Radiation

One of the things that the folks from NASA thought that the class should design for is radiation. Reading off the slides from the SICSA website, there are two sources of radiation that one needs to design for:

Galactic Cosmic Radiation (GCR), and

Large Solar Flares.

GCR is a constant, isotropic source of radiation. Isotropic means that it comes in from all directions. Solar Flares, on the other hand, come from one source: the sun (or any given star, but I'm more concerned about the local Sun versus all the other ones)

It is difficult to protect the crew from GCR, because apparently a given level of protection plateaus after a while. This implies that complete protection requires escalating thicknesses of shielding, which adds mass. The impression that I'm getting from Larry is that GCR-protection may be more trouble than it's worth. That said, one article from science.nasa.gov says that GCR poses the greatest risk, due to Fe⁺²⁶.

This could get very dry.

What makes solar flares dangerous is their intensity and unpredictability. Here I introduce the unit called Röntgen Equivalent Man, "rem". The rem is used to measure radiation dosage. The maximum dosage, as far as I can best determine (sources: 1, 2, and 3) is 25 rem per 30-day period, and 50 rem per year. Older males are apparently able to take more rems than everyone else (male and female).

I had been under the impression last semester that the crew would consist of six males who had already had their families. The concern was that if younger people travelled to Mars, the amount of radiation that they would be exposed to could lead to sterility. However, crew selection is still far away. That doesn't mean that I can't "design" a mission to include certain people, but that I shouldn't expect anything that is print now to be true 20 or 30 or however many years from now.

What I'm trying to find out is:

How many rem's do solar flare events produce?

What does it take to shield those rem's?