Humans 2 Mars
Edited by Andy Ross
Earlier this month at the
Humans 2 Mars
Summit at George Washington University, scientists, NASA officials, private
space company representatives, and others gathered to discuss all the
challenges of a human mission to Mars:
1
Getting off the Earth
A manned Mars mission would be
big. The International Space Station (ISS) has a mass of 4500 tons and
required 31 launches to lift its parts into low Earth orbit (LEO). NASA says
a spaceship capable of taking people to Mars and back might weigh some 1250
tons. Using existing rockets, it would take 70 or 80 launches to lift it to
orbit. Then the ISS took more than a decade to complete. NASA hopes to fly
its Space Launch System (SLS) by 2017. It will take at least 7 big SLS rockets
to put the stuff for a Mars mission into LEO.
2 Fuel storage
Around 80% of the launch mass for a human Mars mission will be
propellant. Objects in LEO circle the world every 90 minutes, half the time
in hot sunlight and half in cold space. The cycling vaporizes liquid
hydrogen and oxygen (rocket fuel), and unless the tanks are vented they may
explode. Hydrogen leaks out of its tanks at a rate of about 4% per month. A
Mars mission that took a year to assemble in LEO would lose more than half
of its fuel before it set off. NASA is working on it.
3 Advanced propulsion
While you want to get people to Mars as fast as possible to minimize
exposure to radiation and weightlessness, their supplies can set off earlier
and go slower. NASA is currently working on solar electric propulsion, but a
Mars mission would need much larger solar electric thrusters than any made
before. Performing a mission to collect a small asteroid and tug it back to
Earth would help move this technology forward.
4 Landing on
Mars
At present we can't land people on Mars. The thin Martian atmosphere is too thin to inflate large
parachutes but too thick for a lander to use downward-facing rockets without
being rocked by turbulence. The Curiosity rover has a mass of 1 ton. Human
missions will require landing at least 40 tons. Landing things that big
will require new technologies that have to be matured and tested. Curiosity
also had a landing ellipse many kilometers across. The next generation of
landers will need accuracy a hundred times better and a way to avoid landing
on top of some other piece of gear on the surface.
NASA is working on hypersonic inflatable
systems. These would inflate and stiffen to form a rigid parachute. But the
key technology for the job is supersonic retropropulsion. Even after slowing
down with a parachute or inflatable, a spacecraft entering the Martian
atmosphere would be supersonic. Sparking a rocket flame would be hard. A
thruster would be injecting its flame into a dynamic environment.
NASA is working on it.
5 Keeping
the crew healthy
Space is a dangerous place for humans.
Solar radiation would raise their risk of cancer and solar flares could
throw lethal doses of radiation at them. A trip out to Mars may take around
8 months. Currently, the best protection is to line a spacecraft with water.
A force field could protect a crew, but this is years or decades away. Also,
microgravity causes a host of odd medical conditions and isolation brings on
a range of psychological issues. A round trip to Mars may take 30 months.
The psychological issues are largely unknown. Crew members on a Mars trip
would have no way to abort their mission and would suffer an increasing time
lag when phoning home.
Once on Mars, the crew would face freezing temperatures and an arid
environment. They would have to live off the land, in what NASA calls
in-situ resource utilization (ISRU). Machines sent ahead of them would
extract oxygen from the atmosphere, mine the soil to make building materials
or rocket fuel, and turn Martian ice to water. But ISRU technologies don't
yet exist. Forget farming on Mars. Experts reckon a human colony would have
to live 15 to 20 years on Mars before it would be worth putting in an
agricultural system.
6 Protecting
ourselves and the planet
Earth life is precious, so the
spacefaring nations have agreed to strict planetary protection standards.
Mars may have once been capable of supporting life, and something there may
still be alive and potentially virulent. We also want to avoid contaminating Mars. Future technologies will have to improve our
ability to seal ourselves from the dangers of Mars and Mars from the dangers
of us. Perhaps the best course would be to put a few missions without
humans on the surface of Mars. People could park in orbit or set up camp on
a Martian moon and teleoperate robots on the surface. They could pick over
the surface for evidence of life and prepare it for people.
7
Dealing with dust
The arid Martian environment has created
tiny dust grains blowing around in the winds. The problem is similar to that
of the gritty moon dust Apollo astronauts encountered. It
could clog up machines and damage their operation. A human crew on Mars will
need dustproof tools. Even Martian soil is thought to be toxic. It contains
perchlorates, which are highly chlorinated salts that can cause problems in
the human thyroid gland. The dust on Mars may also contain carcinogenic
material and produce allergic reactions or pulmonary problems in humans.
Mission planners will need to know how Mars dust hazards human health.
8
Making the plan
The social and political aspects of
a manned Mars mission are likely to be toughest. Many different plans are
floating around, but only one will be chosen as the plan. A human mission is
likely to cost hundreds of billions of dollars and be led by an
international partnership. Building the ISS required
about five years to hammer out a deal, and now the station looks a mess.
Going to Mars is much harder than going
to the Moon.
AR This is quite a laundry list. I say send robots to do all the hard work there first.
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