Service structure

A service structure is a permanent steelframework or tower erected on a rocketlaunch pad that allows assembly, servicing, and crew onboarding of the launch vehicle prior to liftoff.

In NASAlaunches at the Kennedy Space Center, astronauts enter the vehicle through a type of service structure called an "umbilical tower". Immediately before ignition of the rocket's engines, all connections between the tower and the craft are severed, and the connecting bridges swing away to prevent damage to structure and vehicle. An elevator in the tower also allows maintenance crew to service the vehicle.