Crawler Transporter 2 (CT-2) has completed all of the necessary modifications to upgrade it to Super Crawler status. The new Super Crawler is now set to roll out of the VAB on 21 March 2016 ahead of a series of performance tests to validate the transporter’s readiness to handle the massive load of the SLS rocket it will be tasked with ferrying to Pad-39B at Kennedy in 2018.

Crawler Transporter history:

The storied history of the Crawler Transporters (CTs) for NASA began in the early part of the 1960s when the herculean undertaking of moving the Apollo Saturn V moon rocket from its integration facility at the Vehicle Assembly Building (VAB) along the 3 and 4.2 mile crawlerway to the launch pads became a necessary part of U.S. human space program processing.

The two crawlers were designed and built by Marion Power Shovel with components designed and built by Rockwell International for a cost of $14 million (USD) each.

Parts were fabricated off-site and then delivered to the Kennedy Space Center for assembly on-site – as both crawlers were far too massive to be built to completion off-site and then delivered.

Both crawlers were considered “delivered” to NASA at the LC-39 complex area at the Kennedy Space Center in 1965 – at which point they were the largest self-powered land vehicles in the world.

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At completion, both CTs were 40 by 35 meters (131 by 114 ft) and weighed in at 2,721 tonnes (6,000,000 lbs) carried across eight tracks – with each track assembled from 57 shoes, each of which weighing in at 900 kg (1,984 lbs).

Each crawler was also specifically designed with a jacking and leveling system to keep the assembled spacecraft they carried level to within 30cm (1ft) during lifting, lowering, and launch pad ramp climbing operations.

On 26 August 1967, a CT was used to transport a spacecraft from the Vehicle Assembly Building to the launch pad for the first time as the Apollo 4 mission was moved to LC-39A.

Following Apollo 4 through the Apollo-Soyuz Test Program (ASTP) mission in 1975, the two CTs were responsible for moving all of the massive Saturn Vs as well as the Saturn IBs for the Apollo moon missions, the four Skylab missions, and ASTP to pads 39A and 39B.

Following completion of the Apollo program, the crawlers’ primary use was retooled for support for the coming Space Shuttle Program.

From 1979 through 2011, the two CTs – named Hans and Franz – took turns transporting all six of the space shuttle Orbiters (Enterprise, Columbia, Challenger, Discovery, Atlantis, and Endeavour) to the Kennedy launch pads.

These CT Shuttle transport trips included the preflight launch countdown and pad validation operations of the Space Shuttle Enterprise in 1979, the 135 missions of Columbia, Challenger, Discovery, Atlantis, and Endeavour from 1980-2011.

Moreover, the CTs conducted four unique pad transports in the guise of Challenger’s STS 51-E mission (which was cancelled after Challenger was rolled to the pad), the post-STS 51-L recertification initiative with the shuttle Atlantis at Pad 39-B in October-November 1986, and the two STS-400 Hubble rescue mission rollouts of Endeavour to Pad B in 2008 and 2009.

During the tenure of the Shuttle program, both CTs underwent routine maintenance operations to ensure their continued viability throughout the prolong lifetimes of the Shuttles.

However, in 2003, following the loss of the shuttle Columbia on the STS-107 mission, both of the CTs underwent extensive overhauls to upgrade their motor control centers, received new engine and pump ventilation systems as well as new diesel engine radiators and replacements of the two driver cabs on each end of the vehicles.

Six years later, one of the CTs was tasked with moving the Ares I-X test vehicle from the VAB to Pad 39B for what became the only mission of the now-cancelled/retooled Constellation Program.

While the Constellation Program was cancelled following the highly successful test of Ares I-X, it was already known at the time that whatever program followed the Shuttles would require extensive upgrades, systems replacements, and an overall “beefing up” of the Crawlers given their age and wear and tear over the – at the time – nearly 50 years of operations of the transporters.

Preparing for SLS – enter the Super Crawler:

In what became a staged approach to the Super Crawler modifications, the crawlers were first used for the Space Launch System (SLS) Program in November 2011 when one of them transported the Mobile Launcher (ML) that had been constructed for Ares I along the crawlerway and up the ramp to Pad 39B.

While the main purpose of the test was to deliver the ML to the pad to validate the at-the-time ongoing transition of the pad away from Shuttle era technology and into a 21st century launch facility, the test also allowed engineers to evaluate the crawler’s systems and overall performance for the new type of transportation that would be needed for SLS.

As soon as the November 2011 run to the pad with what would be repurposed as the ML for SLS was complete, the crawlers received funding and authorization to proceed through a major refurbishment campaign to make them Super Crawlers, with upgraded systems, replacement of degrading and worn out components, an official life extension for another 20 years, and – most importantly, an upgrade to handle the massive roll out weight of SLS.



For this plan, CT-2 was selected to undergo the transformation process first.

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

In total, 45 areas were worked on and a total of 32 modifications were undertaken, mods that were put under test conditions along the crawlerway in November 2012.

Following these tests, CT-2 returned to VAB High Bay 2 (HB-2) for the next set of Phase I modifications, focusing on the transporter’s roller bearings.

By the start of 2014, CT-1 had completed modifications in line with those already conducted on CT-2, along with being the test bed for new JEL Cylinder Prototype testing.

CT-1 was then used as the test article for a complete generator load bank test while CT-2 – with a fresh set of bearings – was moved out of HB-2 for a short trip before returning to the VAB, allowing for lubrication checks and testing as well as evaluation of the CT’s new rollers, bearings, and shafts on the vehicle’s A and C corners.

CT-2 then underwent a series of driving tests to further validate the completion of Phase I refurbishment work before the crawler was returned to the VAB for the commencement of Phase II of its 20 year life extension plan.

Over the past year, CT-2 has undergone refurbishment of its steering arms and cylinders, installation of larger and more powerful JEL cylinders, refurbishment of traction motor gear boxes, installation of new bearings, and a believed refurbishment of its Multi Purpose Purge Unit platform.

With these modifications now complete, CT-2 is ready to debut at the end of March.

At this point, the crawler will be put through a series of test “runs” along the crawlerway as well as lifting and leveling tests ahead of its first official role for the EM-1 SLS mission.

This first official SLS role will involve moving the massive ML tower from its park site near the VAB into VAB HB-3 in July 2017 ahead of EM-1 SLS stacking operations.

Those stacking operations are currently set to begin in March 2018.

Like Shuttle, stacking of the SLS vehicle will begin with the build-up of the SRBs.

According to the Integrated Mission Milestone Summary, available for download on L2, stacking operations of the twin SRBs will last approximately two months, from March to the end of April 2018.

Following SRB stacking, the massive Core Stage of SLS will be lifted over the transom and lowered between the two SRBs – in a manner similar to how the External Tank was lowered between the SRBs during Space Shuttle stacking operations.

Core Stage mate to the SRBs and the ML’s umbilicals will occur in early-May 2018.

This will be followed in mid-June 2018 by the mating of the ICPS (Interim Cryogenic Propulsion Stage) and Orion on top of the Core Stage.

Following full-up integrated vehicle testing and the Agency Flight Readiness Review, the first of two rollouts to launch pad 39B will occur at the beginning of August.

And this will be CT-2’s time to shine, as the transporter takes NASA’s first stacked and integrated space vehicle to the launch pad for the first time since STS-135/Atlantis rolled to the pad on May 31/June 1 2011.

Under the current Integrated Mission Milestone Summary, SLS will spend approximately one month at launch pad 39B undergoing a dry rehearsal test followed by a wet dress rehearsal to allow the launch teams to evaluate their countdown operations and validate pad and vehicle performance parameters prior to committing to the EM-1 launch campaign.

Following the wet dress rehearsal in mid- to late-August, CT-2 will once again be called upon to transport SLS back to the VAB in late-August for final closeouts and ordnance installation operations.

Once closeout and Ordnance installation is complete, CT-2 will once again ferry the massive SLS rocket out to pad 39B in September for a final, short volley of pad operations before launch on the EM-1 mission – currently slated to occur “by November 2018”.

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