Project 7969 Designs Credit - © Mark Wade

Convair's proposal for the Air Force initial manned space project involved a large-scale manned space station. When pressed, they indicated that a minimum vehicle - a 450 kg, 1.6 m diameter sphere - could be launched by an Atlas within a year.

The spacecraft would be boosted by an Atlas Hustler booster into a 270 km orbit. Deorbit would be accomplished by retrorocket. The spacecraft had a ballistic coefficient (m/CdA) of 250 kg per square meter. It was expected that a first manned orbital flight could be achieved 12 months after a go-ahead.

Typical orbit: 270 km at 28 deg inclination. Length: 1.52 m (4.98 ft). Maximum Diameter: 1.52 m (4.98 ft). Mass: 450 kg (990 lb). Associated Launch Vehicle: Atlas LV-3A / Agena A.

• Baker, David, The History of Manned Spaceflight, Crown, New York, 1981. The best overview of America's manned space programs up to Skylab. Information and details not available anywhere else. Unfortunately out of print and difficult to locate.

• Grimwood, James M., Project Mercury: A Chronology, NASA Special Publication-4001.