Both Crawler Transporters grounded – Crawlerway testing for HLV capability

by Chris Bergin

The two veteran Crawler Transporters (CT) are currently grounded, as evaluations continue into a what is believed to have been a lightning strike on CT-2 – which was being prepared for tasks associated with the Ares I Mobile Launcher (ML). Test results are also being evaluated into how the Crawlerway is expected to perform under the weight of a Heavy Lift Launch Vehicle (HLV).

CT2 Incident:

The two 3,000 ton tracked vehicles have a storied history, responsible for carrying the NASA fleet of vehicles from the Vehicle Assembly Building (VAB) to the launch pads, ever since the Saturn IB and right through to today’s Space Shuttles.

The CTs would live on past the end of the Shuttle era, by transporting Ares I – after successfully debuting with the Ares I-X test vehicle – or a proposed Shuttle Derived Heavy Lift Launch Vehicle (SD HLV).

With at least two more shuttle missions to go, the Constellation Program (CxP) added a task that was set to take place ahead of STS-133’s rollout – to weigh and relocate the newly constructed Ares I ML.

The Ares I ML test and relocate involves both CTs – with the ML being weighed by the Crawler Transporter (CT-1) at its current location at the Mobile Launcher Platform (MLP) refurbishment site, while CT-2 works in tandem by freeing up the new location by moving MLP-1 to the VAB.

CT-1 will then move the Ares I ML the relatively short distance to its new home at the east refurb site, where it will be lowered down on to mounts. The entire operation – which was scheduled for late August – would be spread out over five days.

However, CT-2 was recently struck by lightning – it is believed, though still under an official investigation as to an exact root cause – after the recently installed special electrical equipment was damaged. The issues with the CT were found after a recent checkout, with problems associated with the control boards for the servo valve on the JEL system. The repair work will take around four to six weeks.

“Crawler Transporter-2: Engineering is evaluating an issue with all eight of the Jacking Equalization & Leveling (JEL) servo valves,” noted the NASA Test Director (NTD) in an opening report on the problem (L2). “The four electronic control boards for these valves were removed and sent to the Malfunction Lab for evaluation.

“The Servo valves (have been removed) and valves shipped to the Vendor for evaluation and rebuild. Turnaround estimate is 4-6 weeks. A timeline is being built of events/tasks that have taken place on CT-2 from 1 April through 31 July. Included are: PM’s, repairs, welding, lightning events, and anything else that may help explain the event. Investigation continues as to possible causes of the failure.”

“The investigation continues with further troubleshooting as to the possible cause of the failures,” added a later update. “The failure analysis lab has been asked to do some additional analysis on the circuit cards to look for any data that would support a lightning strike or power supply failure.”

With CT-2 under investigation, CT-1 has also been grounded for the interim. However, it is likely the results of the lab testing will allow for the release of CT-1 in time to support STS-133’s rollout from the VAB, currently scheduled for September 28.

“Once all parts are received back from the vendor and re-installed, testing will be performed to verify no other CT systems were affected,” added the latest NTD update. “The use of CT-1 is currently being constrained by the CT-2 investigation. CT-1 may be released back into service when the failure analysis of the control cards is completed.”

Crawlerway Testing for HLV:

The home track of the CTs is also undergoing a study, as the prospect of a HLV riding down the crawlerway sooner than outlined in the FY2011 budget proposal increasing as the political refinements move forward.

Under what is still the current Program of Record (POR), Ares I is/was to be joined by Ares V – Constellation’s HLV. The Ares V program was rumored to be considering a larger type of Super Crawler, with six tracks, to carry the Ares V to the pad. (Left: Notional image based on early L2 information).

However, the first references to the challenge of ensuring such a heavy vehicle – one with two full fuelled five segment Solid Rocket Boosters (SRBs), as opposed to solely liquid-fuelled vehicles, tanked after arriving at the pad – were provided in this week’s review of construction at the Kennedy Space Center (KSC).

“Study involves testing of various crawlerway rock surfaces to better understand the feasibility of operating a tracked transporter for a heavy-lift program,” noted KSC Construction’s August presentation (L2). “Similar testing was last conducted in the mid-1960s in support of the Apollo Program.”

Initial testing has already been completed on an area of crawlerway just outside of Constellation’s Pad 39B, via a strange looking contraption which aimed to test the impact of over 25 million pounds on the rock surface of the track.

“This compatibility testing was conducted on the crawlerway just outside of LC-39B and was performed at the equivalent anticipated Ares V rollout weight of 25,200,000 pounds versus the Shuttle/Apollo rollout weight of 18,000,000 pounds,” added the presentation.

“Testing results will provide degradation characteristics, rate of deterioration, expected lifecycle of various materials, coefficients of friction and reaction forces exerted upon a crawler-transporter shoe.

“Several surfaces were tested and included rock expected to be optimal for a tracked transporter, rock anticipated to be optimal for a dual-use crawlerway (supporting both a tracked and wheeled transporter), and resilient surfaces targeted to reduce excessive loading of a crawler shoe as it crosses roadways and VAB transitions.”

The findings of the testing, which was conducted by NASA, the United Space Alliance (USA), Architect and Engineering firm Jones Edmunds and Associates (JEA) and a couple of additional contractors, are expected sometime in September. Additional testing will take place, with STS-133’s rollout also aiding the results.

“Testing and site demobilization at LC-39B are now complete, with a report from JEA targeted for September 2010, although there are plans to conduct some additional testing and instrumentation of the crawlerway during the next shuttle rollout,” added the notes.

The iconic 100-foot wide double pathway is made up of a seven foot deep bed of stones, which lies beneath a layer of asphalt and a river rock surface. The surface requires constant maintenance to ensure the smooth passage of the Shuttle during its ride on the CT to the pad.

The latest construction news noted that a major project will be undertaken to repair areas of crawler that lead up to Pad 39A, requiring 32,000 tons of the specialised Alabama river rock to be used.

“This project involves removing and replacing the severely degraded river rock along the surface of the LC-39 crawlerway from Ordnance Road to the Pad A surface. The uniformly rounded river rock surface provides the necessary cushioning and low-friction coefficient characteristics that are critical to all crawler-transporter operations,” added the presentation.

“While the crawlerway foundation includes a minimum of 3 feet of compacted limestone, the minimum depth of the rock surface varies between just 4 inches on the crawlerway straight sections to 8 inches on the curves. The estimated total amount of new rock necessary to complete this project is 32,000 tons.

“All the excavated rock is being stockpiled at the Diverted Aggregate Reclamation and Collection Yard (DARCY) site within the landfill and will be screened into separate piles of fine and larger rock for future reuse throughout KSC as decorative borders, road base and crawlerway repairs.”

Other major work is also listed, including news that Pad 39B will undergo major demolition work, as planned via the Constellation Program. Sources note this work is likely to be placed on hold due to large costs. An article will be published when inquires into the project’s status are addressed.

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