How long does the mission to Mars take

How does the return flight from Mars succeed?

When NASA engineers look at Mars, they see a planet-sized Venus flytrap.

It attracts with the promise of new scientific discoveries - but as soon as we land on it, gravity and adverse climate work together so ominously that it is almost impossible for us to leave the surface of the planet.

And this very prospect is not acceptable. The basic lesson that can be drawn from the novel "The Martian" for space exploration is the realization that the public will not be willing to invest billions of dollars if astronauts end up stranded on a strange celestial body. The most important part of all NASA planning for expeditions to the Red Planet should therefore be the arrangements for the return.

The space shuttle for take-off from Mars, which NASA would have to build for this task - referred to in the novel as the "Mars Ascent Vehicle" or "MAV" for short - represents a considerable technical challenge. Fully fueled, the MAV would be too heavy, to take off from Earth and land safely on Mars.

It would have to be pre-assembled and sent to the Red Planet years before the astronauts arrive. There it would have to get its own fuel from the thin Martian atmosphere.

And then? The MAV would have to be built robustly enough to remain fully functional despite strong sandstorms and merciless UV radiation. If the launch of the MAV is finally successful, the transported astronauts will have to survive for days in its cramped interior until the MAV reaches the spaceship, which is in orbit around Mars waiting to bring the astronauts back to Earth.

The Mars Ascent Vehicle would be a mission within a mission: it would be about nothing less than launching a manned spacecraft from the surface of an alien planet.

And the team would only have one attempt.

TRANSPORT THE PAYLOAD

A mission to Mars would be the first human journey into distant space. A total of up to five spacecraft could be necessary to transport the astronauts and the required cargo to the Red Planet.

Parts of the cargo could be split into smaller units and assembled by the astronauts at the target. However, the MAV is excluded from this. "Nobody wants to stand on Mars and screw machines together, in a space suit and with mittens in the middle of a windy sandy desert," says Michelle Rucker, systems engineer at NASA's Johnson Space Center, summarizing the problems.

In NASA language, the MAV is therefore the “largest indivisible payload element” of the mission. It has an estimated weight of 18 tons. The heaviest object that we have placed on the surface of Mars so far is the Mars rover “Curiosity”. It weighs just under a ton.

Landing an object on Mars - especially one that weighs several tons - is more difficult than landing on Earth, where a capsule ultimately falls from the sky and is slowed down by the atmosphere.

On Mars, where the atmosphere is only a hundredth the density of the earth's atmosphere, “the atmosphere is just enough to cause us problems, but not to be of any use to us,” says Rucker. In other words: the spacecraft gets red hot, but it is not braked.

So NASA is developing devices like the Hypersonic Inflatable Aerodynamic Decelerator - a giant, cone-shaped inflatable heat shield that would also act as a braking system.

The shield would be activated when entering the Martian atmosphere and decelerate the lander from hypersonic to supersonic speed. Rocket engines would then be turned on to initiate a controlled landing.

Astronaut Mark Watney would make the following calculation to determine the requirements for the success of the mission: The landing consumes around five to seven tons of fuel. For the later launch from the surface of Mars, the MAV will need 33 tons of fuel to overcome the gravitational pull of the red planet, to penetrate its atmosphere, to bring the astronauts safely into orbit with their scientific cargo and from there to the Earth Return Vehicle (ERV ) to dock.

And that's just too much. It will be necessary to produce the fuel on Mars itself.

USE AVAILABLE RESOURCES

If expeditions to the Red Planet are to have a chance of success, they must use the resources available there.

By producing fuel on Mars, NASA can reduce the payload required at launch by many tons. And after the completion of the first mission, the equipment could be left behind on Mars to serve as the starting point for a growing infrastructure of facilities that can process not only fuel, but also water and breathable air for future generations of researchers.

The engines of the MAV are powered by methane and liquid oxygen. All of the raw materials needed to make these fuels - carbon, hydrogen and oxygen - are available on the Red Planet if you look in the right places.

Theoretically, oxygen can be extracted from the Martian atmosphere, which consists of 95 percent carbon dioxide (CO2), as well as liquid and ice-shaped water (H2O) that is stored below the surface. The released elements carbon and hydrogen could react with each other to form methane.