Space Weather Web Server
   

Biological Effects of Space Weather

Astronauts | Aircrew & Passengers

Astronaut Radiation Hazards

cosmaunaute.jpg (57435 bytes)

For  long-term space missions, such as the International Space Station (ISS), the protection of astronauts from Space Weather induced effects such as solar proton events is critical. Outside the protective atmosphere of the Earth astronauts are subject to much higher doses of radiation than they woul dotherwise normally receive. This radiation can arise due to solar events such as a solar flare, solar particle event (SPE) or a coronal mass ejection. The flux of galactic cosmic rays, originating from outside the solar system is also greater above the Earth's atmosphere. The most dangerous of these phenomena for astronauts health is a solar particle event. In extreme cases, an astronaut can receive many times his/her maximum safe annual dose within a few hours. Fortunately, not all flares or CMEs produce these particle events.

For example, in the period between the Apollo 16 and 17 manned space missions, one of the largest SPEs ever recorded took place. Computer simulations of the radiation levels an astronaut inside a spacecraft would have experienced during this event have shown that, even inside a spacecraft, the astronauts would have absorbed lethal doses of radiation within 10 hrs after the start of the event.

To put these numbers into context:

The National Council on Radiation Protection makes the following recommendations for astronaut radiation exposure limits: (from NCRP 98).

 
Dose Equivalent mSv for ---
Exposure
Skin
Ocular Lens
Blood forming organs
30 days
1500
1000
250
annual
3000
2000
500
career
6000
4000
1000-4000\a

a: varies with gender & age at initial exposure.

In comparison, the cumulative dose equivalent for the August 1972 particle event, assuming a nominal shielding thickness of Al 2g/cm^2, was measured to be 11,300mSv. This would have been received in a matter of hours rather than over the long period of a career. Luckily an event of this magnitude is a very rare occurrence, but it is clear that the ability to predict these events would be of great benfit in mission planning. If astronauts were given sufficient time to react to a SPE warning, they could enter a storm shelter, or region of their s/c with increased shielding. In this case, a dose equivalent of 11,300mSv could be reduced to just 180mSv.

 

For more information about radiation  limits and damage see:   

 

[Back to Applications Page]