Manned mission to Mars

Concept for NASA Design Reference Mission Architecture 5.0 (2009)

A manned mission to Mars has been the subject of science fiction, engineering, and scientific proposals throughout the 20th century and into the 21st century. The plans comprise proposals not only to land on, but eventually also settle on the planet Mars, its moons, Phobos and Deimos and terraform the planet.

Preliminary work for missions has been undertaken since the 1950s, with planned missions typically taking place 10 to 30 years in the future. The list of manned Mars mission plans in the 20th century shows the various mission proposals that have been put forth by multiple organizations and space agencies in this field of space exploration.

In 2004 the U.S. administration announced a new Vision for Space Exploration naming a manned Mars mission as one of its milestones. No concrete plan has been decided upon, and the proposal is currently being discussed between politicians, scientists, space advocates and in the public. In 2010, a new bill was signed allowing for a manned Mars mission by the 2030s.^[1]

Challenges

Artist's conception of a human mission on the surface of Mars
1989 painting by Les Bossinas of Lewis Research Center for NASA

There are several key challenges that a human mission to Mars must overcome:

1. physical effects of exposure to high-energy cosmic rays and other ionizing radiation^[2][3]
2. physical effects of a prolonged low-gravity environment
3. physical effects of a prolonged low-light environment
4. psychological effects of isolation from Earth
5. psychological effects of lack of community due to lack of real-time connections with Earth
6. social effects of several humans living under crowded conditions for over one Earth year
7. inaccessibility of terrestrial medical facilities

Some of these issues were estimated statistically in the HUMEX study.^[4] Ehlmann and others have reviewed political and economic concerns, as well as technological and biological feasibility aspects.^[5]

While fuel for roundtrip travel could be a challenge, methane and oxygen can be produced utilizing Martian H₂O (preferably as water ice instead of chemically bound water) and atmospheric CO₂ with mature technology.^[6]

One of the main considerations for traveling to Mars from Earth or vice versa is the energy needed to transfer between their orbits. Every 26 Earth months a lower energy transfer from Earth to Mars opens,^[7] so missions are typically planned to coincide with one of these windows. In addition, the low-energy windows varies higher or lower on roughly a 15 year cycle.^[7] For example, there was a minimum in the 1969 and 1971 launch windows, rising to a peak in the late 70s, and hitting another low in 1986 and 1988, and then repeating on the same interval.^[7] A typical estimate of round-trip flight time for a manned expedition to Mars is 400 to 450 days^[8], which could take a toll on astronauts.

20th century proposals

Main article: List of manned Mars mission plans in the 20th century

Over the last century, a number of mission concepts for such an expedition have been proposed. David Portree's history volume Humans to Mars: Fifty Years of Mission Planning, 1950 - 2000 discusses many of these.^[7]

Wernher von Braun proposal (1947 through 1950s)

Wernher von Braun was the first person to make a detailed technical study of a Mars mission.^[7][9] Details were published in his book Das Marsprojekt (1952); published in English as The Mars Project^[10] (1962) and several subsequent works,^[11] and featured in Collier's magazine in a series of articles beginning March 1952. A variant of the Von Braun mission concept was popularized in English by Willy Ley in the book The Conquest of Space (1949), featuring illustrations by Chesley Bonestell. Von Braun's Mars project envisioned nearly a thousand three-stage vehicles launching from Earth to ferry parts for the Mars mission to be constructed at a space station in Earth orbit.^[9][12] The mission itself featured a fleet of ten spacecraft heading to Mars, each one carrying 70 people, bringing three winged surface excursion ships that would land horizontally on the surface of Mars. (Winged landing was considered possible because at the time of his proposal, the Martian atmosphere was believed to be much denser than was later found to be the case.)

In the 1956 revised vision of the Mars Project plan, published in the book The Exploration of Mars by Wernher Von Braun and Willy Ley, the size of the mission was trimmed, requiring only 400 launches to put together two ships, still carrying a winged landing vehicle.^[13] Later versions of the mission proposal, featured in the Disney "Man In Space" film series,^[14] showed nuclear-powered ion-propulsion vehicles for the interplanetary cruise.

U.S. proposals (1950s and 1960s)

Artist's depiction of Mars Excursion Module landed on Mars, from a 1963 NASA study

In 1962, Aeronutronic Ford,^[15] General Dynamics and the Lockheed Missiles and Space Company made studies of Mars mission designs as part of NASA Marshall Spaceflight Center "Project EMPIRE".^[9] These studies indicated that a Mars mission (possibly including a Venus fly-by) could be done with a launch of eight Saturn V boosters and assembly in low Earth orbit, or possibly with a single launch of a hypothetical "post Saturn" heavy-lift vehicle. Although the EMPIRE missions were only studies, and never proposed as funded projects, these were the first detailed analyses of what it would take to accomplish a human voyage to Mars using data from the actual NASA spaceflight, and laid much of the basis for future studies, including significant mission studies by TRW, North American, Philco, Lockheed, Douglas, and General Dynamics, along with several in-house NASA studies.^[9]

Following the success of the Apollo Program, von Braun advocated a manned mission to Mars as a focus for NASAs manned space program.^[16] Von Braun's proposal used Saturn V boosters to launch nuclear-powered (NERVA) upper stages that would power two six-crew spacecraft on a dual mission in the early 1980s. The proposal was considered by (then president) Richard Nixon but passed over in favor of the Space Shuttle.

Soviet mission proposals (1956 through 1970)

Main article: Martian Piloted Complex

Main article: TMK

The Martian Piloted Complex or "'MPK'" was a proposal by Mikhail Tikhonravov of the Soviet Union for a manned Mars expedition, using the (then proposed) N-1 rocket, in studies from 1956 to 1962.

Artist's depiction of TMK-MAVR

Heavy Piloted Interplanetary Spacecraft (known by the Russian acronym TMK) was the designation of a Soviet Union space exploration proposal in the 1960s to send a manned flight to Mars and Venus (TMK-MAVR design) without landing. The TMK spacecraft was due to launch in 1971 and make a three-year long flight including a Mars fly-by at which time probes would have been dropped. The TMK project was planned as an answer from the Soviet Union to the United States manned moon landings. The project was never completed because the required N1 rocket never flew successfully.

The Mars Expeditionary Complex, or "'MEK"' (1969) was another Soviet proposal for a Mars expedition that would take a crew from three to six to Mars and back with a total mission duration of 630 days.

Case for Mars (1981–1996)

Following the Viking missions to Mars, between 1981 and 1996 a series of conferences named The Case for Mars were held at the University of Colorado at Boulder. These conferences advocated human exploration of Mars, presented concepts and technologies, and held a series of workshops to develop a baseline concept for the mission. The baseline concept was notable in that it proposed use of In Situ Resource Utilization to manufacture rocket propellant for the return trip using the resources of Mars. The mission study was published in a series of proceedings volumes^[17][18] published by the American Astronautical Society. Later conferences in the series presented a number of alternative concepts, including the "Mars Direct" concept of Robert Zubrin and David Baker; the "Footsteps to Mars" proposal of Geoffrey A. Landis,^[19] which proposed intermediate steps before the landing on Mars, including human missions to Phobos; and the "Great Exploration" proposal from Lawrence Livermore National Laboratory, among others.

NASA Space Exploration Initiative (1989)

Main article: Space Exploration Initiative

In response to a presidential initiative, NASA made a study of a project for human lunar- and Mars exploration as a proposed follow-on to the International Space Station project. This resulted in a report, called the 90-day study,^[20] in which the agency proposed a long-term plan consisting of completing the Space Station as "a critical next step in all our space endeavors," returning to the moon and establishing a permanent base, and then sending astronauts to Mars. This report was widely criticized as too elaborate and expensive, and all funding for human exploration beyond Earth orbit was canceled by Congress.^[21]

Mars Direct (early 1990s)

Main article: Mars Direct

Because of the distance between Mars and Earth, the Mars mission would be much more risky and more expensive than past manned flights to the Moon. Supplies and fuel would have to be prepared for a 2-3 year round trip and the spacecraft would have to be designed with at least partial shielding from intense solar radiation. A 1990 paper by Robert Zubrin and David A. Baker, then of Martin Marietta, proposed reducing the mission mass (and hence the cost) with a mission design using In Situ Resource Utilization to manufacture propellant from the Martian Atmosphere.^[22][23] This proposal drew on a number of concepts developed by the former "Case for Mars" conference series. Over the next decade, this proposal was developed by Zubrin into a mission concept, Mars Direct, which he developed in a book, The Case for Mars (1996). The mission is advocated by the Mars Society, which Zubrin founded in 1998, as a practical and affordable plan for a manned Mars mission.

NASA Design reference missions (1990s)

Main article: Design reference mission 3.0

NASA Mars habitat concept (1993)

Artist's concept of Mars Orbit Rendezvous between spaceship and Martian ascent stage. (1995)
painting by Pat Rawlings of SAIC for NASA.

In the 1990s NASA developed several conceptual level human Mars exploration architectures. One of these was NASA Design reference mission 3.0 (DRM 3.0). It was a study performed by the NASA Mars Exploration Team at the NASA's Johnson Space Center (JSC) in the 1990s. Personnel representing several NASA field centers formulated a “Reference Mission” addressing human exploration of Mars. The plan describes a human mission to Mars with concepts of operations and technologies to be used as a first cut at an architecture. The architecture for the Mars Reference Mission builds on previous work, principally on the work of the Synthesis Group (1991) and Zubrin’s (1991) concepts for the use of propellants derived from the Martian atmosphere. The primary purpose of the Reference Mission was to stimulate further thought and development of alternative approaches, which can improve effectiveness, reduce risks, and reduce cost. Improvements can be made at several levels; for example, in the architectural, mission, and system levels.

Selected other US/NASA plans (1988-2009):^[24]

1) 1988 “Mars Expedition”

2) 1989 “Mars Evolution”

3) 1990 “90-Day Study”

4) 1991 “Synthesis Group”

5) 1995 “DRM 1”

6) 1997 “DRM 3”

7) 1998 “DRM 4”

8) 1999 “Dual Landers”

9) 1989 Zubrin, et.al*

10) 1994-99 Borowski, et. al

11) 2000 SERT (SSP)

12) 2002 NEP Art. Gravity

13) 2001 DPT/NEXT

14) 2009 DRA 5

21st century proposals

MARPOST (2000/2005)

The Mars Piloted Orbital Station (or MARPOST) is a Russian proposed manned orbital mission to Mars, using a nuclear reactor to run an electric rocket engine. Proposed in October 2000 by Yuri Karash from the Russian Academy of Cosmonautics as the next step for Russia in space along with the Russian participation in the International Space Station, a 30-volume draft project for MARPOST has been confirmed as of 2005.^[25] Design for the ship proposed to be ready in 2012, and the ship itself in 2021.^[26]

ESA Aurora programme (2001+)

Main article: Aurora programme

The European Space Agency had a long-term vision of sending a human mission to Mars by 2030. Laid out in 2001, the project's proposed timeline would begin with robotic exploration, a proof of concept simulation of sustaining humans on Mars, and eventually a manned mission; however, objections from the participating nations of ESA and other delays have put the timeline into question.

ESA/Russia plan (2002)

Another proposal for a joint ESA mission with Russia is based on two spacecraft being sent to Mars, one carrying a six-person crew and the other the expedition's supplies. The mission would take about 440 days to complete with three astronauts visiting the surface of the planet for a period of two months. The entire project would cost $20 billion and Russia would contribute 30% of these funds.^[27]

USA Vision for Space Exploration (2004)

Main article: Vision for Space Exploration

United States President George W. Bush announced an initiative of manned space exploration on January 14, 2004, known as the Vision for Space Exploration. It included developing preliminary plans for a lunar outpost by 2012^[28] and establishing an outpost by 2020. Precursor missions that would help develop the needed technology during the 2010-2020 decade were tentatively outlined by Adringa and others.^[29] On September 24, 2007, Michael Griffin, then NASA Administrator, hinted that NASA may be able to launch a human mission to Mars by 2037.^[30] The needed funds are to be generated by diverting $11 billion^[31] from space science missions to the vision for human exploration.

NASA has also discussed plans to launch Mars missions from the Moon to reduce traveling costs.^[32]

Project Constellation included an Orion Mars Mission.

NASA Design Reference Mission 5.0 (2007)

NASA released initial details of the latest version conceptual level human Mars exploration architecture in this presentation. The study further developed concepts developed in previous NASA DRM and updated it to more current launchers and technology.

NASA Design Reference Mission Architecture 5.0 (2009)

DRMA 5.0 "commuter" Mars base (2009)

NASA released an updated version of NASA DRM 5.0 in early 2009, featuring use of the Ares V launcher, Orion CEV, and updated mission planning. In this document.^[33]

NASA Austere Human Missions to Mars (2009)

Extrapolated from the DRMA 5.0, plans for a manned mars expedition with chemical propulsion. Austere Human Missions to Mars

Mars Society Germany - European Mars Mission (EMM) (2005)

The Mars Society Germany proposed a manned Mars mission using several launches of an improved heavy-lift version of the Ariane 5.^[34] Roughly 5 launches would be required to send a crew of 5 on a 1200 days mission, with a payload of 120,000 kg (260,000 lb) ^[34]

The One-Way Trip Option (2006)

In 2006, former NASA engineer James C. McLane III proposed a scheme to initially colonize Mars via a one way trip by only one human. Papers discussing this concept appeared in The Space Review,^[35] Harper’s Magazine,^[36] SEARCH Magazine^[37] and The New York Times.^[38]

Mars to Stay (2006)

Main article: Mars to Stay

Mars to Stay is the proposal that astronauts sent to Mars for the first time should stay there indefinitely, both to reduce mission cost and to ensure permanent settlement of Mars. Among many notable Mars to Stay advocates, former Apollo astronaut Buzz Aldrin has been a particularly outspoken promoter, suggesting in numerous forums "Forget the Moon, Let’s Head to Mars!" .^[39]

MarsDrive mission design (2008)

The MarsDrive Organization has been working at a series of new human mission designs starting with Mars for Less. Their current design program under Director of Engineering Ron Cordes has discarded many of the Mars for Less elements and is a work in progress as of June 2008. Some of their design philosophy is focused on using current or near term existing launch vehicle systems, permanent human settlement, conceptual EDL systems and enhanced surface ISRU. Their proposed methods of funding the mission are also an alternative to the current plans with a private consortium approach being investigated.

USA's Mars by the mid-2030s (2010)

In a major space policy speech at Kennedy Space Center on April 15, 2010, U.S. President Barack Obama predicted a manned Mars mission to orbit the planet by the mid-2030s, followed by a landing:

By the mid-2030s, I believe we can send humans to orbit Mars and return them safely to Earth. And a landing on Mars will follow. And I expect to be around to see it.

The United States Congress has approved manned missions to the Moon, followed by Asteroid exploration in 2025 and Mars in the 2030s.^[40]

Hundred Year Starship (2010)

In October 2010 NASA Ames Research Center Director Pete Worden introduced the Hundred Year Starship initiative, a project to embark on a one-way mission from Earth to Mars by 2030.^[41] The astronauts would be sent supplies from Earth on a regular basis.^[42]

Russian mission proposals (current)

A number of Mars mission concepts and proposals have been put forth by Russian scientists. Stated dates were for a launch sometime between 2016 and 2020. The Mars probe would carry a crew of four to five cosmonauts, who would spend close to two years in space.^{[citation needed]}

In late 2011, Russian and European space agencies successfully completed the ground-based MARS-500.^[43] The biomedical experiment simulating manned flight to Mars was completed in Russia in July 2009.^[44]

Chinese Mars exploration program

Main article: Chinese Mars exploration program

Little is known of the Chinese Mars exploration program. While the Moon is the first priority, there are plans for Martian exploration that follow upon the work done in the Chinese Lunar Exploration Program. China has been studying the necessity and feasibility of Mars exploration since early 1990s as part of the national "863 Planetary Exploration" project, according to Liu Zhenxing, a researcher from the CAS Center for Space Science and Applied Research (CSSAR).

Preparedness

One NASA concept for an ascent stage to Mars orbit

A number of nations and organizations have long-term intentions to send humans to Mars. The state of their readiness is summarized below.

• The United States has a number of missions currently exploring Mars, with a sample-return planned in the near future. The US does not have a launcher capable of sending humans to Mars, although the Orion spacecraft, currently under development by NASA, could ferry astronauts from the surface of Earth to join a Mars-bound expedition in Earth orbit and then back to Earth's surface once the expedition has returned from Mars. NASA has used the Haughton impact crater on Devon Island as a proving ground due to the crater's similarity with Martian geology.^[45] According to New Scientist, an argon plasma-based VASIMR rocket could reduce the transit time to less than 40 days.^[46]
• The European Space Agency has sent robotic probes, and has long-term plans to send humans but has not yet built a human-capable launcher. There is a proposal to convert ESA's existing Automated Transfer Vehicle (ATV) for crewed launches.
• Russia (and previously the Soviet Union) has sent a large number of probes. It can send humans into Earth-Orbit and has extensive experience with long-term manned orbital space flight due to its space station programs. Russia does not have a launcher capable of sending humans to Mars, although the Kliper program was proposed as the Russian-European counterpart to the United States' Orion Spacecraft. A simulation of a manned Mars mission, called Mars-500, was completed in Russia in November 2011.
• Japan's robotic missions to Mars have so far failed.
• China plans to cooperate with Russia in sending robotic sample return mission to Phobos. China was the third country after Russia and the USA to launch humans into Earth orbit.

Criticism

Some scientists have argued that attempting manned flight to Mars would actually be counterproductive for science. In 2004, the Special committee on the funding of Astrophysics, a committee of the American Physical Society, stated that "shifting NASA priorities toward risky, expensive missions to the Moon and Mars will mean neglecting the most promising space science efforts".^[47]

The debate over whether or not life existed, or indeed still exists on Mars has not been settled. Consequently, a manned mission could contaminate the Martian surface with foreign microbes and compromise the search for indigenous Martian lifeforms.^[48]

Mars analogs

Several "missions" have been undertaken on Earth to simulate the conditions astronauts would experience during a future mission to mars. Among these are:

• Mars-500
• Concordia Station
• Mars Analogue Research Station Program
• Arctic Mars Analog Svalbard Expedition
• Australia Mars Analog Research Station
• European Mars Analog Research Station
• Flashline Mars Arctic Research Station

See also, Category:Human spaceflight analogs

See also

• Artificial gravity
• Colonization of Mars
• Exploration of Mars
• Flashline Mars Arctic Research Station
• Health threat from cosmic rays
• International Mars Society
• Interplanetary spaceflight
• Life on Mars
• List of manned Mars mission plans in the 20th century
• Manned Venus Flyby
• MARS-500
• Mars in fiction
• Mars to Stay
• Space weather
• Zero gravity

References

1. ^ NASA in Transition as Congress OKs New Direction. Clara Moskowitz, 30 September 2010. SPACE.com
2. ^ Saganti, P. B. et al. (2006)
3. ^ Shiga, David (2009-09-16), "Too much radiation for astronauts to make it to Mars", New Scientist (2726), http://www.newscientist.com/article/mg20327266.100-too-much-radiation-for-astronauts-to-make-it-to-mars.html 
4. ^ Horneck and Comet (2006), doi 10.1016/j.asr.2005.06.077
5. ^ Ehlmann, B. L., et al. (2005), doi 10.1016/j.actaastro.2005.01.010
6. ^ Rapp et al. (2005), doi 10.1109/AERO.2005.1559325
7. ^ ^{a b c d e} David S. F. Portree, Humans to Mars: Fifty Years of Mission Planning, 1950 - 2000, NASA Monographs in Aerospace History Series, Number 21, February 2001. Available as NASA SP-2001-4521.
8. ^ When will we land on Mars? - Mar 1965 - Page 86
9. ^ ^{a b c d} Annie Platoff, Eyes on the Red Planet: Human Mars Mission Planning, 1952-1970, (1999); available as NASA/CR-2001-2089280 (July 2001)
10. ^ Wernher von Braun, The Mars Project, University of Illinois Press, Urbana, IL, 1962
11. ^ Wernher von Braun, “The Next 20 Years of Interplanetary Exploration,” Astronautics & Aeronautics, November 1965, pp 24-34.
12. ^ M. Wade, Von Braun Mars Expedition - 1952, in Encyclopedia Astronautica
13. ^ Von Braun Mars Expedition - 1956, in Encyclopedia Astronautica
14. ^ "The Disney-Von Braun Collaboration and Its Influence on Space Exploration" by Mike Wright [1]
15. ^ Franklin Dixon, “Summary Presentation: Study of a Manned Mars Excursion Module,” in Proceeding of the Symposium on Manned Planetary Missions: 1963/1964 Status, NASA TM X-53049 (1964).
16. ^ Wernher von Braun, “Manned Mars Landing Presentation to the Space Task Group,” presentation materials, August 1969 (referenced by Portree, 2001 op cit.
17. ^ Penelope J. Boston, ed., AAS Science and Technology Series Volume 57, Proceedings of The Case for Mars I, 1984 (second printing 1987), ISBN 0-87703-197-5
18. ^ Christopher P. McKay, ed., AAS Science and Technology Series Volume 62, Proceedings of The Case for Mars II, 1985 (second printing 1988) 730p. Hard cover: ISBN 0-87703-219-1, Soft cover: ISBN 0-87703-220-3.
19. ^ Geoffrey A. Landis, "Footsteps to Mars: an Incremental Approach to Mars Exploration," Journal of the British Interplanetary Society, Vol. 48, pp. 367-342 (1995); presented at Case for Mars V, Boulder CO, 26–29 May 1993; appears in From Imagination to Reality: Mars Exploration Studies, R. Zubrin, ed., AAS Science and Technology Series Volume 91 pp. 339-350 (1997). (text available as Footsteps to Mars pdf file
20. ^ NASA, Report of the 90-day study on human exploration of the Moon and Mars, published 11/1989; abstract
21. ^ Dwayne Day, "Aiming for Mars, grounded on Earth," The Space Review February 16, 2004 link
22. ^ R. M. Zubrin, D. A. Baker and O. Gwynne, "Mars Direct: A Simple, Robust, and Cost Effective Architecture for the Space Exploration Initiative," paper AAS 90-168, in The Case for Mars IV: The International Exploration of Mars, Part I, MISSION STRATEGY & ARCHITECTURES, AAS Science and Technology Series Volume 89, Proceedings of The Case for Mars Conference, ed. Thomas R. Meyer, 1997 (ISBN 0-87703-418-4).
23. ^ R. Zubrin and D. A. Baker, "Mars Direct: Humans to the Red Planet by 1999," 41st Congress of the International Astronautical Federation (1990)
24. ^ NASA Austere Human Missions to Mars (2009)
25. ^ Yury Zaitsev (30 March 2005). "Russia Suggests Manned Matrian-Mission Plan". Rianovosty. http://en.rian.ru/onlinenews/20050330/39700840.html. 
26. ^ Vladimir Isachenkov (29 October 2009). "Russia Hopes To Fly Humans To Mars With Nuclear Spaceship". The Huffington Post. http://www.huffingtonpost.com/2009/10/29/russia-hopes-to-fly-human_n_338297.html. 
27. ^ Russia proposes manned Mars mission by 2015 - 08 July 2002 - New Scientist
28. ^ NASA - Lunar Outpost Plans Taking Shape
29. ^ Adringa, J. M. et al. (2005), doi 10.1109/AERO.2005.1559312
30. ^ AFP: NASA aims to put man on Mars by 2037
31. ^ President Bush Announces New Vision for Space Exploration Program
32. ^ The Space Age at 50. National Geographic Magazine, October 2007 issue
33. ^ Version 5 NASA (jan. 2009)
34. ^ ^{a b} http://www.astronautix.com/craft/eurssion.htm
35. ^ James C. McLane III, "Spirit of the Lone Eagle": an audacious program for a manned Mars landing, The Space Review July 31, 2006 link
36. ^ James C. McLane III, "Starship Trooper," Harper's Magazine November 2006. link (pay subscription required)
37. ^ James C. McLane III, "One Way Ticket to Mars," SEARCH Magazine Jan/Feb 2009 link to archived copy
38. ^ Krauss, Lawrence M. (31 August 2009). "A One-Way Ticket to Mars". New York Times. http://www.nytimes.com/2009/09/01/opinion/01krauss.html. Retrieved 07-20-2011. 
39. ^ Buzz Aldrin Speaks Out: Forget the Moon, Let’s Head to Mars, by Eliza Strickland, 26 June 2006, Discover Magazine
40. ^ Congress Mostly Approves New Direction for NASA. Yudhijit Bhattacharjee, 30 September 2010, Science.
41. ^ Hoffer, Steven (27 October 2010). "NASA Planning One-Way Manned Mission to Mars". AOL News. http://www.aolnews.com/surge-desk/article/nasa-hopes-to-send-astronauts-on-one-way-mission-to-mars/19692279. Retrieved 2010-10-31. 
42. ^ Firth, Niall (29 October 2010). "The Hundred Year Starship: The Nasa mission that will take astronauts to Mars and leave them there forever". Daily Mail. http://www.dailymail.co.uk/sciencetech/article-1324192/Hundred-Year-Starship-Mars-mission-leave-astronauts-planet-forever.html. Retrieved 2010-10-31. 
43. ^ Mars-500 crew report good health after experiment - RIAN
44. ^ http://www.russianspaceweb.com/spacecraft_manned_mars.html
45. ^ Mars on Earth. National Geographic Magazine, February 2001 issue
46. ^ Grossman, Lisa. "Ion engine could one day power 39-day trips to Mars". New Scientist. http://www.newscientist.com/article/dn17476-ion-engine-could-one-day-power-39day-trips-to-mars.html?full=true. Retrieved 2009-07-31. 
47. ^ November 22, 2004 - NASA's Moon-Mars initiative jeopardizes important science opportunities, according to American Physical Society Report
48. ^ Lupisella, ML. "Human Mars Mission Contamination Issues." NASA.

External links

• Human Exploration of Mars: The Reference Mission Design Reference Mission 1.0
• Reference Mission Version 3.0, Addedum to Human Exploration of Mars Design Reference Mission 3.0
• Mars Expeditions List of all manned mission projects
• a longer bibliography can be found in the bibliography of Portree's book, available in pdf format from NASA.