[Spaceships] Where are the Capacitors?

[Anaraxes]

The thread to which Ulzgoroth linked mentions that there's not much difference between a closed-system regenerative fuel cell and a rechargable battery. Electrical input to either reverses the chemical reaction that gave you electricity in the first place. Run the chemical reaction again, and you get electricity while the battery discharges / the fuel cell consumes fuel.

Capacitors don't store energy as chemicals, though, so they have a fundamentally different mechanism. They might well have different efficiency per unit volume.

That gets into questions speculating about future super-tech, the relative improvements in each technology, and the metagame questions of what happens to balance if one technology is clearly dominant. So perhaps it's best simply to file off the names and use about the same stats for all three. You might build in a preference at different sizes -- say, capacitors have the least overhead, so they're best in small applications (like current electronics) while batteries have better power density at medium sizes (like current batteries) and fuel cells are best at large sizes that can make up for all the extra stuff to produce the power (like current fuel cells). The piecewise curve along the "best" line for each size is the tech you're actually going to see in the optimally designed ships, and so that curve should be the one you balance.

[ericbsmith]

In 3e Vehicles/GURPS Space:

Excluding the "Power Core" of the power plants,
1 ton of Fusion Plant provided 10 MW
1 ton of Antimatter Plant provided 20 MW
1 ton of Power Cells provide 12.5 MWh

The biggest advantage of Power Cells in 3e Vehicles/Space was that they were extremely compact compared to the Power Plants - in the space of a 1 ton Antimatter Reactor you could fit 6 tons of Power Cells providing 75MWh of power, making them slightly favorable to installing a Power Plant in some circumstances. I'm not sure how you could map that kind of volumetric efficiency into the Starships 4e system (which is solely concerned with Mass, not Volume).

Probably the best way is to ignore mass and look at effect - In 3e a given volume of Power Cells provided about 4x the MWh as the output of an Antimatter Power Plant in MW. In Starships 4e a slice of Antimatter Plant provides 4 PP, so an equivelent slice of Power Cells ought to provide approximately 4x that, or 16 PP hours. In 3e Power Cells were also extremely expensive - something like 25x the cost of a Power Plant of equivelent volume.

[Pomphis]

But note that 4e powercells are much less efficient than 3e powercells were. Compare UT4e p.19 with VE2 p.88.

If you introduce 3e powercells in 4e, they will also be used for other applications, like in handheld weapons.

[ericbsmith]

Originally Posted by Pomphis

But note that 4e powercells are much less efficient than 3e powercells were. Compare UT4e p.19 with VE2 p.88.

If you introduce 3e powercells in 4e, they will also be used for other applications, like in handheld weapons.

These are very large Power Cell banks for use in large vehicles and spaceships. There's no reason they should have any effect on smaller gadgets.

[vicky_molokh]

Originally Posted by ericbsmith

These are very large Power Cell banks for use in large vehicles and spaceships. There's no reason they should have any effect on smaller gadgets.

Except that in 4e, power scales linearly with mass - triple mass, triple power. And so does energy storage, since you get t=E/P=3E/3P, with P=power, E=energy storage, t=time the power source can provide a given power.

[David L Pulver]

Originally Posted by Ulzgoroth

Spaceships doesn't have a concept of power usage over time, as such, but it's utterly trivial to provide one and answer those questions in terms of PP*seconds. In keeping with the irritating current UT policy, PP aren't defined in any real-world terms, which might make it hard to hack together a capacitor bank system.

Actually, it's not UT policy but GURPS policy in general. During the writing of said books, a directive came from the very highest level that UT and HT were to remove all specific references to power outputs (unlike Infinite Worlds).

This is taken as applicable to SPACESHIPS as it's intended as a core book supplement. (It will not apply to VDS.)

Capacitors et al are simply not included because the numbers would get very fiddly due the variation in time scales, and Spaceships was designed under a very specific editorial mandate to Keep It Simple. Also, they really aren't a vital part of most fictional spaceship depictions. (One could assume that capacitors are an integral part of the beam weapons themselves, however.)

[Peter Knutsen]

Originally Posted by SCAR

I see the idea, but Spaceships doesn't have the concept of Power Usage over Time. How much 'Power' does it take to fire a Laser Once, or to run a Reactionless Drive for 4 hours, or maybe 6 hours at half power?

You'd have to define some kind of Power Usage over Time for each system (possibly the same for all).

A simpler solution would be to invent a new category of ships, separate from the one that can be built with the core Spaceships rules. This category is the short-occupancy ship, created according to modified parameters, but gifted with more efficient energy systems (since they are batteries or capacitors, rather than reactors) and needing to connect with a mothership or space port very often. Perhaps every 8 hours.

[capnq]

Originally Posted by Peter Knutsen

A simpler solution would be to invent a new category of ships, separate from the one that can be built with the core Spaceships rules. This category is the short-occupancy ship, created according to modified parameters, but gifted with more efficient energy systems (since they are batteries or capacitors, rather than reactors) and needing to connect with a mothership or space port very often. Perhaps every 8 hours.

That isn't a "solution" at all, if you're trying to design a FTL-drive ship that takes days or weeks to cross interstellar distances.

My theroretical "first steps to space" campaign involves a prototype jump drive that requires a lot of power dumped into it all at once to trigger the jump. The ship I designed (with the GURPS Space 1st ed. rules, IIRC) Jumps .2 light-years in 2 seconds, then needs over 16 minutes to recharge the capacitors. The ship's maiden voyage to Proxima Centauri will take nearly six days, if nothing goes wrong.

[Langy]

The way you do that is by just saying 'that's how the jump drive works' and fold the capicitors required into the ship's Stardrive system. It's roughly how my own FTL drive works.

[vicky_molokh]

Originally Posted by jacobmuller

. . .Fuel Cells . . .

IMO Fuel Cells provide very little PPs compared to reactors to be counted as capacitors.