Final Project

Ragan M.

Legislator:  Gary L. Walker, Representative

(Click on the image above to enlarge.)

Radiation is a major factor in human space travel.  Different types, belt radiation, solar radiation, or galactic cosmic rays, pose different threats, such as systems failure or health hazards.  Scientists are determining ways to reduce the risks or even prevent exposure to space radiation.

As I have stated, there are three major types of radiation that astronauts are exposed to in space.  The types include, belt radiation, solar radiation, and galactic cosmic rays.  Belt radiation comes from particles found in the Earth's magnetic field, which protects us from dangerous radiation in space.  High-energy electrons and ions are forced to circle around the Earth at high altitudes, trapped in two donut shaped regions called the Van Allen Belts or Radiation Belts.  Some parts of the Earth's radiation belts contain lethal does of radiation for an unprotected astronaut even during quiet times.  Solar radiation results from a solar particle event, which sometimes accompanies solar flares.  Solar flares are explosions of incredible power and violence that release energy equivalent to about 100 hurricanes in a matter of minutes.  To equal the power of a hurricane one would have to set off about a thousand nuclear devices per second for as long as the hurricane rages on.  This may be the most potent space radiation hazard to lightly shielded spacecraft.  The last, but not least, is galactic cosmic rays, which consists of particles that originate outside the solar system.  Diffusive shock acceleration explains how galactic cosmic rays are formed. These are cosmic rays that come from outside of our solar system.  Scientists believe that supernova shock waves interacting with plasma creates the cosmic rays that come from outside our solar system.  What does this mean?  Say a bunch of plasma is sitting out in space minding its own business.  All of a sudden there is a nearby supernova explosion.  The supernova blast creates shock waves.  These shock waves sweep over the plasma, squeezing it together.  Whenever the plasma is compressed, some of the plasma particles gain energy.  Each time a particle crosses a shock wave, it can gain more energy.  Now, let’s move on to the hazards these three types of radiation pose to manned missions in space.

In space, crewmembers are subjected to greater amounts of natural radiation than they receive on Earth, exposing them to possible immediate and long-term risks. Long-term exposure to radiation can lead to cancer, cell damage, and damage to reproductive systems. When these highly charged particles come into contact with living tissue, they ionize molecules like water or oxygen. This reaction produces free radicals, which can inflict damage to cells. When cellular DNA is affected by free radicals, certain regions can become damaged and undergo uncontrolled cell division which later manifests itself as cancer. In the short term, exposure can cause nausea and a decrease in blood counts; and in the long term, exposure can cause cancer, cataracts, and death. Children conceived post-flight could have a larger risk of birth defects.  Electrically charged cosmic ray particles from the Milky Way galaxy come from all directions of deep space more or less continuously. Small amounts of shielding can cut out the majority of these rays, but the remainder will give astronauts a somewhat increased risk of cancer.  According to U.S. government standards, the maximum dosage per year is the equivalent of about 10 chest X rays. The Skylab astronauts, who lived for 87 days in space, received about 3 times the maximum allowable dosage for 1 year. Astronauts who fly the Space Shuttle for between 7 and 14 days get the equivalent of about 50 chest X rays, but it takes the equivalent of over 5,000 chest X rays to get radiation sickness.  Using very conservative estimates, a week in space's cosmic ray environment will shorten your life expectancy by about a day.  Statistically, it is very unlikely to give you cancer; but if it does, it will shorten your life by much more than a day.  Since space travel is inherently dangerous even with the present state of the art equipment, cancer due to cosmic rays is considered by most scientists to be a relatively small additional risk.  I disagree with this statement because many people, myself included, have a strong family history of cancer in some form or another.  Because of this, I believe that the issue of radiation is not a “small additional risk.”   If you don’t have any kind of shelter (e.g., if you are out space walking in just your suit), a bad solar flare can kill you.  Another hazard posed by radiation is dangerous levels of high-energy particle radiation build up in the magnetosphere can damage spacecraft microelectronics, posing a serious threat to the safety of astronauts.  Very high doses of radiation can also cause machines to fail by causing the computer inside them to fail.  Therefore, all electronic systems on board would need to have a shielding mechanism.  Regardless of the source, large amounts of radiation exposure can lead to radiation sickness and have the potential to damage the body's chromosomes.  What can we do to ward off this potentially dangerous threat?

Scientists have come up with many ways to protect astronauts from some of the radiation they are exposed to.  For example, water tanks are an idea that may be used in the capsule walls for future human missions to Mars.  Radiation shielding in the Mars vehicle could be a safe haven from solar flares.  A good place for a storm shelter would be in the center of the ship, surrounded by the water tanks.  Also, supplementing the diet of astronauts could be extremely helpful in warding off the ill effects of radiation because antioxidants such as vitamin E, C and beta-carotene are known to neutralize the damaging effects of free radicals. The astronauts could begin taking these supplements as soon as they are chosen to be on a mission, or even when they start their preliminary training. Bone marrow samples collected from crewmembers before flight could be used to regenerate bone marrow should the crewmember be stricken with cancer at a later date. Cryogenic preservation of ova or sperm from astronauts for future use is an option for those that want families after they have visited space (as I stated earlier, children that are conceive post-flight have a higher risk of birth defects).  A lead shield would also help in preventing X-ray radiation from entering the shuttle. The great thing about this solution is the only thing the astronauts would need from earth are the supplements, weather they be in their regular diet or taken as a vitamin. This, of course would have to be done in pre-flight preparation. 

As you can see, radiation affects many things in space flight.  There are three major types, belt radiation, solar radiation, and galactic cosmic rays, but tremendous strides have been made to protect astronauts from them.  There are still improvements that need to be made before radiation hazards are reduced to less than fatal.  You could say that we have come a long way since the unprotected Pre-Apollo and Apollo missions.

My sources include: 

Basic Facts About Space Weather Link from TAS Unit 10 Radiation Page,                       

 In-flight Radiation Measurements Link from TAS Unit 10 Radiation Page,

TAS Human Factor – Unit 10: Radiation Page,

Belt Radiation Link from TAS Unit 10 Radiation Page,

Solar Radiation Link from TAS Unit 10 Radiation Page, and

Galactic Cosmic Rays Link from TAS Unit 10 Radiation Page.

Last Updated: 06/25/01