IB for the ASTP mission in 1975, ahead of the transition towards the Space Shuttle Program (SSP).

After rolling out Saturn launch vehicles, complete with their service tower structures rising into towards the Florida skyline, the CTs role with Shuttle saw the use of the Mobile Launch Platform (MLP) hosting the orbiter with her External Tank and Solid Rocket Boosters (SRBs).

The CT began its Shuttle career by rolling Enterprise to launch pad 39A on 1 May 1979 for testing.

During rollout, Enterprise was driven at various speeds to measure and note the various vibration strains on the fully-mated Shuttle stack. This was used to determine an optimal rollout speed for operational Space Shuttle missions.

Once at the pad, Enterprise helped validate launch pad procedures – with her biggest test and benefit to the ground processing operations coming during the full-up Wet Countdown Dress Rehearsal when she helped simulate External Tank fueling operations for launch.

With vital data already at hand from the Enterprise roll to 39A, Columbia and the STS-1 stack were rolled out the same pad by the CT on December 29, 1980.

As mid-February 1981 arrived, teams at Pad-A began prepping the vehicle for the wet countdown dress rehearsal and Flight Readiness Firing (FRF) of her three Space Shuttle Main Engines (SSMEs). STS-1’s launch took place in April.

The CTs – nicknamed “Hans” and “Franz” – took it in turns to rollout all of the Shuttle stacks for their missions, an always-impressive sight, not least STS-6, as the CT rolled its superstar passenger of Shuttle Challenger out in fog bank over the crawler way at the Kennedy Space Center (KSC) in March, 1983.

Modifications were made throughout the lifetime of the CTs, including ahead of Return To Flight when replacement work was carried out on large amounts of the vehicle, including the huge shoes that make up the tracks on the Crawlers – no small feat considering the CT has eight tracks, two on each corner, with each track consisting of 57 shoes, each shoe weighing in at 1,984 pounds (900 kg).

The CTs continued their role with Shuttle, but also enjoyed what was to be their opening task with the Constellation Program (CxP), rolling the Ares I-X vehicle to Pad 39B for its October, 2009 test flight.

With the Constellation Program cancelled, CT-2 paid its first visit to the Ares Mobile Launcher (ML) in 2010, relocating the newly built structure to its parksite home.

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At the time, the ML faced a bleak future, until lawmakers approved the replacement program for Constellation, calling for the CTs to roll vehicles more akin to the Saturn V’s they used to carry to Complex 39. That vehicle will be the Space Launch System (SLS).

With the Crawlerway tested to show it could handle the massive weight of the Heavy Lift Launch Vehicle (HLV), a test run of the CT with the former Ares ML – since designated to host SLS vehicles – was conducted in November, 2011.

The trip to 39B was taken at a very steady pace, allowing for critical measurements to be taken during the 4.2 mile journey. The CT conducted the roll of the large structure without issue, prior to returning it to near the Vehicle Assembly Building (VAB) after pad testing was completed.

However, it will be a much heavier stack to carry once the SLS is integrated on the ML inside the VAB – with the heaviest SLS rollout weight, including the ML, estimated to be about 14.2 million pounds. As such, CT-2 received approval for modifications, to modernize and beef up its capability almost immediately after completing the ML roll testing.

“After a month of work at the crawler yard park site, we moved inside the VAB,” noted Mary Hanna, CT project manager in the Vehicle Integration and Launch Branch of NASA Ground Systems Development and Operations. “This gave us access to the heavy cranes and it provided weather protection over the past 10 months.”

Under the 20 year life extension, phase 1 of CT-2’s upgrades included JEL (Jacking, Equalizing, and Leveling) valve replacement. Alco E1 & E2 Engine Panel Upgrade, Parking/Service Brakes, Cabin replacement/modifications and the installation of two new massive 1500KW Generator sets.

In total, 45 areas were worked on, right down to new carpets in the cabins. A total of 32 mods were put under test conditions as the Super Crawler departed from the VAB earlier this month.

CT-2 still managed to have a bit of a tantrum about a third of the way down the Crawlerway, stopping at the old Crawler Maintenance Site by the Visitor’s Observation Tower. However, that issue – classed as “minor bugs” was soon worked out of the grumpy CT, allowing it to make the rest of the trip to the pad.

“The height transducer brackets and components were reinstalled and operated as expected. All E3 and E4 (generator/engine) bellows have been repaired, reinstalled and are operating as expected. After a successful steering test, CT-2 propelled up the pad slope and jacked MLP-2 to clearance height,” noted a L2 report on the testing, hosted on the dedicated L2 CT Update Section, including large updates and exclusive modification photos/videos – LINK.

“The CT/MLP combination successfully propelled down the pad slope. All worked was performed using the primary processor. We then switched to the backup processor to perform/validate and experienced a communications problem. The CT/MLP spent the night outside the Pad A gate on shore power. The plan (was initiated) to utilize/validate the new laser system to place the MLP back at Pad A and return to the CT yard.”

CT-2 is expected to take up residency inside the VAB once again for the next set of modifications, beginning in January.

“The next round of work will include replacing the jacking and leveling cylinders and the roller bearing assemblies to accommodate the additional weight of the Space Launch System rocket.” added Terry Berman, project lead for the United Space Alliance (USA).

The plan is to complete all modifications in time for a final set of testing in 2015, ahead of the arrival of the core hardware for the opening SLS launch in 2017.

(Images: Via L2 content from L2’s SLS specific L2 section, which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers – updates on the SLS and HLV, available on no other site. Other image via L2 Historical and NASA)

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