Space Travel & Cosmic Rays

[tsunamisurfer]

Though I can't remember the author/title, I once read a book in which the author claimed that because current aerospace engineering cannot adequately shield space crews from the constant bombardment of cosmic radiation--and because long-term exposure to this radiation supposedly leads to diminished and irreversible cognitive impairment--extended space flights are practically impossible.

A crew of bright astronauts blasting off from Earth would, three years later, arrive at Saturn suffering from mental retardation so profound that they could not operate the ship, much less return safely to Earth.

Can anyone confirm or debunk that suspicious claim?

[fiddlesticks]

Based on what I've read of serious descriptions of the risks in a manned mission to Mars, scientists are much more concerned about the nasty ion storms our own Sun throws off on occasion. Besides the Fantastic Four origin story I've never read that cosmic rays pose an extreme danger to astronauts outside the Van Allen Belts. If scientists can figure out how to shield a spacecraft from solar storms without using too much mass they'll probably be okay from cosmic rays too.

From what I read scientists are much more worried about figuring out how to overcome the problems of bone mass loss while in weightlessness and generally keep a small group of people from killing each other through two years of close contact and isolation.

[Phobos]

I've never seen any studies about developing mental retardation from interplanetary space travel. However, radiation hazards are a real problem for interplanetary travel.
http://itss.raytheon.com/cafe/qadir/q483.html
Even the Gemini/Apollo astronauts had some small radiation exposure just close to home.
http://itss.raytheon.com/cafe/qadir/q2906.html
It is possible to provide shielding; however, the weight of all that shielding becomes too much to launch.

[tsunamisurfer]

Here's an excerpt from the first referenced article:

"And then there is the problem with cosmic rays, and the high energy particles produced by solar storms. These would be lethal to astronauts caught in interplanetary space. This means we have to have ways of predicting when they will happen during a round trip journey lasting hundreds of days. No such ability is currently available."

[Podkayne]

From the National Acadamies website (http://www.nationalacademies.org/ssb/chx1ch2.htm):

Humans conducting extended space voyages face two different radiation hazards: a protracted exposure to galactic cosmic rays at a low dose rate and some probability of exposure to considerably higher doses of solar energetic particles. Depending on the total exposure suffered, these twin effects will increase the probability of stochastic effects (such as cancer and genetic damage) and may also increase the incidence of deterministic effects (physical damage to tissues). The effects of acute irradiation during solar particle events are of particular concern. The high-dose-rate exposures they could inflict on astronauts could cause acute damage to the skin, gut, bone marrow, and germinative tissues and, at a later date, cause cataracts.

(That's copyright the National Acadamy of Sciences--a short exerpt, so it should be kosher.) No mention of retardation. I don't know why one would expect that in a fully-developed human being. If the brain tissue was so profoundly damaged, I'd think you'd just end up dead.

[TheNerd]

As the other posters have pointed out, these are valid concerns, but once again, technology is well on the way to providing solutions.

Recent plasma physics research should provide both more efficient/faster propulsion ( plasma engine (http://spaceflight.nasa.gov/mars/technology/propulsion/aspl/), magnetic plasma solar sail (http://spacescience.com/headlines/y2000/ast04oct_1.htm)), and managable radiation sheilding (plasma "force field" (http://www.space.com/businesstechnology/technology/cold_plasma_000724.html)).

[tsunamisurfer]

Originally posted by Podkayne
From the National Acadamies website (http://www.nationalacademies.org/ssb/chx1ch2.htm):

Humans conducting extended space voyages face two different radiation hazards: a protracted exposure to galactic cosmic rays at a low dose rate and some probability of exposure to considerably higher doses of solar energetic particles. Depending on the total exposure suffered, these twin effects will increase the probability of stochastic effects (such as cancer and genetic damage) and may also increase the incidence of deterministic effects (physical damage to tissues). The effects of acute irradiation during solar particle events are of particular concern. The high-dose-rate exposures they could inflict on astronauts could cause acute damage to the skin, gut, bone marrow, and germinative tissues and, at a later date, cause cataracts.

(That's copyright the National Acadamy of Sciences--a short exerpt, so it should be kosher.) No mention of retardation. I don't know why one would expect that in a fully-developed human being. If the brain tissue was so profoundly damaged, I'd think you'd just end up dead.

-------------
Actually, instead of "mental retardation," which suggests a congenital condition (?), I think the author was implying profound cognitive impairment. If you are questioning the effect of cosmic irradiation as a causative factor of CI, I share your doubts. If, however, you are implying that humans cannot suffer sudden massive cognitive impairment without dying, I would disagree. That said, I'm guessing you meant the former.

[Bear_Nenno]

...generally keep a small group of people from killing each other through two years of close contact and isolation.Ya know, I bet NASA could rake in some big bucks for an upcoming mission to Mars by teeming up with MTV for a new 'reality tv' show. This would be way better than Real World, Road Rules, or any of that network crap like Survivor.

[Demo]

For orbits at 250 - 300 km at 65 degree inclinations to the equator you get about 10 millirads/day.

At this level, you would get 3650 millirads per year or, 3.65 Rads. The occupational exposure limit for people who work in radiology is 5 Rads/year. This number is a very conservative number, below which, no deterministic effects have been seen. (Determinitsic effects are based on threshholds, stochastic are not, since obviously, ionization from a single photon interaction with a cell can cause genetic damage.) So, at this radiation exposure level, the astronauts would be perfectly safe. As a matter of fact, I know a few people who regularly recieve more than 4 Rads annually(x-ray and gamma ray exposure) and seem to have not suffered from it. These are people who have been working in the field for years.

Unfortunately, they didn't list the average exposure for some of the other passages, like the interplanetary and the periods of high solar activity. I'd be interested in seeing those figures.

[Podkayne]

Originally posted by tsunamisurfer
Actually, instead of "mental retardation," which suggests a congenital condition (?), I think the author was implying profound cognitive impairment.

Yes, you're right, I was sloppy with terminology. I think retardation implies that development was "retarded".


If, however, you are implying that humans cannot suffer sudden massive cognitive impairment without dying, I would disagree.

Sorry, I wasn't clear. What I meant was that by the time you had enough radiation damage to the brain to cause cognitive impairment, the radiation would already have done you in by damaging other tissues--the dura mater, for example!

[Phobos]

Originally posted by Bear_Nenno
Ya know, I bet NASA could rake in some big bucks for an upcoming mission to Mars by teeming up with MTV for a new 'reality tv' show. This would be way better than Real World, Road Rules, or any of that network crap like Survivor.

True, that would be a cool show. Too bad is not allowed to make a profit.