Challenger Proved Last Straw for ‘Scary’ Cryogenic Booster Plan

KENNEDY SPACE CENTER, Fla. — As 1985 faded into 1986, NASA was racing the clock to perfect a powerful hydrogen-fueled upper stage to propel the Ulysses and Galileo probes to Jupiter. Both nuclear-powered spacecraft were to be deployed from two space shuttles launched just five days apart in May 1986.