Radiation

Radiation

One of the biggest hazards involved in interplanetary spaceflight is exposure to radiation. During interplanetary spaceflight, once outside of the protection of Earth’s magnetic field, crews will be exposed to radiation from the Sun (from solar flares) and from cosmic radiation (from the rest of the universe). Long-term exposure to radiation (high-energy electrons and protons, gamma rays and X-rays) 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 what are known as 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.

Commander Eileen Collins aboard STS-93

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. The Skylab astronauts, who lived for 87 days in space, received about 3 times the maximum allowable dosage for 1 year.

According to U.S. government standards, the maximum dosage per year is the equivalent of about 10 chest X rays. As a countermeasure, 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. 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.

In addition, cryogenic preservation of ova or sperm from astronauts for future use could be done. 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. If you don't have a storm shelter (e.g., if you are out spacewalking in just your suit), a bad solar flare can kill you.

Astronauts James Newman and Bob Cabana aboard the International Space Station

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. 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 is inherently dangerous with the present state of the art, cancer due to cosmic rays is considered by most scientists to be a relatively small additional risk.

Very high doses of radiation can also cause machines to fail by causing the computer inside them to fail, and computer systems on board will need to have shielding systems.

Questions to think about:

Using the amount of radiation in a chest X ray as your standard, a trip from Earth to Mars (of about 250 days) would give the crew how much radiation exposure?

What kinds of shielding can be designed to protect people and machines from radiation? What materials would you use?

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