Naturally they wanted to include ejector seats to allow pilots a chance to bail out, but first they had to do a lot of testing, and they did it with bears. Bears on drugs. A plane moving nearly twice the speed of sound required particularly robust sort of ejection mechanism of course, and the one designed for the Hustler was just that. The seats would first enclose the pilot or testing bear in an escape pod of sorts, which was then jettisoned from the plane with the help of rockets. When it came to testing, the Air Force found Himalayan and American black bears to be both readily available, and fairly decent approximations of the size, shape, and weight of the human form.