How to send people from Earth to Mars and return safely?

Before the journey back to Mars begins, mankind must overcome many difficulties.

Before any journey back to Mars begins, human beings must overcome many difficulties.

The two main participants are NASA and Space Exploration Technologies. They worked closely together on the mission of the International Space Station, but they had different ideas about the appearance of a manned mission to mars.

Big and small things

The biggest challenge (or limitation) is the quality of the payload (spacecraft, personnel, fuel, supplies, etc.). ) travel is essential.

We still talk about launching something into space just like launching its weight.

The payload mass usually accounts for only a small part of the total mass of the launch vehicle.

For example, Saturn V rocket, which launched Apollo 1 1 to the moon, weighed 3000 tons.

But it can only launch 140 tons (5% of the initial launch mass) into low-earth orbit, and 50 tons (less than 2% of the initial launch mass) into the moon.

Mass limits the size of Mars spacecraft and its role in space. Every maneuver needs to consume fuel to launch rocket engines, and this fuel must be transported into space by spacecraft at present.

Space exploration technology company's plan is that its manned spacecraft will refuel vehicles in space through a separate tanker. This means that more fuel can be put into orbit instead of being launched at once.

Concept map of SpaceX dragon spacecraft landing on Mars. Official photos of Space Exploration Technology Company /Flickr, CC BY-NC

Time is of the essence.

Another challenge closely related to fuel is time.

The task of sending a spaceship without crew to another planet usually involves a complex trajectory around the sun. They use so-called gravity-assisted maneuvers to effectively orbit slingshots around different planets in order to gain enough power to achieve their goals.

This can save a lot of fuel, but it may lead to a task that takes years to reach the destination. Obviously, this is something that human beings are unwilling to do.

Both the Earth and Mars have (almost) circular orbits, and a maneuver called Homan Transfer is the most fuel-efficient way to travel between the two planets. Basically, it goes without saying that this is where the spacecraft burns once in the elliptical transfer orbit from one planet to another.

Homan transfer between the Earth and Mars takes about 259 days (8 to 9 months), which is only possible every two years because of the different orbits of the Earth and Mars around the sun.

The spacecraft can reach Mars in a shorter time (space exploration technology company claims it will take six months), but-you guessed it-it will consume more fuel.

Concept map of SpaceX dragon spacecraft landing on Mars. Official photos of Space Exploration Technology Company /Flickr, CC BY-NC

Time is of the essence.

Another challenge closely related to fuel is time.

The task of sending a spaceship without crew to another planet usually involves a complex trajectory around the sun. They use so-called gravity-assisted maneuvers to effectively orbit slingshots around different planets in order to gain enough power to achieve their goals.

This can save a lot of fuel, but it may lead to a task that takes years to reach the destination. Obviously, this is something that human beings are unwilling to do.

Both the Earth and Mars have (almost) circular orbits, and a maneuver called Homan Transfer is the most fuel-efficient way to travel between the two planets. Basically, it goes without saying that this is where the spacecraft burns once in the elliptical transfer orbit from one planet to another.

Homan transfer between the Earth and Mars takes about 259 days (8 to 9 months), which is only possible every two years because of the different orbits of the Earth and Mars around the sun.

The spacecraft can reach Mars in a shorter time (space exploration technology company claims it will take six months), but-you guessed it-it will consume more fuel.

safe landing

Suppose our spaceship and crew arrive at Mars. The next challenge is landing.

Spacecraft entering the earth can use the resistance generated by interaction with the atmosphere to slow down. This allows the plane to land safely on the surface of the earth (provided that it can withstand the related heating).

But the atmosphere on Mars is about 100 times thinner than that on Earth. This means there is less possibility of resistance, so it is impossible to land safely without some help.

Some missions rely on airbags to land (such as NASA's Pathfinder mission), while others use propellers (NASA's Phoenix mission). The latter needs more fuel.

Life on Mars

A day on Mars lasts 24 hours and 37 minutes, but the similarity with the Earth ends here.

The thin atmosphere on Mars means that it can't keep heat like the earth, so life on Mars is characterized by extreme temperatures in the day-night cycle.

The highest temperature on Mars is 30, which sounds comfortable, but the lowest temperature is-140, and the average temperature is -63. The average winter temperature at the South Pole of the Earth is about 49 degrees below zero.

Therefore, we need to be very careful about where we live on Mars and how we control the temperature at night.

The gravity on Mars is 38% of that on Earth (so you will feel lighter), but the air is mainly carbon dioxide (CO? ) and a few percent of nitrogen, so it can't breathe at all. We need to build a climate-controlled residence there.

Space Exploration Technologies plans to launch several cargo flights, including important infrastructure, such as greenhouses, solar panels and-you guessed it-returning to the mission earth fuel production facility.

Life on Mars will become possible, and some simulation experiments have been completed on Earth to observe how people respond to such existence.

return to earth

The final challenge is to return to the journey and let people return to the earth safely.

Apollo 1 1 entered the earth's atmosphere at a speed of about 40,000 km/h, which was slightly lower than the speed required to leave the earth's orbit.

The reentry speed of spacecraft returning from Mars will vary from 47,000 km/h to 54,000 km/h, depending on their orbits to the Earth.

Before entering our atmosphere, they can slow down to low orbit around the earth at a speed of about 28,800 km/h, but-you guessed it-they need extra fuel to do this.

If they just rush into the atmosphere, it will do all the deceleration for them. We just need to make sure that we don't kill astronauts by gravity or burn them by overheating.

These are just some of the challenges facing mission to mars, and all the technical foundations for achieving this goal are there. We just need to spend time and money to put them together.