Radiation shielding works by forcing incoming particles to lose energy in successive collisions with shield material — thicker or denser shielding stops more before it reaches the body.
dose ~ flux * energy * (1 - shielding_attenuation)
attenuation ~ layers * density
- Incoming particles — galactic cosmic-ray and solar-particle flux striking the spacecraft.
- Shielding layers — shielding material layers (polyethylene, aluminium, water) between space and the crew.
- Particle energy — energy of incoming particles — higher-energy particles penetrate more layers.
- Shield material density — mass density of the shielding material, the main lever on stopping power.
This is the exact trade-off NASA engineers face designing Mars-mission habitats — every extra centimetre of shielding cuts dose but adds mass that costs fuel to launch.