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.
In order to reach space, astronauts 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.
A lethal radiation dosage for a human is 300
rads in one hour, so NASA deemed the missions
a go.
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 which is about the same radiation
you would receive getting two CT scans of
your head.
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.
