Then please explain to my stupid arse how exactly we got to the moon without being melted? Those space suits aren\'t that reputable. - mjps...whatever
Uh, jus WTF do you mean by that? Who\'s doubting their reputability? Why would we melt in space? Sure the Earth\'s atmosphere protects us from a vast majority of the sun\'s heat and radiation.. but those same space suits we used to land on the moon were used in close earth orbit spacewalks. What do you think our astronauts wore when taking EVA\'s to fix sattelites and preform experiments? And why is it so hard to believe that those suits were heat shielded? Have you ever seen those suits scientists wear to study volcanos? Nothing but a thin sheet of aluminum foil!!
Or maybe you\'re talking about the Van Allen Radiation belts. Well, I\'m not an expert, but I found a quip from site at CalTech that might answer your questions.
Regarding the Van Allen belts, and the nature of the radiation in them, they are doughnut-shaped regions where charged particles, both protons and electrons, are trapped in the Earth\'s magnetic field. The number of particles encountered (flux is the technical jargon, to impress your friends!) depends on the energy of the particles; in general, the flux of high-energy particles is less, and the flux of low-energy particles is more. Very low energy particles cannot penetrate the skin of a spacecraft, nor even the skin of an astronaut. Very roughly speaking, electrons below about 1 million electron volts (MeV) are unlikely to be dangerous, and protons below 10 MeV are also not sufficiently penetrating to be a concern. The actual fluxes encountered in the Van Allen belts is a matter of great commercial importance, as communications satellites operate in the outer region, and their electronics, and hence lifetimes, are strongly affected by the radiation environment. Thus billions of dollars are at stake, never mind the Moon! The standard database on the fluxes in the belt are the models for the trapped radiation environment, AP8 for protons, and AE8 for electrons, maintained by the National Space Sciences Data Center at NASA\'s Goddard Spaceflight Center. Barth (1999) gives a summary which indicates that electrons with energies over 1 MeV have a flux above a million per square centimeter per second from 1-6 earth radii (about 6,300 - 38,000 km), and protons over 10 MeV have a flux above one hundred thousand per square centimeter per second from about 1.5-2.5 Earth radii (9,500 km - 16,000 km).
Then what would be the radiation dose due to such fluxes, for the amount of time an astronaut crew would be exposed? This was in fact a serious concern at the time that the Apollo program was first proposed. Unfortunately I have not located quantitative information in the time available, but my recollection is that the dose was roughly 2 rem (= 20 mSv, milli-Sievert).
The time the astronauts would be exposed is fairly easy to calculate from basic orbital mechanics, though probably not something most students below college level could easily verify. You have perhaps heard that to escape from Earth requires a speed of about 7 miles per second, which is about 11.2 km per sec. At that speed, it would require less than an hour to pass outside the main part of the belts at around 38,000 km altitude. However it is a little more complicated than that, because as soon as the rocket motor stops burning, the spacecraft immediately begins to slow down due to the attraction of gravity. At 38,000 km altitude it would actually be moving only about 4.6 km per sec, not 11.2. If we just take the geometric average of these two, 7.2 km per sec, we will not be too far off, and get about 1.5 hours for the time to pass beyond 38,000 km.
Unfortunately calculating the average radiation dose received by an astronaut in the belts is quite intricate in practice, though not too hard in principle. One must add up the effects of all kinds of particles, of all energies. For each kind of particle (electrons and protons in this situation) you have to take account of the shielding due to the Apollo spacecraft and the astronaut space suits. Here are some approximate values for the ranges of protons and electrons in aluminum:
Range in Aluminum [cm] Energy
[MeV] electrons protons
1 0.15 ~ nil
3 0.56 ~ nil
10 1.85 0.06
30 no flux 0.37
100 no flux 3.7
For electrons, the AE8 electron data shows negligible flux (< 1 electron per square cm per sec) over E=7 MeV at any altitude. The AP8 proton compilations indicates peak fluxes outside the spacecraft up to about 20,000 protons per square cm per sec above 100 MeV in a region around 1.7 Earth radii, but because the region is narrow, passage takes only about 5 min. Nevertheless, these appear to be the principal hazard.
These numbers seem generally consistent with the ~2 rem doses I recall. If every gram of a person\'s body absorbed 600,000 protons with energy 100 MeV, completely stopping them, the dose would be about 50 mSv. Assuming a typical thickness of 10 cm for a human and no shielding by the spacecraft gives a dose of something like 50 mSv in 300 sec due to protons in the most intense part of the belt.
For comparison, the US recommended limit of exposure for radiation workers is 50 mSv per year, based on the danger of causing cancer. The corresponding recommended limits in Britain and Cern are 15 mSv. For acute doses, the whole-body exposure lethal within 30 days to 50% of untreated cases is about 2.5-3.0 Gy (Gray) or 250-300 rad; in such circumstances, 1 rad is equivalent to 1 rem.
So the effect of such a dose, in the end, would not be enough to make the astronauts even noticeably ill. The low-level exposure could possibly cause cancer in the long term. I do not know exactly what the odds on that would be, I believe on the order of 1 in 1000 per astronaut exposed, probably some years after the trip. Of course, with nine trips, and a total of 3 X 9 = 27 astronauts (except for a few, like Jim Lovell, who went more than once) you would expect probably 5 or 10 cancers eventually in any case, even without any exposure, so it is not possible to know which if any might have been caused by the trips.
Much of this material can be found in the 1999 "Review of Particle Properties", (see below) in the sections on "Atomic and nuclear properties of materials", on "Radioactivity and radiation protection", and on "Passage of particles through matter".
http://spider.ipac.caltech.edu/staff/waw/mad/mad19.html^^^---- Now, if only they had some guys like THIS on that Fox special, there wouldn\'t be so many questions being asked. Of course, Fox\'s ratings probably wouldda gone down the tubes on this one too. : /
BTW: Didn\'t John Swigert from the Apollo 13 mission die of cancer?
Hmmmmm........
