Photos: Sunset from 40 stories high

NASA's mobile launcher for the Space Launch System is mounted at pad 39B at the Kennedy Space Center this week for fit checks and loads testing.

The towering structure moved to the launch pad Nov. 16 for two weeks of interface checks, loads measurements and testing of the mobile launcher on top of NASA's crawler.

The 390-foot-tall mobile launcher is scheduled to move off the pad Nov. 30 and return to a park site north of the Vehicle Assembly Building, where engineers will begin modifying the platform to support a heavy-lift rocket for exploration missions to asteroids, the moon and Mars.

The mobile launcher was designed for the Ares 1 rocket, which was canceled in 2010. Workers will expand the thrust hole at the base of the platform and install servicing arms and umbilicals up and down the tower.

The Space Launch System weighs more than twice as much as the Ares 1, and it features two solid rocket boosters strapped to the side of a 27.5-foot-wide core stage. The Ares 1 was powered by a single solid rocket booster first stage.

The Space Launch System is scheduled for its first test launch at the end of 2017, and the first crewed mission could follow in 2021 with a flight around the moon.

Launch pad 39B is also undergoing changes after the retirement of the space shuttle program. After demolishing the pad's shuttle-era service structures, NASA is installing and testing new high-tech control systems and fiber-optic cables, repairing propellant tanks, and working on the facility's water tower.

NASA also constructed three 60-story masts to protect future rockets from lightning strikes.

Spaceflight Now visited the mobile launcher at sunset Wednesday.

Credit: Stephen Clark/Spaceflight Now

MORE ROLLOUT PHOTOS >