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Post by Data Cable on Oct 9, 2005 1:32:32 GMT -4
wasn't this a figure intended to reflect the needs of inter planetary travel? Generational interstellar travel, as I recall.
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Post by turbonium on Oct 9, 2005 3:31:23 GMT -4
The VA Belts really only scare those with no understand of what Radiation is.Well, we really don't know all the hazards present within the VA Belts. This article from 1998 points out a previously unknown danger www.sfgate.com/cgi-bin/article.cgi?file=/news/archive/1998/12/08/state0216EST0166.DTLOnce thought to be a slumbering cocoon of charged particles embracing the Earth, new research shows these radiation belts can become extremely powerful in a matter of seconds.
New observations by an array of satellites show changes in the planet's own magnetic field can accelerate electrons in the belts to nearly the speed of light, transforming them into what some researchers describe as ``killer electrons.''
Under those conditions, the charged particles can pierce a sheet of aluminum a half-inch thick, possibly resulting in a catastrophic accumulation of particles in the sensitive electronics of hundreds of orbiting satellites.
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Post by nomuse on Oct 9, 2005 13:10:51 GMT -4
Notice the "hundreds of satellites" that detected this possibility are still operating. This is probably not a daily occurance.
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Post by Count Zero on Oct 10, 2005 1:08:28 GMT -4
I thought (courtesy of OLD A-Level Physics!) that alpha particles only travelled a few inches in air - was this really the system they used? I stand corrected. The Kaktus altimeter uses a gamma source, not an alpha. Good catch & thanks!
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Post by PhantomWolf on Oct 10, 2005 1:56:03 GMT -4
Well I was going ot suggest that if it was an alpha source that it might explain why few banged into the ground.
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Oct 10, 2005 8:34:40 GMT -4
wasn't this a figure intended to reflect the needs of inter planetary travel? Generational interstellar travel, as I recall. I've also heard that the likely original source for this information simply said six feet of shielding. It was a hoax conspiracist who misquoted this to mean six feet of lead. Shielding need not be lead and it is highly unlikely the source was referring to lead.
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Post by gwiz on Oct 10, 2005 8:51:17 GMT -4
This could be a source: NASA 1975 space colony studyIt suggests 4.5 t/m2 of shielding, which equates to about six feet of rock, is necessary to live permanently exposed to cosmic radiation, that is outside the protection of the earth's magnetic field. Obviously, a few days exposure on a lunar mission requires a lot less. Edit. Or about 16 inches of lead.
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Post by Jason Thompson on Oct 10, 2005 11:30:27 GMT -4
Well, we really don't know all the hazards present within the VA Belts.
But we don't have to. Leaving Apollo aside, the number of objects sent through or into the Van Allen belts is simply huge, and it includes manned capsules such as Gemini and other biological samples such as Zond. Some were sent specifically to analyse the belts, some were sent through the belts, some were deliberately placed within the belts. None of them has ceased to function because of the radiation present.
Under those conditions, the charged particles can pierce a sheet of aluminum a half-inch thick, possibly resulting in a catastrophic accumulation of particles in the sensitive electronics of hundreds of orbiting satellites.
Such a catastrophic event, you may note, has yet to happen. In any case, the effect on sensitive electronic equipment is hardly comparable to the effect on a (largely) self-repairing complex biological organism such as a human.
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Post by DaiHoss on Oct 10, 2005 12:03:31 GMT -4
the USSR stated that five feet of lead would be necessary to shield space travellers from the effects of radiation. And I believe them. This could be a source: NASA 1975 space colony studyIt suggests 4.5 t/m2 of shielding, which equates to about six feet of rock, is necessary to live permanently exposed to cosmic radiation, that is outside the protection of the earth's magnetic field. Obviously, a few days exposure on a lunar mission requires a lot less. Edit. Or about 16 inches of lead. 16 inches of lead, as opposed to 60 inches of lead. I reckon someone (A HB) mis-heard 16 as 60!
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Post by Jason Thompson on Oct 10, 2005 12:17:31 GMT -4
Coming in late, I know, but:
And how many people did this contraption bring back from the moon?
Why is that relevant? It never got there in the first place, so it could not have brought anyone back. It never flew because of the distressing tendency to disastrous failure exhibited by its intended launch vehicle. But it was designed to land a man on the Moon and bring him back to an orbiting Soyuz. So why weren't the lander or the Soyuz designed with huge lead shields if the USSR believed, as you claim, it was necessary?
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Post by JayUtah on Oct 10, 2005 12:58:53 GMT -4
Mauldin's Prospects for Interstellar Travel discusses radiation effects and shielding needs in two separate sections. He is specifically speaking of interstellar generational ships -- ships that would have to protect their occupants over the entire course of their lifetimes and attenuate radiation down to very low levels.
The primary concern is cosmic radiation, which ironically is not as bad in cislunar space. The solar wind keeps galactic charged particles from reaching the inner solar system in concentrations necessary to do damage. The secondary concern is induced radiation from relativistic velocities. Zipping through a stationary particle soup at 30% the speed of light will create high-energy particle collisions: radiation. But this is a second-order effect.
Mauldin gives two meters as the required shielding thickness, but he does not give the computation. Nor does he explicitly mention what material he's thinking of. Later he lists possible materials: ice, rock, etc. And he mentions two meters of rock elsewhere in passing.
Mauldin discusses metal shielding in the context of erosion protection. 30% light speed through dust can erode significant hull thickness. The Daedalus starship was to be clad in beryllium in order to withstand erosion. This would attenuate some radiation, but that's not its primary intent.
The "two meters of lead" claim is simply the product of inexperienced people reading irrelevant science.
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Post by JayUtah on Oct 10, 2005 13:02:54 GMT -4
...transforming them into what some researchers describe as ``killer electrons.''
A scary name for an extremely infrequent circumstance. That's why it took us 50 years of flying in the Van Allen belts to discover them.
We don't know everything about the ocean either, but that doesn't keep us from commercial maritime operations.
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Post by gwiz on Oct 10, 2005 13:28:52 GMT -4
Under those conditions, the charged particles can pierce a sheet of aluminum a half-inch thick, possibly resulting in a catastrophic accumulation of particles in the sensitive electronics of hundreds of orbiting satellites. The hundreds of satellites in the van Allen belts include all geostationary communications satellites and the GPS navigation satellites. Some of these satellites have been operating for over twenty years. The occasional failure due to radiation damage, eg the Anik E satellite, are usually associated with solar storms.
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Post by PhantomWolf on Oct 10, 2005 22:42:18 GMT -4
It never flew because of the distressing tendency to disastrous failure exhibited by its intended launch vehicle. Actually the LK flew once in unmanned Earth orbital testing. Basically the same things as Apollo 5. There were to be two further attempts to test it but the Proton launch system exploded before reaching orbit resulting in a failed mission. We don't know everything about the ocean either, but that doesn't keep us from commercial maritime operations. This is actually a very good example. Mankind have been sailing the oceans for centuries and until just the last year we never had absolute proof of things called Killer Waves. These waves are often 60+ feet and can seriously damage and sink modern ships, even cruise liners. No one is sure how or why they form, but they appear suddenly and are deadly, so much so that it is now believed that they are responsible for many of the losses of ships that just vanish. Satellites have shown that they are really quite common, a european device finding hundreds of them. Yet it doesn't prevent us from sailing and it doesn't mean that Columbus faked his trip to the West Indies because of the killer waves either.
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Post by gwiz on Oct 11, 2005 3:20:37 GMT -4
Actually the LK flew once in unmanned Earth orbital testing. Basically the same things as Apollo 5. There were to be two further attempts to test it but the Proton launch system exploded before reaching orbit resulting in a failed mission. Not sure which mission you're thinking of, but there were three successful unmanned tests of the LK, all launched by Soyuz into high-apogee elliptical orbits. I think some of the N1 tests included a functioning LK rather than a mockup, but they were all launch failures, of course.
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