While the walls of the Inspiration Mars spacecraft will initially be lined with water-filled bags to guard against cosmic rays, their contents will be gradually replaced with er, byproduct that will be dehydrated through the bag (possibly using polyethylene) to reclaim and purify water for drinking.
Using a particle accelerator, he demonstrated that cosmic rays colliding with molecules in the atmosphere can, in fact, cause gaseous water vapor to condense into cloud-forming droplets.