Tom Lehrer's old joke is now reality: the radiation shield bikini. Except it's polyethylene, which at high density marshals more hydrogen than a thin water or ice shield might.
NASA limits lifetime-total exposure to 0.6 sieverts. That was based on 1950s assumptions that sieverts to the big toe mattered as much as sieverts to the groin, which even Lehrer wasn't fool enough to believe. The body parts that need the shielding best, in practice, indeed cluster the pelvis. The head doesn't need it as bad, either; this might even be an ancient evolutionary hack.
Geometry is "hexagonal rods", I guess the 9-60mm of that rod being on the Z-axis. So the (unmanned) first Artemis mission successfully tested a 26kg version of this, just by blasting through our Van Allens. Although the results did not make the deadline for the Artemis II followup that just ran.
The plastic /rinkle/ is still, I think, not a solution for a trip to Mars which is further than Tampa. They admit that cosmic rays, as blast through Earth's own magshield, still got through. In a straight shot to our Moon an astronaut can laugh this off. Not in a months-long trip however (and then most want to come home). In our LEO sats we're all tired of running to the shielded part whenever a storm hits.
What this does give to long-term astronauts in orbiting ti[tanio]n cans is the ability to move around an unshielded station under solarflare conditions. Or - better - passing over the south-Pacific anomaly - or in permanent MEO between Van Allens, where I think the belts might shift. Or wandering those prefab corridors although there a magnetic solution could work as well.
Meanwhile they're targeting 16kg.
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