Micro-miniature fusion plants

[rancke]

Assume someone (never mind who, that's a secret ) has the technology to make miniature fusion power plants the size and shape of an AA battery (Cold Fusion, naturally). It fuses stored hydrogen atoms and deliver the power in the form of electricity. What I need is a sense of proportions. If it delivers the same power that an AA battery does, how long will it last? If it's used to power a laser gun, how many shots will it deliver? That sort of thing.

If it stores hydrogen in that lattice thingy (sorry, I don't know the details; the one that allows you to store hydrogen really tight), how much hydrogen could it store and how much would it weigh?


Hans

 

[atpollard]

With or without neutron shielding?
(Just Kidding)

(Real World) From a simple look at fusion and matter to energy conversion, a AA fusion battery could generate 1.5 volts until the Sun burns out (almost). A meaninglessly long amount of time. It would probably shoot a laser for the 10 year warranty period on the weapon.

(Traveller) From the laser backpack of Classic Traveller, a 'backpack' the size of an M16 clip would be capable of 5 shots, so a 'battery' the size of AA or C might be good for 1 shot. I suggest, dividing the size and weight of a 100 shot backpack by 100 to get stats for a 'per shot' battery/reactor in Traveller terms.

 

[rancke]

With or without neutron shielding?
(Just Kidding)

(Real World) From a simple look at fusion and matter to energy conversion, a AA fusion battery could generate 1.5 volts until the Sun burns out (almost). A meaninglessly long amount of time. It would probably shoot a laser for the 10 year warranty period on the weapon.

(Traveller) From the laser backpack of Classic Traveller, a 'backpack' the size of an M16 clip would be capable of 5 shots, so a 'battery' the size of AA or C might be good for 1 shot. I suggest, dividing the size and weight of a 100 shot backpack by 100 to get stats for a 'per shot' battery/reactor in Traveller terms.

The laser backpack is a fusion power plant? That's news to me.

But thanks for the real world perspective. I'll just decrease the size of the backpack by a factor 10 for each tech level. (These babies are supposed to be TL 17).


Hans

 

[robject]

There's another data point that might help fix a ceiling -- the antimatter battery from Twilight's Peak. If I recall, it's the size of a lantern battery, and appears to have enough juice to power a small starship for a decade. One might assume that a fusion battery won't be as powerful. Of course, that seems in line with AT's post.

 

[aramis]

but then we get the MT and FF&S antimatter plants, and neither drops small enough... min AM volume is 20L at TL21, so that toy is probably TL23 or so

 

[far-trader]

Shouldn't it be a simple energy density calculation? (simple for a physicist of course not so simple for me). Not counting required shielding and heat issues of course. Or is that what you worked out/guesstimated atpollard?

 

[robject]

but then we get the MT and FF&S antimatter plants, and neither drops small enough... min AM volume is 20L at TL21, so that toy is probably TL23 or so

Arrr! Good point, and I agree.

 

[atpollard]

Or is that what you worked out/guesstimated atpollard?

Definitely guestimated.
The energy per atom is real small but the number of atoms is mind-numbingly large, so I reckon it will be a real big number.

 

[aramis]

TL21 AM plants are 50MW/L, with a minumum of 20L... and burn 25L of AM a year per liter.

TL 17 are 0.5MW/L, with a minimum 8000L, burning 25cc/year per L.

Both are a mere Cr500/L

 

[Max]

Shouldn't it be a simple energy density calculation? (simple for a physicist of course not so simple for me). Not counting required shielding and heat issues of course.

Hmmm, Rule of Thumb for conversion to pure energy is 97KJ/gram of hydrogen. figure a AA battery (guess) weighs 25g, so an anti-matter battery with total efficiency would be a little under 2.5 MJ. Hot fusion would be about .6% (.006) as efficient as TMA (total matter annihilation), so figure 25g would produce 15KJ if cold fusion is comparable to hot fusion in energy output, just 100% usable .

To the original though, let me see a AA battery is (per wikipedia) @50mm long x @14mm diameter. volume of a AA battery would 50x7x7x3.14 = 7700ish cubic mms or 7.7 ccs which would also be about 7.7 mls (milliliters). no idea what the lattice would have though so stuck there (metallic hydrogen? if you are thinking metallic hydrogen then figure .075g/ml which would be about .5g, resulting in about 300J of fusion energy from your AA battery). Wherever you go from here Deuterium (hydrogen with a neutron proton and an electron) is twice as dense as protium (hydrogen without a neutron, just an electron and a proton) and a more dense form of hydrogen could increase the power from the fusion. Tritium is also almost 3 times as dense as protium and you might even go so far as to use Quatrium (3 neutrons, 1 proton and 1 electron) but that's a far less stable form of hydrogen.


Hmm, not good superbatteries. let me try another way.

Assume Quatrium with 3 neutrons being converted completely to energy per hydrogen atom fused (a nasty assumption but we need to juice up the battery somehow). This would give us about 380KJ/gram a substance running about .3g/ml in density at about 2.3 grams in a AA battery which we can fudge up to 1MJ per battery to make things simpler. a joule = 1 watt/sec so a 1 MJ battery could power a 100KW laser for 10 secs.



dang, screwed the math and it would still be 97Kj/gram just denser grams, of which 3/4th could be converted to energy so only 150KJ from a metallic quatrium AA sized battery. The 97KJ/gram is the sticking point, keep to that and you can figure the rest of the battery - instead of metallic hydrogen use a hydrogen poisoned (saturated) metal like iron or polonium with quatrium massing of about 15g (not total mass, just the mass of quatrium) in your 7.7 ml AA battery to produce 1MJ. Anything above 15 grams would be filler, storage and so forth - if you like the mass of a normal AA 25 g would be fine if you were efficent and you could easily go to 200 g (about 8 times the mass of a RW AA battery) if that worked better. Metallic hydrogen would be light (1/10th the weight of a RW AA battery) but just doesn't have enough umph to make a superbattery.

 

[Icosahedron]

Max, not sure where you got your 'rule of thumb', but:

e=mc^2

= (0.001kg)*(9*10^16) = 9*10^13 or approx 10^14 J/g

This is the energy produced by total conversion - ie a 100% efficient antimatter reaction.

Your estimate of 0.6% efficiency for hot fusion isn't too bad, so that would give 0.6TJ/g for hot fusion, powering your 100kW laser for 6,000,000 secs or about 1500 hours.

So your 25g battery might power it for 37,500 hours or 4.28 years.

Not sure whether this is max theoretical yield, or a practical value for a working reactor - you might have to quarter it for process inefficiency.

IIRC, metal hydride technology theoretically allows a slight storage density advantage over Lhyd, but not much.

IIRC, metallic Hydrogen is much denser, but is unstable. Take it out of a gas giant core and it reverts to normal. I don't think Traveller grav generators are that good.

I don't think I'd want this tech anywhere near MTU; somehow, it just wouldn't be Traveller any more.

 

[mike wightman]

If you believe the TNE grav focused lasers then they are ;-)