A manned mission to Mars has been the subject of science fiction, engineering, and scientific proposals throughout the 20th century and into the 21st century. The plans comprise proposals not only to land on but in the end for settling on and terraforming Mars, while exploiting its moons Phobos and Deimos.

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

As with other interplanetary travel, the energy needed to transfer between planetary orbits hits a low point at intervals fixed by the synodic period. For Earth / Mars trips, this is every 26 Earth months (2 years and 2 months). So missions are typically planned to coincide with one of these launch windows. In addition, the energy needed in the low-energy windows varies on roughly a 15 year cycle. The easiest windows only need 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.

Several types of mission plans have been proposed, such as the opposition class and conjunction class, or the Crocco flyby. However, typical Mars mission plans have round-trip flight times of 400 to 450 days. A fast Mars mission of 245 days round trip could be possible with on-orbit staging. Using Hohmann transfer orbits is a common plan

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 (1962) and several subsequent works, and featured in Collier's magazine in a series of articles beginning March 1952. A variant of the Von Braun mission concept was popularized in English by Willy Ley in the book The Conquest of Space (1949), featuring illustrations by Chesley Bonestell. Von Braun's Mars project envisioned nearly a thousand three-stage vehicles launching from Earth to ferry parts for the Mars mission to be constructed at a space station in Earth orbit. 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.

n 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 the actual NASA spaceflight, and laid much of the basis for future studies, including significant mission studies by TRW, North American, Philco, Lockheed, Douglas, and General Dynamics, along with several in-house NASA studies.

Following the success of the Apollo Program, von Braun advocated a manned mission to Mars as a focus for NASA's manned 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 (then president) Richard Nixon but passed over in favor of the Space Shuttle.

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 manned flight to Mars was completed in Russia in July 2000

In 2012, a Dutch entrepreneur group revealed plans of a fund-raising campaign for a human Mars base to begin in 2023. One difference from other projects is that 'Mars One' is organized as a not-for-profit organization, strives to use worldwide suppliers, with no politics involved. It would be a "one-way" mission, i.e., there will be no return trip to Earth. Astronaut applications are invited from the public all over the world.

In 2018, a telecom orbiter would be sent, a rover in 2020, and after that the base components and its settlers. The base would be powered by 3,000 square meters of solar panels. The SpaceX Heavy rocket would launch flight hardware. The first crew of 4 astronauts would land on Mars in 2025. Then, every two years, a new crew of 4 astronauts would arrive. Current plans specify that the entire mission is to be filmed and broadcast back to Earth as a media event, revenues from which would help fund the program.

0