Mars Direct
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Mars Direct is a proposal for a relatively low-cost manned mission to Mars with current rocket technology. The plan was originally detailed in a research paper by Robert Zubrin and David Baker in 1990. The mission was expanded upon in Zubrin's 1996 book The Case for Mars. The plan is now a staple of Zubrin's speaking engagements and general advocacy as head of the Mars Society, an organization devoted to the colonization of Mars, and has been released in video format.
The proposal
The plan involves launching an unmanned "Earth Return Vehicle" (ERV) directly from Earth's surface to Mars using a heavy-lift booster derived from Space Shuttle components. The booster is no bigger than the Saturn V used for the Apollo missions. Several launches are made in preparation for the manned mission.
The first of these launches the ERV, a supply of hydrogen, a chemical plant and a small nuclear reactor. Once there, a relatively simple set of chemical reactions (the Sabatier reaction coupled with electrolysis) would combine a small amount of hydrogen carried by the ERV with the carbon dioxide of the Martian atmosphere to create up to 112 tonnes of methane and oxygen propellants, 96 tonnes of which would be needed to return the ERV to Earth at the end of the mission. This process would take approximately ten months to complete.
Some 26 months after the ERV is originally launched from Earth, a second vehicle, the "Mars Habitat Unit" (MHU), would be launched on a high-energy transfer to Mars carrying a crew of four. This vehicle would take some six months to reach Mars. During the trip, artificial gravity would be generated by tying the spent upper stage of the booster to the Habitat Unit, and setting them both rotating about a common axis.
On reaching Mars, the spent upper stage would be jettisoned, with the Habitat Unit aerobraking into Mars orbit before soft-landing in proximity to the ERV. Once on Mars, the crew would spend 18 months on the surface, carrying out a range of scientific research, aided by a small rover vehicle carried aboard their MHU, and powered by excess methane produced by the ERV. To return, they would use the ERV, leaving the MHU for the possible use of subsequent explorers. The propulsion stage of the ERV would be used as a counterweight to generate artificial gravity for the trip back.
The initial cost estimate for Mars Direct was put at $55 billion, to be paid over ten years.
Components
Earth Return Vehicle
The ERV is a two-stage vehicle. The upper stage comprises the living accommodation for the crew during their six-month return trip to Earth from Mars. The lower stage contains the vehicle's rocket engines and a small chemical production plant.
| Round trip payload | |
| Crew compartment | 7,100 kg |
| Reaction control system | 400 kg |
| Biconic brake | 2,450 kg |
| Stage 1(dry) | 6,330 kg |
| Stage 2 (dry) | 1,770 kg |
| Mars-bound payload | |
| Hydrogen for propellant production | 5,810 kg |
| SP-100 Reactor | 4,500 kg |
| Earth-bound payload | |
| Crew | 450 kg |
| Suits | 300 kg |
| Consumables (dry food) | 2,000 kg |
| Soil Samples | 150 kg |
| Stage 1 propulsion system | |
| Usable propellant (methane / oxygen) | 70,160 kg |
| Dry mass | 8,850 kg |
| Total engine thrust | 85,237 kgf (835.89 kN) |
| Specific impulse | 373 s (3.65 kN·s/kg) |
| Stage 2 propulsion system | |
| Usable propellant (methane / oxygen) | 25,000 kg |
| Dry mass | 2,560 kg |
| Total engine thrust | 9,059 kgf (88.84 kN) |
| Specific impulse | 373 s (3.65 kN·s/kg) |
Mars Habitat Unit
The MHU is a 2- or 3-deck vehicle, providing a comprehensive living and working environment for a Mars crew. As well as individual sleeping quarters which provide a degree of privacy for each of the crew and a place for personal effects, the MHU includes a communal living area, a small galley, exercise area, and hygiene facilities.
The lower deck of the MHU provides the primary working space for the crew: small laboratory areas for carrying out geology and life science research; storage space for samples, airlocks for reaching the surface of Mars, and a suiting-up area where crew members prepare for surface operations.
The MHU also includes a small pressurized rover that is stored in the lower deck area and assembled on the surface of Mars. Powered by a small methane engine, this is designed to extend the range over which astronauts can explore the surface of Mars.
Protection from harmful radiation while in space and on the surface of Mars (e.g. from solar flares) is provided by a dedicated "storm shelter" in the core of the vehicle.
Since it was first proposed as a part of Mars Direct, the MHU has been adopted by NASA as a part of their Mars Design Reference Mission, which utilizes two MHUs - one of which flies to Mars unmanned, providing a dedicated laboratory facility on Mars, together with the capacity to carry a larger rover vehicle. The second MHU flies to Mars with the crew, its interior given over completely to living / storage space.
To prove the viability of the MHU, the Mars Society has implemented the Mars Analogue Research Station Programme (MARS), which has established a number of prototype MHUs around the world.
| Round Trip Payload | Tonnes |
| Main Structure | 8.52 |
| Decks | 6.00 |
| Airlock / Radiation Shelter | 1.82 |
| 0.30 | |
| Furniture | 0.50 |
| Science Equipment | 1.00 |
| Exercise and Health | 0.20 |
| Plumbing and Lighting | 1.00 |
| Replacement Air (3 charges) | 0.81 |
| Solar Panels | 0.25 |
| Life Support System | 4.00 |
| Consumables for Crew | 11.76 |
| Crew of 6 | 0.45 |
| Personal Effects | 0.70 |
| Spacesuits | 0.30 |
| Pressurized Rover | 2.00 |
| Deployed Surface Science | 0.40 |
| Contingency | 5.00 |
| Total | 45.41 |
Revisions
Since Mars Direct was initially conceived, it has undergone considerable review and development by Zubrin himself, the Mars Society, NASA and Stanford University, and others.
Zubrin and Weaver developed a modified version of Mars Direct, called Mars Semi-Direct, in response to some specific criticisms[1]. The mission consists of two spacecraft, one of which remains in Mars orbit, and propellants are only manufactured for use by a small ascent craft to reach Mars orbit, rather than for the entire return journey. The Mars Semi-Direct architecture has been used as the basis of a number of studies, including the NASA Design Reference Missions.
The NASA model, referred to as the Design Reference Mission, currently on version 5.0, calls for a significant upgrade in hardware (up to 3 launches per mission, not two), and sends the ERV to Mars fully fuelled, parking it in orbit above the planet, where it is reached by a small ascent craft.
The Mars Society and Stanford studies retain the original 2-vehicle mission profile of Mars Direct, but increase the crew size to six.
Mars Society Australia developed their own four-person Mars Oz reference mission, based on Mars Semi-Direct. This study uses horizontally landing, bent biconic shaped modules, and relies on solar power and chemical propulsion throughout[2]. This is in contrast to Mars Direct and the DRMs, which used nuclear reactors for surface power and, in the case of the DRMs for propulsion as well. The Mars Oz reference mission also differs from Mars Direct in assuming, based on space station experience, that spin gravity will not been required.
The Mars Society has argued the viability of the Mars Habitat Unit concept through their Mars Analogue Research Station program. These are two or three decked vertical cylinders ~8 m in diameter and 8 m high. Mars Society Australia plans to build its own station based on the Mars Oz design[3]. The Mars Oz design features a horizontal cylinder 4.7 m in diameter and 18 m long, with a tapered nose. A second similar module will function as a garage and power and logistics module.
Mars Direct was featured on a Discovery Channel programs Mars: The Next Frontier in which were discussed, in part, issues surrounding NASA funding of the project, and on Mars Underground, where the plan is discussed more in-depth.
Currently NASA is in the final stages of implementing a modified Mars Direct approach to both Lunar and Martian exploration. Zubrin's ultimate goal of a fully terraformed and colonized Mars is a long-term, multigenerational goal, but eventually, if NASA's 30 year architecture is carried to fruition, that end might be seen as plausible.
A modified proposal, "Mars for Less" [1], was developed by Grant Bonin and has been adopted as the design reference mission for a new umbrella group of advocates, the MarsDrive consortium [2]. The design retains most of the essential features of Mars Direct, but uses multiple medium-lift rocket launchers that are commercially available today (such as the Ariane V or the Delta rocket) to launch the crew vehicles, and their propulsion, separately, and mate them in orbit. By doing so, the multi-billion dollar development cost of a new launch vehicle is avoided.
A modified proposal has also been offered by Dean Unick, to not return the first immigrant/explorers immediately, or ever. The cost of sending a four or six person team is one fifth to one tenth the cost of returning that same four or six person team. A quite complete lab can be sent and landed for less than the cost of sending back even 50 kilos of rocks. Twenty or more persons can be sent for the cost of returning four. http://www.universetoday.com/2008/10/23/aldrin-mars-pioneers-should-not-return-to-earth/
In fiction
- Mars Direct is the mission mode used in Gregory Benford's novel, The Martian Race, and in Geoffrey A. Landis's novel Mars Crossing, as well as Zubrin's own novel, First Landing.
- Mars Direct forms the basis for the 2000 film Mission to Mars.
- In the Futurama episode "The Luck of the Fryrish", a short clip shows the first man on Mars with a spacecraft that resembles the Mars Habitat Unit.
- In the West Wing episode "The Warfare of Genghis Khan", a NASA staffer describes Mars Direct to the skeptical White House Deputy Chief of Staff Josh Lyman and is able to convince him of its merit.
- Both Mars Direct and Mars for Less concepts figure prominently in Brian Enke's 2004 novel, Shadows of Medusa.
- A Mars Direct scheme is used in Larry Niven's novel Rainbow Mars.
- A Mars Direct scheme is used in Robert M. Blevins' 2005 novel The 13th Day of Christmas.
See also
- TMK
- Manned mission to Mars
- Zubrin, Baker. (1990). "Mars Direct, Humans to the Red Planet by 1999." 41st Congress of the International Astronautical Federation
- The Case for Mars
- In-Situ Resource Utilization
References
- ^ R. Zubrin and D. Weaver "Practical methods for near-term piloted Mars missions". AIAA93-2089,29th AIAA/ASME Joint Propulsion Conference, Monterrey CA, United States, June 28-30th, 1993
- ^ D.Willson and J.D.A Clarke "A Practical Architecture for Exploration-Focused Manned Mars Missions Using Chemical Propulsion, Solar Power Generation and In-Situ Resource Utilisation." Proceedings of the 6th Australian Space Science Conference,p.186-211, 2006
- ^ Mars Society Australia Mars-Oz web site http://www.marssociety.org.au/marsoz.php