A human mission to Mars has been the subject
of science fiction, aerospace engineering,
and scientific proposals since the 19th century.
The plans comprise proposals to land on Mars,
eventually settling on and terraforming the
planet, while utilizing its moons, Phobos
and Deimos.
The exploration of Mars has been a goal of
national space programs for decades. Preliminary
work for missions that would involve human
explorers has been undertaken since the 1950s,
with planned missions typically being stated
as taking place 10 to 30 years in the future
when 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 (2
to 8) group visits Mars for a period of a
few weeks or year, to the permanent colonization
of Mars.
In the 2010s, numerous American, European,
and Chinese agencies were developing proposals
for human missions to Mars. They are now developing
and testing the technologies.
Mars in fiction is a frequent target of exploration
and settlement in books, graphic novels, and
films.
== Travel to Mars ==
The energy needed for transfer between planetary
orbits, or "∆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, such as the opposition class and
conjunction class, or the Crocco flyby. The
lowest energy transfer to Mars is a Hohmann
transfer orbit; a mission to Mars using Hohmann
transfer involves 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 Hohmann transfer of
about 9 months to return to Earth.Shorter
Mars mission plans have round-trip flight
times of 400 to 450 days, but requiring a
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 for 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 extending a flyby mission with
a short stay lander. Basically, a short stay
lander-ascent vehicle would separate from
a "parent" Earth-Mars transfer 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 lifted off
the Earth by half. As a result, Mars missions
have designed interplanetary spacecraft and
landers capable of aero-braking.
== Landing on Mars ==
When an expedition reaches the orbit of Mars,
it may drop into orbit around Mars by either
of two main options: using rockets to slow
down, or aerocapture. The same is true for
missions to the surface. The state of the
atmosphere, the altitude, and the properties
of the landing site must come into consideration
for a surface landing. It may be necessary
to avoid a scientifically interesting site
in the interest of safe touchdown.
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 maximum G-limit to experience, for which
it was noted 5-g's (5 times Earth gravity)
was a common limit to be planned for.There
may be several landers, for example, separate
ones for the crew, a habitat, rover, supplies,
ascent vehicle, etc.
Landed spacecraft on the surface of Mars:
Viking 1 & 2
Mars Pathfinder (includes Sojourner)
MER A & B (Spirit & Opportunity)
Phoenix
Curiosity
== Challenges ==
One of the big challenges to landing on Mars
was overcome by Mariner 4, when it showed
the properties of the atmosphere. Another
was a basic survey of the planet, to know
what place might be suitable to land. This
has been overcome in stages, with major global
surveys done by Mariner 9 and Viking 1 and
2 orbiters, which supported the Viking landers
finding a suitable landing site. Later orbiters
such as Mars Global Surveyor, 2001 Mars Odyssey,
Mars Express, and Mars Reconnaissance Orbiter,
have helped identify the location of water,
a critical resource.
=== Logistical ===
The estimated cost of sending humans to Mars
is roughly 500 billion U.S. dollars, though
the actual costs are likely to be more. The
largest limiting factor for sending humans
to Mars is funding. In the late 1950s, rivalry
between the Soviet Union and the United States
stimulated a national priority to send humans
to the Moon. Under the current global geopolitical
climate, however, government funding of these
programs has decreased. Recent participation
of private companies in space travel and participation
by new nations such as India may present new
opportunities.
Critics argue the immediate benefits of establishing
a human presence on Mars are more esoteric
than practical. Yet proponents of human space
exploration contend that while the short term
benefits will be academic, the symbolism of
establishing a presence in space may garner
public interest to join the cause and spark
global cooperation. Furthermore, experts maintain
that a long-term investment will be necessary
for humanity’s survival.
=== Medical ===
There are several key physical challenges
for human missions to Mars:
Health threat from cosmic rays and other ionizing
radiation. In May 2013, NASA scientists reported
that a possible mission to Mars may involve
great radiation risk based on energetic particle
radiation measured by the RAD on the Mars
Science Laboratory while traveling from the
Earth to Mars in 2011–2012. The calculated
radiation dose was 0.66 sieverts round-trip.
The agency's career radiation limit for astronauts
is 1 sievert. In September 2017, NASA reported
radiation levels on the surface of the planet
Mars were temporarily doubled, and were associated
with an aurora 25-times brighter than any
observed earlier, due to a massive, and unexpected,
solar storm in the middle of the month.
Negative effects of a prolonged weightlessness
environment on human health, including eyesight
visual impairment. (Depends on mission and
spacecraft design).
Psychological effects of isolation from Earth
and, by extension, the lack of community due
to impossibility of real-time connections
with Earth. (Compare Hermit).
Social effects of several humans living under
cramped conditions for more than one Earth
year, possibly two or three years, on the
mission to Mars, and a comparable length of
time on the return to Earth. (Depends on spacecraft
and mission design).
Inaccessibility of terrestrial medical facilities.
Potential failure of propulsion or life-support
equipment.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.
=== Planetary protection ===
Robotic spacecraft to Mars are required to
be sterilized, to have at most 300,000 spores
on the exterior of the craft—and more thoroughly
sterilized if they contact "special regions"
containing water, as 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 microorganisms of thousands
of species of the human microbiota, and these
cannot be removed while preserving the life
of the human. 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.
== Mission proposals ==
=== 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.
==== Wernher von Braun proposal (1947 through
1950s) ====
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.
==== U.S. proposals (1950s, 1960s, and 1970s)
====
From 1957, work was done by General Atomic
on Project Orion, a proposal for nuclear pulse
propulsion spacecraft. If successful, Orion
would have been able to transport extremely
large payloads compared to chemical rocketry,
making crewed missions to Mars and the outer
planets feasible; for example, one of the
early vehicle designs was intended to send
an 800-ton payload to Mars orbit. The Limited
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
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 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.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 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
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.
==== Soviet mission proposals (1956 through
1969) ====
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 ratio was
low and their space program struggled through
disasters like the lost Salyut 1 crew and
explosions of their N1 rocket (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.
==== 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. 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.
==== NASA Space Exploration Initiative (1989)
====
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, 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.
==== Mars Direct (early 1990s) ====
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.
==== International Space University (1991)
====
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.
==== NASA Design reference missions (1990s)
====
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):
1988 "Mars Expedition"
1989 "Mars Evolution"
1990 "90-Day Study"
1991 "Synthesis Group"
1995 "DRM 1"
1997 "DRM 3"
1998 "DRM 4"
1999 "Dual Landers"
=== 21st century ===
==== NASA Design reference missions (2000+)
====
The NASA Mars Design Reference Missions consisted
of a series of conceptual design studies for
human Mars missions, continued in the 21st
century
Selected other US/NASA plans (1988–2009):
==== MARPOST (2000–2005) ====
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 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 was confirmed as
of 2005. Design for the ship was proposed
to be ready in 2012, and the ship itself in
2021.
==== ESA Aurora programme (2001+) ====
The European Space Agency had a long-term
vision of sending a human mission to Mars
in 2033. 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 crewed mission;
however, objections from the participating
nations of ESA and other delays have put the
timeline into question. Nevertheless, a spawn
of this programme, ExoMars, delivered an orbiter
to Mars in 2016
==== 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.
==== USA Vision for Space Exploration (2004)
====
Project Constellation included an Orion Mars
Mission.
(Then United States President) George W. Bush
announced an initiative of crewed space exploration
on January 14, 2004, known as the Vision for
Space Exploration. It included developing
preliminary plans for a lunar outpost by 2012
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.
On September 24, 2007, Michael Griffin, then
NASA Administrator, hinted that NASA may 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.
==== Mars Society Germany – European Mars
Mission (EMM) (2005) ====
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.
==== China National Space Administration (CNSA)
(2006) ====
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 One-Way Trip Option (2006); Mars
to Stay (2006) ====
The idea of a one-way trip to Mars has been
proposed several times. Space activist Bruce
Mackenzie, for example, proposed a one-way
trip to Mars in a presentation "One Way to
Mars – a Permanent Settlement on the First
Mission" at the 1998 International Space Development
Conference, arguing that since the mission
could be done with less difficulty and expense
without a return to Earth, the first mission
to Mars should be a settlement, not a visit.
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.Former Apollo
astronaut Buzz Aldrin is a particularly outspoken
promoter who has suggested in numerous forums
"Forget the Moon, Let's Head to Mars!" In
June 2013, Aldrin wrote an opinion, published
in The New York Times, supporting a crewed
mission to Mars and which viewed the Moon
"not as a destination but more a point of
departure . . . " In August 2015, Aldrin,
in association with the Florida Institute
of Technology, presented a "master plan" for
NASA consideration proposing astronauts with
a "tour of duty of ten years" colonize Mars
before the year 2040.
==== 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) ====
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.
==== NASA Austere Human Missions to Mars (2009)
====
Extrapolated from the DRMA 5.0, plans for
a crewed Mars expedition with chemical propulsion.
Austere Human Missions to Mars
==== USA's Mars orbit by the mid-2030s (2010)
====
In a major space policy speech at Kennedy
Space Center on April 15, 2010, then-U.S.
President Barack Obama predicted a crewed
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 mostly approved
a new direction for NASA that includes canceling
Bush's planned return to the Moon by 2020
and instead proposes asteroid exploration
in 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.
==== Martian Frontier (2007–2011) ====
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.
==== Russian mission proposals (2011) ====
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.
==== 2-4-2 concept (2011–2012) ====
In 2011, Jean-Marc Salotti published a new
proposal for a crewed Mars mission, with a
release in 2012. The 2-4-2 concept is based
on a reduction of the crew size to only 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. In addition, at every step of the
mission, there are 2 astronauts ready to help
the 2 others (2 for 2). This architecture
simplifies the entry, descent and landing
procedures, which are known to be very risky,
thanks to a significant reduction of 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.
==== Boeing Conceptual Space Vehicle Architecture
(2012) ====
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 and to allow for incremental R&D.
==== Mars One (2012) ====
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,
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.
==== Inspiration Mars Foundation (2013) ====
In 2013, the Inspiration Mars Foundation founded
by Dennis Tito revealed plans of a crewed
mission to fly by Mars in 2018 with support
from NASA. NASA refused to fund the mission.
==== Boeing Affordable Mission (2014) ====
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" 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.
==== NASA's Journey to Mars: Pioneering Next
Steps in Space Exploration (2015) ====
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.
Also discussed was the use of robotics to
prepare an underground habitat for the arriving
people. He noted the advantages of living
underground on Mars, especially that it eliminates
the need to construct above ground shielding.
The underground base would be prepared in
advance by an armada of robots. Top surface
activity was not excluded however, just that
the crew would "probably live underground
for the most part".
==== SpaceX Mars transportation infrastructure
(2016-) ====
Since 2016, SpaceX publicly announced a comprehensive
vision to begin the colonization of Mars,
by proposing to develop a high-capacity transportation
infrastructure.
===== ITS launch vehicle =====
In September 2016 at the International Astronautical
Congress, Elon Musk announced the ITS launch
vehicle design (informally discussed earlier
as the Mars Colonial Transporter), that comprised
a large reusable booster topped by a spaceship
or a tanker for in-orbit refueling, as well
as a propellant plant to be built on Mars,
at a base referred to as Mars Base Alpha.
The aspirational objective is to advance the
technology and infrastructure such that the
first humans to Mars could potentially depart
as early as 2024.
===== BFR (Big Falcon Rocket) =====
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 is
called BFR (Big Falcon Rocket). BFR will provide
the on-orbit activity like satellite delivery,
servicing the International Space Station,
Moon mission, as well as Mars mission. There
are two phases for the human mission to Mars
via BFR:
In 2022, at least 2 BFR cargo vehicles will
land on Mars.
They will confirm water resources and identify
hazards.
They will place power, mining and life support
infrastructure for future missions.
In 2024, 2 BFR crew vehicles will take the
first people to Mars.
2 BFR cargo vehicles will bring more equipment
and supplies.
They will place a propellant production plant.
They will build up a base to prepare for expansion.The
BFR is currently under construction, with
sub-orbital flight testing expected in 2019.
==== Mars Base Camp (2016) ====
Mars Base Camp (MBC), an American 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.
==== Deep Space Transport (2017) ====
The Deep Space Transport (DST) is a spacecraft
meant to be launched on top of NASA's SLS
launch vehicle in 2027. It was announced by
NASA in March 2017. It is to dock with the
Deep Space Gateway (DSG) station, which would
be in cis-lunar space after its construction,
in 2027. Current plans show it to be sent
with a crew of 4 to Mars in 2033. It would
not, however, land, but merely remain in Martian
orbit until there is a launch window for a
return. The mission is expected to take about
2 years if all missions in the DSG and DST
from 2021–2030 are successful. This mission
would use the SLS rocket for launches, and
the Orion MPCV to transport the crew to and
from the Earth and the DSG and DST.
== Current intentions by nations and space
agencies ==
A number of nations and organizations have
long-term intentions to send humans to Mars.
The United States has several robotic missions
currently exploring Mars, with a sample-return
planned for the future. The Orion Multi-Purpose
Crew Vehicle (MPCV) is intended to serve as
the launch/splashdown crew delivery vehicle,
with a Deep Space Habitat module providing
additional living-space for the 16-month-long
journey. The first crewed Mars Mission, which
will include sending astronauts to Mars, orbiting
Mars, and a return to Earth, is scheduled
for the 2030s. Technology development for
US government missions to Mars is underway,
but there is no well-funded approach to bring
the conceptual project to completion with
human landings on Mars by the mid-2030s, the
stated objective. NASA is under presidential
orders to land humans on Mars by 2033, and
NASA-funded engineers are studying a way to
build potential human habitats there by producing
bricks from pressurized Martian soil.
The European Space Agency has a long-term
goal to send humans but has not yet built
a crewed spacecraft. It has sent robotic probes
like ExoMars in 2016 and plans to send the
next probe in 2020.
India successfully placed an uncrewed Mars
Orbiter Mission (also called Mangalyaan) satellite
in Mars orbit in 2014. ISRO plans a larger
follow-up mission called Mangalyaan 2 between
2018 and 2020. This mission will likely consist
of a lander and a Mars rover. No plans for
an Indian human mission to Mars have been
made public.
Japan has sent one robotic mission to Mars
in 1998, the Nozomi, but it failed to achieve
Mars orbit. JAXA has proposed a rover mission
called MELOS for an engineering demonstration
of precision landing, and to look for possible
biosignatures on Mars in 2020 or 2022. No
plans for a Japanese human mission to Mars
have been made public.
China's first attempted mission to Mars, the
Yinghuo-1 space probe, was lost with Russia's
sample return mission to Phobos, Fobos-Grunt
in 2011–2012. China plans to develop and
launch an orbiter, lander and rover to Mars
in July or August 2020 with a Long March 5
heavy lift rocket. A crewed phase is planned
for the 2040–2060 timeframe.
Russia plans to send humans in the 2040–2045
timeframe.
== Current intentions by private companies
==
United States-based launch company SpaceX
intends to establish a Mars base in the 2020s,
using the BFR fully reusable launch system.
Two robotic cargo flights are planned to be
launched in 2022 to deliver a massive array
of solar panels, mining equipment, as well
as deliver surface vehicles, food and life
support infrastructure. In 2024 four more
BFR landers will follow: two robotic cargo
flights, and two crewed flights will be launched
to setup the propellant production plant,
deploy the solar park, landing pads, and assemble
greenhouses. Each landed mass will be at least
100 tons of usable payload, in addition to
the spaceship's dry mass of 85 tons.The BFR
is currently under construction, and is planned
to start sub-orbital flight testing in 2019.
== Technological innovations and hurdles ==
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.
Intravenous fluidOne of the medical supplies
that may be needed is intravenous fluid, which
is mostly water but contains other things
so it can be added directly to the human blood
stream. If it can be created on the spot from
existing water then it could spare the weight
of hauling earth-produced units, whose weight
is mostly water. A prototype for this capability
was tested on the International Space Station
in 2010.
Breathing gasesWhile 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.
== Precursor missions ==
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.
=== Crewed flyby ===
An example of this is Inspiration Mars, which
could be compared to the Manned Venus Flyby
(NASA) mission proposal of the 1970s, but
for Mars.
=== Missions to Deimos or Phobos ===
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.
=== Mars sample return missions ===
An uncrewed Mars sample return mission (MSR)
has sometimes been considered to be an essential
precursor to crewed missions to Mars' surface
by the 21st century. 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.
=== Crewed orbital missions ===
Landis and Lupisella proposed to explore Mars
via telepresence from human astronauts in
orbit.A similar idea was the proposed "Human
Exploration using Real-time Robotic Operations"
(HERRO) mission.Another proposed mission was
the Russian Mars Piloted Orbital Station.
== See also ==
== References ==
== Further reading ==
Collins, Michael (November 1988). "Mission
to Mars". National Geographic. Vol. 174 no.
5. pp. 732–764. ISSN 0027-9358. OCLC 643483454.
== 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 & Flybys & Selected Flybys
List of most crewed mission projects to Mars
a longer bibliography can be found in the
bibliography of Portree's book, available
in pdf format from NASA.
