1991: el transbordador espacial Discovery despega en la STS-39, la primera misión de transbordador no clasificada para el Departamento de Defensa de EE. UU.

Space Shuttle Discovery launches on STS-39, the first unclassified shuttle mission for the United States Department of Defense.

Space Shuttle Discovery is a retired American Space Shuttle orbiter. The spaceplane was one of the orbiters from NASA's Space Shuttle program and the third of five fully operational orbiters to be built. Its first mission, STS-41-D, flew from August 30 to September 5, 1984. Over 27 years of service it launched and landed 39 times, aggregating more spaceflights than any other spacecraft as of December 2024. The Space Shuttle launch vehicle had three main components: the Space Shuttle orbiter, a single-use central fuel tank, and two reusable solid rocket boosters. Nearly 25,000 heat-resistant tiles cover the orbiter to protect it from high temperatures on re-entry.