A human mission to Mars has been the subject of science fiction, aerospace engineering, and scientific proposals since the 20th century. Plans include landing on Mars for exploration at a minimum, with the possibility of sending settlers and terraforming the planet and/or exploring its moons Phobos and Deimos also considered.
The exploration of Mars has been a goal of national space programs for decades. Conceptual work for missions that would involve human explorers has been ongoing since the 1950s, with planned missions typically being stated as taking place anywhere between 10 to 30 years from the time they are drafted. The list of crewed Mars mission plans shows the various mission proposals that have been put forth by multiple organizations and space agencies in this field of space exploration. Plans have varied from scientific expeditions, in which a small group (between two and eight astronauts) would visit Mars for a period of a few weeks or year, to the permanent colonization of Mars.
In the 2010s, numerous US, European, and Asian agencies were developing proposals for human missions to Mars.In fiction, Mars is a frequent target of exploration and settlement in books, graphic novels, and films.
The energy needed for transfer between planetary orbits, or "Delta-v", is lowest at intervals fixed by the synodic period. For Earth / Mars trips, this is every 26 months (2 years and 2 months), so missions are typically planned to coincide with one of these launch windows. Due to the eccentricity of Mars' orbit, the energy needed in the low-energy windows varies on roughly a 15-year cycle with the easiest windows needing only half the energy of the peaks. In the 20th century, there was a minimum in the 1969 and 1971 launch windows and another low in 1986 and 1988, then the cycle repeated. The next low-energy launch window occurs in 2033.
Several types of mission plans have been proposed, including opposition class and conjunction class or the Crocco flyby. The lowest energy transfer to Mars is a Hohmann transfer orbit, which would involve an approximately 9 month travel time from Earth to Mars, about five hundred days at Mars to wait for the transfer window to Earth, and a travel time of about 9 months to return to Earth.
Shorter Mars mission plans have round-trip flight times of 400 to 450 days, but would require significantly higher energy. A fast Mars mission of 245 days round trip could be possible with on-orbit staging. In 2014 ballistic capture was proposed, which may reduce fuel cost and provide more flexible launch windows compared to the Hohmann.
In the Crocco grand tour, a crewed spacecraft would get a flyby of Mars and Venus in under a year in space. Some flyby mission architectures can also be extended to include a style of Mars landing with a flyby excursion lander spacecraft. Proposed by R. Titus in 1966, it involved a short stay lander-ascent vehicle that would separate from a "parent" Earth-Mars transfer craft prior to its flyby of Mars. The Ascent-Descent lander would arrive sooner and either go into orbit around Mars or land, and depending on the design offer perhaps 10-30 days before it needed to launch itself back to the main transfer vehicle. (see also Mars flyby).
Aerobraking at Mars was estimated in the 1980s to cut the mass of a Mars mission lifting off from Earth by half. As a result, Mars missions have designed interplanetary spacecraft and landers capable of aero-braking.
Landed spacecraft on the surface of Mars:
When an expedition reaches the orbit of Mars, braking is required to enter Mars orbit proper. Two options are available: rockets or aerocapture. Aerocapture at Mars for human missions was studied in the 20th century. In a review of 93 Mars studies, 24 used aerocapture for Mars or Earth return. One of the considerations for using aerocapture on crewed missions is a limit on the maximum force experienced by the astronauts. The current scientific consensus is that 5g, or 5 times Earth gravity, is the maximum allowable acceleration.
Conducting a safe landing requires knowledge of the properties of the atmosphere, first observed by Mariner 4, and a survey of the planet to identify suitable landing sites. Major global surveys were conducted by Mariner 9 and Viking 1 and two orbiters, which supported the Viking landers. Later orbiters, such as Mars Global Surveyor, 2001 Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter, have mapped Mars in higher resolution with improved instruments. These later surveys have identified the probable locations of water, a critical resource.
The largest limiting factor for sending humans to Mars is funding. The estimated cost is roughly 500 billion U.S. dollars, though the actual costs are likely to be more. Starting in the late 1950s, the early phase of space exploration was conducted as much to make a political statement as to make observations of the solar system. However, this proved to be both wasteful and unsustainable, and the current climate is one of international cooperation, with large projects such as the International Space Station and the planned Lunar Orbital Platform-Gateway being built and launched by multiple countries.
Critics argue that the immediate benefits of establishing a human presence on Mars are outweighed by the immense cost, and that funds could be better redirected towards other programs, such as robotic exploration. Proponents of human space exploration contend that the symbolism of establishing a presence in space may garner public interest to join the cause and spark global cooperation. There are also claims that a long-term investment in space travel is necessary for humanity's survival.
There are several key physical challenges for human missions to Mars:
Some of these issues were estimated statistically in the HUMEX study. Ehlmann and others have reviewed political and economic concerns, as well as technological and biological feasibility aspects. While fuel for roundtrip travel could be a challenge, methane and oxygen can be produced using Martian H2O (preferably as water ice instead of liquid water) and atmospheric CO2 with mature technology.
Robotic spacecraft to Mars are currently required to be sterilized. The allowable limit is 300,000 spores on the exterior of general craft, with stricter requirements for spacecraft bound to "special regions" containing water. Otherwise there is a risk of contaminating not only the life-detection experiments but possibly the planet itself.
It is impossible to sterilize human missions to this level, as humans are host to typically a hundred trillion (1014) microorganisms of thousands of species of the human microbiota, and these cannot be removed. Containment seems the only option, but it is a major challenge in the event of a hard landing (i.e. crash). There have been several planetary workshops on this issue, but with no final guidelines for a way forward yet. Human explorers would also be vulnerable to back contamination to Earth if they become carriers of microorganisms.
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.
Wernher von Braun was the first person to make a detailed technical study of a Mars mission. Details were published in his book Das Marsprojekt (1952, published in English as The Mars Project in 1962) and several subsequent works.Willy Ley popularized a similar mission in English 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. The mission itself featured a fleet of ten spacecraft with a combined crew of 70 heading to Mars, 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. Later versions of the mission proposal, featured in the Disney "Man In Space" film series, showed nuclear-powered ion-propulsion vehicles for the interplanetary cruise.
From 1957 to 1965, work was done by General Atomics on Project Orion, a proposal for a nuclear pulse propulsion spacecraft. Orion was intended to have the ability to transport extremely large payloads compared to chemical rocketry, making crewed missions to Mars and the outer planets feasible. One of the early vehicle designs was intended to send an 800-ton payload to Mars orbit. The Partial Nuclear Test Ban Treaty of 1963 made further development unviable, and work ended in 1965.
In 1962, Aeronutronic Ford, General Dynamics and the Lockheed Missiles and Space Company made studies of Mars mission designs as part of NASA Marshall Spaceflight Center "Project EMPIRE". 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 never proposed for funding, they were the first detailed analyses of what it would take to accomplish a human voyage to Mars using data from actual NASA spaceflight, laying 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.
Following the success of the Apollo Program, von Braun advocated a crewed mission to Mars as a focus for NASA's crewed space program. Von Braun's proposal used Saturn V boosters to launch NERVA-powered upper stages that would propel two six-crew spacecraft on a dual mission in the early 1980s. The proposal was considered by President Richard Nixon but passed over in favor of the Space Shuttle.
In 1975, von Braun discussed the mission architecture that emerged from these Apollo-era studies in a recorded lecture and while doing so suggested that multiple Shuttle launches could instead be configured to lift the two Nuclear Thermal Rocket engine equipped spacecraft in smaller parts, for assembly in-orbit.
The Martian Piloted Complex or "'MPK'" was a proposal by Mikhail Tikhonravov of the Soviet Union for a crewed Mars expedition, using the (then proposed) N1 rocket, in studies from 1956 to 1962. The Soviets sent many probes to Mars with some noted success stories including Mars atmospheric entry, but the overall rate of success was low. (see Mars 3)
Heavy Interplanetary Spacecraft (known by the Russian acronym TMK) was the designation of a Soviet Union space exploration proposal in the 1960s to send a crewed 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 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.
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. It proposed use of in-situ resource utilization to manufacture rocket propellant for the return trip. The mission study was published in a series of proceedings volumes. Later conferences presented alternative concepts, including the "Mars Direct" concept of Robert Zubrin and David Baker; the "Footsteps to Mars" proposal of Geoffrey A. Landis, 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.
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. This resulted in a report, called the 90-day study, 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.
Because of the greater distance, the Mars mission would be much more risky and expensive than past Moon flights. Supplies and fuel would have to be prepared for a 2-3 year round trip and the spacecraft would need at least partial shielding from ionizing radiation. A 1990 paper by Robert Zubrin and David A. Baker, then of Martin Marietta, proposed reducing the mission mass (and hence the cost) by using in situ resource utilization to manufacture propellant from the Martian Atmosphere. This proposal drew on concepts developed by the former "Case for Mars" conference series. Over the next decade, Zubrin developed it into a mission concept, Mars Direct, which he presented in a book, The Case for Mars (1996). The mission is advocated by the Mars Society, which Zubrin founded in 1998, as practical and affordable.
In 1991 in Toulouse, France, the International Space University studied an international human Mars mission. They proposed a crew of 8 traveling to Mars in a nuclear-powered vessel with artificial gravity provided by rotation. On the surface, 40 tonne habitats pressurized to 10 psi (69 kPa) were powered by a 40 kW photovoltaic array.
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) to stimulate further thought and concept development.
Selected other US/NASA studies (1988-2009):
The Mars Piloted Orbital Station (or MARPOST) is a Russian proposed crewed orbital mission to Mars, using a nuclear reactor to run an electric rocket engine. Proposed in October 2000 as the next step for Russia in space along with participation in the International Space Station, a 30-volume draft project for MARPOST was confirmed as of 2005. Design for the ship was proposed to be ready in 2012, and the ship itself in 2021.
In 2001, the European Space Agency laid out a long-term vision of sending a human mission to Mars in 2033. The project's proposed timeline would begin with robotic exploration, a proof of concept simulation of sustaining humans on Mars, and eventually a crewed mission. Objections from the participating nations of ESA and other delays have put the timeline into question, and currently ExoMars, delivered an orbiter to Mars in 2016, have come to fruition.
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.
On 14 January 2004, George W. Bush announced the Vision for Space Exploration, an initiative of crewed space exploration. It included developing preliminary plans for a lunar outpost by 2012 and establishing an outpost by 2020. By 2005, precursor missions that would help develop the needed technology during the 2010s were tentatively outlined. On 24 September 2007, Michael Griffin, then NASA Administrator, hinted that NASA would be able to launch a human mission to Mars by 2037. The needed funds were to be generated by diverting $11 billion 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.
The Mars Society Germany proposed a crewed Mars mission using several launches of an improved heavy-lift version of the Ariane 5. 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). Total project was estimated to cost 10 to 15 billion Euros.
Sun Laiyan, administrator of the China National Space Administration, said on July 20, 2006 that China would start deep space exploration focusing on Mars over the next five years, during the Eleventh Five-Year Plan (2006-2010) Program period. The first uncrewed Mars exploration program could take place between 2014-2033, followed by a crewed phase in 2040-2060 in which crew members would land on Mars and return home. The Mars 500 study of 2011 prepared for this crewed mission.
The idea of a one-way trip to Mars has been proposed several times. In 1988, space activist Bruce Mackenzie proposed a one-way trip to Mars in a presentation at the International Space Development Conference, arguing that the mission could be done with less difficulty and expense without a return to Earth. 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,Harper's Magazine,SEARCH Magazine and The New York Times.
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.
Mars 500, the longest high fidelity spaceflight simulation, ran from 2007 to 2011 in Russia and was an experiment to assess the feasibility of crewed missions to Mars.
Extrapolated from the DRMA 5.0, plans for a crewed Mars expedition with chemical propulsion. Austere Human Missions to Mars
In a major space policy speech at Kennedy Space Center on 15 April 2010, Barack Obama predicted a crewed Mars mission to orbit the planet by the mid-2030s, followed by a landing. This proposal was mostly supported by Congress, which approved cancelling Project Constellation in favor of a 2025 Asteroid Redirect Mission and orbiting Mars in the 2030s. The Asteroid Redirect Mission was cancelled in June 2017 and "closed out" in September of the same year.
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.
In late 2011, Russian and European space agencies successfully completed the ground-based MARS-500. The biomedical experiment simulating crewed flight to Mars was completed in Russia in July 2000.
In 2012, Jean-Marc Salotti published a new proposal for a crewed Mars mission. The '2-4-2' concept is based on a reduction of the crew size to 2 astronauts and the duplication of the entire mission. There are 2 astronauts in each space vehicle, there are 4 on the surface of Mars and there are 2 once again in each return vehicle. If one set of hardware runs into trouble, there are 2 astronauts ready to help the 2 others (2 for 2). This architecture simplifies the entry, descent and landing procedures by reducing the size of the landing vehicles. It also avoids the assembly of huge vehicles in LEO. The author claims that his proposal is much cheaper than the NASA reference mission without compromising the risks and can be undertaken before 2030.
In 2012, a conceptual architecture was published by Boeing, United Launch Alliance, and RAL Space in England, laying out a possible design for a crewed Mars mission. Components of the architecture include various spacecraft for the Earth-to-Mars journey, landing, and surface stay as well as return. Some features include several uncrewed cargo landers assembled into a base on the surface of Mars. The crew would land at this base in the "Mars Personnel Lander", which could also take them back into Mars orbit. The design for the crewed interplanetary spacecraft included artificial gravity and an artificial magnetic field for radiation protection. Overall, the architecture was modular to allow for incremental R&D.
In 2012, a Dutch entrepreneur group began raising funds for a human Mars base to be established in 2023. The mission was intended to be primarily a one-way trip to Mars. Astronaut applications were invited from the public all over the world, for a fee.
The initial concept included an orbiter and small robotic lander in 2018, followed by a rover in 2020, and the base components in 2024. The first crew of four astronauts were to land on Mars in 2025. Then, every two years, a new crew of four would arrive. Financing was intended to come from selling the broadcasting rights of the entire training and of the flight as a reality television show, and that money would be used to contract for all hardware and launch services. In April 2015, Mars One's CEO Bas Lansdorp admitted that their 12-year plan for landing humans on Mars by 2027 is "mostly fiction". The company went bankrupt in January 2019.
On December 2, 2014, NASA's Advanced Human Exploration Systems and Operations Mission Director Jason Crusan and Deputy Associate Administrator for Programs James Reuthner announced tentative support for the Boeing "Affordable Mars Mission Design"[clarification needed] including radiation shielding, centrifugal artificial gravity, in-transit consumable resupply, and a lander which can return. Reuthner suggested that if adequate funding was forthcoming, the proposed mission would be expected in the early 2030s.
This section needs to be updated.January 2018)(
On October 8, 2015, NASA published its strategy for human exploration and colonization of Mars. The concept operates through three distinct phases leading up to fully sustained colonization.
The first stage, already underway, is the "Earth Reliant" phase. This phase continues using the International Space Station until 2024; validating deep space technologies and studying the effects of long duration space missions on the human body.
The second stage, "Proving Ground," moves away from Earth reliance and ventures into cislunar space for most of its tasks. The proposed Lunar Orbital Platform-Gateway would test deep space habitation facilities, and validate capabilities required for human exploration of Mars.
Finally, phase three is the transition to independence from Earth resources. The "Earth Independent" phase includes long term missions on the lunar surface with surface habitats that only require routine maintenance, and the harvesting of Martian resources for fuel, water, and building materials. NASA is still aiming for human missions to Mars in the 2030s, though Earth independence could take decades longer.
In November 2015, Administrator Bolden of NASA reaffirmed the goal of sending humans to Mars. He laid out 2030 as the date of a crewed surface landing, and noted that planned 2020 Mars rover would support the human mission.
In March 2019, Vice President Mike Pence declared "American Astronauts will walk on the Moon again before the end of 2024, "by any means necessary"." This reportedly prompted NASA to accelerate their plans to return to the Moon's surface by 2024. NASA says it will use the Artemis lunar program in combination with the Lunar Gateway as stepping stones to make great scientific strides "to take the next giant leap - sending astronauts to Mars".
The ITS launch vehicle design was a large reusable booster topped by a spaceship or a tanker for in-orbit refueling. The aspirational objective is to advance the technology and infrastructure such that the first humans to Mars could potentially depart as early as 2024.
On 29 September 2017, Elon Musk announced an updated vehicle design for the Mars mission at the International Astronautical Congress. The replacement vehicle for this mission was called BFR (Big Falcon Rocket) until 2019, when it was renamed "Starship". Starship will provide the capability for on-orbit activity like satellite delivery, servicing the International Space Station, Moon missions, as well as Mars missions. There are two phases for the first human mission to Mars via Starship:
Mars Base Camp (MBC) is a US spacecraft concept that proposes to send astronauts to Mars orbit as early as 2028. The vehicle concept, developed by Lockheed Martin, would utilize both future and heritage technology as well as the Orion MPCV built by NASA.
The 'Deep Space Transport (DST), also called Mars Transit Vehicle, is a crewed interplanetary spacecraft concept by NASA to support science exploration missions to Mars of up to 1,000 days. It would be composed of two elements: an Orion capsule and a propelled habitation module. As of April 2018, the DST is still a concept to be studied, and NASA has not officially proposed the project in an annual U.S. federal government budget cycle.
A number of nations and organizations have long-term intentions to send humans to Mars.
Significant technological hurdles need to be overcome for human spaceflight to Mars.
Entry into the thin and shallow Martian atmosphere will pose significant difficulties with re-entry and for a spacecraft of the weight needed to carry humans, along with life support, supplies and other equipment. Should a heat shield be used, it would need to be very large. Retro rockets could be used, but would add significant further weight.
A return mission to Mars will need to land a rocket to carry crew off the surface. Launch requirements mean that this rocket would be significantly smaller than an Earth-to-orbit rocket. Mars-to-orbit launch can also be achieved in single stage. Despite this, landing an ascent rocket on Mars will be difficult. Reentry for a large rocket will be difficult.
In 2014 NASA proposed the Mars Ecopoiesis Test Bed.
One of the medical supplies that might be needed is a considerable mass of intravenous fluid, which is mainly water but contains other substances so it can be added directly to the human blood stream. If it could be created on the spot from existing water, this would reduce mass requirements. A prototype for this capability was tested on the International Space Station in 2010.
While it is possible for humans to breathe pure oxygen, usually additional gases like nitrogen are included in the breathing mix. One possibility is to take in-situ nitrogen and argon from the atmosphere of Mars; however, they are hard to separate from each other. As a result, a Mars habitat may use 40% argon, 40% nitrogen, and 20% oxygen.
An idea for keeping carbon dioxide out of the breathing air is to use re-usable amine bead carbon dioxide scrubbers. While one carbon dioxide scrubber filters the astronaut's air, the other is vented to the Mars atmosphere.
Some missions may be considered a "Mission to Mars" in their own right, or they may only be one step in a more in-depth program. An example of this is missions to Mars' moons, or flyby missions.
Many Mars mission concepts propose precursor missions to the moons of Mars, for example a sample return mission to the Mars moon Phobos - not quite Mars, but perhaps a convenient stepping stone to an eventual Martian surface mission. Lockheed Martin, as part of their "Stepping stones to Mars" project, called the "Red Rocks Project", proposed to explore Mars robotically from Deimos.
Use of fuel produced from water resources on Phobos or Deimos has also been proposed.
An uncrewed Mars sample return mission (MSR) has sometimes been considered as a precursor to crewed missions to Mars' surface. In 2008, the ESA called a sample return "essential" and said it could bridge the gap between robotic and human missions to Mars. An example of a Mars sample return mission is Sample Collection for Investigation of Mars (SCIM). Mars sample return was the highest priority Flagship Mission proposed for NASA by the Planetary Decadal Survey 2013-2022: The Future of Planetary Science. However, such missions have been hampered by complexity and expense, with one ESA proposal involving no less than five different uncrewed spacecraft.
Sample return plans raise the concern, however remote, that an infectious agent could be brought to Earth. Regardless, a basic set of guidelines for extraterrestrial sample return have been laid out depending on the source of sample (e.g. asteroid, Moon, Mars surface, etc.)
At the dawn of the 21st century, NASA crafted four potential pathways to Mars human missions. Of those four, three included a Mars sample return as a prerequisite to human landing; however one did not.
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