The first spacecraft had to be light enough to carry the passenger into space and yet rugged enough to withstand the stresses and heating of launch and reentry.
Soviet designers based their design for a recoverable, human-carrying spacecraft on their experience with sending dogs into space. The spherical return capsule used parachutes to slow its descent, but the cosmonaut had to eject from the capsule at an altitude of 7,000 meters (23,000 feet) to survive the landing. Early Soviet reports of Gagarin's flight omitted this detail.
NASA designed the Mercury capsule for a water landing. A parachute deployed at 7,500 meters (24,500 feet) to slow the spacecraft. Unlike a Vostok cosmonaut, the astronaut stayed inside during the entire descent. During launch, an escape rocket on top could pull the capsule away in an emergency.You can see John Glenn's Mercury capsule Friendship 7 in the Milestones of Flight gallery.