A re-entry vehicle is the part of a spacecraft that is designed to return through Earth's atmosphere. It is built to survive intense heating during high-velocity flight through the atmosphere and to protect the crew and/or instruments until it brings them safely to Earth. Although the technology has changed over time, re-entry vehicles since the early Mercury program have used the same basic design concept: a blunt shape protected by a heat shield.

Early Re-Entry Vehicles

Early re-entry vehicle design benefited primarily from ballistic missile research. Designers initially thought that a re-entry vehicle should have a sleek aerodynamic shape, but launch and wind tunnel tests demonstrated that no known material with that shape could withstand the heat of re-entry. National Aeronautics and Space Administration (NASA) engineer Harvey Allen decided that a blunt-shaped vehicle should be used. The increased air resistance of that type of vehicle...