I've got a few more questions to which I welcome your reponse.

As I mentioned earlier, I'm trying to estimate the radiation dose received by Apollo astronauts during their transit through the Van Allen Belts. I want to be reasonably accurate but I'm also willing to make some simplifying assumptions. Here are some of the things I'm currently considering in my analysis:

► It looks like the only particles that will penetrate the spacecraft shielding are the highest energy protons. Let's say I determine that only protons > 100 MeV have the necessary energy. Of course by the time a 100 MeV proton has passed through the shielding it is no longer a 100 MeV particle; it has lost energy during its penetration. In this case, is it a reasonable assumption to say it takes 100 MeV to penetrate the shielding, thus all particles that penetrate will have 100 MeV less energy than their original energy?

► I've found equations that give the penetration depth of high-energy protons in air and aluminum. Of course the CM shielding consists of, in order of penetration, the epoxy resin heat shield, the stainless steel sheet/honeycomb, the fibrous insulation, and the aluminum sheet/honeycomb. If I convert the penetration depth in aluminum to g/cm^{2}, is it reasonable to assume that an equal mass of some other material will have an equivalent stopping power. It may not be exact but I think it will be close enough. For instance, if I use the formulas to calculate the penetration of a 100 MeV proton and convert to g/cm^{2}, I get 8.8 in air and 9.8 in aluminum. If air and aluminum are that close, then surely other materials such as epoxy resin and stainless steel will be similar.

► Although the numbers indicate that no electrons will penetrate the hull, I want the account for Bremsstrahlung. I've found an equation that gives the fraction of the original electron energy that is converted to X-Rays. Surely these X-rays scatter in all directions, so I think it is a valid assumption to say that 50% of the X-rays travel harmlessly back into space. Do you concur?

► I haven't found much (or at least not much that I understand) about Bremsstrahlung for protons. Most of the literature I've found seems to focus on electrons. Is secondary radiation from protons a big issue that I need to account for? If so, does anybody have any information or equations that will help me?

I'm continuing to work my way through this analysis, so I may answer some of my own questions or come up with new questions. I appreciate any help you can give me. I'll post a link to my article when it is finished so that I can get some critical feedback.

Thanks.