TRANSCRIPT
Freefall in color by many folks.

TRANSCRIPT

Sam: How much shielding do we have?
Florence: Well, shielding is a little complicated. Higher energy gamma rays have more penetrating power. The thumb rule is 5 cm of lead, 10 cm of steel, or 120 cm of water is one ten-thickness.
Florence: A ten-thickness is the amount of material needed to reduce the radiation level to one tenth of the unshielded value.
100 gray, 6 MeV source
5 cm of lead
Radiation level: 10 gray
5 cm of lead
Radiation level: 1 gray
Sam: Wow. That much material wrapped around a spaceship would be heavy... and expensive to accelerate... and we don't have much shielding, do we?