Mobile launch platform begins two weeks of testing
BY STEPHEN CLARK
Posted: November 16, 2011
NASA moved a new 39-story mobile rocket servicing tower to launch pad 39B at the Kennedy Space Center today to test how the enormous structure reacts during the slow-motion crawl on top of a diesel-powered transporter.
Reaching a top speed of 1.1 mph, the crawler adjusted its pace and conducted two emergency stops along the four-mile journey. The tests were designed to measure how the tower reacted to sudden loads and how it moved at different speeds, according to Larry Schultz, NASA's mobile launcher project manager.
Workers set up 3D cameras on the deck of the mobile launch platform aimed at targets high on the tower to measure the amplitude of movements at the top of the structure, Schultz said.
"We want to watch how much the tower moves as you're driving down the crawlerway at various speeds," Schultz said before rollout. What if you slam on the brakes? What happens to the tower?"
NASA expected to top of the tower to sway about the width of a ping pong ball, but engineers desired empirical data on the structure's stiffness now to avoid any surprises closer to the rocket's first launch.
"They're concerned with how much would we expect the rocket to wiggle as we go out to the pad, and in conjunction with that, how does the tower wiggle as we go out," Schultz said.
The crawler arrived at the launch pad around sunset and was hard-down at 6:29 p.m. EST (2329 GMT).
The tower will stay at the launch pad for about two weeks as NASA verifies clearances between the pad surface and the platform. Technicians will also connect electricity lines between the tower and the launch complex.
The 390-foot-tall mobile launcher was completed in 2010 for NASA's Constellation moon program. In the wake of that program's cancellation, the White House and Congress outlined a new goal for NASA to explore a variety of deep space destinations, including asteroids and Mars.
The new exploration program relies on space shuttle hardware and investments already made in the Constellation program, including the launch platform already constructed for the moon project's Ares rocket.
The Space Launch System, a behemoth rocket announced in September, will dispatch cargo and crews from launch pad 39B using the mobile tower moved Wednesday.
The first test flight of the SLS is not scheduled until December 2017, and design engineers will modify the base of the launch mount to support the SLS, which weighs more than twice as much as the Ares 1 rocket.
Workers will expand the 22-foot square hole in the base of the launch platform to support the larger Space Launch System, which is powered off the ground with twin solid rocket boosters and a hydrogen-fueled core.
Instead of the square hole built into the platform during construction, the SLS needs an opening 60 feet long and 30 feet wide. The platform will also be stiffened to support the more powerful rocket.
NASA expects to award a contract to an engineering firm as soon as this month to work on the detailed design of the required changes to the platform's base. It will take about a year to finish the design, then up to another two years to complete the modifications, according to Schultz.
The U.S. government spent $238 million on the mobile launch platform through the end of the Constellation program, and officials estimate it will cost another $100 million to adapt the structure for the Space Launch System.
Originally built for the Apollo program in the 1960s, NASA's two crawlers were outfitted for the space shuttle program and now have a future in the agency's next human space program. At least one of the crawlers will be strengthened to handle the extra load of the Space Launch System, which is taller and heavier than the space shuttle, according to Pepper Phillips, manager of the ground systems for the next-generation rocket.
The mobile launcher is the tallest object since 1975 to be mounted on top of a crawler. The tower is slightly shorter than the Saturn rocket's launch mount, which was last used for the joint U.S.-Soviet Apollo-Soyuz Test Project.
Launch pad 39B's shuttle-era servicing structures were removed earlier this year to make way for a clean pad, where there are no permanent towers besides the facility's three 600-foot-tall lightning masts.