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Old 09-06-2017, 11:35 AM   #1
Michael Thayne
 
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Default [Ultra-Tech] [Spaceships] Weapons that are hard or impossible to miniaturize

In Transhuman Space, particle beams have a minimum size that allows them to be installed on SDVs but not smaller ships. (SDVs are typically SM +10 or +11, though Spaceships 8 mentions particle beams can be installed on ships as small as SM +8.) Spaceships 7 has an optional rule to put similar limits on X-ray lasers, antiparticle beams, and grasers. Some questions about this:
  • How implausible are smaller versions of these weapons?
  • How plausible would it be to lift the limits 1 TL after a weapon is originally introduced?
  • SS7 gives the same size limits for all weapons covered by the optional rule. Is this realistic? I can see particle and antiparticle beams having the same minimum size (depending on how the antiparticles are generated), but would X-ray lasers and grasers have the same minimum size?
  • I've heard one possibility for x-ray laser weapons involves a "free electron laser", but IIUC these both have (a) an even larger minimum size than given in SS7 and (b) are tunable, so such a weapon could also function on other wavelengths for say planetary bombardment, a capability Spaceships lasers don't have. So how could an ~SM +10 x-ray laser with the capability in Spaceships work?
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Old 09-06-2017, 11:52 AM   #2
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Default Re: [Ultra-Tech] [Spaceships] Weapons that are hard or impossible to miniaturize

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Originally Posted by Michael Thayne View Post
[*]How implausible are smaller versions of these weapons?
Not very. The general problem is that you need a certain minimum length and/or radius for any given particle energy, and particle beam performance is heavily dependent on particle energy. This does plausibly vary with tech level, but there's a reason research particle accelerators have gotten bigger and bigger through the years. Free-electron lasers are based on electron accelerators and the wavelength that can be generated depends on the per-particle energy.
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[*]How plausible would it be to lift the limits 1 TL after a weapon is originally introduced?
As long as they're based on accelerator technology, higher TL would reduce but not eliminate the limit.
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[*]SS7 gives the same size limits for all weapons covered by the optional rule. Is this realistic?
No, except maybe by coincidence.
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Old 09-06-2017, 03:18 PM   #3
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Default Re: [Ultra-Tech] [Spaceships] Weapons that are hard or impossible to miniaturize

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Originally Posted by Michael Thayne View Post
  • I've heard one possibility for x-ray laser weapons involves a "free electron laser", but IIUC these both have (a) an even larger minimum size than given in SS7 and (b) are tunable, so such a weapon could also function on other wavelengths for say planetary bombardment, a capability Spaceships lasers don't have. So how could an ~SM +10 x-ray laser with the capability in Spaceships work?
Only very recently has a trick to allow a free-electron laser to produce a clean x-ray beam been figured out, and I'm not sure how well it retains tunability.
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Old 09-06-2017, 03:41 PM   #4
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Default Re: [Ultra-Tech] [Spaceships] Weapons that are hard or impossible to miniaturize

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Not very. Free-electron lasers are based on electron accelerators and the wavelength that can be generated depends on the per-particle energy.
Did you mean to say they're not very implausible or not very plausible?

Quote:
The general problem is that you need a certain minimum length and/or radius for any given particle energy, and particle beam performance is heavily dependent on particle energy. This does plausibly vary with tech level, but there's a reason research particle accelerators have gotten bigger and bigger through the years.
What's the relationship between minimum length and particle energy? As for radius, is that diameter of the circular accelerator?

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As long as they're based on accelerator technology, higher TL would reduce but not eliminate the limit.
What's plausible for how much they'd shrink with TL? Going for -1 SM per TL seems like it might work.

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No, except maybe by coincidence.
I assume grasers would be larger than X-ray lasers? How much bigger?
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Old 09-06-2017, 03:47 PM   #5
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Default Re: [Ultra-Tech] [Spaceships] Weapons that are hard or impossible to miniaturize

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Originally Posted by Michael Thayne View Post
Did you mean to say they're not very implausible or not very plausible?
Not very plausible.
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What's the relationship between minimum length and particle energy? As for radius, is that diameter of the circular accelerator?
Basically linear in both cases.
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What's plausible for how much they'd shrink with TL?
I'd probably go with -2 per TL.
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Old 09-06-2017, 06:01 PM   #6
Michael Thayne
 
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Default Re: [Ultra-Tech] [Spaceships] Weapons that are hard or impossible to miniaturize

Reading up on FELs, it looks like wavelength is inversely proportional to particle energy. Therefore would 1/10x wavelength require 10x the length? That would make FEL grasers limited to truly massive installations, even moreso than x-ray lasers, right?

Last edited by Michael Thayne; 09-06-2017 at 09:32 PM. Reason: said "10x" when I meant "1/10x"
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Old 09-06-2017, 06:07 PM   #7
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Default Re: [Ultra-Tech] [Spaceships] Weapons that are hard or impossible to miniaturize

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Originally Posted by Michael Thayne View Post
Reading up on FELs, it looks like wavelength is inversely proportional to particle energy. Therefore would 10x wavelength require 10x the length? That would make FEL grasers limited to truly massive installations, even moreso than x-ray lasers, right?
Presumably there's tech improvements if they're making them as weapons at all, but yes, you'd expect a FEL at gamma wavelengths to be larger than an X-ray installation.
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Old 09-06-2017, 06:11 PM   #8
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Default Re: [Ultra-Tech] [Spaceships] Weapons that are hard or impossible to miniaturize

Battleship spinal mounts probably count as "massive installations".
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Old 09-06-2017, 06:31 PM   #9
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Default Re: [Ultra-Tech] [Spaceships] Weapons that are hard or impossible to miniaturize

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Battleship spinal mounts probably count as "massive installations".
For comparison, a current-day X-ray free electron laser, the Linac Coherent Light Source, is two miles long.
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Old 09-06-2017, 07:48 PM   #10
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Default Re: [Ultra-Tech] [Spaceships] Weapons that are hard or impossible to miniaturize

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For comparison, a current-day X-ray free electron laser, the Linac Coherent Light Source, is two miles long.
Sure but as you say, weaponization in the first place implies there are some ways to compact it.

Nor are two mile spaceships unheard of in fiction.
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