A facility used to put objects into free fall for microgravity experiments on Earth. NASA's 2.2 Second Drop Tower at the Glenn Research Center began operating in the 1960s. The tower has a free-fall drop of 24.1 m and is used to conduct exploratory microgravity testing for space shuttles and the International Space Station. Approximately 90% of the experiments have involved studies of the effects of microgravity on combustion.

Other drop towers include the Drop Tower Bremen at the Zentrum für Angewandte Raumfahrttechnologie und Mikrogravitation (ZARM; Centre of Applied Space Technology and Microgravity) at the University of Bremen, Germany. The National Space Development Agency (NASDA) uses a drop tower in Toki, Japan, that has a 100-m free-fall segment, providing a microgravity environment for 4.5 seconds.