Section 2.5.1.
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Dealing with Radiation on the Long Trip to Mars

Mars For trips to the moon, radiation is a relatively minor concern

For a three-day trip from Earth to Luna, we only need to control total dosage received in transit each way and track the cumulative lifetime dosage received by our crew. Frequently flyers will also need to track their cumulative lifetime dosage, but the flight crew on the regular moon run will have the greatest exposure.

Mars presents a bigger radiation problem

Since Mars it takes half of a year to get to Mars at the very best, we'll need to worry about the continuous dosage for the crew. We can shorten the voyage by using nuclear rockets, and we can launch from a mass driver on the moon to get way ahead of the rocket equation, but no matter what, it's going to be a long trip.

To control radiation on a Mars ship, we can surround the inhabitants with a layer of rock dust (lunar regolith, obviously) six feet thick. That will reduce the radiation level down to what we experience on Earth's surface.

We can use payload to shield the crew

Of course, there are many variations on the theme. Hauling around a bunch of rock does not sound like the optimum solution. We'd probably use something useful for the shielding, such as water and all the external equipment that the spacecraft will need. We'll put the crew compartments in the center of the structure, with the heaviest neutron shielding toward the sun, so the radiation shielding has to be designed in from the start.

Some might be willing to make the sacrifice

Initial habitat on Mars We also might accept a higher radiation dosage for the crew, even to the point of knowing they will encounter serious medical problems in a few years. We'd probably find volunteers willing to suffer the consequences of such a trip. This approach doesn't appeal to me, but somebody might do it. The ultimate limit is to keep the radiation dosage down to a point where the crew will not suffer from acute radiation sickness during the flight.

This is a serious engineering challenge, but not insurmountable if enough money can be brought to bear on it and we're patient enough to only make the trip during the sun's quiet cycle.

In the future, permanent cruise ships solve the problem

In the long run, we will build massive, spinning space stations that cycle between the Earth and Mars. Those ships, really cities in space, will have the heavy radiation shields required. Passengers and crew will rendezvous with the space stations as they come near, using small rockets with big motors. We will build mass drivers on the moon to catch up with rockets at the Earth end of the trip.

Getting there is half the fun

That gets us there, but as on the moon, people on the surface of Mars will have to contend with the full force of cosmic radiation. Mars does not have Earth's magnetic field or ionosphere to deflect and absorb the stuff any more than the moon. Fortunately, on both the moon and Mars, people will be able to build structures from local material and move into caves. People will not live long on the surface.

So, aside from conditions unique to Mars -- bitter cold, higher gravity, and a thin, poisonous atmosphere balanced against the relatively greater abundance of essential elements -- life on Mars will be very similar to the visions for life of the moon that we present elsewhere on the Artemis Project web site.


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