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Mars Direct
Part of American Mars Expeditions
Mars Direct
Mars Direct
Credit: NASA
American manned Mars expedition. Study 1991. In 1991 Martin Marietta and NASA Ames (Zubrin, Baker, and Gwynne) proposed 'Mars Direct' - a Mars expedition faster, cheaper, and better than the standard NASA plan.

Status: Study 1991. Gross mass: 160,000 kg (350,000 lb).

Key features included:

Mars Direct would be completed in two launches of the proposed Ares heavy lift booster. The first launch would deliver an unfueled and unmanned Earth Return Vehicle (ERV) to the Martian surface. After landing an on-board production plant would generate methane/oxygen propellants. A second launch would deliver the four-person crew. Following eighteen months of extensive exploration of the surface, they would enter the ERV and return directly to Earth. The same launch vehicles and spacecraft developed for Mars Direct could also support a lunar base.

Launch 1: In December 1996, a single Ares launch vehicle would place an unmanned 40 metric ton payload onto a direct trans-Mars trajectory. The payload would consist of:

Launch 2: In 1999 an Ares would launch a manned 80 metric ton payload. This would consist of:

These two launches would constitute the main Mars Direct expedition. But a backup return vehicle would be available, since in 1999 a payload identical to Launch 1 would also be put on a trans-Mars trajectory. If for any reason the Launch 1 ERV was unusable, this payload would provide a backup for the Launch 2 crew. If all went well, it would be used as the return vehicle for the next crew, to be launched in 2001. In this way two ERV's would always available for crew return as missions were sent out every two years. During the eighteen months on the Martian surface, the crew would use the ground vehicle to traverse 22,000 kilometers of Martian terrain within 500 km from the base.

The same equipment could be used to establish a lunar base - in fact it could be tested comprehensively on the moon before committing to the Mars expedition. In the lunar scenario the Ares booster could launch a 59 metric ton payload consisting of the standard Habitation Module with a Lunar orbital capture and lunar descent (LOC/LD) stage. The LOC/LD stage would land the Habitation Module on the Moon. A crew could then be flown to the Moon using an ERV with an LOC/LD stage. This ERV used only the second stage of the Mars ERV for Earth return direct from the lunar surface.

Use of a nuclear thermal rocket (NTR) third stage on the Ares would increase trans-Mars payload by 50%. The NTR stage would have a specific impulse of 900 s, a power of 900 MWth, and a thrust of 45,000 lb. Use of a NIMF (Nuclear rocket using Indigenous Martian Fuel) stage on the lander would provide the Habitation Module with the capability of leaping from one location on the Martian surface to another, using compressed Martian carbon dioxide from the atmosphere as propellant. This would allow 18 sites on the surface to be visited within the 550 days of surface time, as opposed to just one for the baseline expedition.

ERV Mass Breakdown - total 28,500 kg landed on Martian surface:

Habitat Mass Breakdown - total 25,200 kg landed on Martian surface:

Mars Direct Nuclear Thermal Mission Summary:

Mars Direct Chemical Mission Summary:

Crew Size: 4.

Family: Mars Expeditions. Country: USA. Launch Vehicles: Mars tactical rocket, Ares Mars Direct. Agency: NASA, Martin. Bibliography: 1989, 465, 591, 6682.
1991 During the Year - .
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