关于这张图
S73-25696 (15 May 1973) --- An overall view of Pad B, Launch Complex 39, Kennedy Space Center, Florida, showing the Skylab 2/Saturn 1B space vehicle during a Countdown Demonstration Test (CDDT). This is the launch vehicle for the first manned Skylab mission. The vapor being emitted from the vehicle is the venting of cryogenic propellants. Photo credit: NASA
