The realization of a manned space mission to Mars has been discussed well before the beginnings of astronautics, as early as 1940. Initially a science fiction theme, it becomes for some, following the landing of man on the Moon in 1969, the next step in space conquest. But the success of this project requires financial means far superior to those of the Apollo program, itself launched thanks to particularly favorable circumstances (Cold War, economic boom). A manned flight to Mars is also a technical and human challenge beyond compare with a lunar expedition: size of spacecraft, life support system operating in closed circuit over long durations (900 days), reliability of equipment, which cannot be repaired or whose redundancy cannot be systematically ensured, psychological problems of a crew confined in a restricted space in a particularly stressful context, physiological problems arising from the absence of gravity over prolonged periods and the effect of radiation on the organism.

Since the early 1960s, studies on the subject have been carried out and explore scenarios and technical solutions. Several points are particularly debated: opposition or conjunction trajectory, use of nuclear propulsion, crew size, use of aerocapture to brake the craft upon arrival on Mars, landing method on Mars, production of return trip fuel in situ, number and tonnage of spacecraft to launch. The most accomplished preliminary projects come from NASA, pioneer and best-funded civilian space agency, which refines a heavy solution (Mars Design Reference Architecture) requiring placing between 850 and 1,250 tons in low Earth orbit by about ten launches. Others are developed by groups of enthusiasts gathered in associations like the Mars Society, which advocate a less expensive solution, Mars Direct, or Mars Semi-Direct requiring only two, three or four launches depending on the versions. All these scenarios require that key technologies be developed and tested, including aerocapture, landing high masses on Martian soil and extracting resources from the Martian atmosphere or soil.

The project must mobilize enormous financial resources and presents significant risks, while the success of robotic missions on Mars demonstrates the validity of this approach to explore the planet. Thanks to these missions, humans have discovered that Mars does not offer a particularly welcoming environment. The in situ study of the planet's geology by astronauts and the frontier myth, very much alive in the United States, fail to convince decision-makers to take the plunge. NASA and SpaceX are developing craft, such as the heavy launcher SLS and the interplanetary spacecraft Orion, which could contribute to a Martian mission, but there is no coherent project even in the long term for a manned mission to Mars that has begun to be implemented within space agencies in 2019 and since the abandonment of the Constellation program.

Source : wikipedia.org

Going to Mars is good. But how to leave?

In the eyes of NASA engineers, Mars looks like a space carnivorous plant.

The planet enchants us with its promises of great scientific discoveries, but upon landing, gravity and the harsh local climate take care of trapping us there.

Going home is not an option. If there is one lesson to learn from the film "The Martian" about space exploration in the real world, it is that public opinion will oppose spending billions of dollars for astronauts to get stuck on another planet. Which undoubtedly makes the return trip the most important part of any NASA project on the red planet.

The ascent vehicle that NASA will have to build to fulfill this mission, the Mars Ascent Vehicle (MAV), represents a real engineering challenge. With a full tank of fuel, it is too heavy to take off from Earth and land safely on Mars.

The vehicle will instead have to be pre-assembled and then sent to the red planet several years before the arrival of the astronauts, and manufacture its own fuel by pumping it from the thin Martian atmosphere.

And then? The MAV must be strong enough to remain fully operational despite the assaults of gigantic dust storms and grueling UV radiation. After takeoff, the vehicle, in cramped configuration, will have to provide for the needs of the astronauts for several days, as they maneuver towards the orbiting spacecraft that will have the final role of bringing them back to Earth.

The MAV will be a mission within the mission: putting a manned spacecraft into orbit from another planet. All in one go.

Source : nationalgeographic.fr