GURPS Spaceships Power Plants
 

Was playing around with GURPS Spaceships, and decided to work out the power levels of various ship sizes, based on weapon use.

a SM+5 Major Weapons Battery uses one power point to power one 10MJ beam weapon. It can fire this weapon once per 20 seconds, and I'm assuming that the designers are using capacitors to store energy from the power plant so they can use the entire amount of the power point over that period.

10 MJ/20sec gives you 500kW – but only if the weapon is (somehow) 100% efficient. In reality, there's going to be heat loss, so the power required is that 500kW divided by the efficiency.

Scaling to the various size classes gives:
I ran the numbers for several efficiencies to find one that "worked" best, but using more than one column in a single game would result in mismatches.
An Improved beam weapon is simply one that is twice as energy-efficient, allowing two shots of a given power for each 20 second increment.

Under the 33% rules, a SM+7 Fusion Reactor would be rated for 100MW, a massive SM+14 Antimatter Reactor would be 600GW, and (extrapolating to the low end) a 10-pound Fuel Cell for a SM0 sized would give 5kW.

Re: GURPS Spaceships Power Plants
 

Nice. I seem to recall reading somewhere that a beam would produce twice as much waste heat as it fired out the barrel. I have no idea if thats accurate or not, but if it is, the 33% efficiency would be the one to go with.

Re: GURPS Spaceships Power Plants
 

They don't fire once per 20 seconds, you just assess their hit/s once per game turn which happens to be 20 seconds. Actual ROF is something else.
So, if ROF is really 1/s...
+5 = 30mw
+6 = 100mw
etc

Re: GURPS Spaceships Power Plants
 

I don't think thats right. Given that you get a bonus based on RoF, and there are set values for that RoF(pg 58) for different time scales, I believe that firing once per 20 seconds for a regular beam is correct.

Re: GURPS Spaceships Power Plants
 

Yeah, wasn't there a '20 minute' rule from Traveller or something? The RoF in Spaceships (sort of) depends on the turn scale you choose for your specific space combat.

Re: GURPS Spaceships Power Plants
 

Yes, the table on pg 58 covers what the RoF of different weapons are at different time scales. It says 1 for a 20 second time scale, and 3 for a the minute time scale for ordinary beams. Ergo, a beam fires about once every 20 seconds.

Re: GURPS Spaceships Power Plants
 

It seems to depend what kind of laser you use. From Atomic Rocket:

So yeah, 33% is good. It also gives me an excuse to use its rounder numbers, unlike the 40% solution.

Re: GURPS Spaceships Power Plants
 

Does all this assume beam efficiency stays the same across TLs?

Re: GURPS Spaceships Power Plants
 

Other than Improved beams, yes. However, that seems to be what Spaceships is assuming.

Re: GURPS Spaceships Power Plants
 

It pretty much has to; otherwise the PP to fire a laser wouldn't fuel the same RoF for a particle beam, for instance, which would be a major accounting headache if your ship has both.

I suppose you could say that a ship with more-efficient, higher TL equipment could be granted an extra power point every X rounds or so, but the Spaceships system is meant to be simple.

Re: GURPS Spaceships Power Plants
 

Simple? We can't even build a Shuttle with it. Can't even vaguely convert between SS units and RW units without making a theorem based on no less than two scientific wild-mass guesses. You call that simple?

Re: GURPS Spaceships Power Plants
 

Yes. Real World stuff isn't simple. The Shuttle isn't simple. The Spaceships design system is.

Re: GURPS Spaceships Power Plants
 

Yes. The Space Shuttle is pretty much the antithesis of simplicity, for one. And simplicity doesn't require or in any way benefit from information only useful to people doing hard physics gearhead stuff.

I care for the applied physics rather more than the simple, but be fair...

Re: GURPS Spaceships Power Plants
 

I can more-or-less model a weightlifter in GURPS, because GURPS uses pounds for weight. I can't properly model ships with GURPS SS, even without the design stage (i.e. just assigning statistical data), because I have no idea how much a PP is, or what is the effect of Hnd on turning radii (in air) and response delay.

Re: GURPS Spaceships Power Plants
 

Simple in that most of the details are supposed to be abstracted away. This unfortunately makes things more complicated for those of us not content to color within the lines.

Re: GURPS Spaceships Power Plants
 

Turning radii for GURPS 4e are covered fully by the high-speed maneuvering rules in or about the tactical combat chapter, are they not? I'm pretty sure they're a huge failure of realism, but they are there.

As for inability to model ships...if the definition that you're trying to model includes specific power outputs, I don't think you're looking at what you have correctly. Spaceships takes the view that just how many GW your reactor puts out isn't really essential to anything, and to a degree that's true.

Re: GURPS Spaceships Power Plants
 

Well, the radius gained from Basic Speed doesn't always match the RW radius. But I guess that's obvious already.

Re: GURPS Spaceships Power Plants
 

Well, that's what you expect of a simple representation system: inability to model very complicated things.

Re: GURPS Spaceships Power Plants
 

The PP to fire a laser are the same as the ones to fire particle beams at that TL. Spaceships needs a rate of use v rate of production system because it turn length is variable depending on range and speed. However, the longer the turn the more total weapon fires you get in that turn.

I am _not_ sure that 1 PP at TL9 or 10 is the same as 1 PP at TL11 or 12. At least at one point in the playtests when we were trying to deal with using components from multiple TLs this was the case. Perhaps it was changed.

What I can say is that 1 PP is the output of devoting 5% of your ship's mass to a "standard" Power Plant at a given TL. If you firmly believe that the output of power plants per unit of mass should go up as higher tL types replace lower TL ones then you probably don't believe in cross-TL PP.

This is the sort of thing I'm talking about when I say that Spaceships is a deliberately simplified system designed for ease of play. If you keep trying to stretch it, it's going to break on you.

If you want a comprehensive system designed for ultimate flexibility you're going to have to wait for VDS (and possibly convince Kromm that such systems aren't counter-productive to the overall line).

Re: GURPS Spaceships Power Plants
 

If it has changed there are numerous hard to justify consequences, such as high-TL ion drives, refineries, etc consuming more power for no benefit. Also, of course, it would imply n extremely negligent attitude toward mixed-TL settings or designs. Which seems unlikely given that THS is one.

Re: GURPS Spaceships Power Plants
 

That's why we're waiting for GURPS VDS, which will be able to model oddball designs like the Space Shuttle

Other than visually similar Buran, the STS is unlike any other space vehicle ever designed. Even the Buran wasn't anything like the STS since it was lifted on a carrier rocket which had all the propulsive motors and the orbiter simply had the equivalent of the OMSs to boost it the rest of the way.

What I'm saying is is that saying Spaceships is broken because it can't design the Space Shuttle, a one shot technological dead end that should have been shelved as too dangerous, too complex and too expensive in the mid-1970s, is ridiculous. (Ever wonder why Buran only flew unmanned once?)

Re: GURPS Spaceships Power Plants
 

For the record, Spaceships is able to build the Orbiter part of the shuttle with no problems. It's the external fuel tanks that are the hard part of the shuttle system, and I'm slowly working my way through that.

Re: GURPS Spaceships Power Plants
 

I have no doubt about that part. Though since Spaceship goes by mass, and the SRB/ET stack I'm sure masses more than the Orbiter I'd simply bend the rules saying the Upper Stage's (Orbiter) motors use the lower stage's fuel and outright break the rule saying an Upper Stage can't use its motors.

Re: GURPS Spaceships Power Plants
 

<shrug> Spaceships was never intended to be a comprehensive, cover everything design system for heavy-duty simulationist roleplaying purposes.

It's a _simple_ and simplified system for light-duty use in roleplaying and wargaming. There are a _lot_ of things it doesn't do and it breaks when you try and stretch it too far.

Just personally, I'd either avoid mixed TL designs or ignore the realism problems they could cause. Constant PP or variable PP, you get problems either way.

Re: GURPS Spaceships Power Plants
 

Really? What problems do you get with constant PP? I can't think of any off the top of my head.

Re: GURPS Spaceships Power Plants
 

Static energy production tech?

Re: GURPS Spaceships Power Plants
 

It's not particularly static - the various power plants tend to increase in lifetime, and Fusion reactors go from 2 power points up to 4 power points (from regular Fusion to Super Fusion). But yeah, I can definitely see how you could argue that power plants should increase in efficiency as TL increases. Would be an easy fix, too.

Other than that, I see no problems with the static power point system - unlike with a changing power point system, which has many problems and just plain doesn't make sense.

Re: GURPS Spaceships Power Plants
 

<shrug> Then what about the static nature of power input into weapons and other systems?

If Super Fusion generates twice as much as regular fusion why don't the people who invented that make Super Laser systems to exploit that extra power? Why do they keep building weapon systems to the same input specs used 3 TLs ago?

With a full featured system like Ve2 you do get to exploit higher power output.

If you try and use Spaceships for comprehensive simulationism it starts breaking. It's a deliberately arbitrary and abstract system for the sake of simplicity.

Re: GURPS Spaceships Power Plants
 

Because they can't?

I don't know if that makes sense, but it's certainly not inconceivable that you can't scale up your energy weapons' power consumption per ton. Ultratech appears to think more or less that, unless you prefer to believe that Grasers dump phenomenal amounts of heat and are a stupid design decision.

You could assert that all GURPS 4e UT products are pure gameyness with little respect for plausible physics, but I need to see a better case before I'll believe they did that.
Arbitrary and abstract are different! If they threw out the reality rather than hiding it behind abstraction, why did they bother with what I infer are plausible rocket statistics?

Re: GURPS Spaceships Power Plants
 

The energy capacity of UT Power cells is _mostly_ undefined. However, on p. 19 under Exploding Power cells you will see that if Power cells do explode or can even cab be made to explode under certain circumstances they become more dangerous at higher TLs.

Also, on p.88 under the demolitions section we see that plasma explosives (which should conceptually be like an exploding power cell) are twice as efficient at TL12 as they were at TL11.

Finally, back to p.19 there's the section on cross-TL use of power cells where using a lower TL cell in a higher TL device can leave the higher tL one functioning at reduced power while putting a higher TL cell in a lower TL device can be dangerous.

None of this would apply if a power cell was a power cell was a power cell across different TLs. At most you'd have warning about incompatible adapters, but that'd be by manufacturer and not TL.

So yeah, I assume that a TL12 Graser that gets the same number of shots from a given power cell size as TL11 Xaser is in fact using more energy, basically twice as much.

What I assume about waste heat is no more than "it's manageable at that TL". Waste heat is usually something that Goes Away as part of the process of producing gameable abstractions.

Re: GURPS Spaceships Power Plants
 

That's just an inconsistency between Ultra-Tech and Spaceships. In Ultra-Tech, you need to use more power to make a Graser do as much damage as a UV Laser. In Spaceships, you don't.

Personally, I think Spaceships might be the more believable of the two options.

Re: GURPS Spaceships Power Plants
 

Actually in UT, UV lasers do half as much damage as Grasers. The big deal though is the armor divisor. The net result of that is that grasers give 10x the armor penetration. You think you get that for free?

I don't see what the great strain of disbelief is. You all know that a PP isn't the same unit for ships of different sizes (SMs to be specific) even at the same TL.

You also know (or should by now) a PP is unit of constant output (like a kilowatt) over any time period rather than fixed quantity of energy like a kilojoule. That's the only reason PP use doesn't go up with Turn length.

Given that PP is already so flexible and arbitrary, why are you all so sure that they're the same unit over multiple TLs?

Re: GURPS Spaceships Power Plants
 

I'm aware of the bits that suggest higher TL powercells have more power. I ignore them deliberately because:

-They're just bad. You can't make low-TL power sources provide the output of high-TL power sources? In what physics? You might need a backpack full of electronics to replace a AA battery sized device, but I won't believe you can't do it. Similarly, putting a high-TL cell in a low-TL device might be a problem, if you do it stupidly, but building an adapter should not be hard.

-They're unusably vague. Maybe a higher-TL power cell is supposed to make your gadget work longer...too bad nothing provides a hint of how much longer.

-They imply that future people can't see any reason to refine a proven, efficient technology rather than (or even as well as) roll out questionable, grossly inefficient successors.

-Waste heat doesn't magically go away. Thermodynamics does not work like that! (Unless you use a black hole for a heat sink.)

Actually, yes. I think you get that for free from putting out your energy in a very different wavelength. And I think you achieve that wavelength at low-to-no cost by virtue of having a 3 TL advantage.

Hum. UT and SS seem to have...problems with regards to lasers. At TL9, Spaceships gives us a laser weighing under half a ton that does 30d(2). UT gives us a laser with that output weighing 4 tons. At TL10 you can get the Spaceships 3kj laser...but the space fighters have already been using them for decades? Similarly, UT thinks, for some reason, that neutral particle beam weapons are TL11/12. Spaceships thinks they're TL10, and the size ranges overlap.
What's flexible and arbitrary about the above? PP are ship-specific...naturally they change with SM. One tank of fuel is a lot more mass for a bigger ship, but I'd hardly call it flexible or arbitrary. Nor do I see anything either flexible or arbitrary about a Power Point being a unit of power. You know, energy over time.

But the big one, of course, is that mixing TLs is in no way discouraged, and rather may be mandated since many components apparently don't improve with TL. So if you want to tell me that at TL12 I need to spend...more than four times as much energy to power an ion drive, I have a problem. For that matter, if you want to tell me that in addition to their improved endurance, my fuel cells are generating several times more power at TL11-12, I have a problem.

Re: GURPS Spaceships Power Plants
 

Well, you ranted about one of them anyway, You ignored the Exploding Power Cells and the Plasma Explosives.

Re: GURPS Spaceships Power Plants
 

I just tried to run the math for the fuel cell systems. If I did it right, it looks like it's thermodynamically impossible for them to work if a power point is more than 0.75 MW/ton. Which suggests the laser efficiency figure may need to be shifted a bit to the higher range.

Also seems like it says bad things about the feasibility of PP scaling with TL, unless chemical power is secretly not supposed to be used at higher TLs.
You can try to back-calculate a scale for variable power cells from those if so inclined, yes. Though I think (belying my claim that "nothing provides a hint", I suppose) you shouldn't do that below TL11, because the performance figures for assorted devices tend to double each TL, when they have improvement listed.

Re: GURPS Spaceships Power Plants
 

Just being thorough, but Exploding Power Cells applies before TL11.

As an observation, 4e's numberphobia for UT devices can be a real pain in the but sometimes. 3e really was clearer on this sort of thing.

Re: GURPS Spaceships Power Plants
 

It does, but I would not assume that the REF and the total energy content of the power cell necessarily move identically. Batteries don't explode very well even for their energy content, but hypothetical high-density energy storage options can be much more volatile. The factors of 4 in REF from TL 9 to 10 to 11 run well ahead of the factor-of-two performance improvements.
I never saw 3e, but I agree wholeheartedly with the first part.