Flying to the Moon is dangerous. Radiation, for example, can threaten both spacecraft and their human cargoes.

The first threat is the Van Allen radiation belts. Earth’s magnetic field traps charged particles from the Sun in these doughnut-shaped zones. They extend from a few hundred miles above the surface out to about 35 thousand miles.

A long stay inside the belts could cause radiation sickness. But when Apollo 11 headed to the Moon 50 years ago, the crew faced little danger from the belts. Their trajectory avoided the belts’ most dangerous regions, and they zipped through the belts in a few hours.

After they cleared the belts, the astronauts still faced threats from the Sun. An especially big solar storm could have caused serious radiation sickness in astronauts who were on the Moon, requiring an immediate return to Earth.

To keep the astronauts safe, NASA kept a close eye on the Sun. And the Apollo mothership’s aluminum hull blocked most radiation. So Apollo astronauts received doses that were equal to no more than a few dozen chest X-rays. The doses were spread out over several days, though, and they covered the astronauts’ entire bodies. So the radiation wasn’t strong enough to cause damage.

Future missions may spend a lot more time on or around the Moon than Apollo did. So planners will need to spend more time thinking about how to keep astronauts safe from the dangers of spaceflight.

We’ll have more about Apollo 11 tomorrow.

Script by Damond Benningfield