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Old 12-09-2018, 09:43 PM   #311
lwcamp
 
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Default Re: [Ultra-Tech] What does the TL10 battlefield look like

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Originally Posted by Rupert View Post
Why should they have less range? Space to ground has to go through as much atmosphere as ground to orbit.
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Originally Posted by Ulzgoroth View Post
Scattering earlier in the beam path might have a larger impact on on-target energy, mightn't it?
No. The math of scattering from a beam is clear. As long as the scattering is linear (more about non-linear scattering in a bit) the proportion of the beam lost is the same no matter which way you are going.

For practical considerations, visible and infrared laser scattering will be linear. For near ultra-violet, you start to get significant two-photon absorption at high intensities. This means that as a laser nears its focal point, the proportion of energy scattered from the beam goes up. This benefits the planet-based people. They can build a near-UV laser cannon that does not suffer two-photon absorption as the beam is going away, because it is still quite wide at that point. The orbital forces, who need their beams to be focused to a tight spot when they arrive at the planet, are in a different pickle. Their beams will be intense enough at that point to suffer significant extra absorption, which will greatly degrade their performance. Since ultraviolet can hold a tight focus at greater distances than visible or infrared wavelengths, the planetary defenders can shoot farther than the orbital attackers.

Of course, all this is based on real physics, not GURPS game stats. I know some people don't like to get reality messing up their game, so if not you can just ignore all this (but then, you're not allowed to try to justify differences in propagation based on path direction using physics either).

For those who are interested, I did make an attempt to get as-realistic-as-possible laser weapons for GURPS here:
http://panoptesv.com/RPGs/Equipment/...asers.php?HR=0
However, since it is not compatible with Ultra-Tech, it is a bit off-topic for this discussion.

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Old 12-09-2018, 10:01 PM   #312
Andreas
 
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Default Re: [Ultra-Tech] What does the TL10 battlefield look like

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Originally Posted by Michael Thayne View Post
Re: 100GJ lasers, it's also worth noting that in the basic space combat system, Extreme range carries a -16 penalty to hit. Even with +1 for being 1GJ or more, +2 for a fixed mount, and +4 for target SM that's still -9. Assigning gunner skill levels is largely at the GM's discretion, but unless your gunners are super elite you're hitting 10% of the time or less. That's before ECM, which can be quite effective in space combat (as I found when I did the simulations described in this thread).
Computers are already very good at doing that kind of targeting, so I don't think it makes much sense for a GM to not use vert high skill levels, unless the setting has computer technology which is very far behind their laser weapons.

Last edited by Andreas; 12-09-2018 at 10:08 PM.
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Old 12-09-2018, 10:34 PM   #313
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Default Re: [Ultra-Tech] What does the TL10 battlefield look like

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Originally Posted by lwcamp View Post
No. The math of scattering from a beam is clear. As long as the scattering is linear (more about non-linear scattering in a bit) the proportion of the beam lost is the same no matter which way you are going.
Well, scattering may not be the main issue. There's two effects that are uneven, though I'm not sure how important they are and they point in opposite directions.

Assuming total range is substantially greater than the depth of the atmosphere, and a beam that is focused to a point, the beam will be much wider (during its atmospheric passage) for the ground attacker than for the space attacker. This will result in far more heating of the beam path for the space attacker, increasing distortion and possibly resulting in plasma formation that will turn the atmosphere opaque to the beam. On the other hand, the effect of atmospheric distortion on final spot size will depend on how far the beam goes after the distortion occurs.
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Old 12-10-2018, 06:59 AM   #314
AlexanderHowl
 
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Default Re: [Ultra-Tech] What does the TL10 battlefield look like

What about using a lower intensity secondary laser to create a vacuum channel through the atmosphere a millisecond before the higher intensity primary laser activates? While it would not work for a weak laser, a 100 GJ laser could easily have a 100 MJ secondary laser create a vacuum channel, meaning that the effective atmospheric pressure that the 100 GJ laser would experience would be trace (for the millisecond that the vacuum channel lasts). It would not be feasible for a space attack on the ground though, as even the smallest difference in position at origin would cause the vacuum channel to be in the wrong place when the beams got to the atmosphere (for example, a divergence of position of a million to one would result in the primary beam being 10 m from where it should be at a distance of 10,000 km).
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Old 12-10-2018, 09:58 AM   #315
Michael Thayne
 
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Default Re: [Ultra-Tech] What does the TL10 battlefield look like

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Originally Posted by Andreas View Post
Computers are already very good at doing that kind of targeting, so I don't think it makes much sense for a GM to not use vert high skill levels, unless the setting has computer technology which is very far behind their laser weapons.
You can argue for giving all the AI gunners skill-18 but it's not what GURPS tends to assume. At TL10 AIs tend to end up with middling skill levels.

Last edited by Michael Thayne; 12-10-2018 at 11:28 AM.
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Old 12-10-2018, 10:46 AM   #316
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Default Re: [Ultra-Tech] What does the TL10 battlefield look like

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Originally Posted by Michael Thayne View Post
You can argue for giving all the AI gunners skill-18 but it's not what GURPS tends to assume. At TL10 AIs tend to end up with middling skill levels.
I assume you meant to respond to me there. Skill 18 would be rather low for TL 10 dedicated gunnery programms. It is probably best to assume that the skill is high enough that accuracy is limited by other things such as the mechanical properties of the weapon.

GURPS tends to assume? Is that for Transhuman space? Either way, gunnery programs should at the very least be as good as what could be developed with our current technology in order to be plausible.
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Old 12-10-2018, 11:28 AM   #317
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Default Re: [Ultra-Tech] What does the TL10 battlefield look like

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I assume you meant to respond to me there. Skill 18 would be rather low for TL 10 dedicated gunnery programms. It is probably best to assume that the skill is high enough that accuracy is limited by other things such as the mechanical properties of the weapon.

GURPS tends to assume? Is that for Transhuman space? Either way, gunnery programs should at the very least be as good as what could be developed with our current technology in order to be plausible.
I'm unaware of any GURPS sources that assume routine use of skill-18 or higher gunnery programs. In 3e Transhuman Space lasers automatically hit and the gunner roll is mostly to focus them to better punch through armor, but for that aspect, which is treated as harder to automate, AIs aren't any better than humans. 4e approaches laser weapons differently, obviously. Transhuman Space: Interstellar Wars technically lets you get skill-18 gunner programs, but they're Complexity 10. Reign of Steel 4e typically gives AIs modest DX and maybe 4 points in their main shooting skill.

If you want to make a case for realism, you can argue that the targeting systems in Spaceships already assume a great deal of computer assistance (explicitly +9 for targeting with active sensors). But the other side of this is that while realistically, AI capabilities are likely to be highly uneven, superhuman in some areas but very limited in others, spelling out how that works in detail is a major world-building challenge and most sci-fi settings either make AIs comparable to humans for most tasks, maybe slightly worse, unless the AI is a unique specimen like Star Trek's Data.
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Old 12-10-2018, 12:03 PM   #318
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Default Re: [Ultra-Tech] What does the TL10 battlefield look like

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Originally Posted by Michael Thayne View Post
I'm unaware of any GURPS sources that assume routine use of skill-18 or higher gunnery programs. In 3e Transhuman Space lasers automatically hit and the gunner roll is mostly to focus them to better punch through armor, but for that aspect, which is treated as harder to automate, AIs aren't any better than humans. 4e approaches laser weapons differently, obviously. Transhuman Space: Interstellar Wars technically lets you get skill-18 gunner programs, but they're Complexity 10. Reign of Steel 4e typically gives AIs modest DX and maybe 4 points in their main shooting skill.

If you want to make a case for realism, you can argue that the targeting systems in Spaceships already assume a great deal of computer assistance (explicitly +9 for targeting with active sensors). But the other side of this is that while realistically, AI capabilities are likely to be highly uneven, superhuman in some areas but very limited in others, spelling out how that works in detail is a major world-building challenge and most sci-fi settings either make AIs comparable to humans for most tasks, maybe slightly worse, unless the AI is a unique specimen like Star Trek's Data.
Are there even any non-AI gunnery programs in those sources? You don't need any AI for aiming a laser in space. That is pretty much just a simple geometry problem! Rather than looking for AI skill levels, a better approach might be to just assume that there are easily availiablle non-AI programs with near perfect aiming capabilities, just like there would be numerous other programs which aren't mentioned in the books.

+9 isn't enough (and it should probably allow you to fire at a certain level of skill rather than give a bonus like that). It is very common for AIs in fiction to be very good at some of the tasks that computers are known to excel at. This is of course as you noted, a major world-building challenge, and misstakes are made, but it is possible to do reasonably well if you at least check that your future technology isn't worse than what could be developed today.
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Old 12-10-2018, 01:38 PM   #319
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Default Re: [Ultra-Tech] What does the TL10 battlefield look like

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Originally Posted by Andreas View Post
Are there even any non-AI gunnery programs in those sources? You don't need any AI for aiming a laser in space.
By "non-AI" do you mean "not statted as characters"? This is true of Traveller's gunnery programs. (Though the choice of terminology is a bit odd, since in the real world "AI" often refers to things that don't make much sense to stat as characters in GURPS.)

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+9 isn't enough (and it should probably allow you to fire at a certain level of skill rather than give a bonus like that).
Well, I didn't write the rules, and re-writing the rules requires more ambition than I have.
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Old 12-10-2018, 01:43 PM   #320
Michael Thayne
 
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Default Re: [Ultra-Tech] What does the TL10 battlefield look like

One other thing I'd add: a lot of the programs that aren't explicitly mentioned in GURPS are either going to be in the category of "basic software to use a skill at all" or something that gives a +1 or +2 bonus to the skill. When a program replaces a PC skill entirely that's a big deal and there are plenty of examples of this being made quite explicit in the rules (robofacs and automeds, for example).
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