During its maiden voyage in May 1962, a Centaur upper stage rocket, mated to an At l a sb o o s t e r, exploded 54 seconds after launch, engulfing the rocket in a huge fireball. In ve s t i g a t i o nre vealed that Centaur's light, stainless-steel tank had split open, spilling its liquid-hyd rogen fueld own its sides, where the flame of the rocket exhaust immediately ignited it. Coming less thana year after President Kennedy had made landing human beings on the Moon a national p r i o r i t y, the loss of Centaur was regarded as a serious setback for the National Aeronautics and Space Administration (NASA). During the failure investigation, Homer Newell, Di rector of Space Sciences, ruefully declared: "Taming liquid hydrogen to the point where expensive oper-ational space missions can be committed to it has turned out to be more difficult than anyone supposed at the outset."