Service structure

Space Shuttle Discovery is carried by a Crawler-transporter, a launch tower is visible in the background

A service structure is a permanent steel framework or tower erected on a rocket launch pad that allows assembly and servicing of the launch vehicle.

In NASA launches, astronauts enter the rocket 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.

Kennedy Space Center

During the NASA Space Shuttle program, the structures at the Launch Complex 39 pads contained a two-piece access tower system, the Fixed Service Structure (FSS) and the Rotating Service Structure (RSS). The FSS permitted access to the Shuttle via a retractable arm and a "beanie cap" to capture vented liquid oxygen (LOX) from the external fuel tank. The RSS contained the Payload Changeout Room, which offered "clean" access to the orbiter's payload bay, protection from the elements, and protection in winds up to 60 knots (110 km/h).

The FSS on Pad 39A was constructed from most of the top of the umbilical tower of Mobile Launcher 2, while the FSS that was on 39B was constructed from most of the top of the umbilical tower of Mobile Launcher 3 (Mobile Launcher 3 would later become Mobile Launcher Platform 1 for the Shuttle).

In 2011 NASA removed both the fixed and rotating service structures from their pad at LC-39B to make way for a new generation of launch vehicles. Likewise in 2017-2018 SpaceX removed the rotating service structure from LC-39A and modified the fixed service structure to adapt it for the new series of launch vehicles to be launched there.

Certain rockets such as the Delta and the Saturn V use structures consisting of a fixed portion and a mobile portion; the former is named the "umbilical tower" and the latter is known as the "mobile service tower" or "mobile service structure," but often referred to as a gantry. This mobile structure is moved away from the vehicle several hours before launch.

White room

Closeout crew members help astronaut Andrew Feustel in the Launch Complex 39 white room prior to launch of STS-125

The white room was the small area used by astronauts to access the spacecraft during human flights up through the Space Shuttle program. The room takes its name from its white paint, which was used in Project Gemini. The room was first used in Project Mercury. Its use and white color (since Gemini) continued through subsequent programs of Apollo and the Space Shuttle.

NASA used this room for astronaut final preparations before entering the spacecraft such as donning parachute packs, putting on spacesuit helmets and detaching portable air-conditioning units. In 2014, NASA planned to move the White Room to a museum. As of the Crew Dragon Demo-2 mission, SpaceX uses the term White Room to refer to the end of the Crew Access Arm at LC-39A. On the first launch attempt, NASA and SpaceX began a tradition to sign either the "meatball" NASA insignia or the SpaceX logo at the end of the Crew Access Arm.

Baikonur Cosmodrome

Similarly, Soviet-and Russian-designed service structures such as those at Baikonur Cosmodrome Site 31 feature rotating crane-like "tower arms" that stand upright to service and secure the vehicle. The tower arms then pivot outward away from the rocket at launch.