There’s an invisible, magnetic force field surrounding our planet, protecting us from harmful solar wind that could annihilate Earth. But, this protective blanket is also a swirling ring full of deadly radiation. And to leave Earth’s atmosphere, astronauts have to pass through it. The Van Allen belts are rings of energetically charged particles that have been captured by Earth's magnetic field.
They got their name from this physicist, James Van Allen. Back in the 1950s, Van Allen launched a rockoon, a rocket lifted by a balloon above the atmosphere, and it detected the first hint of radiation at higher altitudes. Then, Explorer 1, the first American satellite to orbit Earth, launched in January 13, 1958. Explorer 1 confirmed that Earth’s magnetosphere was trapping the subatomic particles.
The Van Allen belts were the first major scientific discovery of the early Space Age, and they posed a serious challenge for space travel. High-speed subatomic particles can tear through DNA, increasing the risks of cancer and other diseases. So sending astronauts through these particles is not ideal, and even though they’re flying in a shielded spacecraft, doses of radiation can still seep through. But there’s no way around the Van Allen belts and In order to reach space, astronauts have to pass through them.
First, they have to travel through the inner belt, which is comprised of protons, and then through the outer belt, which has mostly high energy-electrons. One solution, proposed by Mr. Van Allen himself, suggested detonating a nuclear bomb in the inner belt to clear out radiation. While Van Allen’s plan wasn’t executed, in 1962, the United States did carry out a nuclear test in space, dubbed Starfish Prime. They wanted to see if detonating a 1.4 megaton bomb in low-Earth orbit could augment and expand the Van Allen Belts, but the explosion actually ended up adding more radiation around our planet. So, for the Apollo missions, NASA had to create a radiation barrier within the spacecraft and figure out a trajectory that avoided the thickest, most radioactive part of the belts while traveling as fast as possible. Scientists determined that if the speed of the Apollo spacecraft was about 25,000 kilometers per hour, it would take a spacecraft about 52.8 minutes to pass through the belts. Scientists found that the radiation dose received during that amount of time would be, at most, 11.4 rads and that’s without the protection of a spacecraft. And since a lethal radiation dose for a human is 300 rads in one hour, NASA deemed the missions a go. And if you want to see exactly how they calculated it all… hit pause now. After all that, it turned out, that during the Apollo missions, the average radiation doses on the skin of the astronauts came out to be 0.38 rad.
So while the Van Allen belts are lethal, they could really only kill an astronaut if they were to spend several days in their radioactive vicinity. So while the Van Allen belts are lethal, they could really only kill an astronaut if they were to spend several days in their radioactive vicinity. And despite the challenges the belts create when leaving Earth, we should actually be thanking them for protecting life on our planet from utter annihilation.