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#1 2003-11-13 18:25:15
- Bill White
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- Registered: 2001-09-09
- Posts: 2,114
Re: Radiation dangers - Recent solar flares
This fictional alternate history points out that it is a pretty darn good thing that a MarsDirect style vessel was not travelling somewhere between Earth and Mars during teh recent solar flare activity.
Any comments?
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#2 2003-11-13 18:34:33
- Byron
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- From: Florida, USA
- Registered: 2002-05-16
- Posts: 844
Re: Radiation dangers - Recent solar flares
This fictional alternate history points out that it is a pretty darn good thing that a MarsDirect style vessel was not travelling somewhere between Earth and Mars during teh recent solar flare activity.
Any comments?
I'll say...
I think this recent burst of solar activity (which may perform an encore when those mega-spots rotate back into "our" side of the Solar System) should be a lesson that even after nearly four years after solar maximum you can still get killer solar storms.
All missions to Mars should be planned as if they will encounter a major solar storm...because Murphy's Law will ensure that one will happen when people are sailing from Earth to Mars, even if the mission takes place at solar minimum. In that case, it really shouldn't matter at what point in the solar cycle the mission takes place...if the ship's ready, they should go...provided that they can withstand the most powerful solar flares without undue difficulty.
B
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#3 2003-11-13 19:05:35
- Ad Astra
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- Registered: 2003-02-02
- Posts: 584
Re: Radiation dangers - Recent solar flares
In James A. Michener's excellent "Space," a solar flare spells disaster for the fictional Apollo 18 mission. Just something we should consider while planning to send humans past LEO and to the moon and beyond.
Who needs Michael Griffin when you can have Peter Griffin? Catch "Family Guy" Sunday nights on FOX.
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#4 2004-05-27 09:11:04
- Palomar
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- From: USA
- Registered: 2002-05-30
- Posts: 9,734
Re: Radiation dangers - Recent solar flares
http://www.space.com/businesstechnology … ml]Article from space.com
"Youngquist's team envisions a spacecraft equipped with what's called a --->multipole electrostatic radiation shield<---, a radiation guard made up of three electrically charged spheres set in a line along the axis of the ship. The center sphere, set close or even attached to the crew module, would be positively charged, while two outrigger spheres on either side would carry a negative charge. Together, the combination should be enough to repel both high-energy protons and electrons that would otherwise penetrate a spacecraft."
*Also discusses spacesuit issues (radiation; lack of Marsian protective magnetic field; weight/bulk; sandstorm protection).
--Cindy
We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...
--John Sladek (The New Apocrypha)
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#5 2004-05-27 11:32:24
- Ian Flint
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- From: Colorado
- Registered: 2003-09-24
- Posts: 437
Re: Radiation dangers - Recent solar flares
I don't understand much about radiation but...
Looking at Zubrin's estimates from "Case for Mars" he averaged three of the worst solar flares in recent history including the one from 1972 which had an intensity of 14,000 rems (according to the above story). So, the average he uses could have been about 10,000 rems. (He didn't give a number.) The 90,000 rems mentioned in the story (I hope these numbers are factual) is only 9 times more intense than Zubrin's average. He got the rem dosage in the shelter down to 8 rems using 35 grams/ square cm of supplies as shielding. (Not even enough to produce radiation sickness.)
Now here is my question -- Is radiation shielding linear? If it is then to stay under the 75 rem limit (signs of radiation sickness appear above 75 rems.) there need be NO CHANGES whatsoever to Zubrin's design. 75 rem / 8 rem (shelter) = 9.375. The shelter could handle 93,750 rems. Now this is all based on my assumption that radiation shielding is a linear function.
So, either nobody knows what they are talking about or I'm an idiot. 
Someone please enlighten me.
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#6 2004-05-27 21:41:55
Re: Radiation dangers - Recent solar flares
I think there are a places in *The Case for Mars* where he gives shielding thickness and dosages, and doesn't look to me like doubled thickness halves the dosage. So I don't think there is a direct relationship, but who knows what the relationship is.
-- RobS
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#7 2004-05-28 06:57:52
- bolbuyk
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- From: Utrecht, Netherlands
- Registered: 2004-04-07
- Posts: 178
Re: Radiation dangers - Recent solar flares
This depends on the kind of radiation, also.
I don't know the formula's, but I'm nearly sure it's not linear.
About the solar flares. As far as I know, but reliable information is rather hard to get, with a quiet sun, about half of the radiation is from deep-space sources (Nova's eg) and half is from the Sun. We should have to protect the whole ship from this radiation, because this radiation comes from all angles. For Solar Flares, radiation is required in just one direction: So use propellant for this. When you have a hydrogen-rich fuel, it's an excellent kind of protection.
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#8 2004-05-28 07:31:35
- Palomar
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- From: USA
- Registered: 2002-05-30
- Posts: 9,734
Re: Radiation dangers - Recent solar flares
*The article I quoted above (you already know about this plan...but I have a question):
"Spacecraft designers may also use a ship's own cryogenic fluids as a radiation screen by arranging the cargo tanks containing them around crew compartments.
'In most [mission] scenarios, you need liquid hydrogen for fuel and you need water,' explained Richard Wilkins, director of NASA's Center for Applied Radiation Research at Prairie View A & M University in Texas, conducting one study into liquid shield approaches. 'And these are all considered materials that are particularly good for cosmic ray shielding.'"
*But what about shielding if the spaceship is *nuclear* powered?
(Maybe it's been discussed here before, but I don't recall)
--Cindy
We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...
--John Sladek (The New Apocrypha)
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#9 2004-05-28 08:21:54
- GCNRevenger
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- From: Earth
- Registered: 2003-10-14
- Posts: 6,056
Re: Radiation dangers - Recent solar flares
A nuclear powerplant will be easy to shield against, they do it on submarines all the time with fairly light-weight blocks of plastic, I imagine spiked with Boron. Beryllium Oxide works pretty well too. You could also reduce the dose further by pumping some drinking water into a tank between you and the reactor, but ultimatly I don't think thats a big problem. The Boeing design had the reactor on the far end of a long truss and possibly LH2 tanks in between.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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