July 12, 1961 - Two candidates for the second manned U.S. spaceflight tested their reflexes today. Marine Lieut. Col. John H. Glenn Jr. (left) and Air Force Capt. Virgil I. Grissom (right) took turns in a "procedures" trainer that also gave them practice in what to do should something go wrong during the flight. A final physical exam this weekend will lead to the selection of an astronaut for the 15-minute sub-orbital ride aboard a Mercury capsule atop a Redstone rocket. The flight is set for next Tuesday. The astronaut left behind this time will serve as the "back-up" to the other and will be expected to make a spaceflight late next month.