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SLF:JAQ SFDJS
2007-Aug-04, 01:23 AM
How did they know during Apollo how much radiation shielding was needed for their spacecrafts and their space suits? They are not even sure today how much shielding they will need on the return to the moon. I've read here that the Apollo astronauts were not in the Van Allen belts very long so they did not receive much exposure. But on the moon which is radioactive they were exposed to cosmic rays, solar radiation, x-rays, gamma rays, beta rays, protons, neutrons for days. Why didn't any of the Apollo astranouts get sick from the radiation?

Moose
2007-Aug-04, 01:32 AM
You should read this (http://www.clavius.org/envradintro.html) page and this (http://www.clavius.org/envrad.html) page for about 95% of the answer. The rest of the answer is that Apollo wasn't the first object to enter the Van Allen belts. I can't remember, offhand, the name of the probe, but I'm pretty sure I remember Jay mentioning it in the Van Allen Belt page somewhere.

JayUtah
2007-Aug-04, 01:46 AM
How did they know during Apollo how much radiation shielding was needed for their spacecrafts and their space suits?

Because they had been studying it continuously for nearly a decade beginning with Explorer I.

They are not even sure today how much shielding they will need on the return to the moon.

Of course they are. They just don't know yet how to reconcile it with other mission requirements and constraints. If I know how far it is to Las Vegas, but I don't know how exactly I'm going to get there, I can still tell everyone that "my getting to Las Vegas will be a problem," without intending that to mean I don't know what the goal is.

But on the moon which is radioactive...

That's news to astrophysicists.

...they were exposed to cosmic rays, solar radiation, x-rays, gamma rays, beta rays, protons, neutrons for days.

I hate to alarm you, but you're being exposed to those exact same hazards right now, as well as dozens of known carcinogens.

Why didn't any of the Apollo astranouts get sick from the radiation?

Because there wasn't as much radiation as conspiracy theorists say. A better question is why the world's astrophysicists don't seem surprised at the astronauts' general good health.

OneHotJupiter
2007-Aug-04, 02:34 AM
I'd say better than 'general' good health. Nine out of twelve men that walked on the moon are still living and one of the deceased was in great health when an accident claimed his life , that almost ALL of them still live and breathe is a little surprising to me. Not that I'm complaining (I love those guys)

01101001
2007-Aug-04, 03:02 AM
The rest of the answer is that Apollo wasn't the first object to enter the Van Allen belts.

Wikipedia: Van Allen radiation belt (http://en.wikipedia.org/wiki/Van_Allen_radiation_belt)


The presence of a radiation belt had been proposed by Nicholas Christofilos prior to the Space Age and was confirmed by the Explorer I on January 31, 1958, and Explorer III missions, under Dr.James Van Allen at the University of Iowa. The trapped radiation was first mapped out by Sputnik 3, Explorer IV, Pioneer III and Luna 1.

Daryl71
2007-Aug-04, 03:06 AM
But on the moon which is radioactive

Last time I checked, everything emits radiation, even if it's only an infinitesimally small amount. It's not like the Moon's some sort of cosmic radiation sponge, and glows green during the daytime.

The Backroad Astronomer
2007-Aug-04, 03:07 AM
It is the duration of exposure, intensity, and type of radition that matters.
(this the thrid attempt to post this, the last two tries the power was knocked by lighting.)

Van Rijn
2007-Aug-04, 05:03 AM
How did they know during Apollo how much radiation shielding was needed for their spacecrafts and their space suits? They are not even sure today how much shielding they will need on the return to the moon.


If they want to go back for a short visit, like the Apollo flights, they can have pretty much the same shielding. If they want to go back and stay there a bit longer, they'll need more shielding. If they want to stay long term, they'll have to have even more shielding, and prepare for the occasional solar storm.


But on the moon which is radioactive


Guess what? So are you. For instance, the potassium 40 (http://www.orau.org/ptp/collection/consumer%20products/potassiumgeneralinfo.htm) in you accounts for a significant portion of your yearly radiation dosage. It's meaningless to say something is radioactive unless you quantify it. Pretty much everything is a little radioactive. The surface of the moon is radioactive in the same sense as you, a chunk of dirt, or ocean water is. That is to say: Not very.



they were exposed to cosmic rays, solar radiation, x-rays, gamma rays, beta rays, protons, neutrons for days. Why didn't any of the Apollo astranouts get sick from the radiation?

Because there wasn't anywhere near enough radiation to cause radiation sickness. There wasn't even enough to significantly increase their chances of developing cancer.

Jason Thompson
2007-Aug-04, 09:08 AM
How did they know during Apollo how much radiation shielding was needed for their spacecrafts and their space suits?

Because, believe it or not, they actually did some research on the subject before they sent men there. The Moon was studied in depth, as was the space environment. Explorer satellites, Lunar Orbiter, Surveyor, Ranger, Russian Luna probes, even the Mercury and Gemini flights had radiation dosimeters.


They are not even sure today how much shielding they will need on the return to the moon.

The planned lunar missions are long duration flights. They have totally different radiation shielding requirements from the short Apollo missions. They know how much shielding they will need. They're just not sure the best way to go about it without compromising the rest of the flight too badly.


I've read here that the Apollo astronauts were not in the Van Allen belts very long so they did not receive much exposure. But on the moon which is radioactive they were exposed to cosmic rays, solar radiation, x-rays, gamma rays, beta rays, protons, neutrons for days. Why didn't any of the Apollo astranouts get sick from the radiation?

What is your source for claiming the Moon is radioactive? How radioactive is it? How does the radiaition exposure there differ from the radiation exposure here? Numbers are required, or else you are just handwaving.

Maksutov
2007-Aug-04, 09:38 AM
You know, I'm getting really disappointed by the decline in quality (if such a thing were possible) in the HB claims over the last few years. For example, the OP didn't even mention alpha particles.

Guess they're running out of original material, which is underscored by the constant recycling of useless, worn-out, old HB claims.

http://www.cosgan.de/images/smilie/muede/d045.gif

Swift
2007-Aug-04, 03:39 PM
You know, I'm getting really disappointed by the decline in quality (if such a thing were possible) in the HB claims over the last few years. For example, the OP didn't even mention alpha particles.

Guess they're running out of original material, which is underscored by the constant recycling of useless, worn-out, old HB claims.

http://www.cosgan.de/images/smilie/muede/d045.gif
Which is exactly why we have to go back to the moon and on to Mars, to get more material for the HBers! ;)

Tucson_Tim
2007-Aug-04, 03:44 PM
You guys shouldn't waste your time responding. GHGF:TTHG:SFGG (or whatever her ID is) almost never responds to the answers.

R.A.F.
2007-Aug-04, 03:46 PM
SLF:JAQ SFDJS...other than the OP, will you be participating in this thread??

Just curious...

Drbuzz0
2007-Aug-04, 04:27 PM
It is the duration of exposure, intensity, and type of radition that matters.
(this the thrid attempt to post this, the last two tries the power was knocked by lighting.)

Absolutely correct. The type of radiation was, at least in part, high energy particles, which would be somewhat attenuated or blocked by the spacecraft and space suits. The duration during the pass through the van allen belts especially was very short. The times of the flights were not during sun storms or other hazardous times.

The amount of radiation the astronauts were exposed to was relatively small, all things considered. It might be equivalent to getting a couple of x-rays and then taking a trans-continental flight.

In theory, any radiation exposure will increase the chances of cancer because it can cause genetic damage. In practice that small an amount is unlikely to have enough effect to really notice any increased probability, especially with such a small group. And it would be far too little for any acute symptoms of radiation sickness.

sts60
2007-Aug-04, 04:49 PM
SLF:JAQ SFDJS wrote: <another seagull post>


GoAT.

JayUtah
2007-Aug-04, 05:25 PM
The general strategy for Apollo shield design was, "Build the ship as if there was no special need for radiation sheilding." Then see how much shielding you got just from the normal structure, skin, etc. If there are any serious problems, solve them at that place in the design, such as adding polymer or fibrous panels or simply using a thicker skin material. In other words, radiation shielding was not a primary design criterion. It did not "drive" the design. The CM was not intended to survive "hard" radiation, nor was any expected during Apollo missions. The more dangerous solar flares are not common enough to worry about. So you get enough shielding incidentally from the ordinary construction.

However for long-duration missions that won't work. Radiation mitigation is a primary design criterion, so we can't just re-use Apollo designs and strategies. That doesn't mean we "still don't know how to do it." I means we have a different problem now than we had. Engineers aren't put off by problems that haven't been solved yet: that's what engineers like.

Bob B.
2007-Aug-04, 06:40 PM
You guys shouldn't waste your time responding. GHGF:TTHG:SFGG (or whatever her ID is) almost never responds to the answers.

That is soooo rude.

I had the same thing happen to me in this thread (http://www.bautforum.com/space-exploration/61122-spacecraft-rocket-questions.html). My answers to the OP's questions went ignored because the OP abandoned the thread after about an hour and never returned. If there isn't a forum rule against that, there should be. A person certainly doesn't have to partake in a thread if they don't want to, but if a person starts a thread they ought to be obligated to participate and acknowledge responses. It is just common courtesy.
_

Serenitude
2007-Aug-04, 07:43 PM
I think we have done this poster as discourtesy, and would like to apologize on behalf of BAUT. Although seagull posting is quite common here, it has yet to be even 24 hours. We know little of this person and there real-life obligations. I think we're better than that, as frustrating and useless as the all-too-common seagull postings are.

Edit: Forgot response to OP: You are new, but please remember that you are expected to interact with any threads you create in the ATM or CT section. Otherwise, your posting is taken as "seagull" style, (drop a load of crap and fly off...). It's bad form, and actually bannable if repeated. Please try to keep this in mind, and avoid this appearance.

sts60
2007-Aug-04, 09:07 PM
Well, I am generally pretty willing to give the benefit of the doubt. But the OP in this thread has had several threads with no or minimal followup to his/her original breathless "could it be...?" posts. If SLF:JAQ SFDJS eventually returns this thread and actually participates, rather than merely dropping more unsubstantiated claims or insinuations, I will be happy to apologize.

Obviousman
2007-Aug-04, 09:29 PM
re: the radioactive Moon claim...

I'm guessing that it comes from this:


Out in deep space, radiation comes from all directions. On the Moon, you might expect the ground, at least, to provide some relief, with the solid body of the Moon blocking radiation from below. Not so.

When galactic cosmic rays collide with particles in the lunar surface, they trigger little nuclear reactions that release yet more radiation in the form of neutrons. The lunar surface itself is radioactive!

http://science.nasa.gov/headlines/y2005/08sep_radioactivemoon.htm

(my bolding)

andyschlei
2007-Aug-04, 10:01 PM
However for long-duration missions that won't work. Radiation mitigation is a primary design criterion, so we can't just re-use Apollo designs and strategies. That doesn't mean we "still don't know how to do it." I means we have a different problem now than we had. Engineers aren't put off by problems that haven't been solved yet: that's what engineers like.

I have always wondered if there would be some way to generate a strong local magnetic field to protect astronauts in much the same way Earth's magnetic field protects us. Many books (Red Mars for example) have the travelers hide in the middle of large water tanks. I have not read a sci fi book that used magnetic fields. Imagine a giant MRI in the sky.

Is this even marginally possible?

JayUtah
2007-Aug-04, 11:51 PM
Active shielding was considered as early as the 1960s and is still on the plate, but it requires far more power than our current spacecraft designs can generate. Plus it doesn't work for x-rays or gamma rays. But it remains a valid physical idea whose engineering time hasn't yet come.

Water makes a very good passive shield substance.

SLF:JAQ SFDJS
2007-Aug-05, 12:31 AM
Yes, the Nasa article did state the moon was radioactive. I agree with some of the statements above.

Van Rijn
2007-Aug-05, 12:38 AM
Yes, the Nasa article did state the moon was radioactive.


But do you now understand the context of that statement (which is, at best, an oversimplification)?


I agree with some of the statements above.

What do you disagree with, and why?

SLF:JAQ SFDJS
2007-Aug-05, 12:51 AM
I agree that we are exposed to radiation on Earth but not to the extent the Nasa astronauts would have been on the moon. The moon has been bombarded by solar radiation and cosmic radiation for billions of year. The moons atmosphere offers no protection.

Van Rijn
2007-Aug-05, 01:37 AM
I agree that we are exposed to radiation on Earth but not to the extent the Nasa astronauts would have been on the moon.


Where on the Earth? Exposed for how long on the Earth versus how long on the Moon? For the same amount of time, astronauts on the moon received slightly more radiation than they would from natural sources most places on Earth. But compared to their total dose, on Earth, it was inconsequential. Here's an article on the subject. (http://lsda.jsc.nasa.gov/books/apollo/S2ch3.htm) From there:

Radiation doses measured during Apollo were significantly lower than the yearly average of 5 rem set by the U.S. Atomic Energy Commission for workers who use radioactive materials in factories and institutions across the United States.


The moon has been bombarded by solar radiation and cosmic radiation for billions of year.


But that does not make the surface of the moon significantly radioactive. The quotation Obviousman referred to was discussing secondaries - immediate effects of high energy strikes upon the surface.


The moons atmosphere offers no protection.

The moon has no atmosphere, true. But there has to be radiation first for that to be an issue. And, yes, there was some, but not so much as to cause problems for their short stay.

Count Zero
2007-Aug-05, 02:54 AM
How did they know during Apollo how much radiation shielding was needed for their spacecrafts and their space suits?

Because the US launched more than 40 probes to measure the radiation environment from low Earth orbit to interplanetary space. Here is a partial list:

1958 February 1 - Explorer 1: Perigee: 347 km Apogee: 1,859 km. Discovered radiation belt around Earth.
1958 March 26 - Explorer 3: Perigee: 186 km Apogee: 2,799 km. Radiation & micrometeoroid data.
1958 July 26 - Explorer 4: Perigee: 257 km Apogee: 1,352 km. Mapped project Argus radiation.
1958 October 11 - Pioneer 1: Apogee 113854 km
1958 December 6 - Pioneer 3: Apogee 102,332 km. Discovered 2nd radiation belt
1959 February 17 - Vanguard 2: Perigee: 557 km Apogee: 3,049 km. Studied magnetosphere.
1959 March 3 - Pioneer 4: Lunar fly-by, Solar orbit. Measured radiation near the Moon.
1959 August 7 - Explorer 6: Perigee: 245 km Apogee: 42,400 km. First Earth photo; radiation data.
1959 September 18 - Vanguard 3: Perigee: 512 km Apogee: 3,413 km. Radiation & micrometeoroid data.
1959 October 13 - Explorer 7: Perigee: 523 km Apogee: 857 km. Magnetic field and solar flare data.
1960 November 3 - Explorer 8: Perigee: 394 km Apogee: 1,331 km. Ionospheric research.
1960 March 11 - Pioneer 5: Solar orbit. Mapped magnetic fields in interplanetary space.
1961 March 25 - Explorer 10: Perigee: 221 km Apogee: 181,100 km. Magnetic field data.
1961 April 27 - Explorer 11: Perigee: 480 km Apogee: 1,458 km. Gamma ray data.
1961 June 29 - Injun 1: Perigee: 869 km Apogee: 992 km. Radiation data.
1961 August 16 - Explorer 12: Perigee: 790 km Apogee: 76,620 km. Radiation and solar wind data.
1962 August 27 - Mariner 2: Solar orbit, Venus fly-by. Returned radiation and solar wind data.
1962 October 2 - Explorer 14: Perigee: 2,558 km Apogee: 96,229 km. Magnetosphere studies.
1962 October 27 - Explorer 15: Perigee: 306 km Apogee: 17,610 km. Radiation decay data.
1962 December 13 - Injun 3: Perigee: 240 km Apogee: 2,406 km. Radiation decay data.
1963 November 27 - Explorer 18: Perigee: 192 km Apogee: 197,616 km. Interplanetary radiation data.
1964 August 25 - Explorer 20: Perigee: 857 km Apogee: 999 km. Ionospheric research.
1964 October 4 - Explorer 21: Perigee: 191 km Apogee: 95,590 km. Magnetic field, radiation data.
1964 October 10 - Explorer 22: Perigee: 872 km Apogee: 1,053 km. Ionospheric and geodetic data.
1964 November 21 - Explorer 25: Perigee: 526 km Apogee: 2,319 km. Radiation data.
1964 November 28 - Mariner 4: Solar orbit, Mars fly-by. Returned radiation and solar wind data.
1964 December 21 - Explorer 26: Perigee: 284 km Apogee: 10,043 km. Radiation and solar wind data.
1965 April 29 - Explorer 27: Perigee: 932 km Apogee: 1,309 km. Ionospheric and geodetic data.
1965 May 29 - Explorer 28: Perigee: 229 km Apogee: 261,206 km. Magnetic field, radiation data.
1965 November 19 - Explorer 30: Perigee: 671 km Apogee: 856 km. Solar radiation data.
1965 November 29 - Explorer 31: Perigee: 505 km Apogee: 2,833 km. Ionospheric research.
1965 December 16 - Pioneer 6: Solar orbit. Studied Solar wind and Sun’s magnetic field.
1966 July 1 - Explorer 33: Perigee: 265,679 km Apogee: 480,762 km. Magnetic field, radiation data.
1966 August 17 - Pioneer 7: Solar orbit. Monitored Solar wind and cosmic rays.
1967 May 24 - Explorer 34: Perigee: 242 km Apogee: 214,379 km. Radiation, magnetic field data.
1967 June 14 - Mariner 5: Solar orbit, Venus fly-by. Returned radiation and solar wind data.
1967 July 19 - Explorer 35: Lunar orbit, Perigee: 484 km Apogee: 675 km. Earth magnetic tail measurements.
1967 December 13 - Pioneer 8: Solar orbit. Returned Solar radiation data.
1968 March 5 - Explorer 37: Perigee: 353 km Apogee: 433 km. Solar radiation data.
1968 August 8 - Explorer 40: Perigee: 679 km Apogee: 2,489 km. Radiation data.
1968 November 8 - Pioneer 9: Solar orbit. Returned Solar radiation data.
1969 June 21 - Explorer 41: Perigee: 80,374 km Apogee: 98,159 km. Cislunar radiation data.
1971 March 13 - Explorer 43: Perigee: 1,845 km Apogee: 203,130 km. Earth magnetosphere research.
1971 July 8 - Explorer 44: Perigee: 433 km (269 mi). Apogee: 632 km. Solar radiation data.
1971 November 15 - Explorer 45: Perigee: 272 km Apogee: 18,149 km. Studied magnetosphere, energetic particles.
1972 September 23 - Explorer 47: Perigee: 201,100 km Apogee: 235,600 km. Investigated cislunar radiation, Earth's magnetosphere, interplanetary magnetic field.

JayUtah
2007-Aug-05, 04:13 AM
Yes, the Nasa article did state the moon was radioactive.

About as radioactive as a baked potato. The secondary radiation the article refers to is barely detectable.

JayUtah
2007-Aug-05, 04:21 AM
I agree that we are exposed to radiation on Earth but not to the extent the Nasa astronauts would have been on the moon.

Do you know the extent? If I asked you for a number representing mean ambient radiation on the lunar surface, could you give me one?

If you agree that radiation occurs in different amounts, and that not all amounts are immediately harmful, then you should realize that you can't just wave your hands about "radiation" without knowing how much is there.

The moon has been bombarded by solar radiation and cosmic radiation for billions of year.

That doesn't make it radioactive. Secondary radiation doesn't build up. It works like a white shirt fluorescing under ultraviolet light. You get the purple glow as long as the light is on. When you turn off the light, the shirt doesn't keep glowing. Contrary to what you see on television, exposing something to radiation doesn't generally make it radioactive itself.

The moons atmosphere offers no protection.

No one said it did. What kind of protection do you think was needed, and how do you know that?

Jason Thompson
2007-Aug-05, 09:57 AM
I agree that we are exposed to radiation on Earth but not to the extent the Nasa astronauts would have been on the moon.

That is a quantitative statement. Please provide numbers to back it up. After all, ten times a very small number is still a very small number.


The moon has been bombarded by solar radiation and cosmic radiation for billions of year.

What kind, how long, and how much difference does it make. Being bombarded with radiation for billions of years doesn't make an object radioactove.

Occam
2007-Aug-05, 10:59 AM
Seriously guys, how do you find the strength to carry on under the onslaught of such wilful ignorance?

Ronald Brak
2007-Aug-05, 11:14 AM
Well I know scientists have said the moon is not radioactive and levels of radioactivity have been directly measured on the moons surface, so that's pretty convincing. However, on the other hand, in one episode of Buffy the Vampire Slayer they said that anything that has been in space can be tracked because it gives of cosmic rays, a type of radiation, so in fairness I'd have to say the jury is still out on this issue.

Dave J
2007-Aug-05, 02:36 PM
Well I know scientists have said the moon is not radioactive and levels of radioactivity have been directly measured on the moons surface, so that's pretty convincing. However, on the other hand, in one episode of Buffy the Vampire Slayer they said that anything that has been in space can be tracked because it gives of cosmic rays, a type of radiation, so in fairness I'd have to say the jury is still out on this issue.
I'm looking for the smiley face or wink icon here...don't see it...

R.A.F.
2007-Aug-05, 03:38 PM
Well I know scientists have said the moon is not radioactive and levels of radioactivity have been directly measured on the moons surface...

Something I don't understand..."scientists" say the Moon is not radioactive, yet radioactivity has been measured on the Moons surface by, I assume, these same "scientists"???

That doesn't make sense...


...on the other hand, in one episode of Buffy the Vampire Slayer they said that anything that has been in space can be tracked because it gives of cosmic rays, a type of radiation, so in fairness I'd have to say the jury is still out on this issue.

The "jury is out" because of something you saw on Buffy??

That really doesn't make sense.

Laguna
2007-Aug-05, 04:39 PM
[...] However, on the other hand, in one episode of Buffy the Vampire Slayer they said [...]
You meant that as a joke, did you?
I seriously hope so...

Joe Durnavich
2007-Aug-05, 05:17 PM
Oh, come on folks! I hope this is not a sign that the Internet has caused us to require a smiley to know when someone is joking.

R.A.F.
2007-Aug-05, 06:28 PM
I think you're right, Joe...my apologies....

ineluki
2007-Aug-05, 08:07 PM
Oh, come on folks! I hope this is not a sign that the Internet has caused us to require a smiley to know when someone is joking.

That comes from spending too much time with conspircy theorists, even the most outlandish claim could still be their serious opinion.

However, I don't think a CT who really believes this, wouldn't have survived for more than 3000 posts on this board.

SLF:JAQ SFDJS
2007-Aug-07, 07:50 PM
This is one of the sources for the radiaton exposure on and traveling to the moon.

http://video.csupomona.edu/NASA/DestinationTomorrow25-035.asx

A video about the problems of radiation returning to the moon and on to Mars. Pretty much anywhere outside the protection of the Earth's magnetosphere. Funny how they talk about finding a material to achieve this feet as using metal would be too heavy and thick to lug into space. Don't explain how Apollo did it though and it seams like they are starting from scratch.

Grashtel
2007-Aug-07, 08:40 PM
This is one of the sources for the radiaton exposure on and traveling to the moon.

http://video.csupomona.edu/NASA/DestinationTomorrow25-035.asx

A video about the problems of radiation returning to the moon and on to Mars. Pretty much anywhere outside the protection of the Earth's magnetosphere. Funny how they talk about finding a material to achieve this feet as using metal would be too heavy and thick to lug into space. Don't explain how Apollo did it though and it seams like they are starting from scratch.
The Apollo missions were much shorter duration than a Mars mission and the new Moon missions are planned to be, radiation exposure that is acceptable for ~10 days is a major problem for an 18 month one, particularly as the 18 month one is likely to get hit by a major solar event unlike Apollo.

JayUtah
2007-Aug-07, 08:42 PM
Long-duration missions and short-duration (e.g., Apollo) missions take fundamentally different approaches to radiation protection. What worked for Apollo won't necessarily work for long stays on the surface or long cruises to Mars. So in some ways new missions are indeed starting from scratch.

The Moon itself is not radioactive. But someone on the lunar surface is exposed to hazards from cosmic and solar radiation, and to small secondary effects.

Lethargic
2007-Aug-07, 10:41 PM
According to table 2 on http://lsda.jsc.nasa.gov/books/apollo/S2ch3.htm the dose received by the apollo astronauts was between only .16 and 1.14 rads.

Where's the problem?

Kelfazin
2007-Aug-07, 11:08 PM
This is one of the sources for the radiaton exposure on and traveling to the moon.

http://video.csupomona.edu/NASA/DestinationTomorrow25-035.asx

A video about the problems of radiation returning to the moon and on to Mars. Pretty much anywhere outside the protection of the Earth's magnetosphere. Funny how they talk about finding a material to achieve this feet as using metal would be too heavy and thick to lug into space. Don't explain how Apollo did it though and it seams like they are starting from scratch.

Are you planning on answering any of the questions presented to you on this thread?

Van Rijn
2007-Aug-08, 12:34 AM
Are you planning on answering any of the questions presented to you on this thread?

What are the outstanding questions at this point?

The key issues for me are: Does SLF now understand that the Apollo astronauts did not receive large radiation doses? Does he understand the fundamentals as to why?

Kelfazin
2007-Aug-08, 12:49 AM
What are the outstanding questions at this point?

Here's what I see as outstanding:

What is your source for claiming the Moon is radioactive? How radioactive is it? How does the radiaition exposure there differ from the radiation exposure here?


Yes, the Nasa article did state the moon was radioactive.
But do you now understand the context of that statement (which is, at best, an oversimplification)?


I agree that we are exposed to radiation on Earth but not to the extent the Nasa astronauts would have been on the moon.
Where on the Earth? Exposed for how long on the Earth versus how long on the Moon?

I agree that we are exposed to radiation on Earth but not to the extent the Nasa astronauts would have been on the moon.
Do you know the extent? If I asked you for a number representing mean ambient radiation on the lunar surface, could you give me one?
The moons atmosphere offers no protection.
No one said it did. What kind of protection do you think was needed, and how do you know that?



I agree that we are exposed to radiation on Earth but not to the extent the Nasa astronauts would have been on the moon.
That is a quantitative statement. Please provide numbers to back it up. After all, ten times a very small number is still a very small number.

Quote:

The moon has been bombarded by solar radiation and cosmic radiation for billions of year.
What kind, how long, and how much difference does it make. Being bombarded with radiation for billions of years doesn't make an object radioactove.

And now you can add to that:


The key issues for me are: Does SLF now understand that the Apollo astronauts did not receive large radiation doses? Does he understand the fundamentals as to why?

JayUtah
2007-Aug-08, 12:49 AM
He owes us a quantitative argument for, a clarification of, or a retraction of the insinuation that the Apollo astronauts would have been exposed to a level of radiation consistent with causing illness that should have manifested itself by now.

Jim
2007-Aug-08, 02:55 AM
SLF:JAQ SFDJS;1044557, you have opened yet another thread while there are questions pending in this thread.

This is becoming too much of a habit with you. Before you continue with your new thread, please address the questions raised here (http://www.bautforum.com/conspiracy-theories/62955-apollo-radiation-2.html#post1044505).

PhantomWolf
2007-Aug-08, 05:09 AM
According to table 2 on http://lsda.jsc.nasa.gov/books/apollo/S2ch3.htm the dose received by the apollo astronauts was between only .16 and 1.14 rads.

Where's the problem?
Well this is the problem. They were exposed to that in 10 days! They got what most people get in 360 days in just 10. Not imagine what sort of doses the new crews will bwe getting when they spend 30-40 days up there and you'll see the problem, well NASA's one. The HB's have an entirely different problem, but that can't be corrected short of elective surgery I fear.

novaderrik
2007-Aug-08, 06:01 AM
Here's what I see as outstanding:
Quote:
Originally Posted by Jason Thompson View Post
What is your source for claiming the Moon is radioactive? How radioactive is it? How does the radiaition exposure there differ from the radiation exposure here?
Quote:
Originally Posted by Van Rijn View Post
Quote:
Originally Posted by SLF:JAQ SFDJS
Yes, the Nasa article did state the moon was radioactive.
But do you now understand the context of that statement (which is, at best, an oversimplification)?
Quote:
Originally Posted by Van Rijn View Post
Quote:
Originally Posted by SLF:JAQ SFDJS
I agree that we are exposed to radiation on Earth but not to the extent the Nasa astronauts would have been on the moon.
Where on the Earth? Exposed for how long on the Earth versus how long on the Moon?
Quote:
Originally Posted by JayUtah View Post
I agree that we are exposed to radiation on Earth but not to the extent the Nasa astronauts would have been on the moon.
Do you know the extent? If I asked you for a number representing mean ambient radiation on the lunar surface, could you give me one?
The moons atmosphere offers no protection.
No one said it did. What kind of protection do you think was needed, and how do you know that?
Quote:
Originally Posted by Jason Thompson View Post
Quote:
Originally Posted by SLF:JAQ SFDJS
I agree that we are exposed to radiation on Earth but not to the extent the Nasa astronauts would have been on the moon.
That is a quantitative statement. Please provide numbers to back it up. After all, ten times a very small number is still a very small number.

Quote:
Quote:
The moon has been bombarded by solar radiation and cosmic radiation for billions of year.
What kind, how long, and how much difference does it make. Being bombarded with radiation for billions of years doesn't make an object radioactove.
And now you can add to that:

Quote:
Originally Posted by Van Rijn
The key issues for me are: Does SLF now understand that the Apollo astronauts did not receive large radiation doses? Does he understand the fundamentals as to why?


those really are some outstanding questions..
i await some outstanding answers..

Kelfazin
2007-Aug-08, 03:48 PM
A check of SFL's public profile shows they were online this morning, but I guess we can give them the benefit of the doubt, maybe they were just checking the board before heading to work (I know I do that sometimes too). Hopefully answers will be coming soon.

dgavin
2007-Aug-08, 04:07 PM
SLF,

I think you have a bad understanding of what it takes to block radiation.

Here is an experiment you can run at home.

Hold your hand next too (not above) about 12 inches (40cm's) from an buring incadecent lightbulb. You will be able to feel the Infared Radiation from the bulb.

Now hold a single sheet of white paper between your hand and the light bulb. You'll find that thin sheet of paper is it all it takes to block the IR radiation from that bulb.

Now look at X-Ray vests. A thin 1/4 inch (6mm) vest made of lead beads is anought to block the X-Ray from a medical machine. X-Rays are almost as strong as gamma rays.

Cosmic Rays are particle's however not EM Radiation, this makes them even easier to block.

If you were to equate it out compared to X-Ray's, having the same amount of radiation of both, a simple peice of lead foil would suffice for Cosmic Rays as opossed to the 1/4inch sheilding needed for X-Rays.

Jason Thompson
2007-Aug-08, 04:18 PM
Actually, lead would be a terrible material for cosmic rays. Particle radiation such as high energy protons and electrons is best shielded by light metals, plastics or water. In heavy metals such as lead you get secondary radiation actually emitted from the material you are using to block the radiation.

SLF:JAQ SFDJS
2007-Aug-08, 07:24 PM
Nasa.org was my primary source. This is where the claim originated. Nasa- Radiactive moon and Taking a Radioactive Bath - Space Daily.

Dangerously radioactive
More dangerouse environment as a whole on the moon
Yes, oversimplified but accurate
We are exposed for example - solar radiation on Earth. Greater risk on the moon.
In relative terms
Not at moment
Going back to the moon and Mars the mean ambient radiation would not be a smart way to design a spacecraft or suit.
More protection needed
More shielding considering the unkowns that are coming to light since the Apollo missions like the problems of shielding agains cosmic radiation and the extent of neutron radiation scattering at the surface of the moon.
Nasa says the moon is radioactive.

NEOWatcher
2007-Aug-08, 07:31 PM
Nasa.org was my primary source. This is where the claim originated. Nasa- Radiactive moon and Taking a Radioactive Bath - Space Daily.
Link please, so we can see the context.

Besides, Nasa.org has nothing to do with the space agency, and if you go to that site, you get blasted with stuff. Evidence that you may not be citing real examples.

JayUtah
2007-Aug-08, 07:55 PM
Nasa.org was my primary source.

And it was discussed, not that it has anything to do with NASA.

Nasa says the moon is radioactive.

It then went on to explain that it is detectable secondary radiation, which is not at all the same as saying the Moon is radioactive. And we know from other sources the magnitude of that secondary radiation, which is not significant for Apollo missions.

You were asked to provide numerical quantities for your claim or to withdraw your assertion about the supposed hazard to Apollo astronauts. Do you intend to satisfy that request? I do not accept your continued handwaving.

nauthiz
2007-Aug-08, 07:59 PM
Would the chair I'm sitting on and the coffee I'm drinking also have detectable secondary radiation?

NEOWatcher
2007-Aug-08, 08:03 PM
Would the chair I'm sitting on and the coffee I'm drinking also have detectable secondary radiation?
If they have carbon, you can even tell how old they are from the radiation that is detected.
If you're using the canary method? No.

nauthiz
2007-Aug-08, 08:07 PM
If they have carbon, you can even tell how old they are from the radiation that is detected.

:doh:

JimTKirk
2007-Aug-08, 10:21 PM
Nasa.org was my primary source. <snip>

Try www.nasa.gov next time. Having nasa in the URL does not mean it is NASA.:)

PhantomWolf
2007-Aug-08, 10:31 PM
The thing I find the funniest about this sort of topic is that these new sources of radiation are just like earthquakes or meteorites. If you get the stats on the number of earthquakes detected, or meteorites found for each year over the last 50 odd years, you'll see that both have been trending upwards, sometimes by significant amounts. Does that mean we have been having more earthquakes or getting hit by more meteorites? Nope, it means that our ability to detect and report them is getting better and picking up ones we would have missed previously. The reason that we didn't know about the secondary gamma radiation that the moon creates on being hit by cosmic rays is because it so insignificant that the detectors that where sent pre-Apollo just couldn't pick it up. It is only as our tools have gotten so much better and capable of detecting minute amounts of radiation that we have detected it. It's a bit like demanding to know how people could have been drinking the water from the local supply and living because the new spectroscope has now detected that there is 0.0006% Arsenic in it, so everyone who previously drank it should have been poisoned off.

Van Rijn
2007-Aug-09, 12:02 AM
Since the responses are almost impossible to understand without context, I added the questions below. I think I got things mostly right.



What is your source for claiming the Moon is radioactive?
Nasa.org was my primary source. This is where the claim originated. Nasa- Radiactive moon and Taking a Radioactive Bath - Space Daily.

How radioactive is it?
Dangerously radioactive

How does the radiaition exposure there differ from the radiation exposure here?
More dangerouse environment as a whole on the moon

But do you now understand the context of that statement (which is, at best, an oversimplification)?
Yes, oversimplified but accurate

Where on the Earth? Exposed for how long on the Earth versus how long on the Moon?
We are exposed for example - solar radiation on Earth. Greater risk on the moon.

Do you know the extent?
In relative terms

If I asked you for a number representing mean ambient radiation on the lunar surface, could you give me one?
Not at moment

No one said it did. What kind of protection do you think was needed, and how do you know that?
Going back to the moon and Mars the mean ambient radiation would not be a smart way to design a spacecraft or suit.
More protection needed
More shielding considering the unkowns that are coming to light since the Apollo missions like the problems of shielding agains cosmic radiation and the extent of neutron radiation scattering at the surface of the moon.
Nasa says the moon is radioactive.


The key issues for me are: Does SLF now understand that the Apollo astronauts did not receive large radiation doses? Does he understand the fundamentals as to why?

?

SLF:JAQ SFDJS
2007-Aug-09, 02:49 AM
Sorry about that. Yes they were Nasa.gov articles. But I assume you already new that. So is Nasa.gov not a reputable site to obtain information from.

Kelfazin
2007-Aug-09, 03:17 AM
Sorry about that. Yes they were Nasa.gov articles. But I assume you already new that. So is Nasa.gov not a reputable site to obtain information from.

Can you provide actual links to the data you used to make your assertion? The NASA site has a lot of information.

SLF:JAQ SFDJS
2007-Aug-09, 03:33 AM
science.nasa.gov/headlines/y2005/08sep_radioactivemoon.htm

The video link from post #40 Destination Tomorrow is very educational on the radioactivity of the moon and the ionizing radiation that they cannot shield against.

Not from Nasa - Taking A Radioactive Bath On The Moon
http://www.spacedaily.com/news/lunar-05zx.html

Kelfazin
2007-Aug-09, 03:51 AM
science.nasa.gov/headlines/y2005/08sep_radioactivemoon.htm

The information you found on that was refuted in post #27 (http://www.bautforum.com/1042882-post27.html), post #29 (http://www.bautforum.com/1042922-post29.html) , and post #30 (http://www.bautforum.com/1042924-post30.html). Do you have a response to their refutations?


The video link from post #40 Destination Tomorrow is very educational on the radioactivity of the moon and the ionizing radiation that they cannot shield against.

The information in that video was refuted in post #41 (http://www.bautforum.com/1044362-post41.html), and post #42 (http://www.bautforum.com/1044363-post42.html). Do you have a response to their refutations?

JayUtah
2007-Aug-09, 04:07 AM
So is Nasa.gov not a reputable site to obtain information from.

It depends what information you need and how you intend to use it. As a federal agency, NASA is given many roles to play, from research to operations to education. NASA publicists offer a wide array of packaging. On NASA TV, for example, you can see extremely sappy programs meant for basic education of school-aged children and also raw downlinks from ISS and shuttle missions meant for the geeky.

The print and web content runs a similar gamut. Some information is summarized for laymen. Other information is fully detailed. You can't nit-pick the summaries and expect people to take you seriously. I can go to nih.gov or hud.gov and download basic information about health and homebuying, or I can visit those same sites and get detailed findings and recommendations that go into full detail and are expected to be read by professionals. If something in the detailed explanations isn't covered in or appears to contradict a summary, that's simply the nature of summarization.

Blindly referring to the domain name isn't a justification for your misuse of information you found there.

Now on to your other answers.

Dangerously radioactive

You have presented no basis for that judgment. You have the burden to define what "dangerous" means in this context and show what hard data about the lunar surface meets that definition.

More dangerouse environment as a whole on the moon

How much more? "More than here" does not count as "dangerous" in the sense of healt hazards. The point in bringing up radiation levels on Earth was to show that different amounts of radiation exist everywhere, and not all detectable levels are thereby necessarily dangerous. That is, you can't just say "There's radiation" and assume that any amount above zero is dangerous to the point of illness.

So you owe us first a quotation for how much radiation is dangerous and then a measurement of how much there is on the lunar surface.

Yes, oversimplified but accurate

No; that's a contradiction. A simplification may be accurate, but an oversimplification by definition is not; it's a simplification that omits important detail.

Greater risk on the moon.

How much greater? You don't get to say it's more and therefore too dangerous.

[I know the extent] in relative terms

Relative terms are still quantitative. Give us a relative estimate. You're simply begging the question that "more than Earth" is necessarily "dangerous."

If it takes 100 units of radiation to cause sickness, and you get 1 unit of radiation on Earth just by living on it, and you know that some other environment is qualitatively more of a radiation hazard, you know it must give you at least 2 units, but that's not an adequate argument for saying it "must" give you the 100 that would harm you.

You cannot wave your hands and speak in generalities. You must provide a number. And unfortunately you admit you cannot, so you have no argument.

More shielding considering the unkowns that are coming to light since the Apollo missions...

No. You're trying to impose the constraints of one kind of mission upon another, and argue that since the mismatched constraints weren't met, there's something fishy. You can't restrict yourself to such generalities and presume your criticism still has merit.

Neutron scattering on the lunar surface adds negligible exposure for astronauts performing three 6-hour EVAs. The risk of serious damage from cosmic rays was also insignificant for those short missions. It is not irresponsible to ignore negligible risks when you keep the missions short.

For longer missions those considerations become important. 18 hours of exposure to neutron scattering has no biological risk. But if you're on the Moon for six months, it does. We have to be more careful if we're going to undertake missions orders of magnitude longer. Similarly the risk of solar activity was extremely small for Apollo astronauts, but quite high for Mars astronauts and long-term lunar explorers.

If the risk is small, you ignore it. If it's large, you figure out how to mitigate it or neutralize the effect. Those are qualitatively different approaches to a solution. So you can't look at plans being made now and wonder why similar plans weren't made in 1969. You can't say that the Apollo missions were fishy because they weren't planned exactly like different missions we contemplate for the future.

What actual evidence do you have that the known radiation environment was an insurmountable hazard to the Apollo astronauts, keeping in mind that exposure duration dictates the risk?

sts60
2007-Aug-09, 04:20 AM
Sorry about that. Yes they were Nasa.gov articles. But I assume you already new that. So is Nasa.gov not a reputable site to obtain information from.

No. In your previous post (
http://www.bautforum.com/conspiracy-theories/62955-apollo-radiation-2.html#post1045144) you said you were looking at nasa.org:
Nasa.org was my primary source. This is where the claim originated.
Nasa.org is not a NASA site; people were simply responding to your incorrect reference.

science.nasa.gov/headlines/y2005/08sep_radioactivemoon.htm

The video link from post #40 Destination Tomorrow is very educational on the radioactivity of the moon and the ionizing radiation that they cannot shield against.

It's not educational unless you understand the context. The article is discussing long-duration missions, not the brief stays of the Apollo crews.

You are claiming, or at least insinuating, that radiation would have prevented humans from successfully exploring the Moon during the Apollo program. OK, then tell us: what types of radiation did they encounter, for how long? What were the fluxes and energies?

Handwaving is not acceptable. We have a great deal of data from literally dozens of probes prior to Apollo in cislunar space and on the Moon. We have direct radiation dosimetry data gathered by the astronauts themselves. And we have additional direct and indirect data gathered by literally hundreds of other missions since then.

If you wish to dispute this data, kindly describe quantitatively the environment that you think existed and would have proved an insurmountable obstacle to Apollo. References to articles for a popular reading audience do not impress me.

JayUtah
2007-Aug-09, 04:31 AM
I think it's worth emphasizing that the additional steps being taken for longer-duration missions are due mostly to the duration of the missions and not to discoveries of new radiation sources. NASA is not saying, "Look at all the things we didn't know about in 1969; we had better beef up our spacecraft." The 1969 picture of radiation exposure would still have necessitated more rigorous protection for long-duration missions.

Van Rijn
2007-Aug-09, 05:44 AM
science.nasa.gov/headlines/y2005/08sep_radioactivemoon.htm


The second paragraph reads:

"We really need to know more about the radiation environment on the Moon, especially if people will be staying there for more than just a few days," says Harlan Spence, a professor of astronomy at Boston University.

Emphasis added.

I'll repeat my question: Do you now understand that the Apollo astronauts did not receive large doses of radiation? And by "large" that would be in comparison to safety standards for workers in the nuclear industry.

Jim
2007-Aug-09, 01:06 PM
For longer missions those considerations become important. 18 hours of exposure to neutron scattering has no biological risk. But if you're on the Moon for six months, it does. We have to be more careful if we're going to undertake missions orders of magnitude longer. Similarly the risk of solar activity was extremely small for Apollo astronauts, but quite high for Mars astronauts and long-term lunar explorers.

At the risk of oversimplifying, let me put this in a much more familiar context... ultraviolet radiation and a trip to the beach.

If I take my family to the beach and we stay out in the sun with no protection for, say, 20 minutes, then head home, odds are we could get nothing more then slight tans.

However, if we stayed in the sun with no protection all day, we'd probably get very burned.

That doesn't mean we can't go to the beach and stay all day. It simply means we need to determine the right amount and type of protection for the length of time we want to stay.

It also doesn't say we could never have gone to the beach because the UV exposure is "too dangerous."

sts60
2007-Aug-09, 01:45 PM
Indeed. When I lived in Tucson, we didn't have tide tables, but we did have sun-intensity tables, calibrated for "minutes in sun to redden [average] skin". Clearly, there was an ultraviolet radiation hazard. In fact, one woman who feel asleep while sunbathing quite literally died of radiation burns and hyperthermia from hours of exposure.

Does that mean that Tucson was uninhabitable? If so, that's news to me and hundreds of thousands of other people who have live or have lived there.

Swift
2007-Aug-09, 01:50 PM
It also doesn't say we could never have gone to the beach because the UV exposure is "too dangerous."


Does that mean that Tucson was uninhabitable? If so, that's news to me and hundreds of thousands of other people who have live or have lived there.

It also proves that "surfing" and similar "beach" activities are a hoax, since no one would ever expose themselves to such dangerous levels of UV radiation and the government would have outlawed such dangerous things.

:whistle:

SLF:JAQ SFDJS
2007-Aug-09, 08:49 PM
Nasa says the moon is radioactive. How much more conclusive can that be? The astronauts are classified as radiation workers. It's also amazing that they state that they do not have a way to shield against this inoizing radiation. These heavy ions and charged particles traveling at the speed of light. The surface of the moon is abundant in neutron radiation. Apollo could not have the shielding for this radiation if they don't have it today.

R.A.F.
2007-Aug-09, 08:57 PM
Apollo could not have the shielding for this radiation if they don't have it today.

Handwaving...are you reading any of the posts on this thread??

Van Rijn
2007-Aug-09, 08:57 PM
SLF, please answer my question:

Do you now understand that the Apollo astronauts did not receive large doses of radiation?

SLF:JAQ SFDJS
2007-Aug-09, 09:00 PM
I have read that yes but, Is it true or just regurgetated nonsense?

Van Rijn
2007-Aug-09, 09:04 PM
Nasa says the moon is radioactive. How much more conclusive can that be?


As we've already covered, so are you. So, no, that statement alone is not enough to draw any conclusions.



The astronauts are classified as radiation workers.


More accurately, the dose they received was well under safety standards for workers in the nuclear industry. They did not have a large radiation dose.



It's also amazing that they state that they do not have a way to shield against this inoizing radiation.


Who said that? What is the exact statement? There are methods for shielding, but as we've covered repeatedly, there are tradeoffs depending on requirements, especially with the length of the mission.

Van Rijn
2007-Aug-09, 09:05 PM
I have read that yes but, Is it true or just regurgetated nonsense?

I'm not asking if you read it, I'm asking if you understand it. Apparently you don't.

SLF:JAQ SFDJS
2007-Aug-09, 09:07 PM
Post #40 Destination Tomorrow video by Nasa.

Van Rijn
2007-Aug-09, 09:11 PM
Post #40 Destination Tomorrow video by Nasa.

That's not an answer. I repeat: Who said it? What is the exact statement?

nomuse
2007-Aug-09, 09:16 PM
And I'm looking forward to learning more about these charged particles that travel at the speed of light!

Kelfazin
2007-Aug-09, 09:20 PM
Nasa says the moon is radioactive. How much more conclusive can that be? The astronauts are classified as radiation workers. It's also amazing that they state that they do not have a way to shield against this inoizing radiation. These heavy ions and charged particles traveling at the speed of light. The surface of the moon is abundant in neutron radiation. Apollo could not have the shielding for this radiation if they don't have it today.

For the Nth time, and please note these are direct questions and must be answered per board rules:

1. How much radiation in what amount of exposure time does it take to cause illness for a human?

2. How much radiation is there on the moon?

You have made a quantitative assertion, you need to answer these questions with actual numbers.

Just for edification:
quan·ti·ta·tive –adjective
1.that is or may be estimated by quantity.
2.of or pertaining to the describing or measuring of quantity.

Jason Thompson
2007-Aug-09, 09:25 PM
Nasa says the moon is radioactive. How much more conclusive can that be?

The luminous strips on the hands of my alarm clock are radioactive. The smoke detector on my ceiling has a radioactive source in it. The rock under aberdeen is radioactive. Once and for all will you please grasp the concept that this is meaningless without NUMBERS attached to it.


It's also amazing that they state that they do not have a way to shield against this inoizing radiation.

What they state is that they have no way to effectively shield against that radiation for long duration exposure such as any future lunar astronauts will be exposed to.


Apollo could not have the shielding for this radiation if they don't have it today.

But the key issue we've been trying to get you to grasp is whether or not they needed it for the short Apollo missions. Radiaition exposure has different effects depending on intensity and length of exposure. In many ways it is far more dangerous to spend months in a low level radiation environment than it is to receive a short burst of high intensity radiation. A chest x-ray will not harm you. Sit in lower intensity x-rays for months at a time and you will very likely get sick. Do you understand this?

Apollo was a short flight with the astronauts spending a few days out in space. Future missions are planned to last months or even years. What was fine for Apollo in terms of radiation shielding will be hopelessly inadequate for the planned missions because of their duration.

JayUtah
2007-Aug-09, 09:28 PM
Nasa says the moon is radioactive. How much more conclusive can that be?

Summaries are not conclusive just because they are phrased simply. You insist on remaining at the summary level of understanding, when there have been many attempts made to explain in detail what is meant by that statement.

But the bottom line is that you are not able to say how radioactive the Moon is, or substantiate numerically whether that level of radiation poses a health hazard. You are simply begging the question.

The astronauts are classified as radiation workers.

Meaningless. That simply means they are allowed more occupational exposure per year than the general public, for administrative and regulatory purposes.

It's also amazing that they state that they do not have a way to shield against this inoizing radiation.

...for long-term missions. Apollo was not a series of long-term missions.

These heavy ions and charged particles traveling at the speed of light.

That is physically impossible.

The surface of the moon is abundant in neutron radiation.

Exactly how much? I want a number. This is a formal request for you to supply the number or withdraw the claim.

Apollo could not have the shielding for this radiation if they don't have it today.

Apollo didn't need the shielding, for reasons already explained at length. You seem to believe radiation effects can be mitigated only by shielding. That is not true. Radiation effects can be mitigated also by limiting the duration of the exposure. Apollo mitigated radiation effects by limiting exposure. What actual data do you have that this would not have been effective?

SLF:JAQ SFDJS
2007-Aug-09, 09:36 PM
There was too much neutron radiation at the surface of the moon especially being on the sunlit side there was even more ionizing radiation. Check out the hotspots for neutron radiation on the moon. There was no way they could have come back with no DNA damage or any adverse affects surfacing throughout their lives from this exposure. The shielding necessary has not been developed yet to protect against these heavy ions, atoms, etc, in space and at the surface of the moon. During Apollo the weight of the materials available to achieve this for a craft back then negates the plausibliity of actual moon walking in suits.

Swift
2007-Aug-09, 09:37 PM
Nasa says the moon is radioactive. How much more conclusive can that be? The astronauts are classified as radiation workers. It's also amazing that they state that they do not have a way to shield against this inoizing radiation. These heavy ions and charged particles traveling at the speed of light. The surface of the moon is abundant in neutron radiation. Apollo could not have the shielding for this radiation if they don't have it today.
Ok, to some measurable quantity the moon is radioactive and the Apollo astronauts went there and were exposed. SO WHAT? It does not disprove Apollo (if that is what you are trying to do).

As we all keep pointing out, a poison is determined by how much you are exposed to and for how long. For the couple of days the Apollo astronauts spent there, it wasn't a problem. But if future missions are going to last weeks, it is a problem.

Think of it this way.... if I get one chest x-ray a year, it is not a problem for x-ray exposure. If I get 20 a year, it might start to be a problem. If I get 20 a day, everyday for a year (over 7000 chest x-rays), I'm probably going to have health problems. (I am only using that as an example, I'm not comparing to being on the moon to a chest x-ray).

Van Rijn
2007-Aug-09, 09:38 PM
There was too much neutron radiation at the surface of the moon especially being on the sunlit side there was even more ionizing radiation. Check out the hotspots for neutron radiation on the moon. There was no way they could have come back with no DNA damage or any adverse affects surfacing throughout their lives from this exposure. The shielding necessary has not been developed yet to protect against these heavy ions, atoms, etc, in space and at the surface of the moon. During Apollo the weight of the materials available to achieve this for a craft back then negates the plausibliity of actual moon walking in suits.

Wrong thread. Please put it in the correct thread. When you do, please add the numbers for "too much" and how this applies to the Apollo astronauts.

sts60
2007-Aug-09, 09:42 PM
Nasa says the moon is radioactive. How much more conclusive can that be?

Handwaving. How radioactive?

The astronauts are classified as radiation workers.

Handwaving. What specifically do you think this means?

It's also amazing that they state that they do not have a way to shield against this inoizing radiation.

Why? How much radiation was expected for a short Apollo mission? What types? fluxes? energies? Total exposure? Time to stop handwaving and provide numbers to back up your claim.

These heavy ions and charged particles traveling at the speed of light.

No, they do not. You would fail high-school physics with such a claim.

The surface of the moon is abundant in neutron radiation.

No, it is not "abundant" in any sense meaningful for a short surface stay. You are completely failing to grasp the context. But you could try to back this claim up by providing a quantitative estimate for the neutron fluxes and energies and a total expected dosage for an Apollo mission.

Apollo could not have the shielding for this radiation if they don't have it today.

Handwaving. You have not established what types, fluxes, and energies of radiation were encountered, what the expected dosage would have been, what types of shielding would have been necessary and why, and you have no answer for why the actual measured dosages for the crews were well within acceptable bounds.

JayUtah
2007-Aug-09, 10:28 PM
SLF:JAQ SFDJS, let's try a different approach.

Let's say you were stopped by a traffic policeman and given a ticket for speeding. But let's say the policeman was unable to tell you or the judge how fast you were going. Let's say all he can tell is that you were going faster than some other car, but he can't say how much faster, or how fast that other car was going. The only thing he can say is that you were going faster than it.

Naturally you don't want to pay the fine. It would be appropriate to point out that the crime of speeding doesn't mean going faster than some other car; it means going faster than the posted speed limit. The speed limit allows for speeds greater than zero, and there are many speeds greater than zero, but less than the posted limit. You only have to pay the fine if it can be proven you were going faster than the posted limit, not just faster than some arbitrary car.

This is why we require you to give actual numerical measurements for the radiation effects you cite.

You can't say that they are dangerous simply because they exist any more than your policeman can say you were speeding simply because you were not standing still. There are speeds that are legal and safe just the same as there are levels of radiation exposure that are inconsequential.

You are using loaded language such as "abundant" and "dangerous" that implies you know the amounts in question. But you do not, so your claims are as inappropriate as those of the policeman who says you were speeding but doesn't actually know whether you were or not.

ranb
2007-Aug-09, 10:37 PM
.....Radiation doses measured during Apollo were significantly lower than the yearly average of 5 rem set by the U.S. Atomic Energy Commission for workers who use radioactive materials in factories and institutions across the United States......

Actually your link has at least one mistake. 5 rem per year is one of the limits for ionizing radiation exposure to the whole body. The average for nuclear workers is lower. For instance, Sailors and Naval shipyard workers rarely exceed 0.5 rem per year. After 23 years of receiving occupational exposure, I was extended to 0.75 rem per year allowed.

I agree the astronauts received less than 5 rem on their missions though.

Ranb

captain swoop
2007-Aug-09, 10:38 PM
he is a troll forget it you are banging your heads. and he is laughing. And don't give me ther old rope about the 'lurkers' they have all seen it a dozen times.

Orion437
2007-Aug-10, 01:11 AM
I´ve just found some specific article that may help the OP understand.

http://klabs.org/richcontent/Tutorial/radiation/space_rad_health/spaceflight_radiation_health_program.htm

Just my two cents.

Sorry for my english.

Van Rijn
2007-Aug-10, 01:20 AM
I´ve just found some specific article that may help the OP understand.

http://klabs.org/richcontent/Tutorial/radiation/space_rad_health/spaceflight_radiation_health_program.htm


Doubtful, since that primarily is pointing out the issues with the radiation environment and long term exposure. The fact is we know how much the Apollo astronauts received, and that's already been discussed.

Gillianren
2007-Aug-10, 05:56 AM
he is a troll forget it you are banging your heads. and he is laughing. And don't give me ther old rope about the 'lurkers' they have all seen it a dozen times.

No one's forcing you to read, Cap. Personally, I find the information fascinating.

Infinity Watcher
2007-Aug-10, 05:01 PM
FWIW here (http://en.wikipedia.org/wiki/Radiation_poisoning#0.05.E2.80.930.2_Sv_.285.E2.80 .9320_REM.29) is the wiki article on radiation poisoning, specifically the link points to the bit on different dosages. Radiation toxicity depends on time exposed and dose, now we have a source stating that the astronauts received less than 5 rem, according to the wiki link this dose wouldn't even induce a drop in red cell count (I'm tempted to say biochemical changes but I don't think that's really correct given that the risk of cancer in the long term is affected).

SLF:JAQ SFDJS
2007-Aug-10, 08:17 PM
They weren't just exposed for a few days. More 3-4 days on the moon. 8 days transit. More like 12 to 14 days exposed to Cosmic radiation.

Dave J
2007-Aug-10, 08:29 PM
SLF,
The spacecraft was built with shielding of the space radiation in mind...what in the normal environment would not be attenuated or stopped by a inch of aluminum, and layers of insulating materials?
...and lead isn't necessary to stop radiation out there...for the inevitable raising of the issue.

JayUtah
2007-Aug-10, 08:30 PM
More like 12 to 14 days exposed to Cosmic radiation.

Make up your mind. In your first post you say

But on the moon which is radioactive they were exposed to cosmic rays, solar radiation, x-rays, gamma rays, beta rays, protons, neutrons for days.

And you've been harping consistently on the notion "the moon is radioactive" and waving your hands wildly about neutron scattering and all this other stuff related only to the lunar surface itself. Now that your feet are being held to the fire on that point, you try to change horses and talk about the translunar coast instead.

The fact remains that you have absolutely no idea how much radiation exposure the Apollo astronauts would have been subjected to on the lunar surface, in lunar orbit, in Earth orbit, on the way there or back, or even standing in a NASA parking lot. You have absolutely no idea how much radiation exposure is required to cause health problems, DNA damage, or death. You have absolutely no idea what the quantitative difference in the radiation parameters might be in a 15-minute suborbital flight, a 12-day lunar mission, a 6-month ISS sojourn, or a 2-year Mars mission.

You haven't so far been able to express one single aspect of your belief in terms of an actual quantity. You simply wave your hands and claim it's "dangerous."

The time has come for you to put up or pipe down. Give actual numbers for the radiation exposures relevant to your claims, and tell how you arrived at them. This is the second formal request for that information. The board rules require you to respond as a condition of continued participation.

NGCHunter
2007-Aug-10, 08:35 PM
They weren't just exposed for a few days. More 3-4 days on the moon. 8 days transit. More like 12 to 14 days exposed to Cosmic radiation.

First of all I'd like to point out that the command module was MUCH better shielded than the lunar module. While in cis-lunar space inside the command module the astronauts were completely safe from radiation from every source for a period of days or even weeks, the only concern came during lunar landings when two astronauts would be fairly vulnerable to solar events, none of which occured during the apollo missions. I got tired of not seeing any numbers on this thread, so here's some hard numbers; a chart of the radiation doses sustained by the various apollo crews in rads: http://lsda.jsc.nasa.gov/books/apollo/Resize-jpg/ts2c3-2.jpg Very low results, of course, not nearly enough to cause any sickness or medical issues. If you accept that their short stays on the lunar surface wouldn't be lethal, then you have to accept that their longer transit times are actually safer due to greater shielding. As jay already pointed out, first you were ranting about the lunar surface being dangerous due to neutron radiation (despite the fact that neutron radiation was barely detectable compared to other sources), now you reverse heading entirely and claim that cislunar space was MORE dangerous? That just doesn't add up in the slightest. If you think it does, post your quantitative evidence.

JayUtah
2007-Aug-10, 08:50 PM
While in cis-lunar space inside the command module the astronauts were completely safe from radiation from every source for a period of days or even weeks.

Not from every source. Certainly from the ambient and from most solar events. However, the X-class event in August(?) 1972 would have exposed an Apollo crew in the CM to a substantial dose. But of course there was no mission in progress when that event occurred, and there was only that one event of such magnitude in the entire Apollo operational period 1969-1972. There were only three events during that same period (that and two lesser ones) that would have produced biologically observable effects.

Kelfazin
2007-Aug-10, 09:02 PM
They weren't just exposed for a few days. More 3-4 days on the moon. 8 days transit. More like 12 to 14 days exposed to Cosmic radiation.

I also repeat, for the 2nd time:

For the Nth time, and please note these are direct questions and must be answered per board rules:

1. How much radiation in what amount of exposure time does it take to cause illness for a human?

2. How much radiation is there on the moon?

You have made a quantitative assertion, you need to answer these questions with actual numbers.

Just for edification:
quan·ti·ta·tive –adjective
1.that is or may be estimated by quantity.
2.of or pertaining to the describing or measuring of quantity.

Please see bold, italic, underlined, red text.

SLF:JAQ SFDJS
2007-Aug-10, 09:03 PM
I concede. Until I find some some new evidence.

NGCHunter
2007-Aug-10, 09:03 PM
While in cis-lunar space inside the command module the astronauts were completely safe from radiation from every source for a period of days or even weeks.

Not from every source. Certainly from the ambient and from most solar events. However, the X-class event in August(?) 1972 would have exposed an Apollo crew in the CM to a substantial dose. But of course there was no mission in progress when that event occurred, and there was only that one event of such magnitude in the entire Apollo operational period 1969-1972. There were only three events during that same period (that and two lesser ones) that would have produced biologically observable effects.

NASA claims that, provided they were in the command module, the astronauts would have survived the Auguest 4-9 1972 event (at least long enough to complete the mission). I stand corrected as far as them being "totally" safe, and I guess their survivability is debatable had they encountered that X-class event, but here's what a report from Johnson Spac Center says about it:

"In terms of hazard to crewmen in the heavy, well shielded Command Module, even one of the largest solar-particle event series on record (August 4-9, 1972) would not have caused any impairment of crewmember functions or ability of the crewmen to complete their mission safely. It is estimated that within the Command Module during this event the crewmen would have received a dose of 360 rads to their skin and 35 rads to their blood-forming organs (bone and spleen)."
-RADIATION PROTECTION AND INSTRUMENTATION, J. Vernon Bailey, LJSC

Obviously the point stands that in any solar event you're far better off in the command module than in the lunar module or on an eva.

Kelfazin
2007-Aug-10, 09:35 PM
http://lsda.jsc.nasa.gov/books/apollo/Resize-jpg/ts2c3-2.jpg

now lets take these exposure levels and compare them to a symptom chart (http://www.radsafe.pitt.edu/ManualTraining/SectionIII.htm)


TABLE 3: SUMMARY OF EFFECTS ON HUMANS
OF SHORT-TERM WHOLE BODY EXTERNAL EXPOSURE TO RADIATION

Dose (rads)
Effects on humans

0 to 25
(0 - 0.25 Gy)
No detectable clinical effects. Delayed effects may occur.

25 to 100
(0.25 - 1 Gy)
Slight transient reductions in lymphocytes and neutrophils. Disabling sickness not common; exposed individuals should be able to proceed with usual tasks. Delayed effects possible, but serious effects on the average person very improbable.

100 to 200
(1 - 2 Gy)
Nausea and fatigue, with possible vomiting above 125 rads in about 20-25% of people. Reduction in lymphocytes and neutrophils, with delayed recovery. Delayed effects may shorten life expectancy (on the order of 1%).

200 to 300
(2 - 3 Gy)
Nausea and vomiting on first day. Latent period up to 2 weeks, perhaps longer. After latent period, symptoms appear but are not severe: loss of appetite, general malaise, sore throat, pallor, petechia, diarrhea, moderate emaciation. Recovery likely in about 3 months unless complicated by poor health or superimposed injury or infection.

300 to 600
(3 - 6 Gy)
Nausea, vomiting, and diarrhea in first few hours. Latent period with no definite symptoms perhaps as long as 1 week. Epilation, loss of appetite, general malaise, and fever during 2nd week, followed by hemorrhage, purpura, petechia, inflammation of mouth and throat, diarrhea, and emaciation in 3rd week. Some deaths in 2-6 weeks; possible eventual death to 50% of those exposed at about 450 rads; convalescence of others about 6 months.

600 or more
( >6 Gy)
Nausea, vomiting, and diarrhea in the first few hours. Short latent period, with no definite symptoms, in some cases during first week. Diarrhea, hemorrhage, purpura, inflammation of mouth and throat, and fever toward end of first week. Rapid emaciation and death as early as the second week, with possible eventual death of up to 100% of those exposed.

So if the astronauts would have been in an environment that was completely unsurvivable (100% fatality) they would have needed a short-term exposure of 600 or more rads. The worst exposure was A14 at 1.14 rads. They launched on January 31, and landed February 5th. It took them 6 days to rack up 1.14 rads. In order to get over 600, they would have needed to be in space, with the same radiation conditions, for 3,157 days, or roughly 8 1/2 years (not exactly short-term!).

JayUtah
2007-Aug-10, 10:00 PM
NASA claims that, provided they were in the command module, the astronauts would have survived the Auguest 4-9 1972 event (at least long enough to complete the mission).

That is correct. If normal radiation protocols had been followed, the astronauts would have recieved a substantial dose, but not a fatal dose. And the effects would not have become apparent until after the mission was concluded. NASA is here thinking about crew effectiveness in terms of mission success, along the same lines as a military mission assessment where the mission is generally considered more important than any one asset assigned to it. Nowadays that sort of amoral calculation probably wouldn't work. Intuitively we want spacecraft engineered to protect the crew because the crew are human beings worth protecting, not just so they can complete the mission.

Obviously the point stands that in any solar event you're far better off in the command module than in the lunar module or on an eva.

It stands firm. The astronauts on the lunar surface would probably have had enough advance warning of an impending particle event to return to the LM, lift off, rendezvous with the CSM and transfer to the CM prior to receiving severe exposure.

sts60
2007-Aug-11, 01:50 AM
I concede. Until I find some some new evidence.
Well, here's the thing. What you had wasn't evidence; it was simply context-free misinterpretation of mostly popular articles. If you posted all these claims without evaluating them quantitatively, how will you be able to tell if the next thing you read is "evidence" or not?

Seriously. Yes, the Moon is radioactive; so is the Earth. Yes, the astronauts were exposed to ionizing radiation from space; so are you, me, and everyone else. Yes, a long-duration stay on the Moon poses considerable challenges in radiation protection; but so does a long stay on the ISS. Using your reasoning to date, I can clearly show that no one lives on Earth or the ISS. You'll get nowhere if you simply intepret what you read without context and without quantitative examination.

Also, why are you sure ("until") you'll find "new evidence"? Have you considered that you might have simply been wrong?

JayUtah
2007-Aug-11, 02:16 AM
Substitute ammunition for evidence and you'll have something perhaps a bit more accurate.

Sleepy
2007-Aug-11, 10:14 AM
http://lsda.jsc.nasa.gov/books/apollo/Resize-jpg/ts2c3-2.jpg

Why was the Apollo 14 exposure slightly higher than the other missions which landed and conducted multiple excursions to the surface?

JayUtah
2007-Aug-11, 04:26 PM
You'll see significant fluctuation anyway, especially for periods of a small number of days where short-term effects (e.g., small flares) can exert more influence on the variance. But the most likely effect is Apollo 14's more direct route through the Van Allen belts. The inclination of the translunar coast orbit is dictated in large part by the desired lunar arrival conditions, which in turn is dictated by the location of the landing site. That doesn't always play nice with the orientation of the Van Allen belts that week.

In books the solar system seems to line up nicely. In reality the solar system is a hodge-podge of objects spinning in odd orbits on planes oddly tilted to one another, all at inharmonic speeds. It fits together a little like a child's first birdhouse. Celestial mechanics is ruthlessly messy, and the messiness falls within the scope of what has to be computed and considered for space flight. The Southern Atlantic Magnetic Anomaly (notated SAA on Mission Control displays, for fans of the NASA Channel) is one example of parts of the solar system that you'd think ought to line up, but don't.

Davidoc
2007-Aug-13, 01:07 PM
I read that the Apollo Astronauts were in the Van Allen radiation belt for a couple of hours and that you would need about 2 feet of lead to shield you from the radiation, the walls on the space craft were only thin and not even made out of lead.

JayUtah
2007-Aug-13, 01:11 PM
Where did you read that you need two feet of lead to shield you from Van Allen belt radiation?

Jason Thompson
2007-Aug-13, 01:30 PM
I read that the Apollo Astronauts were in the Van Allen radiation belt for a couple of hours and that you would need about 2 feet of lead to shield you from the radiation, the walls on the space craft were only thin and not even made out of lead.

Where did you read that?

Any elementary textbook on radiation will tell you that lead is just about the worst material to shield against the type of radiation found in the van allen belts. It's particle readiaiton, best shielded against by thin layers of light metals such as aluminium, plastics or water. Guess what there was lots of in the Apollo spacecraft.

Davidoc
2007-Aug-13, 01:39 PM
I read it on some Apollo conspiracy site last week, i cant remember what the address id, i'll try and find it. It was obviously just some fool talking nonsense.

JayUtah
2007-Aug-13, 01:52 PM
I don't think it's necessary to find the exact address unless there's something else specific there you had a question about. Whether the person who said it was a fool is debatable, but the notion that you need two feet of lead to shield against the Van Allen belts for a few hours is indeed nonsense. Conspiracy theory web sites haven't historically been a reliable source of information on spacecraft design and operation.

Jason Thompson
2007-Aug-13, 01:55 PM
I read it on some Apollo conspiracy site last week,

Ah, there's your problem... :)

JayUtah
2007-Aug-13, 04:45 PM
When someone says you need lead in order to shield against Van Allen belt radiation or solar radiation, that's a pretty good indicator that he hasn't studied the problem and is probably just repeating what someone else told him.

Lead, concrete, rock, and other dense materials are sometimes required to shield against strong electromagnetic wave radiation. Where the hazard is gamma rays or x-rays you would choose that kind of material.

The Van Allen belts are composed of charged particles -- protons, electrons, and helium nucleii. So is the dangerous component of solar and cosmic radiation.

Protection by shielding involves putting something between you and the particles that absorbs them. Dense materials will do that, of course, but at a price. When a charged particle is absorbed in the shielding, the absorption triggers the release of secondary radiation in the form of braking radiation. An atom's behavior when it absorbs one of these wayward particles causes its electrons to get happy briefly, and then drop back down to their ground states. That drop releases a photon. The wavelength of the photon depends on the atomic mass of the atom that did the absorbing. Lead, steel, beryllium, and other heavy metals (heavy in the sense of physical density as well as atomic mass) happen to emit secondary radiation in the x-ray band, which isn't a good thing.

Now two feet of lead will indeed shield you from Van Allen belt radiation. Also from microwaves, gamma rays, cell phone reception, your in-laws, and the effects of a modest tactical nuclear device. That's substantial shielding.

It would work in this case because the incoming charged particles would be absorbed in the outermost layer of lead while the x-rays induced there would be absorbed by the inner layers. In fact, all that would probably happen within the first few millimeters of the shielding, leaving the remaining several centimeters as dead mass.

Many materials are capable of absorbing charged particles effectively and are thus useful as shielding. If the secondary radiation shortens in wavelength as atomic mass increases, then what you need is something that has a very light atomic mass, but can occur in physical densities sufficient to put enough practical mass behind each unit area of incidence. Shielding is thus often specified as grams per square centimeter (of incident area). Hydrogen atoms are very light, but free hydrogen in gaseous form isn't dense enough to work. Its liquid and solid forms are impractical for engineering.

So we compromise by hooking that hydrogen up with other atoms into chemical compounds that can provide higher physical densities with better handling and manufacturing properties. Water will work, but it too has handling issues. We then turn to the various polymer substances that hook hydrogen onto carbon and sometimes oxygen in creative ways. One of the best candidates these days is high-density polyethylene (HDPE), the stuff they make hard-hats out of. The carbons and oxygens in these various compounds don't have as good absorption properties as the hydrogen, but they serve to hold lots of hydrogen in place and keep it physically dense and manufacturable without incurring too great a braking radiation penalty.

Many natural products such as wood and felt would be suitable shielding, if provided in enough thickness.

Aluminum also works, being an atomically light metal as well as having mechanical and thermal properties that make it a good aerospace material for other reasons. Because its braking radiation edges into dangerous territory, you need a substantial thickness of it. For missions lasting around ten years, suitable shielding for electronics such as to attenuate it to ground levels against solar flares and Van Allen belt encounters would amount to a thickness in single-digit centimeters.

Lead foil would work too, but you're going to build the spacecraft out of aluminum anyway. Why not just attenuate the incident radiation with your pressure- and load-bearing structure too, if it's sufficient? Even when proper thicknesses are contemplated (and two feet is overkill by several orders of magnitude), lead is qualitatively not the best choice.

The odd behavior of braking radiation results in some interesting behavior. If shielding is too thin it will actually increase the radiation load on the payload. As particles are trapped in the outer layers the absorption creates x-rays, which are more penetrating than the original particle. So you have a minimum shield thickness that does no more than attenuate the total radiation picture down to the unshielded level. Then you add additional shielding to attenuate the secondary.

Swift
2007-Aug-13, 04:57 PM
An atom's behavior when it absorbs one of these wayward particles causes its electrons to get happy briefly, and then drop back down to their ground states.
Oh boy, happy electrons!!!! And I thought those up quarks were the only emotional sub-atomic particles. ;)

Kelfazin
2007-Aug-13, 04:58 PM
I love this forum :)

Dave J
2007-Aug-13, 05:38 PM
Maybe that post of Jay's needs a sticky...excellent explanation for us laymen.

JayUtah
2007-Aug-13, 05:43 PM
The photon is the atomic hangover that results from electrons on a weekend returning to the Monday morning ground state. The more heinously populated the atom, the more annoying the hangover.

Waspie_Dwarf
2007-Aug-13, 06:53 PM
Having a hangover would explain why every electron I have ever met is just so negative.

Kelfazin
2007-Aug-14, 07:03 PM
When someone says you need lead in order to shield against Van Allen belt radiation or solar radiation, that's a pretty good indicator that he hasn't studied the problem and is probably just repeating what someone else told him.

Lead, concrete, rock, and other dense materials are sometimes required to shield against strong electromagnetic wave radiation. Where the hazard is gamma rays or x-rays you would choose that kind of material.

The Van Allen belts are composed of charged particles -- protons, electrons, and helium nucleii. So is the dangerous component of solar and cosmic radiation.

Protection by shielding involves putting something between you and the particles that absorbs them. Dense materials will do that, of course, but at a price. When a charged particle is absorbed in the shielding, the absorption triggers the release of secondary radiation in the form of braking radiation. An atom's behavior when it absorbs one of these wayward particles causes its electrons to get happy briefly, and then drop back down to their ground states. That drop releases a photon. The wavelength of the photon depends on the atomic mass of the atom that did the absorbing. Lead, steel, beryllium, and other heavy metals (heavy in the sense of physical density as well as atomic mass) happen to emit secondary radiation in the x-ray band, which isn't a good thing.

Now two feet of lead will indeed shield you from Van Allen belt radiation. Also from microwaves, gamma rays, cell phone reception, your in-laws, and the effects of a modest tactical nuclear device. That's substantial shielding.

It would work in this case because the incoming charged particles would be absorbed in the outermost layer of lead while the x-rays induced there would be absorbed by the inner layers. In fact, all that would probably happen within the first few millimeters of the shielding, leaving the remaining several centimeters as dead mass.

Many materials are capable of absorbing charged particles effectively and are thus useful as shielding. If the secondary radiation shortens in wavelength as atomic mass increases, then what you need is something that has a very light atomic mass, but can occur in physical densities sufficient to put enough practical mass behind each unit area of incidence. Shielding is thus often specified as grams per square centimeter (of incident area). Hydrogen atoms are very light, but free hydrogen in gaseous form isn't dense enough to work. Its liquid and solid forms are impractical for engineering.

So we compromise by hooking that hydrogen up with other atoms into chemical compounds that can provide higher physical densities with better handling and manufacturing properties. Water will work, but it too has handling issues. We then turn to the various polymer substances that hook hydrogen onto carbon and sometimes oxygen in creative ways. One of the best candidates these days is high-density polyethylene (HDPE), the stuff they make hard-hats out of. The carbons and oxygens in these various compounds don't have as good absorption properties as the hydrogen, but they serve to hold lots of hydrogen in place and keep it physically dense and manufacturable without incurring too great a braking radiation penalty.

Many natural products such as wood and felt would be suitable shielding, if provided in enough thickness.

Aluminum also works, being an atomically light metal as well as having mechanical and thermal properties that make it a good aerospace material for other reasons. Because its braking radiation edges into dangerous territory, you need a substantial thickness of it. For missions lasting around ten years, suitable shielding for electronics such as to attenuate it to ground levels against solar flares and Van Allen belt encounters would amount to a thickness in single-digit centimeters.

Lead foil would work too, but you're going to build the spacecraft out of aluminum anyway. Why not just attenuate the incident radiation with your pressure- and load-bearing structure too, if it's sufficient? Even when proper thicknesses are contemplated (and two feet is overkill by several orders of magnitude), lead is qualitatively not the best choice.

The odd behavior of braking radiation results in some interesting behavior. If shielding is too thin it will actually increase the radiation load on the payload. As particles are trapped in the outer layers the absorption creates x-rays, which are more penetrating than the original particle. So you have a minimum shield thickness that does no more than attenuate the total radiation picture down to the unshielded level. Then you add additional shielding to attenuate the secondary.

I've been thinking about this a little more in relation to the EMU Extravehicular Visor Assembly (EVVA). Is the gold visor used for light filtering and radiation protection? Would gold be a poor choice because of its density? Is the clear visor made from HDPE?

JayUtah
2007-Aug-14, 07:27 PM
The clear visor is made of Lexan, a polycarbonate. In the fully deployed configuration the astronaut has the Lexan fishbowl helmet, a transparent Lexan visor, and the gold-coated Lexan visor. Lexan is naturally opaque to ultraviolet. The gold coating is for EM attenuation in optical wavelengths. The EMU and LEVA are designed for protection against ambient radiation, but not against any substantially elevated activity.

JeDi
2007-Aug-20, 03:56 PM
When a charged particle is absorbed in the shielding, the absorption triggers the release of secondary radiation in the form of braking radiation. An atom's behavior when it absorbs one of these wayward particles causes its electrons to get happy briefly, and then drop back down to their ground states. That drop releases a photon. The wavelength of the photon depends on the atomic mass of the atom that did the absorbing. Lead, steel, beryllium, and other heavy metals (heavy in the sense of physical density as well as atomic mass) happen to emit secondary radiation in the x-ray band, which isn't a good thing.

I'd like to put some corrections onto this. First, braking radiation (continuous spectrum) and relaxation of electronic (core hole, in the case of x-rays) states (discrete spectrum) are two completely different, actually unrelated phenomena. With respect to x-ray emission from metal surfaces they just happen to occur in roughly the same energy band, but this is mostly by pure coincidence.

The high energy edge of the continuous part (braking) is solely determined by the energy of the impacting particle, its tailing function, i.e. the intensity distribution towards lower photon energies, is mainly governed by the average electron density in the material. The comparison of the spectra of aluminium (low e--density, rather smooth hill-like distribution) and tungsten (high e--density, strong peak at the edge, steep decrease towards low energies) at the same influx energy is a prime textbook example for this. The effective cross section of atomic cores may play a similar role, but for electrons at least it seems of less importance. Atomic mass plays no role of its own here.

The energy of core hole relaxation is (sort of) a function of atomic number, but even quite light elements reach the x-ray band. Aluminium anodes are in fact used for normal (i.e. non-soft) x-ray spectroscopy. It appears quite difficult to even reach the soft x-ray band at all, using anode emission. Before the broad availability of suitable synchrotron radiation, tricky thingies like yttrium anodes had to be used for this.

What may be of some relevance here is the competition of x-ray and Auger emission, where instead of a photon yet another electron is emitted. The ratio depends on the atomic number, the Auger effect is most prominent for light elements (carbon is a standard subject of Auger spectroscopy) while heavier elements yield more x-ray emission. This may result in a lower yield of secondary radiation seen in (pseudo) transmission at a given thickness.

So the picture with respect to particle shielding is that materials with moderate electron density, by braking the incoming particles gently, spread the energy over the lower energy range, thus favouring conversion into heat by reabsorption - which is what you finally want. Furthermore light elements tend to emit less x-rays by specific emission (core holes) than heavy elements.

Beryllium, by the way, isn't a heavy metal by atomic mass (9), number (4) or mass density (1.9g/cm-3 at RT), rather one of the lightest.

And as a last nitpick: atomic mass is quite irrelevant here, it is the atomic number that counts, i.e. nuclear charge. Yes, for your explanation they correlate well and atomic mass has made its way as a dirty idiom, but next time you do mass spectroscopy, you will see the difference. Don't lose your way in the isotopic forrest! :)

Donnie B.
2007-Aug-20, 04:07 PM
Don't lose your way in the isotopic forrest! :)I, for one, will be sure to drop some baryonic breadcrumbs. :whistle:

JayUtah
2007-Aug-20, 07:56 PM
I'd like to put some corrections onto this.

Thanks; you're hired.