Proj 7969 Republic Credit - © Mark Wade

Republic's studies for the Air Force or NACA initial manned space project started at the beginning of 1958. Their unique concept was a lifting re-entry vehicle, termed the Ferri sled.

Republic's spacecraft was a 1,800 kg vehicle of triangular planform with a 75 degree leading-edge sweep. A 60 cm diameter tube ran continuously around the leading and trailing edge. This tube also served as a propellant tank for final-stage, solid-propellant rockets located in each wing tip. The concept was dubbed the Ferri sled, and had been conceived in 1956 by a team led by Antonio Ferri and at the Gruen Applied Science Laboratories.

The pilot was housed in a small compartment on the top side. Aerodynamic and reaction controls would be available to the pilot, but normally he would only monitor the spacecraft systems. Deorbit would be accomplished with a modest retrofire delta V of 8 m/sec followed by varying the lift to drag of the vehicle. A heat-transfer ring in the front of the nose allowed a stabilized glide after re-entry of 5,800 kilometers per hour. The spacecraft had a ballistic coefficient (m/CdA) of 130 kg per square meter. An Inconel heat shield was used and the pilot would experience only low G forces during re-entry. The pilot would eject from the capsule at subsonic speed over the recovery area and parachute down to earth. It was expected that a first manned orbital flight could be achieved 21 months after a go-ahead.

In the January 1958 presentation the spacecraft would be boosted by an Atlas + Polaris booster into a 241 km orbit for a 240 hour mission. Later Republic advocated an all-solid propellant launch vehicle comprised three or four stages. The four stage version consisted of a Minuteman first stage, a Polaris first stage, a Minuteman upper stage, and a Jumbo rocket fourth stage. Republic Aviation representatives briefed both USAF and NACA Headquarters personnel on their concept without much success. A similar Space General concept, the FIRST re-entry Glider, was developed extensively in the 1960's, but never reached flight status.

Design Life: 10 days. Typical orbit: 240 km at 28 deg inclination. Mass: 1,800 kg (3,900 lb).

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

• 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.