A Mars Mission Reassembled in Orbit

Transcript

In the 1990s, NASA’s Design Reference Missions were planning studies, not missions that flew. The 1997 plan changed a basic trade from the 1993 design: how to launch and assemble the spacecraft for a journey to Mars. Earth-orbit assembly means bringing separately launched pieces together in orbit around Earth, before setting off. In the 1997 plan, nuclear propulsion stages and Mars-bound spacecraft would launch separately, then dock together in Earth orbit. The 1993 design instead relied on a single large heavy-lift rocket and did not assemble the vehicles in orbit. The change was intended to reduce mass. The 1997 plan would send 303 tons to Mars, 75 tons less than the 1993 plan. Portree explains that the weight savings could remove the need for the large heavy-lift rocket, potentially the costliest part of the mission, and make a cheaper, Shuttle-derived launch system possible. His account gives that redesign rationale; it does not establish why the proposal remained on paper. The key lesson is that changing where the spacecraft came together could change both the mass sent to Mars and the launch costs.