Spaceflight Insider

Mobile Launcher test drive inches SLS one step closer to Exploration Mission-1

Engineers test the movement of the Orion crew access arm on the Mobile Launcher prior to rolling the structure to Pad 39B for fit checks. Photo Credit: NASA

A Chinese proverb roughly states: “A journey of a thousand miles begins with one step.” While this adage rings true for those undertaking Earthly ventures, it is also fitting for the launch of NASA‘s Space Launch System (SLS).

The Mobile Launcher arrives at Pad 39B for fit checks. Photo credit: NASA

The Mobile Launcher arrives at Pad 39B for fit checks. Photo Credit: NASA

Before the super heavy-lift rocket can soar skyward on its inaugural mission to the Moon on Exploration Mission-1 (EM-1), it must first make the 4.4-mile (7.24-kilometer) trip from the Vehicle Assembly Building (VAB) to Launch Pad 39B

In preparation for the flight, engineers and technicians with the agency’s Exploration Ground Systems took the 11-million pound (4.99-million kilogram) Mobile Launcher (ML) on its maiden journey to the pad to begin fit checks for the nearly 380-foot (115.8-meter) tall structure. The operation, conducted over a two-day period, marks a key milestone for the program.

“The mobile launcher is being moved to begin the next big program phase for verification and validation of all systems when it is connected to the pad and VAB systems,” stated Cliff Lanham, lead project manager for the mobile launcher, in a release issued by NASA.

The ML will remain at LC-39B for several days as engineers test utility connections and integration with key ground hardware, such as with the sound suppression and  environmental control systems.

Once the checks are complete, the ML will ride back to the VAB to begin a year’s worth of testing and checks inside the world’s tallest single-story building.

Though this is the first time the hardware has made the journey to Pad 39B in its SLS configuration, it actually marks the second trip for the ML to the launch site. Prior to the cancellation of the Constellation Program, the ML, sitting atop the multi-tracked Crawler Transporter (CT), made the trip to Pad 39B to undergo similar fit checks for the Ares I rocket.

The Constellation Program was cancelled, along with the Ares I launch vehicle, by the Obama Administration in 2009. Portions of Constellation were saved (the Orion spacecraft) with others, namely the Ares V super-heavy lift rocket, were re-purposed and renamed (a modified version of the rocket’s design became the SLS).

Testing of the ML will be conducted both on-site at Pad 39B, as well as from the Young-Crippen Firing Room at Kennedy’s Launch Control Center (LCC).

While there were some early reports that the ML had a significant lean, or deflection, that may have impacted the alignment of important umbilical connections and access arms, it would appear that those concerns might have been exaggerated.

With those issues laid to rest, engineers and technicians should begin working on the ML inside High Bay 3 in the VAB.

At present, EM-1 is slated to take place as soon as 2020. If everything continues to go as it is currently planned, EM-2 will return NASA astronauts to deep space missions as soon as 2023.

“This testing is necessary to ensure the systems will function as designed and to validate the systems operate as expected under the test conditions,” concluded Lanham.






Curt Godwin has been a fan of space exploration for as long as he can remember, keeping his eyes to the skies from an early age. Initially majoring in Nuclear Engineering, Curt later decided that computers would be a more interesting - and safer - career field. He's worked in education technology for more than 20 years, and has been published in industry and peer journals, and is a respected authority on wireless network engineering. Throughout this period of his life, he maintained his love for all things space and has written about his experiences at a variety of NASA events, both on his personal blog and as a freelance media representative.

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