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Old 12-29-2017, 08:12 PM   #11
weby
 
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Default Re: Accumulators: A concept for GURPS Spaceships

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Originally Posted by starslayer View Post
With that said power cells which start appearing at TL9+ seem to have solved this issue, having discharge rates fast enough for rapid fire lasers and energy capacity in excess of any modern battery while only being trivially heavier.
In fact the basic TL9 power cells have way less energy/weight than the best current day batteries(late TL 8), but indeed much higher discharge rates. In fact a TL 9 cell is about equal to a high end current LI battery in total energy, but can get it out really fast.

So the power cells have not solved the issue, instead they have made the default to be fast discharge cell instead of a maximum total energy one.
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Old 12-29-2017, 08:24 PM   #12
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Default Re: Accumulators: A concept for GURPS Spaceships

It seems the accumulators are space opera science, or supersicence. It was the Britania that used Accumulators. (Also, when Kinnison and Van Bursic were marooned on Delgon, they used the output of an ATOMIC POWER PLANT for hours to recharge their power armor and blasters.

They may not belong in rivet-counting stories, but there's room for Space Opera here.
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Old 12-29-2017, 10:58 PM   #13
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Default Re: Accumulators: A concept for GURPS Spaceships

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It seems the accumulators are space opera science, or supersicence. It was the Britania that used Accumulators. (Also, when Kinnison and Van Bursic were marooned on Delgon, they used the output of an ATOMIC POWER PLANT for hours to recharge their power armor and blasters.
Which is in fact realistic, given the tech. The nuke plant they were tapping was a primitive one by their standards, probably something akin to ours today, and the devices they were recharging could store immense amounts of energy, they had to be able to do so to do what they did.
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Old 12-30-2017, 05:55 PM   #14
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Default Re: Accumulators: A concept for GURPS Spaceships

I vaguely recall that the power busbars in ships would be several feet thick. Given how rich Civilization was, wouldn't it be better to spring for silver to get the resistance loss and waste heat down?
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Old 12-30-2017, 07:02 PM   #15
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Default Re: Accumulators: A concept for GURPS Spaceships

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I vaguely recall that the power busbars in ships would be several feet thick. Given how rich Civilization was, wouldn't it be better to spring for silver to get the resistance loss and waste heat down?
This is an area where Smith dodged reality while addressing it. In reality, silver or copper either one would not be enough, the energy loads passing through either would have vaporized the bus bars and the whole ship too.

Later in the same story, the Patrol comes into contact with a society that knows how to make room-temp superconductors better than anything we have now, but in fact, for their ships and machines to work at all, they'd need superconductors to handle those power loads. They'd absolutely have to have superconductors to make a Dauntless at all.

After all, if you're using multi-petawatt power levels, even if you're running at 99.9% efficiency somehow, that remaining .1% loss adds up to terawatts of heat in a machine comparable in size to a modern naval warship.

Copper, silver, aluminum, any of them would have resistance losses well above .1%.
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Old 12-31-2017, 07:21 AM   #16
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Default Re: Accumulators: A concept for GURPS Spaceships

OK, I knew what I was talking about in my first post but it seems I forgot that no one else knew the specifics I left out because they were not needed. After all, you are all electronic techs, right?

The measure of a capacitor is the Farad. A farad is the ability to store a specific number of electrons - a coulomb, or 6.242 x 10 to the 18 electrons. Most capacitors are rated in micro-farads and are about the size of the fingernail of your pinky, or maybe as large as your thumb.

So, to get the charge necessary, as implied in the stories, the capacitors would have to be on the order of Giga-farads if not larger. So, either the capacitors are each larger than Manhattan, with more than one available to allow for multiple shots, or the scientists of that era found a way to store a coulomb of electrons in a capacitor the size of one today that stores a Nano-coulomb.

Capacitors "bleed" all the time as electrons flow away from the capacitor into the circuit. The larger the capacitor the more the bleed. Usually this is countered by constantly charging the capacitor. Capacitors are often used to smooth out the ripples in a DC circuit, where the current above a certain value is shunted into the capacitor and the capacitor bleed some current into the circuit when the DC value is lower than wanted. So, unless these huge capacitors can be charged almost instantly, the engines have to constantly replace the bleed amount.
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Old 12-31-2017, 08:24 AM   #17
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Default Re: Accumulators: A concept for GURPS Spaceships

Just for some real world numbers on the sort of sizes your going to need:

The already existing supercapacitor:
(https://en.wikipedia.org/wiki/Supercapacitor )

Assuming that we don't make any further strides in this technology in terms of energy density (which may or may not be possible, my understanding is we are quite close to the theoretical limits already) you store ~200 wh/m^3 in a supercap. To get to a GWh of power, you would therefore need 5km^3 of space for your 'accumulator'

Superconducting loop magnetic energy storage already is a thing (https://en.wikipedia.org/wiki/Superc...energy_storage ); admittedly for niche applications right now, but apparently we could already achieve 1 GWh of energy with 160km of superconducing coil assuming you aren't doing anything fancy with stacking small coils inside large coils you would need 7.345km^3 (assuming 130mm spacing between each loop). Give that massive size for the loop, I think we can safely assume ten loops are possible (so one largest loop and then incrementally smaller ones inside), lets assume that we can do this a hundred times (it would be more like 300-500 loops because each loop would have a smaller distance than the first, giving about 130mm between each loop)- we are looking at 73.45m^3 of space way better than the supercap above, but requiring superconductors, cooling, conversions, enough teslas to rip the iron out of your body if you were unfortunately next to it (which also precludes it from being supported by anything magnetic, or being next to structural components of the ship, and something that strains under lorentez forces with every discharge, and any damage to the not very strong ceramics at supercooled temperatures which are supporting the whole mess results in an instantaneous and catastrophic discharge that turns the whole thing into a self-propelling rail gun projecile with 1 GWh of power. IE this practically needs a LOT of shielding (non-magnetic shielding), as well as support infrastructure, and probably some thoughts about causing it to catastrophically fail AWAY from the ship rather than INTO it, which will radically increase its size.
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Old 12-31-2017, 02:34 PM   #18
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Default Re: Accumulators: A concept for GURPS Spaceships

The thing to remember about a Smithian accumulator is that it isn't a capacitor or a battery. It's a totally different technology, probably based on physics we don't understand, like a lot of the rest of their tech.

An accumulator is defined not by how it works, but by what it does, i.e. store large amounts of energy with the ability to release it very fast. How it does it matters less than what it does.

How much energy does a Smithian accumulator store? He never gives hard figures, but lower bounds can be estimated by observing what the technology does. The answer is 'a freakin' lot'. They can power hand weaponry with more than enough juice to vaporize large masses like humans, or sections of walls. (It takes far more energy to vaporize a human than it does to kill one.)

The shipboard accumulators can store significant amounts of energy relative to their total-conversion based power plants.

Remember the old Star Trek TOS trope of the phase pistol set to turn into a bomb? There were a couple of incidents where it was shown that this could be done, and Kirk says at one point (paraphrasing) that such a pistol bomb could have blown the side of the ship out if they hadn't stopped it.

That's completely realistic, given the displayed performance of the phaser pistols (rapid vaporization of large masses, etc.). That much energy packed into a small space will make a dandy bomb if it gets released instantly.

The Smithian accumulators have similar storage densities, or higher.
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Old 12-31-2017, 02:36 PM   #19
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Default Re: Accumulators: A concept for GURPS Spaceships

Quote:
Originally Posted by starslayer View Post
Just for some real world numbers on the sort of sizes your going to need:

The already existing supercapacitor:
(https://en.wikipedia.org/wiki/Supercapacitor )

Assuming that we don't make any further strides in this technology in terms of energy density (which may or may not be possible, my understanding is we are quite close to the theoretical limits already) you store ~200 wh/m^3 in a supercap. To get to a GWh of power, you would therefore need 5km^3 of space for your 'accumulator'

Superconducting loop magnetic energy storage already is a thing (https://en.wikipedia.org/wiki/Superc...energy_storage ); admittedly for niche applications right now, but apparently we could already achieve 1 GWh of energy with 160km of superconducing coil assuming you aren't doing anything fancy with stacking small coils inside large coils you would need 7.345km^3 (assuming 130mm spacing between each loop). Give that massive size for the loop, I think we can safely assume ten loops are possible (so one largest loop and then incrementally smaller ones inside), lets assume that we can do this a hundred times (it would be more like 300-500 loops because each loop would have a smaller distance than the first, giving about 130mm between each loop)- we are looking at 73.45m^3 of space way better than the supercap above, but requiring superconductors, cooling, conversions, enough teslas to rip the iron out of your body if you were unfortunately next to it (which also precludes it from being supported by anything magnetic, or being next to structural components of the ship, and something that strains under lorentez forces with every discharge, and any damage to the not very strong ceramics at supercooled temperatures which are supporting the whole mess results in an instantaneous and catastrophic discharge that turns the whole thing into a self-propelling rail gun projecile with 1 GWh of power. IE this practically needs a LOT of shielding (non-magnetic shielding), as well as support infrastructure, and probably some thoughts about causing it to catastrophically fail AWAY from the ship rather than INTO it, which will radically increase its size.
That's interesting.

It also touches on something important: any form of high-density energy storage, if the physics allows for it to come out fast, is a potential bomb.
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Old 12-31-2017, 05:31 PM   #20
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Default Re: Accumulators: A concept for GURPS Spaceships

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That's interesting.

It also touches on something important: any form of high-density energy storage, if the physics allows for it to come out fast, is a potential bomb.
Just like some Samsung phones today are potential fires, and these are low tech (compared to space) and small.
If it isn't designed to come out fast, smashing it should get it to come out. That's why I listed Smithian Accumulators as volatile systems.

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