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pvtpylot
2002-Jun-03, 11:42 PM
Thanks to all of those who've posted the great links, photos, experiments, etc. Your intended audience may be missing the point, but I sure am learning a lot. I'm not sure how some of you keep your patience quotas so high but please keep it up. It's made for some entertaining and informative reading. Just wanted you all to know that someone appreciates the effort.

jrkeller
2002-Jun-04, 03:38 AM
First of all, you're welcome.

I don't find it that taxing dealing with the HB types. I've tutored college and high schools students for over twenty years. I've also taught at several unversities, both as a teaching assistant and a adjunct professor. In those times, I've run across a lot of people with varying intelligence and some of them require a lot of patience. The only real difference is that my students really wanted to learn, while most HBs just want to argue and try and violate laws of physics.

I also like doing it because I've learned a lot more about the space program.

GO Wings

Silas
2002-Jun-04, 03:50 AM
Dittos! Jay Utah, you've got to be one of the most dogged and determined heroes of reason and rationality: you keep on keeping on, when most of the rest of us would (and perhaps have) just given up.

The scientific method advances knowledge largely by the demolition of falsehood, as much if not moreso than by the support of truth. This becomes much more difficult when falsehood is deliberate.

The notion that the Apollo 11 landings were faked is a deliberate falsehood. It has clearly shown itself to be intentional and self-knowing.

That form of anti-knowledge is the most difficult of all to oppose. While we must make room for honest error, and we must make room for exploration and experimentation, we must also fight a rear-guard action against those who seek to damage the structures of knowledge.

Jay, you are a sentry on the walls, defending us against the barbarian hordes.

Thanks you; you can never be sufficiently rewarded, but at least you may know that you are honored.

Silas

pvtpylot
2002-Jun-04, 04:26 AM
On 2002-06-03 23:38, jrkeller wrote:

GO Wings

Oh yeah! But, won't the games on ESPN be live via phony satellites?
/phpBB/images/smiles/icon_biggrin.gif

GrapesOfWrath
2002-Jun-04, 11:04 AM
On 2002-06-03 23:38, jrkeller wrote:
GO Wings

Canes in 6

sts60
2002-Jun-04, 04:10 PM
I'll just do a little blatant me-to'ing. Thanks to JayUtah, jrkeller, and all you other guys. Excellent work, and lots of it too.

SpacedOut
2002-Jun-04, 05:22 PM
Ill add my me-to. No matter how often we go through this, I always seem to learn something new.

Thanks!

JayUtah
2002-Jun-04, 06:56 PM
You're all welcome. But it's obvious nothing said here will have any effect on Cosmic Dave except to provide him with opportunities to quote selectively, split hairs, misquote, and misrepresent whatever he needs to in order to retain his beliefs.

I grow tired of the tedium of trying to explain things to people who arrogantly parade their ignorance and are quite proud of it. I'll probably take a few days off, as the B.A. suggests.

Aodoi
2002-Jun-04, 07:18 PM
Well Jay, while Cosmic Dave may be more dense than a black hole and less flexible than adamantium, I've quite enjoyed your responses and learned a fair amount from them. Thanks for the info. /phpBB/images/smiles/icon_smile.gif

Alas, in terms of getting though to Cosmic Dave you might have to go with a classic movie line: "The only winning solution is not to play." I think you've more than established his impenetrability to reason. Excellent responses delivered in a reasoned tone... it's hard to beat.

Anyway, This is just my long winded way of saying "me too" /phpBB/images/smiles/icon_biggrin.gif

Silas
2002-Jun-04, 09:33 PM
On 2002-06-04 14:56, JayUtah wrote:
You're all welcome. But it's obvious nothing said here will have any effect on Cosmic Dave except to provide him with opportunities to quote selectively, split hairs, misquote, and misrepresent whatever he needs to in order to retain his beliefs.


And you've shown that, conclusively. I think I was most impressed by your efforts in taking pictures to show how shadows really work. You've won the war; no rational person, reading this thread, could fail to see that your answers are correct, both in form and in content.



I grow tired of the tedium of trying to explain things to people who arrogantly parade their ignorance and are quite proud of it. I'll probably take a few days off, as the B.A. suggests.


Nobody deserves it more. I recommend the shimmering canals of Barsoom. (Whenever I get really, really tired of "real life," I find that a dose of Edgar Rice Burroughs is one heck of a fine tonic!)

I think one of my messages got lost: how thick is the hull of the Apollo CM? I'm sure it provides a goodly measure of radiation shielding!

"Endeavor to Perservere."

Silas

JayUtah
2002-Jun-04, 09:55 PM
You've won the war; no rational person, reading this thread, could fail to see that your answers are correct, both in form and in content.

I agree, but I'm sure Dave's entourage will similarly claim victory. The problem with arrogant uninformed people is that they tend to flock.

Nobody deserves it more. I recommend the shimmering canals of Barsoom.

I actually own a first edition of Thuvia, Maid of Mars.

I think one of my messages got lost: how thick is the hull of the Apollo CM?

It didn't get lost. It's just that it doesn't have a simple answer.

You have two hulls, an inner pressure hull and an outer aerodynamic hull and heat shield. There's a bunch of felt-like fibrous insulation between them. That stuff is not too bad for absorbing particles without the side effects of dense metals.

Each hull is composed of sandwich (kind of like foamcore, only made of metal). The inner hull is made of aluminum sandwich between 1.5 inches and 0.25 inch thick, depending on where on the spacecraft you look. The outer hull is made of steel alloy sandwich between 0.5 and 2.5 inches.

Now a lot of that honeycomb sandwich is air, so it's not as if you have 1-4 inches of solid metal. But yes, it's enough to reduce the radiation exposure from x-rays, protons, "killer" electrons, and what-have-you to a safe exposure for a couple of weeks.

M_Welander
2002-Jun-04, 10:33 PM
Yeah, just who was that cosmicdave guy? I kind of ended up on this board in the middle of his claims, and I tried to be as nice as possible to him, but now when he's gone... Well, let's just say this: most of the concepts presented here my mother would have understood after two minutes, and cosmicddave was here a week or so and didn't seem to understand *anything*.

I think something's seriously wrong with him.

Anyway, it's been highly entertaining to follow the debate.

Oh, and since the debate was raging when I first started to write here, I didn't get a chance to introduce myself. My name is Mattias Welander, I'm 24 and from Sweden. I hope to get my Master's degree in Computer Science later this year. I run a software company, and I'm interested in space exploration, paleontology and movie making. Well, that's me, so 'Hi!' everybody!

Once again, thanks for the entertaining discussion!

Andrew
2002-Jun-04, 10:46 PM
If you want to know about how much radiation shielding aluminium will afford, this space radiation chart gives a little nomogram of proton energy and range in aluminium:

Radiation Chart (http://www.nsbri.org/Radiation/E3.jpg)

As evident from the nomogram, a 100MeV proton (highest figure I've seen quoted for the Van Allen Belts) has a range in aluminium of 5gm/cm^2. Aluminium has a density of 2.7g/cm^3 so that's a range of only 1.9cm for a solid sheet.
You should check my working though.
I could be way off in my understanding.

Peter B
2002-Jun-04, 11:12 PM
Hi Mattias and welcome to the board.

Your CG pictures were interesting. It's amazing what people can do with computers these days (but how long have we been saying THAT for?). /phpBB/images/smiles/icon_smile.gif

Tomblvd
2002-Jun-04, 11:16 PM
On 2002-06-04 18:33, M_Welander wrote:
Yeah, just who was that cosmicdave guy? I kind of ended up on this board in the middle of his claims, and I tried to be as nice as possible to him, but now when he's gone... Well, let's just say this: most of the concepts presented here my mother would have understood after two minutes, and cosmicddave was here a week or so and didn't seem to understand *anything*.

If you notice, CD didn't get anywhere near your posts except for the obligatory "cosmicdave handwave". Those CG sims were very good.


I think something's seriously wrong with him.

I don't think you'll see anybody disagree with that statement.



Oh, and since the debate was raging when I first started to write here, I didn't get a chance to introduce myself. My name is Mattias Welander, I'm 24 and from Sweden. I hope to get my Master's degree in Computer Science later this year. I run a software company, and I'm interested in space exploration, paleontology and movie making. Well, that's me, so 'Hi!' everybody!


Welcome to the board Matt (if I can call you that). Your computer expertise will be a great addition.

M_Welander
2002-Jun-04, 11:31 PM
Thank you. Yes, you can call me Matt if you want!

Yes, in fact, I did notice that cosmicdave never seemed to notice the shadow CG images, even though he posted in the same thread as where they were!

One thing about them that I noticed today, that I find quite interesting, is this:

When I set up the sun lit scene, I had absolutely no knowledge at all about the scene. All I had was the photo, taken from cosmicdave's own site. When I set up the CG scene to try to match the image, I found out that it was only possible with a sun light at an angle of about 10 degrees. No other angle, and no other kind of light could match it. Then, today, I read a post here that the lighting situation was indeed about 10 degrees sunlight! That's kind of fun!

(Some English language corrections needed. Sorry for that.)

<font size=-1>[ This Message was edited by: M_Welander on 2002-06-04 19:33 ]</font>

JayUtah
2002-Jun-05, 12:00 AM
Well, your chart seems a little weird. The graph part at the top is a simple chart of flux versus energy for cislunar particle radiation. Energy is, well, energy. Higher-energy particles penetrate farther into various substances. Flux is kind of like density. Say you have a piece of infinitely thin paper and you draw a one centimeter square on it. The flux is how many particles pass through that square in one second (or per other unit time). (We'll forego isotropism this time.)

What you should notice from your graph is that, generally, the higher the flux the lower the energy. So while there are some incredibly energetic particles out there, that aren't that many of them. Most of the particles you will encounter are low energy, meaning they have low penetrating power.

So go grab some random cubic meter of space out in the Van Allen backwoods. It will contain a whole soup of particles: protons, neutrons, helium nucleii, electrons, photons, and a whole bunch of particles bussed in from neighboring belts to satisfy anti-segregation laws. The majority of the particles in your cubic meter will be low-energy. Just put on a regular leather work glove and most of them won't bother you.

But there will be a few bad apples. They'll go right through your gloves. They're in the minority, but they're there. Now if you're lucky, the particles will go right through your glove, your hand, and right out the other side without disrupting anything. What you don't want is for that particle to get too close to a molecule and stir up the electron clouds. Or worse, slam headlong into one of those molecules. That's especially dangerous because the debris from that collision will produce more particles.

The bottom part of your graph is a little cryptic. Basic penetration is simply given in linear units like millimeters, for some substance, particle, and energy. Let me check my notes for a second.

[flip, flip, flip]

Okay, for a 10 MeV proton the mean penetration range in aluminum is about 0.8 mm.

[flip, flip, flip]

For a 1 MeV electron the mean penetration range in aluminum is about 2 mm.

The quantity expressed as a mass per unit area is a shielding specification. That is, if I were describing the shielding on a spacecraft I would say it was something like, "five grams aluminum per square centimeter."

It also relates to absorbed dose. Remember that we measured flux in particles that pass through a square centimeter per unit time. If we put a gram of some material (aluminum, water, human tissue, etc.) behind that centimeter and count how many particles get absorbed by that gram, we have a relationship between standard measurements of flux and standard measurements of absorbed dose (rads).

The little particles zoom through our square centimeter window and whip into that substance, depositing energy in it by disruption and collision. As soon as they have deposited 100 ergs, you have a rad. If the substance in question is human tissue, and you know what kind of particles they are, you can compute the human dose in rems.

So it's still kind of unclear what they're trying to show by the scale labeled "proton range in aluminum."

The cool thing about shielding is that you don't have to stop every particle. In fact, in the time it took you to read this sentence there's a good chance a proton or two whizzed right through you. You only have to reduce the exposure to a safe level, not to zero.

Silas
2002-Jun-05, 12:35 AM
.The cool thing about shielding is that you don't have to stop every particle. In fact, in the time it took you to read this sentence there's a good chance a proton or two whizzed right through you. You only have to reduce the exposure to a safe level, not to zero.


Bingo! If that proton (or some other particle or ray) hits a dead skin cell, well, no problem at all. If it hits a muscle or nerve or blood cell or a bit of bone or cartilage, again, it is very likely that nothing will happen.

If it hits the nucleus of a reproducing cell, then it *might* cause genetic damage, which, in the vast majority of cases, will simply cause the cell to die.

In a *tremendously* small number of cases, it might cause the cell to become cancerous...

Radon is vastly more dangerous to us, here on earth, than X-rays from space.

And don't even start talking about smoking cigarettes....

Silas

JayUtah
2002-Jun-05, 01:26 AM
Just to add: a 100 MeV proton penetrates aluminum about 30-40 cm. You were interested in 100 MeV protons and I gave figures from 10 MeV protons.

GrapesOfWrath
2002-Jun-05, 03:47 AM
On 2002-06-04 07:04, GrapesOfWrath wrote:
Canes in 6


Maybe I was wrong

pvtpylot
2002-Jun-05, 04:02 AM
On 2002-06-04 23:47, GrapesOfWrath wrote:


On 2002-06-04 07:04, GrapesOfWrath wrote:
Canes in 6


Maybe I was wrong

Yep, you were /phpBB/images/smiles/icon_smile.gif

Jovianboy
2002-Jun-05, 04:25 AM
My tuppence-worth:

1. From me also, thanks Jay and others. I, too, have learned a tremendous amount (even though it was all but lost on poor old dave).

2. Hello and welcome Mattias. I'm also a Newbie (in terms of my posting frequency - I actually spend more time lurkin' around the backthreads). I assume your name is the Swedish form for Matthew (which is my name, by the way). Please correct me if I'm wrong here (I seem to remember the Greek form being similar but with an 'H' - Matthias?).

Cheers,

JB (Matthew)

pvtpylot
2002-Jun-11, 04:55 AM
On 2002-06-04 07:04, GrapesOfWrath wrote:


On 2002-06-03 23:38, jrkeller wrote:
GO Wings

Canes in 6


Well, no matter what happens NC fans sure have done the league proud. Sorry for the off-topic post...um...Apollo rules!