At the writing of this article, the risks appear to be acceptable. However with slight modifications to the procedures, significant improvements to the current radiation shielding can be achieved and made compliant with the principal of ALARA (As low as reasonably achievable.) This principal takes into consideration that some risks are necessary for space exploration.
There are 2 types radiation studied. Solar (from our sun) and GCRS (Galactic cosmic rays from outside of our Solar System. Solar radiation is composed mainly of Protons, Neutrons, Electrons and Photons. These particles are traveling at low speed and can be blocked by the space craft itself. Other stars outside of our Solar System do produce these particles. Only a small fraction of them are aimed at the Earth and they have a low enough energy to be considered negligible in this discussion. The second type of radiation to be concerned about are GCRS. These particles have high mass and are traveling near the speed of light. These particles are hard to stop without heavy shielding in the form of bulk shielding or active machinery generating a force field which is also too heavy. GCRS can travel through a space craft and harm the occupants.
Shielding from GCRS creates secondary and tertiary radiation which has to be considered also. Secondary radiation is waves or particles resulting from the deceleration of the initial particle. This type or radiation can also be hazardous to astronauts. This second type of radiation is called “Bremsstralung Radiation” or braking radiation. This also has to be stopped by a GCR shield. Since heavy shielding and force field machinery can not be used due to weight which would require more fuel, other improvements should be considered. Much research has been done using complicated Differential Equations and Monte Carlo simulations, to sort through the many variables in radiation shielding.
I will outline in this article to additions to the deep space mission which will add little if not negligible weight to the space craft. The first will be a medical suggestion and the second will be an engineering change. Radiation can cause cell damage and cancer can develop. Inflammation can start when cells are damaged. Over time chronic inflammation can cause cell damage and leed to cancer. I recommend between Mars and Earth taking an anti-inflammatory medication. A medication like Aspirin should be considered. The dosage and type of medication would have to be approved by the medical staff.
A second part of the medical suggestion is to take something to neutralize the free radicals produced in cells by radiation. The free radicals can be neutralized by certain anti-oxidants such as Vitamin C and E. High dosage Vitamin C and E can be taken with the approval of a doctor.
Next I will explain how to improve radiation protection for the head since this is the most critical area of the body for proper decision making during space travel. Cosmic rays can affect the brain and central nervous system. It is already known that patients undergoing radiation treatment for brain tumors can suffer severe neurological affects such as problems with cognition and memory. For this reason I am suggesting a protective helmet be worn during travel between Earth and Mars. This helmet will be relatively heavy and should not be worn when accelerating and decelerating when its weight would be felt. This helmet will be worn when in a weightless condition on the way to Mars.
The material the helmet will be made of is Polyethylene, lead and water. Polyethylene is 50% better at shielding solar radiation and 15% better at shielding cosmic rays than aluminum. Also polyethylene produces significantly less secondary radiation than the heavier materials aluminum and lead. A good starting point for a helmet would be the following: An outer layer of 1/2 inch thick lead and an inner layer of 3 inches of polyethylene with a 1 inch water cavity in the middle of the polyethylene. This would be an over all thickness of 3 1/2 inches (8.89 cms). This helmet would have to be tested and perfected. It is definitely better than leaving the head unprotected.