Cosmic Radiation Shielding


Cosmic rays are high-energy atomic nuclei (primarily protons), or electrons moving at high speeds. Cosmic rays collide with slow-moving atomic nuclei producing a shower of secondary particles, which then decay or collide with other nuclei. Cosmic radiation produces radioisotopes and gamma radiation which can kill a living organism or mutate it's DNA. Cosmic radiation can penetrate easily through a spacecraft, and deep into a planetary atmosphere.

There are three ways to shield against cosmic radiation: a strong, consistant magnetic field; a thick planetary atmosphere or; a solid barrier made of high-density elements (primarily metals).

A strong magnetosphere and thick atmosphere can protect a planet from a majority of cosmic radiation. However, we've not yet achieved a level of technology that will allow us to protect spacecraft with a strong magnetic field, as such we must rely on a high-density physical barrier. The best measure (that I can find) of an elements ability to protect against cosmic radiation, is the neutron cross section value. The higher the value, the better the protection. The following is a list of elements and their neutron cross section values.

Elements-IsotopesNeutron cross-section (barns)
Gadolinium49000Lanthanide
Samarium5900Lanthanide
Europium4600Lanthanide
Boron-103837
Cadmium2450
Dysprosium920Lanthanide
Iridium425
Mercury374
Indium194
Silicon171
Erbium160Lanthanide
Rhodium145
Thulium105Lanthanide
Hafnium104
Gold98.7
Rhenium90
Lutetium84Lanthanide
Holmium65Lanthanide
Silver63.6
Neodymium49Lanthanide
Cobalt37.2
Nickel37.2
Chlorine35.5
Ytterbium35Lanthanide
Caesium29
Scandium27.2
Krypton25
Xenon25
Terbium23Lanthanide
Tantalum20.5
Tungsten18.4
Osmium15
Manganese13.3
Selenium11.7
Praseodymium11.4Lanthanide
Platinium10
Lanthanum8.98Lanthanide
Palladium6.9
Bromine6.8
Iodine6.2
Titanium6.1
Antimony5.4
Tellurium5.4
Vanadium5.06
Arsenic4.3
Copper3.78
Thallium3.4
Chromium3.1
Gallium2.9
Molybdenum2.6
Ruthenium2.6
Iron2.56
Germanium2.2
Potassium2.1
Nitrogen1.91
Barium1.3
Yttrium1.28
Strontium1.2
Niobium1.15
Zinc1.1
Tin0.63
Cerium0.6Lanthanide
Sodium0.53
Calcium0.43
Rubidium0.38
Hydrogen0.332
Aluminium0.233
Zirconium0.184
Phosphorus0.180
Lead0.171
Magnesium0.063
Neon0.04
Bismuth0.034
Fluorine0.01
Beryllium0.009
Helium0.007
Lithium0.005
Boron-110.005
Carbon0.004
Oxygen0.000

Note: Radioactive elements emit their own radiation, and as such aren't included.