Will we land humans on Mars within a generation?
It sounds like science fiction, but the idea of a manned mission to Mars is genuinely plausible. The question is: do we have the patience, the political will and – more importantly – the money to make it happen?
Let’s assume the mission will involve a six-month flight to Mars, two months on the planet and a six-month flight back.
“We have sent more missions to Mars than anywhere else in space. Only about half of these have been successful.”
Other than the moon, we have sent more missions to Mars than anywhere else in space. However, only about half of these have been successful. We have learned a lot from our successes and failures, but sending anything into space remains difficult. Sending humans into space is harder still. Like any other project, planning and preparation would be key to success.
Getting unmanned spacecraft, supplies and equipment to Mars is already technically feasible. However, landing large loads on Mars is tricky. Using current technology, 900kg – the mass of the Curiosity rover – is about the limit. Curiosity landed via a sky-crane and a 15m parachute, but this technology can’t be scaled up any further.
Human missions will need between 5,000kg and 30,000kg payloads. NASA recently tested the Low-Density Supersonic Decelerator (LDSD) system – a saucer-shaped “supersonic inflatable aerodynamic decelerator” with a 30m-wide chute – for landing such large items on Mars. The parachute deployed, but it was ripped to shreds. The data is now being analysed to discover what went wrong, but it will take time.
“The weather on Mars is grim – astronauts would face an average temperature of -55C, surface winds of up to 80mph and dust storms and whirlwinds.”
The weather on Mars is grim – astronauts would face an average temperature of -55C, surface winds of up to 80mph and dust storms and whirlwinds (also called “dust devils”). The pressure is only 1% of that on Earth, and the atmosphere contains over 95% carbon dioxide. Also, Mars has no magnetosphere, so radiation hits the surface. Therefore, humans would need to stay in enclosed habitats that offer similar protection to a spacecraft, and would need airlocks and spacesuits to venture onto the planet’s surface.
On the International Space Station (ISS), the oxygen and nitrogen levels, as well as the pressure, are the same as at sea level on Earth – about 21% oxygen and 78% nitrogen at 1.01 bar. The oxygen is supplied mainly by electrolysis of water into hydrogen and oxygen; this is not recyclable and so isn’t sustainable. Additional oxygen, nitrogen and pressurisation services are available on the ISS from refillable tanks, but, again, these are not sustainable solutions. So, before humans could arrive – and stay – on Mars, they would need a steady supply of oxygen, water and nitrogen.
Nitrogen can be extracted from the Martian atmosphere, and there is some water on Mars; the ice caps contain mainly frozen carbon dioxide, but also a little water, and there is water frozen in the ground. However, the technology for extracting this water has not been tested in the reduced gravity of Mars.
The carbon dioxide already on Mars could be split to make oxygen. To do this, power would be required. Solar panels would work on Mars, but since the planet is 1.5 times further away from the sun than Earth is, it will either take longer – unless we provide more units – or require larger panels.
“Solar panels would work on Mars, but since the planet is 1.5 times further away from the sun than Earth is, it will either take longer.”
The Russian cosmonaut Valeri Polyakov stayed in space for 438 consecutive days, and astronauts have been aboard the ISS continuously for nearly 15 years. These accomplishments have lead to many improvements and developments in environmental control and life-support systems. However, many of these systems depend on regular re-supply missions being sent from Earth. Some of the systems designed for the ISS rely on the microgravity experienced in space and would have to be adapted for Mars gravity.
As well as carbon dioxide, which can be removed with a molecular sieve, we also produce small amounts of other gases, including methane, ammonia, acetone, methyl alcohol and carbon monoxide. To prevent these gases from accumulating in the spacecraft and the Mars habitat, activated charcoal filters – similar to the chemicals used in home water filters – would probably be used. This charcoal would need to be replaced regularly. It would be possible to take enough filters for a return mission, but this is the sort of problem that would need to be addressed before a settlement were established on the red planet.
The Earth’s atmosphere and magnetosphere protects humans from radiation, solar flares, gamma rays and X-rays, ultraviolet radiation and cosmic rays. Any successful mission to Mars would require precautions to protect astronauts from these. The best material to block high-energy radiation is hydrogen, but a shield constructed from pure hydrogen is impractical with current technology. Materials with a high hydrogen content, like polyethylene – the material from which supermarket bags are made – could be used, but a system is not yet fully developed. Water is also good and, since water recycling is not 100% efficient, an extra supply would be required. This could be used as radiation protection for most of the journey.
Researchers are working on protective substances that may be taken prior to radiation exposure to limit the damaging effects. Vitamins C and A reduce the damage caused by radiation, and work is being conducted into ways to help the body after damage has occurred. For example, damaged cells could be instructed to destroy themselves.
“The best material to block high-energy radiation is hydrogen, but a shield constructed from pure hydrogen is impractical with current technology.”
There is also the problem of meteoroids to contend with. Meteoroids travel at average speeds of about 20 km/s. Because of their high speed, even small ones can cause serious damage to a spacecraft – a small hole in a critical wall could have life-threatening consequences. Whipple shields protect against anything less than about 1cm in diameter, while items larger than about 10cm can be tracked by radar and avoided. However, items between 1cm and 10cm in diameter are dangerous, since they can pierce a spacecraft hull but are difficult to track. An effective method of protecting from meteoroids of this size is yet to be developed.
Reaction Engines Ltd have completed preliminary studies that determined it is possible to split Mars’ atmosphere of carbon dioxide into carbon monoxide and oxygen for use as a rocket fuel (this also requires water). Together with Airborne Engineering Ltd, they conducted static tests on a rocket engine using carbon monoxide as the fuel and oxygen as the oxidiser. The result was a not-very-high-performance rocket. However, since gravity is lower on Mars than on Earth, the tests showed that these fuels would enable a single stage to Mars orbit to be achieved. This means the fuel for the return mission could be generated on Mars and would not have to be carried all the way from Earth.
The technological challenges involved in getting humans to Mars could be overcome in the next 20 years. However, jumping the hurdles of political will and financing required to design and test possible solutions would be much harder.
Dr Lucy Rogers is a fellow of the Royal Astronomical Society and the Institution of Mechanical Engineers and a freelance writer and journalist
Images: European Space Agency, NGSF, Christian Reimer and NASA, used under Creative Commons.
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