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 Post subject: Re: Particle Beams?
PostPosted: Wed Jul 28, 2010 5:54 pm 
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James DR Raskob wrote:
Ken Burnside wrote:
A different way to put it:

Within the technology assumptions given, AV:T is both internally consistent, and goes out of its way to avoid breaking laws of physics during the actual play of the game.


And that's why I like this game. :-) BTW, Ken, when is 2.0 coming out so I can get my copy? (Duck)

Chipping in my $0.01 here, having different weapons can be a way to give factions an identity. Right now XC swarm you under with masses of kinetics, as does NR. Olympia has their SR lasers, etc. If you could handwave the right assumptions, perhaps Altiplano might turn out to like particle beams, and lack the combat experience or realistic full-scale testing to realize that a weapon that looks good on paper isn't all that hot in practice. People who want to try PBs can play Altiplano, people who don't want the extra rules play the normal fleets.


Actually I think Ken's concern is more that a NBP would be problematic since it would likely break the game due to radiation issues when it hits and having long range and high damage relative to lasers (though it might be harder to aim with). But I don't want to speak for him.


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 Post subject: Re: Particle Beams?
PostPosted: Thu Jul 29, 2010 2:53 pm 
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Roman Brunecky wrote:
Actually I think Ken's concern is more that a NBP would be problematic since it would likely break the game due to radiation issues when it hits and having long range and high damage relative to lasers (though it might be harder to aim with). But I don't want to speak for him.


I think you're right, I'm just noting that if you can come up with a playable version of a NPB, there might be room for it in the game. I'm not sufficiently familiar with particle beams to say what unobtanium and handwavium need to be used to make such a beam, I'm just noting that as Olympia uses ZDPB and Altiplano's navy is still undefined in published material, there's an opening.

I'm a gears-and-fire mechanical engineer who dabbles in space stuff. I last touched particle physics back in college. OTOH, I've done enough world-building myself to be able to spot opportunities to introduce something to a world without breaking it or retconning.

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 Post subject: Re: Particle Beams?
PostPosted: Fri Jul 30, 2010 10:49 am 
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James DR Raskob wrote:
Roman Brunecky wrote:
Actually I think Ken's concern is more that a NBP would be problematic since it would likely break the game due to radiation issues when it hits and having long range and high damage relative to lasers (though it might be harder to aim with). But I don't want to speak for him.


I think you're right, I'm just noting that if you can come up with a playable version of a NPB, there might be room for it in the game. I'm not sufficiently familiar with particle beams to say what unobtanium and handwavium need to be used to make such a beam, I'm just noting that as Olympia uses ZDPB and Altiplano's navy is still undefined in published material, there's an opening.

I'm a gears-and-fire mechanical engineer who dabbles in space stuff. I last touched particle physics back in college. OTOH, I've done enough world-building myself to be able to spot opportunities to introduce something to a world without breaking it or retconning.


Well from what I have read about the topic I see it as a fairly practical and nasty weapon, with the main "real" issues that I've read about mainly relating to power use, power storage, and then aiming.

I have read that penetration of NPB is on the order of centimeters but the target material is undefined (I'm assuming either steel or aluminum), Ken seems to make it sound more like meters. And from my understanding penetration depth should only be a function of material density since its mainly the probability of the neutral particle hitting another atomic nuclei. So the denser the spacing of nuclei (or bigger nuclei) the more chance of the neutral particle hitting something. But I'm not knowledgeable enough to calculate a penetration depth in a specific material based on things like lattice structure of said material and so forth.

In any event the penetration would have a stochastic nature to it with some percentage of particles probably capable of making all the way through the ship, some hitting in the armor, some hitting in between. And if the armor is made of heavy material I think statistically speaking alot of the particles would have a better chance of encountering material there.

Increasing the power of the beam (velocity/nuclei/ number of nuclei) should just make it split target nuclei more dramatically (causing more radiation).

Shielding the crew from whatever gets "irrradiated" is largely doable IMO (demron type rad suits/shielded storage), and if its basically not the crew itself or their consumables it should be "survivable".

Also I wonder what the neutron radiation flux near a star where the rabbit holes are supposed to be is?


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 Post subject: Re: Particle Beams?
PostPosted: Fri Jul 30, 2010 10:56 am 
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Roman Brunecky wrote:

Also I wonder what the neutron radiation flux near a star where the rabbit holes are supposed to be is?


Most of the neutrons in stellar fusion remain in the star; it's protons that are the big issue, since they have a stellar sized magnetic field pushing them out.

And it's a concern. :)

Check out the damage allocation rules and propose a game mechanic for what you think will happen. I'm willing to be convinced, if it can add to the fun. You can check these out with the AV:T tutorial on the downloads area.

I am mostly concerned with the following process:

1) We add it to the game.
2) Someone comes by a year later and asks why our particle beams aren't being used to {insert physically plausible description of one shot kill} because of how they penetrate.

Everything I've ever been led to understand on them is that the items most vulnerable to a particle beam hit are the crew and electronics - both of which turn into 'one shot, one kill' weapons which aren't fun to play.

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 Post subject: Re: Particle Beams?
PostPosted: Sun Aug 01, 2010 8:20 am 
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You can already suck all of the possible fun out of AV:T using the weapons systems that already exist in the game, and extrapolating for maximum practicality and lethality.

Everybody should really be using nothing except super-long range nuclear missiles and the longest possible ranged lasers as antimissile weapons. The ships wouldn't be on the map, and they wouldn't maneuver during the course of the game. It would be nothing but an antimissile exercise, that you could just program into a little app and "solve" the battle in a few seconds.

Not much fun, really.

Adding more weapons that further encourage the intellectual exercise above don't really improve things.

AV:T is much more about quasi-realism than pretty much any space wargame, ever.
However, it's still primarily about fun. The designers have to work very hard to keep it that way, dodging all of the relatively easy "solutions" to the setting.
-Kle.


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 Post subject: Re: Particle Beams?
PostPosted: Mon Aug 02, 2010 9:22 am 
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Ken Burnside wrote:
Roman Brunecky wrote:

Also I wonder what the neutron radiation flux near a star where the rabbit holes are supposed to be is?


Most of the neutrons in stellar fusion remain in the star; it's protons that are the big issue, since they have a stellar sized magnetic field pushing them out.

And it's a concern. :)

Check out the damage allocation rules and propose a game mechanic for what you think will happen. I'm willing to be convinced, if it can add to the fun. You can check these out with the AV:T tutorial on the downloads area.

I am mostly concerned with the following process:

1) We add it to the game.
2) Someone comes by a year later and asks why our particle beams aren't being used to {insert physically plausible description of one shot kill} because of how they penetrate.

Everything I've ever been led to understand on them is that the items most vulnerable to a particle beam hit are the crew and electronics - both of which turn into 'one shot, one kill' weapons which aren't fun to play.


Ken,

My argument Is that while they may be powerful they also come with a lot of potential trade offs that may not make them into some sort of uberweapon and that may make it worth examining. I've mentioned the issues with aiming as a key one, as well as potentially making a spinal mount weapon (depending on how you accelerate and neutralize the particles) The main advanage over lasers would obviously be longer theoretical range (limited by what you can hit with it). I'm a bit leery of the various damage effects however.

It may be that given the penetration of particle beams they are these sorts of uber-weapons. But realistically NPB's are basically a highly directional form of radiation. Which I think may be shielded against.

Again, I'm curious as to your penetration argument, and everything I've been able to find on NPB's from the Air force and other sources seems to suggest penetration on the order of centimeters, whereas you seem to imply penetration on the order of meters. That order of magnitude is a pretty critical difference when it comes to armor/shielding. So I think thats worth looking into.

Also I believe your "neutron" argument is not a good one, particularly when it comes to penetration. I think the reason you are using the neutron approximation is because it is the same mass as a proton but without a charge, I think this is problematic since any realistic neutral particle beam will have its electron cloud intact. In the simplest case, a hydrogen atom will have an electron shell which will "interact" with the electron shells of whatever it hits. When that happens the unshielded proton is all of a sudden very charged and that can be dealt with electric fields or dense electron cloud materials. So realistically the "empty" space argument counting only nuclei/nuclei interactions doesn't really hold since you have to include the rather large electron cloud. And once that interacts you now are dealing with charged particles. So I don't know what AVT armor looks like, but at a guess at some point it has some spacing in it which realistically you could put a charge on various layers of the armor to deflect these charged particles or a demron type material. Sure at some point the protons can and will hit something causing damage and radiation, but you should be able to strategically shield crew compartments as well as electronics (realistically this should already be on the ship as radiation shielding).

With regard to how much damage is done, I would need an idea of how much energy the ship can use to power a beam as well as some rough guess at energy efficiency. So with regard to energy and particles, realistically we are talking about say a high speed hydrogen atom, or perhaps a heavier atom. To do on the order of "tank gun energies ~1MJ" you need on the order of micromoles of hydrogen going 50-99% C. With an efficiency of say 20% for the NPB (no idea if thats realistic or if its 1% or what) then you need 5MJ of energy per 1MJ of damage done. And realistically I'm not sure all that energy will be dumped into the target at 100% efficiency. I would guess that the type of damage is realistically of the breaking molecular bonds type (electrons/protons) and then potentially some splitting of nuclei (protons). Both should release thermal energy as well as disrupting the molecular structure of the armor so there is that as a potential "damage mechanism"

Anyhow just throwing that out there. Any particle physicists want to chime in on this?


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 Post subject: Re: Particle Beams?
PostPosted: Mon Aug 02, 2010 11:47 am 
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Roman:

Look at the existing rules in the tutorial. Tell me how a particle beam hit - as a damage allocation procedure - would work and how it would be different from a laser weapon.

If it ISN'T different, why are we bothering? If it IS different, how is it different, and why does this make the game more enjoyable?

Quote:
With regard to how much damage is done, I would need an idea of how much energy the ship can use to power a beam as well as some rough guess at energy efficiency.


One damage point is 50 MJ delivered to a spot size of ~8cm diameter, more or less instantaneously. Lasers range from 20% efficient to about 3% efficient. The energy that does not turn into damage on the target is turned into waste heat. Each turn of cooldown on a laser after it fires is flushing about ~650 kJ of waste heat. There are systems that allow you to flush more heat by using an expendable coolant, but they aren't standard equipment.

Quote:
I would guess that the type of damage is realistically of the breaking molecular bonds type (electrons/protons) and then potentially some splitting of nuclei (protons). Both should release thermal energy as well as disrupting the molecular structure of the armor so there is that as a potential "damage mechanism"


You're arguing physics. I'm arguing game mechanics. I do not care if the physics say these should exist, if they break the game. Is that clear enough?

You have the burden of proof to demonstrate that these will add something worthwhile to the game. To do that, you have to express your argument in game terms, and then back them up with physics arguments.

Please meet my requirements on this, or stop posting on this subject. I do not have the time to constantly argue with you, and I have told you what you need to do to convince me.

I've given the data on weapons, the definition of a damage point, and the rate of waste heat dissipation for a weapon after it cools down. Those terms are not open for debate; changing them would require changing far too much of the game to make it worth my time, which is ultimately the argument you have to overcome here.

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 Post subject: Re: Particle Beams?
PostPosted: Mon Aug 02, 2010 6:59 pm 
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Ken Burnside wrote:
Roman:

Look at the existing rules in the tutorial. Tell me how a particle beam hit - as a damage allocation procedure - would work and how it would be different from a laser weapon.

If it ISN'T different, why are we bothering? If it IS different, how is it different, and why does this make the game more enjoyable?

Quote:
With regard to how much damage is done, I would need an idea of how much energy the ship can use to power a beam as well as some rough guess at energy efficiency.


One damage point is 50 MJ delivered to a spot size of ~8cm diameter, more or less instantaneously. Lasers range from 20% efficient to about 3% efficient. The energy that does not turn into damage on the target is turned into waste heat. Each turn of cooldown on a laser after it fires is flushing about ~650 kJ of waste heat. There are systems that allow you to flush more heat by using an expendable coolant, but they aren't standard equipment.

Quote:
I would guess that the type of damage is realistically of the breaking molecular bonds type (electrons/protons) and then potentially some splitting of nuclei (protons). Both should release thermal energy as well as disrupting the molecular structure of the armor so there is that as a potential "damage mechanism"


You're arguing physics. I'm arguing game mechanics. I do not care if the physics say these should exist, if they break the game. Is that clear enough?

You have the burden of proof to demonstrate that these will add something worthwhile to the game. To do that, you have to express your argument in game terms, and then back them up with physics arguments.

Please meet my requirements on this, or stop posting on this subject. I do not have the time to constantly argue with you, and I have told you what you need to do to convince me.

I've given the data on weapons, the definition of a damage point, and the rate of waste heat dissipation for a weapon after it cools down. Those terms are not open for debate; changing them would require changing far too much of the game to make it worth my time, which is ultimately the argument you have to overcome here.


Ken,

Fine, I guess we are done. I posted in the Science area, not the Rules Questions & Proposals or General Discussion area because I was curious as to the physics of these beams and so far all I have gotten in reply was that I somehow wanted to change your rules and it would break the game FWIW I never recall seriously proposing changing anything. I merely asked why they weren't included and was curious as to the physics of why. I guess I can see some of the things I posted might be interpreted that way (the aiming problems/size etc) but honestly it was only my intent to generate some scientific conversation on the topic.

I do strongly disagree with some of the logic used to generate your physics answers as the assumptions that they are based on make very little sense to me. Namely using neutrons. Which I think would absolutely give you the wrong answers with regard to any sort of damage modeling since there is to my knowledge any way to generate a coherent neutron beam and real particles would interact with matter in very different ways.

But since its you and I tossing this back over the fence without much other input I guess we can let it be.


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 Post subject: Re: Particle Beams?
PostPosted: Tue Aug 03, 2010 8:51 pm 
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Roman, my apologies for getting testy on this.

But I don't get to look at this entirely from the perspective of "Is the science right/cool/neat." I also have to look at this from the perspective of "Oh, God. If this changes, then I have to change {insert list of 15 cascade changes} which change {insert list of 300 cascade changes} and then make sure that I didn't miss anything.

Thinking about that JUST as I'm working A) on laying out 2nd edition and B) prepping for GenCon...was a little overwhelming.

If it makes you happier - in the very first draft of the game (called Delta V), the SRLS series of lasers were called Particle Beams. They had wider variance between the worst possible roll and the best possible roll as an explanation for the aiming issue (and this persists into the current table). They were more power efficient than the lasers I was using.

And then I got into the discussion we've had here. Only at much greater length with a lot more equations flying around. While I wish I had all that information at my fingertips, it was ~7-5 years ago, and much the same way you likely don't remember all the details of, say, fixing a hairy BIOS issue on a computer you worked on in 2003, I don't remember ALL the hairy details of that discussion.

Except that I was eventually convinced to turn the particle beams into 2400 nanometer lasers with a more efficient conversion process to keep the damage tables I had, since they worked game mechanically...and that everything I'd thought I'd known about particle beams (a few centimeters of penetration, then causing thermal explosions) turned out to be very very wrong.

The kind of weapon I see as particle beams can be seen in GURPS Transhuman Space on page 182.

Quote:
Particle Accelerators
These weapons accelerate focused beams of neutral subatomic particles to speeds approaching that of light. They are shorter ranged and more costly than [UV wavelength] lasers, but more lethal, killing crews via radiation damage. All nations restrict civilian spacecraft from possessing particle beam weapons.


A quick and dirty look at GURPS' radiation rules are such that, honestly, attempting to 'storm shelter' against a particle beam weapon is futile. Any particle beam worth mounting as a weapon will overwhelm any storm shelter you'd put on a ship, and GURPS' rules don't really track particulate radiation as opposed to ionizing radiation.

When I talked to the people who helped research that for SJ Games, I got the explanations I gave here - making a 'hydrogen atom' beam by ionic acceleration results in high rates of beam scatter due to thermal effects from de-ionization. (You are, after all, stripping an electron off of an atom moving at near-c speeds). You also get Coulomb repulsion because the de-ionization is less than perfect. You get ranges roughly comparable to a proton beam for about the same energy cost.

When I cross checked this with Jeremy Williams, I got told that, if anything, the tech assumptions in AV:T would make these weapons even worse...but that the good news is that nobody knows how to make a beam of focused neutrons, so we can simply say that nobody figured out the trick.

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 Post subject: Re: Particle Beams?
PostPosted: Wed Aug 04, 2010 10:58 am 
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Ken Burnside wrote:
Roman, my apologies for getting testy on this.

But I don't get to look at this entirely from the perspective of "Is the science right/cool/neat." I also have to look at this from the perspective of "Oh, God. If this changes, then I have to change {insert list of 15 cascade changes} which change {insert list of 300 cascade changes} and then make sure that I didn't miss anything.

Its fine Ken, but again you do have a rules proposal section and a science section here, and conflating the two isn't doing you or I any good. I purposefully didn't post this topic in new rules proposals for a reason. And once again, I can be happy with an AVT without P-beams, I'm just mainly curious about the science.

Ken Burnside wrote:
Thinking about that JUST as I'm working A) on laying out 2nd edition and B) prepping for GenCon...was a little overwhelming.

If it makes you happier - in the very first draft of the game (called Delta V), the SRLS series of lasers were called Particle Beams. They had wider variance between the worst possible roll and the best possible roll as an explanation for the aiming issue (and this persists into the current table). They were more power efficient than the lasers I was using.

And then I got into the discussion we've had here. Only at much greater length with a lot more equations flying around. While I wish I had all that information at my fingertips, it was ~7-5 years ago, and much the same way you likely don't remember all the details of, say, fixing a hairy BIOS issue on a computer you worked on in 2003, I don't remember ALL the hairy details of that discussion.

Except that I was eventually convinced to turn the particle beams into 2400 nanometer lasers with a more efficient conversion process to keep the damage tables I had, since they worked game mechanically...and that everything I'd thought I'd known about particle beams (a few centimeters of penetration, then causing thermal explosions) turned out to be very very wrong.

The kind of weapon I see as particle beams can be seen in GURPS Transhuman Space on page 182.

Quote:
Particle Accelerators
These weapons accelerate focused beams of neutral subatomic particles to speeds approaching that of light. They are shorter ranged and more costly than [UV wavelength] lasers, but more lethal, killing crews via radiation damage. All nations restrict civilian spacecraft from possessing particle beam weapons.


A quick and dirty look at GURPS' radiation rules are such that, honestly, attempting to 'storm shelter' against a particle beam weapon is futile. Any particle beam worth mounting as a weapon will overwhelm any storm shelter you'd put on a ship, and GURPS' rules don't really track particulate radiation as opposed to ionizing radiation.


When I talked to the people who helped research that for SJ Games, I got the explanations I gave here - making a 'hydrogen atom' beam by ionic acceleration results in high rates of beam scatter due to thermal effects from de-ionization. (You are, after all, stripping an electron off of an atom moving at near-c speeds). You also get Coulomb repulsion because the de-ionization is less than perfect. You get ranges roughly comparable to a proton beam for about the same energy cost.

When I cross checked this with Jeremy Williams, I got told that, if anything, the tech assumptions in AV:T would make these weapons even worse...but that the good news is that nobody knows how to make a beam of focused neutrons, so we can simply say that nobody figured out the trick.


I really wonder about this bit in red. I mean in interplanetary space you already have alot of radiation (high and low energy), thus your crew compartments and sensitive electronics should be shielded anyway from assorted high energy particles.

Now with regard to some of this science discussion you've had, while I'm not a particle physicist I do have a background with various atomic/nuclear scale stuff (mainly in NMR/chemistry etc) and also lower/medium levels of radiation (background in X-ray crystallography and dealing with assorted radionucleotides). And this is where I'm largely coming from.

And I really question some of the arguments you (or perhaps the people at SJ games that have convinced you have made). I may well be wrong but I'm really having trouble with a few parts of the argument presented. And in one (or more) cases I think we may be talking about different things:

I assume you are talking about neutron beams (or a fully uncharged beam) mainly due to the dispersion problem with charged beams. Of course we both know that there is no good way to make a coherent neutron beam. And I wonder if some of the damage issues you are talking about only exist in the case of a neutron beam (the high level of penetration).
I have never been talking about neuron beams because I don't think the physics and engineering justify them at all.
I also see this "neutron argument" on the atomic rockets page, but the argument seems to switch in the middle somewhere from neutral particles (i.e. a real uncharged atom in my mind) to neutrons without any explanation, which I find odd. Perhaps I'm missing something as to rationale for the switch. But at any rate I am not talking about neutron beams.

With regard to the non-charged Hydrogen or heavy ion (mercury) beam I am aware of the issues with neutralizing them and the residual couplings and dispersion based on that.
But as far as I can imagine the "mostly uncharged" beam would still have much less dispersion than a fully charged beam would. And I would posit that with some creative engineering it may be possible to actually get them "fully" neutralized. So one could I guess approximate what the range then might look like using the example of a theoretical neutron beam.

That being said once you have said neutral (not neutron) beam I do think that the interactions with matter would be very different compared to that of neutrons (the empty space argument works only for neutrons since they are small and can only interact by hitting nuclei). I do think you would have lots of "surface" electronic interactions between the electrons and protons of the hydrogen beam, but relatively very little nulclei splitting (I think most of the energy would be lost in the electronic interactions). I think you would see lots of e- shell collisions and transfers and remission of energies, probably several times (and this would result in assorted radiation effects). But I just don't see it happening "meters" into any solid object (nor have I found any literature to support the meters assertion (yes I "briefly"looked around and repeatedly found a few papers talking about penetration on the order of cm). Essentially my assertion is that what you end up doing is the moment the "neutral particle" hits something (likely early on) it becomes a charged particle(s) and behaves as such.

I may be wrong here but about the only thing I can think of with regard to increasing the "power" of a beam is that it would increase the number of particles in a given pulse or the mass of the particle since velocity is going to be roughly fixed at some fraction of "c". And since "penetration" is basically a probability game which at one point approaches certainty, about the only thing I can think increasing the power would do is that it would increase is the amount of near surface disruption. I.e. the velocity of the beam has nothing to with penetration in a conventional sense. It means the particle has more energy to dump into the target material.


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 Post subject: Re: Particle Beams?
PostPosted: Wed Aug 04, 2010 11:23 am 
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Roman Brunecky wrote:
Its fine Ken, but again you do have a rules proposal section and a science section here, and conflating the two isn't doing you or I any good. I purposefully didn't post this topic in new rules proposals for a reason. And once again, I can be happy with an AVT without P-beams, I'm just mainly curious about the science.


You may want to revisit your first few posts on the subject. In your second post, you ask about including them in a future supplement, which brings us into rules territory.

Mike Z


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 Post subject: Re: Particle Beams?
PostPosted: Thu Aug 05, 2010 8:19 am 
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Mike Zebrowski wrote:
Roman Brunecky wrote:
Its fine Ken, but again you do have a rules proposal section and a science section here, and conflating the two isn't doing you or I any good. I purposefully didn't post this topic in new rules proposals for a reason. And once again, I can be happy with an AVT without P-beams, I'm just mainly curious about the science.


You may want to revisit your first few posts on the subject. In your second post, you ask about including them in a future supplement, which brings us into rules territory.

Mike Z


You got me, I guess I did bring it up in that post as an addendum. I officially recant.

Also, one of the aforementioned papers, 50cm is about the max as I read it. And most of it is in the first few cm.

http://resources.metapress.com/pdf-prev ... ze=largest


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 Post subject: Re: Particle Beams?
PostPosted: Thu Aug 05, 2010 4:10 pm 
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Roman Brunecky wrote:
Also, one of the aforementioned papers, 50cm is about the max as I read it. And most of it is in the first few cm.

http://resources.metapress.com/pdf-prev ... ze=largest


Could you reference some other sources, preferably with full text? Unless I miss my guess, you're reading this one sideways.

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 Post subject: Re: Particle Beams?
PostPosted: Fri Aug 06, 2010 9:13 am 
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Ethan McKinney wrote:
Roman Brunecky wrote:
Also, one of the aforementioned papers, 50cm is about the max as I read it. And most of it is in the first few cm.

http://resources.metapress.com/pdf-prev ... ze=largest


Could you reference some other sources, preferably with full text? Unless I miss my guess, you're reading this one sideways.


Ethan,
So here is my problem with this, I've looked around and there are damn few papers on any sort of particle beam penetration that I can find at all, the ones below are what I have found that is the most relevant. If you have some paper sitting around showing meters of penetration I really would like to see it. I'm honestly not trawling the literature just to back up my position, this is literally what I have found. And not one single paper I have been able to find supports a penetration depth on the order of meters position. If you have one please let me know as I would like to read it. But the stuff out there is on the order of cm.

You can get the full text on that....
http://www.springerlink.com/content/g4n28r67wq7kp581/
And that graph shows penetration depth in relevant materials, in cm not m....

http://trshare.triumf.ca/~buckley/wttc/ ... nz%27s.pdf
Another paper this time using gas as a target and lower energy particles, again pen depth in the cm range.

Medical particle beams
http://www.medical.siemens.com/siemens/ ... icle_e.pdf

deposition in mm/cm in low density material.

http://books.google.com/books?id=l9wtYZ ... on&f=false

Finite penetration depths (The interaction volumes I was talking about)

http://en.wikipedia.org/wiki/File:BraggPeak.png
Bragg peak of various energies. again order of cm in tissue.

http://en.wikipedia.org/wiki/Stopping_p ... diation%29
Stopping power of various materials. It seems that there is a exponential type of curve when stopping (bragg peak) particles (thus limiting penetration depth).


There is also this bit, though not terribly informative. But given the context of missile defense, the whole missile warhead might have a 1-2m diameter total, thus if your pen depth is on the order of meters its mainly gonna go through such a missile.

http://www.fas.org/spp/starwars/program/npb.htm

"At relatively low powers, the penetrating beam can enter platforms and payloads, producing considerable heat and uncontrollable ionization. Thus, the NPB is useful at the low end of the spectrum of force, producing circuit disruption without necessarily permanently damaging the target system. At higher powers, the NPB most easily damages and destroys sensitive electronics, although it is fully capable of melting solid metals and igniting fuel and explosives"

"Since the beam deposits its energy deep into the target's atomic structure, the primary weapon effect is penetrating heat deposited so rapidly it causes great damage. "

The main mechanism they allude to is thermal which I would agree with.


Some info in general here on current programs/methodologies
http://www.globalsecurity.org/space/systems/npb.htm

Neato Beam neutralizer
http://iopscience.iop.org/0957-0233/16/ ... 12_016.pdf


http://www.alpharubicon.com/basicnbc/Ra ... ration.htm
Not the most "scientific" site, but it has a bunch of graphs for nuclear types of radiation.


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 Post subject: Re: Particle Beams?
PostPosted: Fri Aug 06, 2010 7:25 pm 
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There are a bunch of things going on in this thread and I'm not even sure what you're question(s) really is (are) at this point.

As far as I could tell, you ruled out charged particle beams early on, so I'm not sure why you're bringing up proton beams here. Almost all of the citations below are for ions, where are seriously different beast (no electronic stoppage being a big one). Now, we know that proton beams "stop" fairly predictably, which is what makes them useful for cancer treatment: they can pass through tissue with little effect and the "burst" in the tumor volume (shades of meson guns...).

Roman Brunecky wrote:
Also, one of the aforementioned papers, 50cm is about the max as I read it. And most of it is in the first few cm.

http://resources.metapress.com/pdf-prev ... ze=largest


I think that you literally read this one sideways. The premise is that the proton beam spreads with distance, so that it hits with much wider radius than its initial one centimeter collimation. Experimentally, it seems that you could represents the beam with a direction/power lobe, similar to those used in portraying radar lobes.

In the graph, the X-axis reads "r, cm" for "radius in centimeters." In other words, the X-axis shows readings at various distances from the center point of the beam along the surface of the plate. The Y-axis shows relative flux at the given radius--not an absolute value, but a value relative to that of the proton flux at the center impact point. Section a, showing neutron flux, starts out at a lower value because there's just less neutron flux than proton flux.

The table is difficult to interpret completely because there are no units given for flux. Certainly, values of .82 protons/cm^2/s don't make much sense. Similarly, 82% penetration of the 25mm plate at the center point seems high. (25mm is the approximate thickness of aluminum plate the produces 75g/cm.) In any case, there seem to be a fair number of protons coming out the far side of the plate and there's quite a bit of "spalling" of neutrons as well.

It's interesting to note that doubling the thickness of the material halved the number of protons making it through. With a little thought experiment, I would expect the same to be true for neutrons: Whether or not a neutron is stopped by a layer of material is statistical, based on the density of the material (we'll ignore splitting nuclei for the moment). Let's say that one layer has a 50% chance of stopping a neutron. For large numbers, that approximates stopping 50% of the neutrons. Each additional layer cuts the number of neutrons by half. That's a pretty rapid fall off.

Suppose, however, that only the first layer is the full thickness and the subsequent layers are "thin" (their ability to stop neutrons is relatively low). That might be the case with armor (good at stopping radiation) on a ship and circuit boards and people. The problem for the circuit boards and people is that it doesn't require stopping many neutrons to do great damage to them.

Roman Brunecky wrote:
Ethan,
So here is my problem with this, I've looked around and there are damn few papers on any sort of particle beam penetration that I can find at all, the ones below are what I have found that is the most relevant. If you have some paper sitting around showing meters of penetration I really would like to see it. I'm honestly not trawling the literature just to back up my position, this is literally what I have found. And not one single paper I have been able to find supports a penetration depth on the order of meters position. If you have one please let me know as I would like to read it. But the stuff out there is on the order of cm.


Depends on whether you're talking about charged beams or neutron beams. The FAS link makes it clear that the penetration is on the order of meters.


Roman Brunecky wrote:
You can get the full text on that....
http://www.springerlink.com/content/g4n28r67wq7kp581/
And that graph shows penetration depth in relevant materials, in cm not m....


Unfortunately, it's $34 and I don't have $34 interest in this ...

Roman Brunecky wrote:
http://trshare.triumf.ca/~buckley/wttc/pdf/2004/Saturday%20pdf/Gas%20pdf/John%20Lenz%27s.pdf
Another paper this time using gas as a target and lower energy particles, again pen depth in the cm range.

Medical particle beams
http://www.medical.siemens.com/siemens/ ... icle_e.pdf

deposition in mm/cm in low density material.


Again, specifically a charged particle beam, so not relevant to the penetration effects of neutron beams, which I would suspect to be significantly greater than those of "neutral" beams.

Roman Brunecky wrote:
http://books.google.com/books?id=l9wtYZ_iCCIC&pg=PA1403&lpg=PA1403&dq=particle+beam+penetration&source=bl&ots=n88Uyw7BJn&sig=g8elY7VlFr4BA0llD0GUmfmizPs&hl=en&ei=gSJcTKyVAYf2tgPusJzKDw&sa=X&oi=book_result&ct=result&resnum=9&ved=0CDgQ6AEwCDgo#v=onepage&q=particle%20beam%20penetration&f=false

Finite penetration depths (The interaction volumes I was talking about)

http://en.wikipedia.org/wiki/File:BraggPeak.png
Bragg peak of various energies. again order of cm in tissue.

http://en.wikipedia.org/wiki/Stopping_p ... diation%29
Stopping power of various materials. It seems that there is a exponential type of curve when stopping (bragg peak) particles (thus limiting penetration depth).


There is also this bit, though not terribly informative. But given the context of missile defense, the whole missile warhead might have a 1-2m diameter total, thus if your pen depth is on the order of meters its mainly gonna go through such a missile.


Keep in mind the proton example I gave above. In some cases the target may be so "thin" that you need to kill a fly with a sledgehammer. To produce enough heat or other effects in the target, you have to get the target to stop X number of protons. If you only have 5% stoppage, your beam needs to have 20 times the power needed for the 5% that actually do something, and the other 95% are wasted by overpenetration.

Roman Brunecky wrote:
http://www.fas.org/spp/starwars/program/npb.htm

"At relatively low powers, the penetrating beam can enter platforms and payloads, producing considerable heat and uncontrollable ionization. Thus, the NPB is useful at the low end of the spectrum of force, producing circuit disruption without necessarily permanently damaging the target system. At higher powers, the NPB most easily damages and destroys sensitive electronics, although it is fully capable of melting solid metals and igniting fuel and explosives"


It's the "uncontrollable ionization" that's so icky for electronics and people--that's what Ken was talking about early on.

Roman Brunecky wrote:
"Since the beam deposits its energy deep into the target's atomic structure, the primary weapon effect is penetrating heat deposited so rapidly it causes great damage. "

The main mechanism they allude to is thermal which I would agree with.


Unlike the various proton examples, this talks about neutrons and specifies penetrations in meters. Given the rest of the text, it's not clear what type of target they're talking about here. And it certainly indicates "deep." If you're hitting a nuke, yeah, you're going to produce an amazing amount of heat, just because the material is so dense and it's stopping the neutrons so effectively.

Roman Brunecky wrote:
Some info in general here on current programs/methodologies
http://www.globalsecurity.org/space/systems/npb.htm

Neato Beam neutralizer
http://iopscience.iop.org/0957-0233/16/ ... 12_016.pdf


http://www.alpharubicon.com/basicnbc/Ra ... ration.htm
Not the most "scientific" site, but it has a bunch of graphs for nuclear types of radiation.


A closing comment:

Charged particle beams don't look like very good weapons in AV:T, compared to lasers. They spread too much, so they waste a lot of their penetration ability. They could scrub away layers of armor or damage sensors, but they don't cover a wide enough area for that! Overall, they don't seem to stack up against the lasers.

Neutron beams look as though they have just the problems that Ken described, in terms of game breaking. Relatively low-powered NPBs can have impressive penetration. At the power levels that AV:T weapons use, the "leakage" to tens of meters of depth would be great enough to blow electronics and kill crew (or at least make them the walking dead). Sure, the stuff in front of that might slag, but if you're melting weapons the size of multiple tractor-trailers along with ship structure, the 5%, or even 1%, that slip through are going to be fatal.

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