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article imageNASA's crawler-transporter takes mobile launcher for a ride

By Karen Graham     Sep 4, 2018 in Technology
The SLS Mobile Launcher reached a major milestone, as it rolled to Pad 39B atop Crawler Transporter -2 on Friday. It will be rolled back to the Vehicle Assembly Building (VAB) for a year’s worth of verification and validation testing this weekend.
The 11 million pound towering structure to be used for liftoffs of NASA’s Space Launch System (SLS) rolled from a construction site to pad 39B at NASA's Kennedy Space Center in Florida atop Crawler Transporter -2 (CT-2).
After checking out the umbilicals and other attachments to be used at the launch pad, the SLS Mobile Launcher (ML) will again be moved back to the VAB where it will undergo systems testing and validation for a year before being ready to accept the first SLS rocket ahead of Exploration Mission -1 (EM-1).
The Space Launch System’s mobile launch platform approaches a fork in the crawlerway leading to la...
The Space Launch System’s mobile launch platform approaches a fork in the crawlerway leading to launch pad 39B, in the background.
NASA/Jamie Peer Image
That feat was an accomplishment in itself, and perhaps something many people don't think about too much. - I'm talking about the massive crawler-transporters used to carry vehicles on the Mobile Launcher Platform, and after each launch return to the pad to take the platform back to the VAB.
The last time the crawler-transporter and a mobile launch pad were rolled out together was in 2011, so there is a whole generation of space enthusiasts who have yet to hear about NASA's amazing and massive CTs.
NASA's two crawler-transporters
NASA actually has a pair of tracked vehicles used to transport spacecraft from NASA's Vehicle Assembly Building (VAB) along the Crawlerway to Launch Complex 39. They were designed and built by Marion Power Shovel Company using components designed and built by Rockwell International at a cost of $14 million apiece.
When the CTs were completed, they became the largest self-powered land vehicle in the world. They are 40 meters (131 feet) long and 35 meters (114 feet) wide. The height of the CTs can be adjusted 6 to 8 meters (20 to 26 f33t) and they are also capable of being balanced so the launch vehicle is always perfectly level.
The curb weight or you could say the weight of each Crawler-transporter without anything on its deck is a massive 2,721 tons (6,000,000 lb). With this much weight to move around, it takes some powerful engines, too. After an upgrade in 2003, each crawler had 16 traction motors, powered by four 1,000 kW (1,341 hp) generators, in turn, driven by two 2,050 kW (2,750 hp) V16 ALCO 251C diesel engines.
In 2012, Crawler-Transporter -2 (CT-2) was given another upgrade that involved "new engines, new exhausts, new brakes, new hydraulics, and new computers," to increase its lifting capacity from 5,400,000 to 8,200,000 kg (12,000,000 to 18,000,000 lb).
NASA crawler-transporter - 2000
NASA crawler-transporter - 2000
Kennedy Space Center has been using the same two crawlers, now nicknamed "Hans" and "Franz", since their initial delivery in 1965. In their lifetime, they have traveled more than 5,500 kilometers (3,400 miles), about the same driving distance as from Miami to Seattle - and all at the incredibly turtle-like maximum speed of 1.6 kph (1 mph) loaded, or 3.2 kph (2 mph) unloaded.
And for space trivia lovers, did you know that on January 21, 2000, the two crawler-transporters were added to the National Register of Historic Places (NRHP Registry #99001643).
Space Shuttle Challenger is carried by a Crawler-transporter on the way to its launch pad  prior to ...
Space Shuttle Challenger is carried by a Crawler-transporter on the way to its launch pad, prior to its final flight before being destroyed in the Space Shuttle Challenger disaster in January 1986.
We will be hearing more about the CT-2 over the coming year. NASA is targeting the first launch of SLS for 2020 when it will send the Orion space capsule on a trip around the moon. The SLS will tower more than 30 stories tall and will become the most powerful launcher in the world once it debuts.
Pad 39B was originally built for the Saturn 5 moon rocket and was also used during the Apollo, Skylab, and Apollo–Soyuz programs. The launch pad was then used to transport Space Shuttles from 1981 to 2011.
More about NASA, SLS, mobile launch pad, Vehicle Assembly Building, pad 39B
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