Mercury-Redstone 4

Mercury-Redstone 4 carried Virgil 'Gus' Grissom aboard Liberty Bell 7 on July 21, 1961. The second American human spaceflight followed a suborbital trajectory from Cape Canaveral's Launch Complex 5 and splashed down in the Atlantic after approximately fifteen and a half minutes. Grissom experienced about five minutes of weightlessness and exercised manual spacecraft controls during the flight. The spacecraft introduced a larger viewing window requested by the astronauts and an explosively released side hatch that was lighter than the earlier mechanically operated hatch. These changes made the mission an engineering test as well as a further evaluation of pilot performance. The flight itself succeeded, but the side hatch released prematurely during recovery. Water entered the capsule, Grissom exited, and a helicopter recovered him from the sea. Liberty Bell 7 sank and was not salvaged until 1999. The episode distinguished successful launch and flight operations from the separate difficulties of recovering a spacecraft and its pilot at sea.