Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Jan 4, 2006 11:34:59 GMT -4
Neutrons can be very damaging and can alter the properties of the material they are bombarding. Yes, in extreme cases, neutrons can cause a chunk of the appropriate material to change its properties quite rapidly, become extremely hot, create an explosion that destroys a large part of a city, makes a nice mushroom cloud, etc.... Very funny, but that's not what I was referring to. Of course neutrons can trigger nuclear fission, but most elements are not fissionable. In some cases neutrons will be absorbed into the nuclei, thus changing the isotope. I just found the following Web pages that give a nice explanation: hps.org/publicinformation/ate/q609.htmlhps.org/publicinformation/ate/q2877.html
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Post by PhantomWolf on Jan 4, 2006 12:07:10 GMT -4
Actually referancing a Solar Flare X-event to a Hurricane isn't that bad an anology. We know that the Gulf of Mexico gets several hurricanes a year, and we know that the odds are that you're likely to be dead if you get caught out in a fishing boat in one. Using the same logic as the Hoax proponents do, it's impossible for anyone to go out fishing in the Gulf of Mexico because they'd be killed by a hurricane.
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Jan 4, 2006 12:15:10 GMT -4
After looking over the Health Physics Society web page, I've found some really good general information about radiation. If you're interested in learning more, the following pages should really help: Radiation BasicsRadiation EffectsAnd the following page specifically discusses lead garments: Lead Garments (Aprons, Gloves, etc.)I found the following Q&A particularly interesting:
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Post by iamspartacus on Jan 4, 2006 13:13:40 GMT -4
Actually referancing a Solar Flare X-event to a Hurricane isn't that bad an anology. We know that the Gulf of Mexico gets several hurricanes a year, and we know that the odds are that you're likely to be dead if you get caught out in a fishing boat in one. Using the same logic as the Hoax proponents do, it's impossible for anyone to go out fishing in the Gulf of Mexico because they'd be killed by a hurricane. A good analogy PW. There was one notable massive solar flare during the Apollo era on August 2 1972 and lasted for 10 days. This occurred between A16's return and before A17's flight. This would have caused problems to the Apollo crews should they have been caught in it but they weren't despite what the HBs say. The following link tells you more about it: science.nasa.gov/headlines/y2005/27jan_solarflares.htm
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Post by Retrograde on Jan 4, 2006 14:02:46 GMT -4
Very funny, but that's not what I was referring to. Of course neutrons can trigger nuclear fission, but most elements are not fissionable. In some cases neutrons will be absorbed into the nuclei, thus changing the isotope. Yes, I understood. Sorry to lead the discussion astray On a different note, though, is there any predictability to solar flares? (I suppose even if there is, it's probably not good for the length of time taken by, for example, a mission to Mars...) N
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Post by JayUtah on Jan 4, 2006 14:13:45 GMT -4
That depends on what definition of prediction interests you.
If you want to know when the next X-class flare will happen, I can't possibly tell you.
But if you want to know the probability of an X-class solar event happening during the period 1 February to 15 February 2006, we can work that out for you. It's still a probability, of course, but it's useful in predicting whether you want to go undertake a space mission during that period.
And by observing various parameters of solar activity we can get up to 18 hours' warning of an impending event.
It's not unlike predicting terrestrial weather. On what day will our next rainstorm in Utah happen? Haven't the faintest idea. What are the chances of rain in Utah between 1 Feb. and 15 Feb.? Historical data give us a basis for computing a probability. Will it rain today? Well, if the sky is cloudy and threatening, better take and umbrella. If it's clear and sunny, don't worry about it.
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Post by Retrograde on Jan 4, 2006 14:15:41 GMT -4
So if an HB tells you you need a lead suit to survive on the Moon ask him which type of radiation he has in mind (electromag or particulate, see if he knows the difference). Ask him how strong he thinks it is up there (make sure he gives you a measurement with units and a verifiable source for his information). He won’t of course, they never do! No, definitely not, the response will likely be along the lines of You don't need to be a scientist, it's just common sense, we need big concrete walls around nuclear power plants, how can a little space suit protect the astronaut. Most of these guys argue that the public is stupid and brainwashed anyway, which makes their appeal to common sense a little, let's say, odd...
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Post by Retrograde on Jan 4, 2006 14:23:38 GMT -4
That depends on what definition of prediction interests you. I mean prediction in the sense that, conditional on things which I can observe at this time, the probability of a solar flare within the next X units of time is greater or less than the unconditional probability. Of course, even then, it might be of limited usefulness, if you can observe something that tells you the probability of a flare within an interval of time is 0.0101 instead of the normal 0.01, that's not particularly helpful... From your subsequent comments, though, I am guessing that your probability in this case would be the same if the period were 9 October to 23 October 2017, correct? This is more what I had in mind, but 18 hours isn't much. If they're suiting up and getting ready for launch, you can stop them, but if they're already gone, oh well... Thanks.
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Post by nomuse on Jan 4, 2006 16:03:11 GMT -4
Not to confuse the issue, but during a thread a few months back I got rather familiar with the gamma-radiation-from-lunar-surface thing. The mechanism is -- roughly! -- that high-energy cosmic ray photons strike atoms in the top cm of lunar soil, knocking loose neutrons which are mostly recaptured by that same soil. The result is a bit of neutron flux, and a fair amount of gamma; one photon for each emmision or capture event.
By "fair amount" I must qualify that it is detectable -- not that it constitutes a major health hazard!
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Post by JayUtah on Jan 4, 2006 17:03:23 GMT -4
From your subsequent comments, though, I am guessing that your probability in this case would be the same if the period were 9 October to 23 October 2017, correct?
If you're referring to the 11-year solar cycle by choosing 2017, then that's a defensible statement. We expect that the probability of a solar event at any two congruent points in the solar cycle will be roughly equal.
This is more what I had in mind, but 18 hours isn't much.
No, it isn't. But if you're on the lunar surface that's enough time to get back to the LM, take off, and rendezvous with the heavier and more protective CSM. You'll be better protected in the CSM in lunar orbit than on the surface in a suit or the LM. There are, of course, certain phases the mission such as translunar and transearth coasts that don't offer many contingency options.
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Jan 4, 2006 18:05:37 GMT -4
I was just skimming over this thread and I was struck by the stark contrast between the responses the members of this forum gave to Powermac’s questions versus the typical response one receives when asking the hoax merchants a question. Here everyone was knowledgeable about the subject, happy to help, and provided detailed explanations. Contrast this with Jason Thompson’s recent encounter with Bart Sibrel: -------------------- JT: At what time did the Russians hold a five-to-one superiority over the Americans in manned hours in space as claimed on your Web site? BS: It was prior to Apollo. JT: Does your figure include Project Gemini? BS: Yes. JT: I've found information about Gemini that gives flight durations and the project gave NASA over 1000 hours of space flight under its belt. Did Russia really have over 5000 hours and, if so, what is your source for this information? BS: It was from a promotional video from the Kennedy or Johnson administration aimed at producing interest in the necessity of bridging the space gap between America and Russia. I borrowed the video so I’m unable to provide the title. JT: How can you be sure the 5:1 figure still applied by the time of Apollo since you can't recall when the original quote was made on the borrowed video? BS: You’ll have to take that up with the man who made the original quote. However, may I suggest you watch the smoking gun footage in my video A Funny Thing Happened On The Way To The Moon. -------------------- Sibrel provides only the sparsest of answers, he assumes no responsibility for the accuracy of his claims, and when put on the spot he evades the question, switches subjects, and gives a sales pitch for his video.
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Post by Retrograde on Jan 4, 2006 18:17:33 GMT -4
From your subsequent comments, though, I am guessing that your probability in this case would be the same if the period were 9 October to 23 October 2017, correct?If you're referring to the 11-year solar cycle by choosing 2017, then that's a defensible statement. We expect that the probability of a solar event at any two congruent points in the solar cycle will be roughly equal. Um, yes, that's what I meant. It certainly wasn't the case that I just picked a date at random, and happened to pick one that coincides with the solar flare cycle, no, that's not what happened at all, I'm surprised anyone would even think that's what happened OK, so we have long-term cyclicality, which presumably can reduce risk but might require years of waiting, and very short-term predictability, which might help some of the time, but won't others. So it sounds to me like, barring some breakthroughs in ability to forecast flares, there isn't a whole lot that can be done to avoid these things, other than a) being lucky, or b) appropriate shielding. Sound right? Thanks again.
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lenbrazil
Saturn
Now there's a man with an open mind - you can feel the breeze from here!
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Post by lenbrazil on Jan 4, 2006 19:30:04 GMT -4
How much is distance a factor? I assume most longer trips would be away from the Sun. If a manned craft was close to Jupiter would it be in less danger than if it was landing on the moon?
BTW How long would it take using current technology to reach Jupiter? Is there any technology under development that might significantly reduce travel time in space?
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Post by papageno on Jan 4, 2006 19:55:12 GMT -4
In some cases neutrons will be absorbed into the nuclei, thus changing the isotope. For a while I used in my experiments Germanium crystals that were doped by having Germanium isotopes transmute after exposure to neutrons from a nuclear reactor (keyword: neutron transmutation doping). By the way, at that time I was working in Germany. ;D
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Post by JayUtah on Jan 4, 2006 20:07:58 GMT -4
How much is distance a factor?
Ambient radiation flux obeys the inverse square law. However, keep in mind that as solar ambient decreases, galactic cosmic radiation increases. (You can't win for losing.)
Many solar events (e.g., coronal mass ejections) are directional. If they miss you altogether, how lucky you are. However, they tend to disperse with distance as well, something approaching an inverse square relationship, but with significant lesser-order effects. Think: shotgun blast.
I assume most longer trips would be away from the Sun.
A reasonable assumption. No manned missions to Venus or Mercury are in the works. Low-energy transfers to outer planets won't get any closer to the sun than the Earth already is.
If a manned craft was close to Jupiter would it be in less danger than if it was landing on the moon?
No, because Jupiter is itself a source of considerable radiation.
BTW How long would it take using current technology to reach Jupiter?
On the order of years, depending on launch date and therefore relative planetary positioning.
Is there any technology under development that might significantly reduce travel time in space?
For manned missions, not really. We are working toward ever-more-powerful propulsion, but at a certain point the human organism's tolerance becomes the limiting factor. Given that there doesn't seem to be much promise in higher-energy transfers, the research is being directed toward crew duration and equipment longevity.
This is where the ISS starts pulling its mass. We can test equipment and methods for manned longevity and failure characteristics in a space environment without having to undertake a mission. We often complain about being limited to Earth orbit, but you can simulate years in space on a trans-Jupiter mission that way without actually having to try to go to Jupiter.
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