In 1962 the US carried out a series of high-altitude nuclear tests , notably Starfish Prime , which demonstrated that the burst of x-rays released by a warhead can travel long distances . In the lower atmosphere they travel only a few meters before interacting with the air , which is one of the major mechanisms creating the fireball that forms around the explosion . In space , their mean free path was on the order of tens of kilometers . When the x-rays strike solid material they cause it to heat so rapidly that shock waves form . These can be powerful enough to break up an RV 's heat shield or cause it to separate from the airframe . In March 1965 , Bell was given the go-ahead to develop a new Zeus design based on this concept , and entered detailed planning in October
Starfish Prime
Starfish Prime
Sentinel program