1956 Passenger Ship Credit - © Mark Wade

The 1956 version of Von Braun's Mars design was slashed by 50% in mass, while the number of passengers was increased from 10 to 12. The passengers would be housed in a 7.9-m-diameter sphere during the 963 day mission to Mars, in Mars orbit, and back to earth. The Passenger Vessel would perform four major maneuvers: Trans-Mars Injection, Mars Orbit Insertion, Trans-Earth Injection and Earth Orbit Insertion.

The crew quarters were divided in three decks: an upper control deck, with a transparent dome for the navigator to take star sightings; and two decks of living quarters. A fireman's pole ran through the center for use by the crew in getting around the ship in zero gravity. At the bottom of the passenger sphere was an airlock for access to space. The internal atmosphere would be oxygen/helium, at 0.54 atmospheres pressure.

Crew Size: 12. Design Life: 1000. Length: 37.00 m (121.00 ft). Basic Diameter: 7.90 m (25.90 ft). Maximum Diameter: 25.40 m (83.30 ft). Mass: 1,700,000 kg (3,700,000 lb). Main Engine Thrust: 3,530.000 kN (793,570 lbf). Main Engine Propellants: nitric acid/hydrazine. Main Engine Propellants: 1,640,000 kg (3,610,000 lb). Main Engine Isp: 297 sec. Spacecraft delta v: 9,000 m/s (29,500 ft/sec).

• Miller, Ron, The Dream Machines, Krieger, Malabar, Florida, 1993. ISBN: 0894640399. Sensational chronological roundup of text, photos, and sketches of virtually every spacecraft and launch vehicle design every conceived but never built. A gold mine for space-struck baby boomers. More at amazon.com...

• Portree, David S. F., Humans to Mars: Fifty Years of Mission Planning, 1950 - 2000, NASA Monographs in Aerospace History Series, Number 21, February 2001. Excellent overview of American plans for sending men to Mars.