NASA’s top executive concentrating on human spaceflight, Doug Loverro, has resigned just a week before the scheduled start of a milestone space mission. Loverro became NASA’s associate administrator for human exploration and operations last December, and was playing a leading role in NASA’s Artemis moon program as well as preparations for next week’s launch of a SpaceX Crew Dragon mission to the International Space Station. That mission, set for liftoff on May 27 from NASA’s Kennedy Space Center in Florida, is due to send NASA astronauts Doug Hurley and Bob Behnken to the station for a stay that could last...