At NASA's Kennedy Space Center in Florida a tractor levels out the gravel after the crawler transporter.

At NASA's Kennedy Space Center in Florida, a tractor levels out the gravel after the six-million-pound crawler-transporter passed by on its way from the Vehicle Assembly Building to Launch Pad 39A. The test drive is designed to check out recently completed modifications to ensure the crawler-transporter's ability to carry launch vehicles such as the space agency's Space Launch System heavy-lift rocket to the pad.

NASA's Ground Systems Development and Operations Program is leading the 20-year life-extension project for the crawler. A pair of behemoth machines called crawler-transporters has carried the load of taking rockets and spacecraft to the launch pad for more than 40 years at NASA’s Kennedy Space Center in Florida. Each the size of a baseball infield and powered by locomotive and large electrical power generator engines, the crawler-transporters will stand ready to keep up the work for the next generation of launch vehicles projects to lift astronauts into space. For more information, visit http://www.nasa.gov/exploration/systems/ground/index.html Photo credit: NASA/Ben Smegelsky