In June 1962 NASA funded studies with several contractors on Operations and Logistics for Space Stations. McDonnell's study was dated 20 March 1963 and proposed three alternatives, all of which could be boosted by either a Titan 3M or Saturn IB Launch Vehicle, and all of which would be equipped with aft-mounted docking systems. The first two were variants of McDonnell's Gemini capsule, but the third was a new winged spaceplane, capable of accommodating two crew plus four passengers.

Crew Size: 6. Mass: 14,000 kg (30,000 lb).