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Design Reference Mission 4 SEP

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DRM 3 SEP Credit: NASA

Status: Study 1998.

Only five shuttle-derived vehicles would be required to put the expedition into low earth orbit versus eight required in the 1997 Design Reference Mission. Removing the backup habitat lander saved two of these launches. The other launch was saved by eliminating the four nuclear thermal rocket stages needed in the 1993 and 1997 DRM's and replacing them with SETV's and three chemical stages.

The SETV itself had a starting mass of 123 metric tons and was 194.6 m across its solar arrays. The solar cells powered two Russian-built Hall thrusters. Due to the long time spent in the radiation belts during the slow spiral away from the earth, each SETV was expected to last for two missions only before it had to be abandoned. Only perigee burns would be made to boost the orbit, and it would take six to twelve months for the SETV to move its payload - a cargo vehicle and a small chemical trans-Mars injection stage - into a 300 km x 400,000 km orbit. The chemical stage would then boost the cargo vehicle on a six month transfer trajectory to Mars. Then the SETV would begin the long process of bringing itself back down to a 300 km circular orbit of the earth. The second mission would place an unmanned Mars landing vehicle into the same 300 x 400,000 km orbit. The crew would be launched separately in a lightweight taxi to rendezvous and dock with the spacecraft prior to the chemical stage's boost toward Mars. In this way the long period of zero-gravity and radiation exposure during the SETV's long ascent would be avoided.

Design Reference Mission SEP Mission Summary:

• Summary: Refine DRM 3.0; SEP Prop Option
• Propulsion: Solar Electric
• Braking at Mars: aerodynamic
• Mission Type: conjunction
• Split or All-Up: split
• ISRU: ISRU
• Launch Year: 2011
• Crew: 6
• Outbound time-days: 180
• Mars Stay Time-days: 570
• Return Time-days: 150
• Total Mission Time-days: 900
• Total Payload Required in Low Earth Orbit-metric tons: 400
• Total Propellant Required-metric tons: 130
• Propellant Fraction: 0.32
• Mass per crew-metric tons: 66
• Launch Vehicle Payload to LEO-metric tons: 75
• Number of Launches Required to Assemble Payload in Low Earth Orbit: 6
• Launch Vehicle: Magnum