Gerard O’Neill devoted a whole chapter in his The High Frontier, the space settler’s bible, to the dangers of space colonization. O’Neill addresses several dangers related to space colonization, but we will focus on what is probably the greatest danger of living in space: radiation. The facts are plain and simple: there’s a lot of radiation in space, and it’s bad for human health. more precise it’s lethal. Hence the question arise, can we protect ourselves against this space radiation? And how can we do this?
Without adequate protection against space radiation, space colonization will not be possible. Not only will radiation significantly reduce people’s lifespan, but it will also increase the number of mutations in the human genome. This might result in an increase of children born with genetic diseases.
Fortunately, we can protect people and space settlements from radiation. Late British engineer Paul Birch has proposed several methods to deal with this problem. These methods are: passive shielding, electro static and magnetic shielding. Either of these methods can be used alone, but combinations are possible.
The simplest method of protecting space settlements from space radiation is passive shielding. The idea behind this method is that radiation permeate badly through thick layers of matter. The thicker the layer, the less radiation will permeate through it. This method has, however, a major disadvantage: the shield needs to be very heavy. Birch has calculated that 42 tonne per person will be needed. Though this might not be a serious concern for a space settlement, which has a relatively slow speed, but for fast-moving space ships this will be a big issue.
The kinetic energy of an object depends on both its velocity and its mass. Basically kinetic energy is the energy needed to give an object with mass m a velocity v. Therefore the greater the mass of a space ship is, the more energy it will take to give it a certain velocity. Passive shielding is a solution for space settlements, but not for space ships.
A space based civilization cannot without inter-settlement shipments. And therefore Birch has proposed two other methods, the electrostatic and the magnetic shielding. Though the former method does lower the required mass needed for shielding, it’s still quiet high for a space ship and hence more suitable for larger structures such as settlements.
The magnetic shielding method only require 3.1 tonne per person. This method works exactly in the same way as the Earth’s magnetic field protects terrestrial life from space radiations, by deflecting it. An “artificial” magnetic field can be created by letting an electric current flow though a wire.
The main advantage of passive shielding to active shielding, is that it never fails. Further the shield can be incorporated into the structure of the settlement. On the other hand magnetic shielding is the only suitable solution for space ships. A combination of these three methods of shielding can be appropriate in specific situations.
Birch, Paul. Radiation Shields for Ships and Settlements. Journal of the British Interplanetary Society, Vol. 35, pp. 515-519, 1982.