NASA’s Crawler Transporter -2 (CT-2) is continuing to enjoy its first outing in over a year, as its roll to Pad 39B tests its latest modifications ahead of an active role with the Space Launch System (SLS). Its trip at the pad began last week, but was staggered to mark the 50th anniversary of the famous crawlers on Monday, both of which are being re-purposed for SLS, following their previous roles with the Saturn rocket and the Space Shuttle.



Crawler Transports – The New Era:

The CTs have been part of the space program since the the 1960s, with fabrication of the behemoth machine’s parts initiated in 1963 at their birth site in Ohio.

Contractor Marion completed 90 percent of the design and began to ship parts of the vehicle in March 1964. This allowed assembly of the first CT at Merritt Island, which was completed in November of that year.

Live testing began in 1965, with the first Crawler put through its paces that summer, moving the Launch Umbilical Tower (LUT) one mile along two short stretches of road to test how the CT would perform on different surfaces. As a result, this week marks the 50th anniversary of the CTs.

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).

Now the CTs would find themselves transporting the Mobile Launch Platform (MLP) – complete with the Shuttle orbiter, her External Tank and Solid Rocket Boosters (SRBs) – to the pads.

The CT opened 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 vital data already at hand from the Enterprise roll to 39A, Columbia and the STS-1 stack were rolled out to the same pad by the CT on December 29, 1980. STS-1’s launch kicked off the Shuttle era the following year.

The CTs 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 – a massive 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).

While the CTs continued their role with Shuttle, the opening task with the Constellation Program (CxP) involved the rollout of the Ares I-X vehicle to Pad 39B for its October, 2009 test flight.

CT-2 paid its first visit to the Ares Mobile Launcher (ML) – not involved with the Ares I-X launch – in 2010, relocating the newly built structure to its parksite home. However, this was during an uncertain time, with the Constellation Program being closed down.

The CTs found themselves being re-purposed yet again, this time with the 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 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 over 14 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.

CT-2’s upgrades began with JEL (Jacking, Equalizing, and Leveling) valve replacement.

The upgrades included the Alco E1 & E2 Engine Panel upgrades, Parking/Service Brakes improvements, Cabin replacement/modifications and the installation of two new massive 1500KW Generator sets.

Classed as a 20 year life extension effort under NASA’s Ground Systems Development and Operations Program (GSDO) effort, 45 areas were worked on – right down to new carpets in the cabins – with a test roll down the Crawlerway from the VAB conducted in 2012.

CT-2 returned to the VAB to take up residency inside the giant building’s High Bay 2 (HB-2) for the next set of modifications, focusing on the modification work on the roller bearings.

It was soon joined by CT-1 in High Bay 3 (HB-3), as it too began upgrades, opening with asbestos abatement/removal tasks ahead of the engine control room modifications.

CT-1 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.

“The Test confirmed the max power output for each generator. Also, the test served as the baseline for Temperature and Airflow around locations of the MPPU’s and the MPPU Porch,” per L2’s CT upgrade section.

“The Porch is slated to be installed on End 3 of CT-2 in a year or two.”

CT-1 was recently seen at the old Saturn Mobile Service Structure (MSS) park site at the A/B Crawlerway spilt, keeping Mobile Launch Platform -2 (MLP-2) company.

Meanwhile, CT-2 – with a fresh set of bearings – moved out of HB-2 for a short trip before returning to the VAB, allowing for lubrication checks and testing last year.

The CT was taken on a test run around the VAB to a point just behind OPF 1.

The test – according to L2’s CT upgrade section – helped evaluate the CT’s new rollers, bearings and shafts on the vehicle’s A and C corners, along with a new Strain and Temperature System.

The CT then made another move, this time to its CT yard – a familiar port of call for the Crawlers.

CT-2 then rolled to the east side of the VAB through the curves and then back to the SRM Road, twice.

It then returned to the CT Yard for a refuel and some maintenance.

After a brief CT yard stay, CT-2 was moved back to the VAB for continuation of Phase II modifications.

All of the modifications to CT-2 are expected to be completed by early 2016.

“Crawler Transporter (CT) Team received the refurbished CT gear-box components,” added L2’s CT Upgrade Section.

“Two of the shafts have been successfully installed and the remainder will be installed as part of the gear-box project.

“Prior to shoe installation a spin test will take place to check for proper installation in preparation for a planned rollout.

Those upgrades have since been completed, with a test run of CT-2 to Pad 39B taking place on Wednesday. L2 schedule information showed weather this move was scheduled to start at 8am on Wednesday.

“VAB CT Move: CT-2 will move from VAB, Hi-Bay 2 to Pad 39B on 2/18/15 at 0800 Eastern,” per L2’s CT Upgrade section.

The start time was slightly later in the day – after teams had to fix a minor controller module problem – before KSC information confirmed the CT was rolling.

It was initially thought the CT would take several hours to roll down the crawlerway. However, the CT first made a short trip to an area between OPF-1 and the CT Yard, in the middle of the Tow Way, allowing for the adjusting of Tread Belts.

The main roll was conducted on Monday, timed to coincide with the anniversary, allowing for photo opportunities and further promotion of NASA’s future ambitions relating to deep space exploration.

CT-2’s destination – Pad 39B – is now deep into its transition to become a “clean pad”. It was recently announced it will receive a new Flame Deflector and associated Flame Trench, required to help the pad deal with the immense thrust of the SLS.

Everything remains on track for CT-2 is to carry out its first operational role by picking up the Mobile Launcher (ML) – which is continuing conversion work for SLS – before carrying it inside the VAB, all likely taking place in late 2017 or early 2018.

This will be a key part of the build up to Exploration Mission -1 (EM-1), with the first Space Launch System (SLS) expected to be stacked on the ML for a roll to Pad 39B.

The first rollout is expected to test all of the systems, along with pad fit checks.

The stack will likely roll back to the protection of the VAB ahead of launch preparations for the first mission rollout of the Heavy Lift Launch Vehicle (HLV) with Orion, for the Exploration Mission -1 (EM-1) pad flow to lift-off, culminating in the first mission of the new era in mid-2018.

(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. Final image of SLS via L2 Artist Nathan Koga. Other image via L2 Historical and NASA)

(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/)