“ We considered a spherical water phantom in a spherical spacecraft shell, and analyzed how the radiation dose absorbed in the phantom depends on the aluminum s

“ We considered a spherical water phantom in a spherical spacecraft shell, and analyzed how the radiation dose absorbed in the phantom depends on the aluminum spacecraft shielding thickness (surface density values of 0, 5, 10, 20, 30, 40, 50, and 60 g•cm^2)” To help you make sense of those gcm2 values, a 1 cm cube of aluminum has a density of 2.7g and presents (roughly) 1 cm^2 surface area when part of a sphere, so it’s “0cm thick, 2cm thick, 4cm thick, 8cm thick, 12cm thick,…” etc. The first and most important point is that this should be titled “Spaceships flying to Mars declared unsafe for humans”, as the study concerns itself solely with radiation received in travelling to Mars. It has nothing to do with Mars itself and in fact their result is probably broadly true of any spaceflight above low earth orbit. Other potential titles might be “Aluminum declared insufficient for radiation shielding”* or “1 Sievert limit declared impractical for interplanetary spaceflight”. *: Although they do claim that more complicated multilayer systems using other materials as well would only get at most 20% more protection; it seems the fundamental issue is what we think of as “radiation shielding” is more like “radiation heatsink”, and as you absorb more and more radiation from space, that energy will have to go somewhere - in the form of secondary radiation released by the shielding itself.