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===Space Exploration Initiative===
===Space Exploration Initiative===


On July 20, 1989, [[George H. W. Bush]] — then President of the United States — announced plans for what came to be known as the [[Space Exploration Initiative]] (SEI). In a speech on the steps of the [[National Air and Space Museum]] he described long-term plans which would culminate in a manned mission to the surface of Mars.<ref>{{cite web |title= Remarks on the 20th Anniversary of the Apollo 11 Moon Landing |url= http://bushlibrary.tamu.edu/research/public_papers.php?id=712&year=1989&month=all |date= 2012 |accessdate= September 1 2012}}</ref>
On July 20, 1989, [[George H. W. Bush]] — then President of the United States — announced plans for what came to be known as the [[Space Exploration Initiative]] (SEI). In a speech on the steps of the [[National Air and Space Museum]] he described long-term plans which would culminate in a manned mission to the surface of Mars.<ref>{{cite web |title= Remarks on the 20th Anniversary of the Apollo 11 Moon Landing |url= http://bushlibrary.tamu.edu/research/public_papers.php?id=712&year=1989&month=all |year= 2012 |accessdate= September 1, 2012}}</ref>


By December 1990, a study to estimate the project's cost determined that long-term expenditure would total approximately 450 billion dollars spread over 20 to 30 years.<ref>{{cite web |title= 90 Day Review: The 90 day review of President H.W. Bush's SEI plan |url= http://history.nasa.gov/90_day_study.pdf |date= October 19, 2010 |accessdate= September 1, 2012}}</ref> The "90 Day Study" as it came to be known, evoked a hostile Congressional reaction towards SEI given that it would have required the largest single government expenditure since the [[Second World War]].<ref name = "Mars Underground">{{cite video | people = Scott J. Gill (Director), Joshua B. Dasal (Writer), Scott J. Gill (Writer)| title = The Mars Underground| medium = Documentary | location = Denver, Colorado, USA| date = 2007| url = http://www.imdb.com/title/tt0437325/ }}</ref> Within a year, all funding requests for SEI had been denied.
By December 1990, a study to estimate the project's cost determined that long-term expenditure would total approximately 450 billion dollars spread over 20 to 30 years.<ref>{{cite web |title= 90 Day Review: The 90 day review of President H.W. Bush's SEI plan |url= http://history.nasa.gov/90_day_study.pdf |date= October 19, 2010 |accessdate= September 1, 2012}}</ref> The "90 Day Study" as it came to be known, evoked a hostile Congressional reaction towards SEI given that it would have required the largest single government expenditure since the [[Second World War]].<ref name = "Mars Underground">{{cite video | people = Scott J. Gill (Director), Joshua B. Dasal (Writer), Scott J. Gill (Writer)| title = The Mars Underground| medium = Documentary | location = Denver, Colorado, USA| date = 2007| url = http://www.imdb.com/title/tt0437325/ }}</ref> Within a year, all funding requests for SEI had been denied.


[[Dan Goldin]] became [[NASA Administrator]] on April 1, 1992, officially abandoning plans for near-term human exploration beyond Earth orbit with the shift towards a "faster, better, cheaper" strategy for robotic exploration.<ref>{{cite web |last = Thompson |first = Elvia |last2 = Davis |first2 = Jennifer |title= Daniel Saul Goldin |date = November 4 |year = 2009 |accessdate= September 1 2012 |url= http://history.nasa.gov/dan_goldin.html}}</ref>
[[Dan Goldin]] became [[NASA Administrator]] on April 1, 1992, officially abandoning plans for near-term human exploration beyond Earth orbit with the shift towards a "faster, better, cheaper" strategy for robotic exploration.<ref>{{cite web |last = Thompson |first = Elvia |last2 = Davis |first2 = Jennifer |title= Daniel Saul Goldin |date = November 4, 2009 |accessdate= September 1, 2012 |url= http://history.nasa.gov/dan_goldin.html}}</ref>


===Development===
===Development===
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<blockquote>The exact opposite of the correct way to do engineering.<ref name = "Mars Underground" /></blockquote>
<blockquote>The exact opposite of the correct way to do engineering.<ref name = "Mars Underground" /></blockquote>


Zubrin's alternative to this "Battlestar Galactica" mission strategy (dubbed so by its detractors for the large, nuclear powered spaceships that supposedly resembled [[Battlestar_Galactica_(ship)|the science-fiction spaceship of the same name]]) involved a longer surface stay, [[Interplanetary_travel|a faster flight-path]] in the form of a conjunction class mission, [[in-situ resource utilization]] and craft launched directly from the surface of Earth to Mars as opposed to be being assembled in orbit or by a space-based [[drydock]].<ref name = "The Case for Mars">{{cite book| last = Zubrin | first = Robert | authorlink = Robert Zubrin | coauthors = Richard Wagner, Arthur C. Clarke (Foreward) | title = The Case for Mars | publisher = Free Press; | edition = 1st Touchstone Ed edition | date = October 16, 1996 | page = 51 | language = English | url = http://www.amazon.com/The-Case-Mars-Settle-Planet/dp/0684835509 | isbn = 0684835509
Zubrin's alternative to this "Battlestar Galactica" mission strategy (dubbed so by its detractors for the large, nuclear powered spaceships that supposedly resembled [[Battlestar Galactica (ship)|the science-fiction spaceship of the same name]]) involved a longer surface stay, [[Interplanetary travel|a faster flight-path]] in the form of a conjunction class mission, [[in-situ resource utilization]] and craft launched directly from the surface of Earth to Mars as opposed to be being assembled in orbit or by a space-based [[drydock]].<ref name = "The Case for Mars">{{cite book| last = Zubrin | first = Robert | authorlink = Robert Zubrin | coauthors = Richard Wagner, Arthur C. Clarke (Foreward) | title = The Case for Mars | publisher = Free Press; | edition = 1st Touchstone Ed edition | date = October 16, 1996 | page = 51 | url = http://www.amazon.com/The-Case-Mars-Settle-Planet/dp/0684835509 | isbn = 0684835509
}}</ref> After receiving approval from management at Marietta, a 12-man team within the company began to work out the details of the mission. While they focused primarily on more traditional mission architectures, Zubrin began to collaborate with colleague [[David Baker]] on an extremely simple, stripped-down and robust strategy. Their goal to "use local resources, travel light, and live off the land" became the hallmark of Mars Direct.<ref name = "Mars Underground" />
}}</ref> After receiving approval from management at Marietta, a 12-man team within the company began to work out the details of the mission. While they focused primarily on more traditional mission architectures, Zubrin began to collaborate with colleague [[David Baker]] on an extremely simple, stripped-down and robust strategy. Their goal to "use local resources, travel light, and live off the land" became the hallmark of Mars Direct.<ref name = "Mars Underground" />


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===First Launch===
===First Launch===
[[File:Mars Direct Sequence.jpg|thumb|Depiction of the first 5 launches required for the mission.]]
[[File:Mars Direct Sequence.jpg|thumb|Depiction of the first 5 launches required for the mission.]]
The first flight of the Ares rocket (not to be confused with the similarly named rocket of the now defunct [[Constellation Program]]) would bring an unmanned Earth Return Vehicle to the red planet after a 6 month cruise phase, with a supply of [[hydrogen]], a chemical plant and a small [[nuclear reactor]]. Once there, a series of chemical reactions (the [[Sabatier reaction]] coupled with [[electrolysis]]) would be used to combine a small amount of hydrogen (8 tons) carried by the Earth Return Vehicle with the [[carbon dioxide]] of the Martian atmosphere to create up to 112 tonnes of [[methane]] and [[oxygen]]. This relatively simple chemical engineering procedure was utilized regularly in the 19th and 20th centuries<ref>{{cite web |url= http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1912/press.html |title= The Nobel Prize in Chemistry 1912 |author= Professor H.G. Söderbaum |date= 2 Sep 2012 |accessdate= 2 September 2012}}</ref>, and would ensure that only 7% of the return propellant would need to be carried to the surface of Mars.
The first flight of the Ares rocket (not to be confused with the similarly named rocket of the now defunct [[Constellation Program]]) would bring an unmanned Earth Return Vehicle to the red planet after a 6 month cruise phase, with a supply of [[hydrogen]], a chemical plant and a small [[nuclear reactor]]. Once there, a series of chemical reactions (the [[Sabatier reaction]] coupled with [[electrolysis]]) would be used to combine a small amount of hydrogen (8 tons) carried by the Earth Return Vehicle with the [[carbon dioxide]] of the Martian atmosphere to create up to 112 tonnes of [[methane]] and [[oxygen]]. This relatively simple chemical engineering procedure was utilized regularly in the 19th and 20th centuries,<ref>{{cite web |url= http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1912/press.html |title= The Nobel Prize in Chemistry 1912 |author= Professor H.G. Söderbaum |date= 2 Sep 2012 |accessdate= 2 September 2012}}</ref> and would ensure that only 7% of the return propellant would need to be carried to the surface of Mars.


96 tonnes of methane and oxygen would be needed to send the Earth Return Vehicle on a trajectory back home at the conclusion of the surface stay, the rest would be available for Mars rovers. The process of generating fuel is expected to require approximately ten months to complete.
96 tonnes of methane and oxygen would be needed to send the Earth Return Vehicle on a trajectory back home at the conclusion of the surface stay, the rest would be available for Mars rovers. The process of generating fuel is expected to require approximately ten months to complete.
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===Landing and Surface Operations===
===Landing and Surface Operations===


Upon reaching Mars, the upper stage would be jettisoned, with the Habitat Unit [[aerobraking]] into Mars orbit before soft-landing in proximity to the Earth Return Vehicle. Precise landing would be supported by a radar beacon started by the first lander. 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 Mars Habitat Unit, and powered by the methane produced by the Earth Return Vehicle.
Upon reaching Mars, the upper stage would be jettisoned, with the Habitat Unit [[aerobraking]] into Mars orbit before soft-landing in proximity to the Earth Return Vehicle. Precise landing would be supported by a radar beacon started by the first lander. 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 Mars Habitat Unit, and powered by the methane produced by the Earth Return Vehicle.


===Return and Follow-up Missions===
===Return and Follow-up Missions===
Line 52: Line 52:
===Launch Vehicle===
===Launch Vehicle===


The plan involves several launches making use of heavy-lift boosters of similar size to the [[Saturn V]] used for the [[Apollo program|Apollo]] missions, which would potentially be derived from [[Space Shuttle]] components. This proposed rocket is dubbed "Ares", which would utilize space shuttle [[Space_Shuttle_Solid_Rocket_Booster|Advanced Solid Rocket Boosters]], a modified shuttle external tank, and a new Lox/LH2 third stage for the trans-Mars injection of the payload. Ares would put 121 tonnes into a 300 km circular orbit , and boost 47 tonnes toward Mars.<ref>{{cite web |url= http://www.astronautix.com/lvs/areirect.htm |title= Ares Mars Direct |author= Mark Wade |accessdate=1 September 2012}}</ref>
The plan involves several launches making use of heavy-lift boosters of similar size to the [[Saturn V]] used for the [[Apollo program|Apollo]] missions, which would potentially be derived from [[Space Shuttle]] components. This proposed rocket is dubbed "Ares", which would utilize space shuttle [[Space Shuttle Solid Rocket Booster|Advanced Solid Rocket Boosters]], a modified shuttle external tank, and a new Lox/LH2 third stage for the trans-Mars injection of the payload. Ares would put 121 tonnes into a 300&nbsp;km circular orbit, and boost 47 tonnes toward Mars.<ref>{{cite web |url= http://www.astronautix.com/lvs/areirect.htm |title= Ares Mars Direct |author= Mark Wade |accessdate=1 September 2012}}</ref>


===Earth Return Vehicle===
===Earth Return Vehicle===
Line 72: Line 72:
Zubrin and Baker pitched Mars Direct at the [[Marshall Spaceflight Center]], where reception was generally positive. Flown around the country, the engineers' plan generated significant interest. When their tour culminated in a demonstration at the [[National Space Society]] they received a standing ovation.<ref name = "Mars Underground" /> The plan gained rapid media attention shortly afterwards.
Zubrin and Baker pitched Mars Direct at the [[Marshall Spaceflight Center]], where reception was generally positive. Flown around the country, the engineers' plan generated significant interest. When their tour culminated in a demonstration at the [[National Space Society]] they received a standing ovation.<ref name = "Mars Underground" /> The plan gained rapid media attention shortly afterwards.


Resistance to the plan came from teams within NASA working on the [[Space_Station_Freedom|Space Station]] and advanced propulsion concepts, as their work would no longer be required to reach Mars. The NASA administration rejected Mars Direct. Zubrin remained committed to the strategy, and after parting with David Baker attempted to convince the new NASA administration of Mars Direct's merits in 1992.<ref name = "Mars Underground" />
Resistance to the plan came from teams within NASA working on the [[Space Station Freedom|Space Station]] and advanced propulsion concepts, as their work would no longer be required to reach Mars. The NASA administration rejected Mars Direct. Zubrin remained committed to the strategy, and after parting with David Baker attempted to convince the new NASA administration of Mars Direct's merits in 1992.<ref name = "Mars Underground" />


After being granted a small research fund at Martin Marietta, Zubrin and his colleagues successfully demonstrated an in-situ propellant generator which achieved an efficiency of 94%. No chemical engineers partook in the development of the demonstration hardware. After showing the positive results to the [[Johnson Space Center]], the NASA administration still held several reservations about the plan.<ref name = "Mars Underground" />
After being granted a small research fund at Martin Marietta, Zubrin and his colleagues successfully demonstrated an in-situ propellant generator which achieved an efficiency of 94%. No chemical engineers partook in the development of the demonstration hardware. After showing the positive results to the [[Johnson Space Center]], the NASA administration still held several reservations about the plan.<ref name = "Mars Underground" />


In November 2003, Zubrin was invited to speak to the U.S. Senate committee on the future of space exploration. <ref name = "Mars Underground" /> Two months later the [[Bush administration]] announced the creation of the Constellation program, a manned spaceflight initiative with the goal of sending humans to the Moon by 2020. While a Mars mission was not specifically detailed, a plan to reach Mars based on utilizing the [[Orion spacecraft]] was tentatively developed for implementation in the 2030s. The program's funding was denied in 2011 by the Obama administration and the Constellation program ended.
In November 2003, Zubrin was invited to speak to the U.S. Senate committee on the future of space exploration.<ref name = "Mars Underground" /> Two months later the [[Bush administration]] announced the creation of the Constellation program, a manned spaceflight initiative with the goal of sending humans to the Moon by 2020. While a Mars mission was not specifically detailed, a plan to reach Mars based on utilizing the [[Orion spacecraft]] was tentatively developed for implementation in the 2030s. The program's funding was denied in 2011 by the Obama administration and the Constellation program ended.


==Revisions==
==Revisions==
Line 87: Line 87:


===Design Reference Mission===
===Design Reference Mission===
The NASA model, referred to as the [[Design Reference Mission]], on version 5.0 as of September 1st 2012, calls for a significant upgrade in hardware (at least 3 launches per mission, rather than two), and sends the ERV to Mars fully fueled, parking it in orbit above the planet for subsequent rendezvous with the MAV.
The NASA model, referred to as the [[Design Reference Mission]], on version 5.0 as of September 1, 2012, calls for a significant upgrade in hardware (at least 3 launches per mission, rather than two), and sends the ERV to Mars fully fueled, parking it in orbit above the planet for subsequent rendezvous with the MAV.


===Mars Direct and SpaceX===
===Mars Direct and SpaceX===
[[File:Mars Direct SpaceX.jpg|thumb|The Dragon capsule with an inflatable module swinging from a tether.]]
[[File:Mars Direct SpaceX.jpg|thumb|The Dragon capsule with an inflatable module swinging from a tether.]]
With the potentially imminent advent of low cost [[Heavy_Lift_Launch_Vehicle|heavy lift capability]], Zubrin has posited a dramatically lower cost manned Mars mission utilizing hardware developed by [[space transport]] company [[SpaceX]]. In this simpler plan, a crew of two would be sent to Mars by a single [[Falcon Heavy]] launch, the [[Dragon spacecraft]] acting as their interplanetary cruise habitat. Additional living space for the journey would be enabled through the use of inflatable add-on modules if required. The problems associated with long-term weightlessness would be addressed in the same manner as the baseline Mars Direct plan, a tether between the Dragon habitat and the TMI (Trans-Mars Injection) stage acting to allow rotation of the craft.
With the potentially imminent advent of low cost [[Heavy Lift Launch Vehicle|heavy lift capability]], Zubrin has posited a dramatically lower cost manned Mars mission utilizing hardware developed by [[space transport]] company [[SpaceX]]. In this simpler plan, a crew of two would be sent to Mars by a single [[Falcon Heavy]] launch, the [[Dragon spacecraft]] acting as their interplanetary cruise habitat. Additional living space for the journey would be enabled through the use of inflatable add-on modules if required. The problems associated with long-term weightlessness would be addressed in the same manner as the baseline Mars Direct plan, a tether between the Dragon habitat and the TMI (Trans-Mars Injection) stage acting to allow rotation of the craft.


The Dragon's heatshield characteristics could allow for a safe descent if landing rockets of sufficient power were made available. Research at NASA's [[Ames Research Center]] has demonstrated that a robotic Dragon would be capable of a fully propulsive landing on the Martian surface. On the surface, the crew would have at their disposal 2 Dragon spacecraft with inflatable modules as habitats, 2 ERVs, 2 Mars ascent vehicles and 8 tonnes of cargo.
The Dragon's heatshield characteristics could allow for a safe descent if landing rockets of sufficient power were made available. Research at NASA's [[Ames Research Center]] has demonstrated that a robotic Dragon would be capable of a fully propulsive landing on the Martian surface. On the surface, the crew would have at their disposal 2 Dragon spacecraft with inflatable modules as habitats, 2 ERVs, 2 Mars ascent vehicles and 8 tonnes of cargo.

Revision as of 23:00, 16 September 2012

The Habitat Unit and the Earth Return Vehicle on Mars.

Mars Direct is a proposal for a manned mission to Mars that is designed to be both cost-effective and possible with current technology. It was originally detailed in a research paper by NASA engineers Robert Zubrin and David Baker in 1990, and later expanded upon in Zubrin's 1996 book The Case for Mars. It now serves as a staple of Zubrin's speaking engagements and general advocacy as head of the Mars Society, an organization devoted to the colonization of Mars.

History

Space Exploration Initiative

On July 20, 1989, George H. W. Bush — then President of the United States — announced plans for what came to be known as the Space Exploration Initiative (SEI). In a speech on the steps of the National Air and Space Museum he described long-term plans which would culminate in a manned mission to the surface of Mars.[1]

By December 1990, a study to estimate the project's cost determined that long-term expenditure would total approximately 450 billion dollars spread over 20 to 30 years.[2] The "90 Day Study" as it came to be known, evoked a hostile Congressional reaction towards SEI given that it would have required the largest single government expenditure since the Second World War.[3] Within a year, all funding requests for SEI had been denied.

Dan Goldin became NASA Administrator on April 1, 1992, officially abandoning plans for near-term human exploration beyond Earth orbit with the shift towards a "faster, better, cheaper" strategy for robotic exploration.[4]

Development

While working at Martin Marietta designing interplanetary mission architectures, Robert Zubrin perceived a fundamental flaw in the SEI program. Zubrin came to understand that if NASA's plan was to fully utilize as many technologies as possible in support of sending the mission to Mars, it would become politically untenable. In his own words;

The exact opposite of the correct way to do engineering.[3]

Zubrin's alternative to this "Battlestar Galactica" mission strategy (dubbed so by its detractors for the large, nuclear powered spaceships that supposedly resembled the science-fiction spaceship of the same name) involved a longer surface stay, a faster flight-path in the form of a conjunction class mission, in-situ resource utilization and craft launched directly from the surface of Earth to Mars as opposed to be being assembled in orbit or by a space-based drydock.[5] After receiving approval from management at Marietta, a 12-man team within the company began to work out the details of the mission. While they focused primarily on more traditional mission architectures, Zubrin began to collaborate with colleague David Baker on an extremely simple, stripped-down and robust strategy. Their goal to "use local resources, travel light, and live off the land" became the hallmark of Mars Direct.[3]

Mission Scenario

First Launch

File:Mars Direct Sequence.jpg
Depiction of the first 5 launches required for the mission.

The first flight of the Ares rocket (not to be confused with the similarly named rocket of the now defunct Constellation Program) would bring an unmanned Earth Return Vehicle to the red planet after a 6 month cruise phase, with a supply of hydrogen, a chemical plant and a small nuclear reactor. Once there, a series of chemical reactions (the Sabatier reaction coupled with electrolysis) would be used to combine a small amount of hydrogen (8 tons) carried by the Earth Return Vehicle with the carbon dioxide of the Martian atmosphere to create up to 112 tonnes of methane and oxygen. This relatively simple chemical engineering procedure was utilized regularly in the 19th and 20th centuries,[6] and would ensure that only 7% of the return propellant would need to be carried to the surface of Mars.

96 tonnes of methane and oxygen would be needed to send the Earth Return Vehicle on a trajectory back home at the conclusion of the surface stay, the rest would be available for Mars rovers. The process of generating fuel is expected to require approximately ten months to complete.

Second Launch

Some 26 months after the Earth Return Vehicle is originally launched from Earth, a second vehicle, the "Mars Habitat Unit", would be launched on a 6-month long low energy transfer trajectory to Mars, and would carry a crew of four astronauts (the minimum number required so that the team can be split in two without leaving anyone alone). The Habitat Unit would not be launched until the automated factory aboard the ERV had signaled the successful production of chemicals required for operation on the planet and the return trip to Earth. During the trip, artificial gravity would be generated by tethering the Habitat Unit to the spent upper stage of the booster, and setting them rotating about a common axis. This rotation would produce a comfortable 1G working environment for the astronauts, freeing them of the debilitating effects of long term exposure to weightlessness.[3]

Landing and Surface Operations

Upon reaching Mars, the upper stage would be jettisoned, with the Habitat Unit aerobraking into Mars orbit before soft-landing in proximity to the Earth Return Vehicle. Precise landing would be supported by a radar beacon started by the first lander. 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 Mars Habitat Unit, and powered by the methane produced by the Earth Return Vehicle.

Return and Follow-up Missions

To return, the crew would use the Earth Return Vehicle, leaving the Mars Habitat Unit for the possible use of subsequent explorers. On the return trip to Earth, the propulsion stage of the Earth Return Vehicle would be used as a counterweight to generate artificial gravity for the trip back.

Follow-up missions would be dispatched at 2 year intervals to Mars to ensure that a redundant ERV would be on the surface at all times, waiting to be utilized by the next crewed mission or the current crew in an emergency. In such an emergency scenario, the crew would trek hundreds of kilometers to the other ERV in their long-range vehicle.

Components

The Mars Direct proposal includes a component for a Launch Vehicle "Ares", an Earth Return Vehicle (ERV) and a Mars Habitat Unit (MHU).

Launch Vehicle

The plan involves several launches making use of heavy-lift boosters of similar size to the Saturn V used for the Apollo missions, which would potentially be derived from Space Shuttle components. This proposed rocket is dubbed "Ares", which would utilize space shuttle Advanced Solid Rocket Boosters, a modified shuttle external tank, and a new Lox/LH2 third stage for the trans-Mars injection of the payload. Ares would put 121 tonnes into a 300 km circular orbit, and boost 47 tonnes toward Mars.[7]

Earth Return Vehicle

File:Mars Direct ERV.jpg
Dimensions of the Earth Return Vehicle.

The Earth Return Vehicle 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.

Mars Habitat Unit

File:Mars Direct Hab Interior.jpg
Interior diagram of the Mars Habitat Unit.

The Mars Habitat Unit is a 2- or 3-deck vehicle providing a comprehensive living and working environment for a Mars crew. In addition to individual sleeping quarters which provide a degree of privacy for each of the crew and a place for personal effects, the Mars Habitat Unit includes a communal living area, a small galley, exercise area, and hygiene facilities with closed-circle water purification. The lower deck of the Mars Habitat Unit 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. Protection from harmful radiation while in space and on the surface of Mars (e.g. from solar flares) would be provided by a dedicated "storm shelter" in the core of the vehicle.

The Mars Habitat Unit would also include a small pressurized rover that is stored in the lower deck area and assembled on the surface of Mars. Powered by a methane engine, it is designed to extend the range over which astronauts can explore the surface of Mars out to 320 km.

Since it was first proposed as a part of Mars Direct, the Mars Habitat Unit has been adopted by NASA as a part of their Mars Design Reference Mission, which utilizes two Mars Habitat Units - 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 Mars Habitat Unit flies to Mars with the crew, its interior given over completely to living and storage space.

To prove the viability of the Mars Habitat Unit, the Mars Society has implemented the Mars Analogue Research Station Program (MARS), which has established a number of prototype Mars Habitat Units around the world.

Reception

Zubrin and Baker pitched Mars Direct at the Marshall Spaceflight Center, where reception was generally positive. Flown around the country, the engineers' plan generated significant interest. When their tour culminated in a demonstration at the National Space Society they received a standing ovation.[3] The plan gained rapid media attention shortly afterwards.

Resistance to the plan came from teams within NASA working on the Space Station and advanced propulsion concepts, as their work would no longer be required to reach Mars. The NASA administration rejected Mars Direct. Zubrin remained committed to the strategy, and after parting with David Baker attempted to convince the new NASA administration of Mars Direct's merits in 1992.[3]

After being granted a small research fund at Martin Marietta, Zubrin and his colleagues successfully demonstrated an in-situ propellant generator which achieved an efficiency of 94%. No chemical engineers partook in the development of the demonstration hardware. After showing the positive results to the Johnson Space Center, the NASA administration still held several reservations about the plan.[3]

In November 2003, Zubrin was invited to speak to the U.S. Senate committee on the future of space exploration.[3] Two months later the Bush administration announced the creation of the Constellation program, a manned spaceflight initiative with the goal of sending humans to the Moon by 2020. While a Mars mission was not specifically detailed, a plan to reach Mars based on utilizing the Orion spacecraft was tentatively developed for implementation in the 2030s. The program's funding was denied in 2011 by the Obama administration and the Constellation program ended.

Revisions

Since Mars Direct was initially conceived, it has undergone regular review and development by Zubrin himself, the Mars Society, NASA, Stanford University and others.

Mars Semi-Direct

Zubrin and Weaver developed a modified version of Mars Direct, called Mars Semi-Direct, in response to some specific criticisms.[8] This mission consists of three spacecraft and includes a "Mars Ascent Vehicle" (MAV). The ERV remains in Mars orbit for the return journey, while the unmanned MAV lands and manufactures propellants for the ascent back up to Mars orbit. The Mars Semi-Direct architecture has been used as the basis of a number of studies, including the NASA Design Reference Missions.

When subjected to the same cost-analysis as the 90-day report, Mars Semi-Direct was predicted to cost 55 billion dollars over 10 years, capable of fitting into the existing NASA budget.

Design Reference Mission

The NASA model, referred to as the Design Reference Mission, on version 5.0 as of September 1, 2012, calls for a significant upgrade in hardware (at least 3 launches per mission, rather than two), and sends the ERV to Mars fully fueled, parking it in orbit above the planet for subsequent rendezvous with the MAV.

Mars Direct and SpaceX

File:Mars Direct SpaceX.jpg
The Dragon capsule with an inflatable module swinging from a tether.

With the potentially imminent advent of low cost heavy lift capability, Zubrin has posited a dramatically lower cost manned Mars mission utilizing hardware developed by space transport company SpaceX. In this simpler plan, a crew of two would be sent to Mars by a single Falcon Heavy launch, the Dragon spacecraft acting as their interplanetary cruise habitat. Additional living space for the journey would be enabled through the use of inflatable add-on modules if required. The problems associated with long-term weightlessness would be addressed in the same manner as the baseline Mars Direct plan, a tether between the Dragon habitat and the TMI (Trans-Mars Injection) stage acting to allow rotation of the craft.

The Dragon's heatshield characteristics could allow for a safe descent if landing rockets of sufficient power were made available. Research at NASA's Ames Research Center has demonstrated that a robotic Dragon would be capable of a fully propulsive landing on the Martian surface. On the surface, the crew would have at their disposal 2 Dragon spacecraft with inflatable modules as habitats, 2 ERVs, 2 Mars ascent vehicles and 8 tonnes of cargo.

Other Studies

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,[9] where Mars Direct and the DRMs used nuclear reactors for surface power and, in the case of the DRMs for propulsion as well. The Mars Oz reference mission also differs in assuming, based on space station experience, that spin gravity will not be required.

Mars Analogue Research Stations

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.[10] 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 issues were discussed surrounding NASA funding of the project, and on Mars Underground, where the plan is discussed more in-depth.

Alternatives

A modified proposal, "Mars for Less", was developed by Grant Bonin, and has been adopted as the design reference mission for a new umbrella group of advocates, the MarsDrive consortium. 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. However, the orbital rendezvous required, while potentially reducing cost, has inherent risks.

A modified proposal, called "Mars to Stay", involves not returning the first immigrant/explorers immediately, or ever. Dean Unick has suggested the cost of sending a four or six person team could be one fifth to one tenth the cost of returning that same four or six person team. Depending on the precise approach taken, a quite complete lab could be sent and landed for less than the cost of sending back even 50 kilos of Martian rocks. Twenty or more persons could be sent for the cost of returning four.[11]

In fiction

See also

References

  1. ^ "Remarks on the 20th Anniversary of the Apollo 11 Moon Landing". 2012. Retrieved September 1, 2012.
  2. ^ "90 Day Review: The 90 day review of President H.W. Bush's SEI plan" (PDF). October 19, 2010. Retrieved September 1, 2012.
  3. ^ a b c d e f g h Scott J. Gill (Director), Joshua B. Dasal (Writer), Scott J. Gill (Writer) (2007). The Mars Underground (Documentary). Denver, Colorado, USA.
  4. ^ Thompson, Elvia; Davis, Jennifer (November 4, 2009). "Daniel Saul Goldin". Retrieved September 1, 2012.
  5. ^ Zubrin, Robert (October 16, 1996). The Case for Mars (1st Touchstone Ed edition ed.). Free Press;. p. 51. ISBN 0684835509. {{cite book}}: |edition= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: extra punctuation (link)
  6. ^ Professor H.G. Söderbaum (2 Sep 2012). "The Nobel Prize in Chemistry 1912". Retrieved 2 September 2012.
  7. ^ Mark Wade. "Ares Mars Direct". Retrieved 1 September 2012.
  8. ^ Zubrin, R.; Weaver, D. (June 28-30th, 1993). Practical methods for near-term piloted Mars missions. AIAA93-2089,29th AIAA/ASME Joint Propulsion Conference. Monterrey CA, United States. CiteSeerx: 10.1.1.23.1915. {{cite conference}}: Check date values in: |date= (help)
  9. ^ 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
  10. ^ Mars Society Australia Mars-Oz web site
  11. ^ Aldrin: Mars Pioneers Should Not Return to Earth
Further reading
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