Balloon flight will help scientists understand how to shield Mars crews NASA Science

If it rains, you put up an umbrella. If you expect a meteor shower, you build the spacecraft with shielding that blunts the blow when particles arrive. But what do you do for radiation? After almost four decades of human spaceflight, we still are grappling with the challenge of protecting space crews from cosmic rays and other radiation hazards. Part of the problem is understanding fully the composition and energies of cosmic rays.