English: This 1964 NASA Flight Reserch Center photograph shows the Lunar Landing Research Vehicle (LLRV) Number 1 in flight at the South Base of Edwards Air Force Base. When Apollo planning was underway in 1960, NASA was looking for a simulator to profile the descent to the moon's surface. Three concepts emerged: an electronic simulator, a tethered device, and the ambitious Dryden contribution, a free-flying vehicle. All three became serious projects, but eventually the NASA Flight Research Center's (FRC) Landing Research Vehicle became the most important.