Mars Semi-Direct 1991

American manned Mars expedition. Study 1991. Mars Semi-Direct was a NASA concept bridge between Zubrin's Mars Direct and NASA's Design Reference Mission 1.0. It was essentially a low-cost version of Boeing's STCAEM.

Mars Semi-Direct Mission Summary:

• Summary: Concept bridge between Mars Direct and Design Reference Mission 1.0; low cost STCAEM
• Propulsion: Nuclear thermal
• Braking at Mars: aerodynamic
• Mission Type: conjunction
• Split or All-Up: split
• ISRU: ISRU
• Launch Year: 1997
• Crew: 4
• Mars Surface payload-metric tons: 40
• Outbound time-days: 180
• Mars Stay Time-days: 550
• Return Time-days: 170
• Total Mission Time-days: 900
• Total Payload Required in Low Earth Orbit-metric tons: 220
• Total Propellant Required-metric tons: 170
• Propellant Fraction: 0.77
• Mass per crew-metric tons: 55
• Launch Vehicle Payload to LEO-metric tons: 105
• Number of Launches Required to Assemble Payload in Low Earth Orbit: 2
• Launch Vehicle: Ares Mars Direct