Mercury-Redstone 4, also known as Liberty Bell 7, was a suborbital spaceflight mission conducted by NASA on July 21, 1961. It was the second crewed flight in the Mercury program and was piloted by astronaut Virgil "Gus" Grissom. The mission lasted about 15 minutes, reaching an altitude of approximately 190 kilometers before safely returning to Earth. The spacecraft was launched atop a Redstone rocket from Cape Canaveral, Florida. After a successful flight, the capsule splashed down in the Atlantic Ocean. However, it sank shortly after recovery due to a hatch malfunction, leading to a significant investigation into the incident.