Polywell transportation: how small?

If polywell fusion is developed, in what ways will the world change for better or worse? Discuss.

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Tom Ligon
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Postby Tom Ligon » Mon Jun 09, 2008 9:14 pm

Truckers would rather let their motors idle than shut 'em down.

I can see using a big start-cart to get them going. Big homopolar flywheel-motor-generator, perhaps, if they can get used to the name. One at the truck terminal, maybe one at major truck stops.

Frankly, I doubt they'll ever work at a size useful for a truck. We've had electric trains for nearly a century now, so that application is a no-brainer. Put powerplants along the rail routes, don't bother making them portable.

Trucks will continue to need fuel, but maybe hydrogen will work, or a hydrocarbon produced from CO2 and water or from an agwaste. I won't claim we have this technology licked yet, but I'm sure we can with the right economic incentive and an adequate energy source to drive it.

Not that I think it would work, but if Focus Fusion does work, that might scale down better. Picture little Focus Fusion spark plugs (the device does sort of have that look to it) blasting a boron fusion burst into air in a piston engine. I predict truckers would not like an electric truck due to the lack of diesel rumble, but this contraption should have a satisfying sound to it.

MSimon
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Postby MSimon » Tue Jun 10, 2008 2:11 am

TallDave wrote:I'd be surprised if Polywell can work as a power source for anything smaller than a carrier. And I'm guessing it carries a small fission reactor to start up the fusion reactor.


Rotating machinery would do nicely for delivering a start up pulse. It might have other pulse uses as well.

With a reactor on the order of 10 to 15 ft in dia for 100 MWth with direct conversion (BFRDC) I see room in lots of ships for a BFR.
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Roger
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Postby Roger » Tue Jun 10, 2008 2:34 am

TallDave wrote:I'd be surprised if Polywell can work as a power source for anything smaller than a carrier. And I'm guessing it carries a small fission reactor to start up the fusion reactor.


Good point, reminds me of the shut down/start up probs in the Thresher/Scorpion era.
I like the p-B11 resonance peak at 50 KV acceleration. In2 years we'll know.

djolds1
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Postby djolds1 » Tue Jun 10, 2008 6:41 am

Roger wrote:
TallDave wrote:I'd be surprised if Polywell can work as a power source for anything smaller than a carrier. And I'm guessing it carries a small fission reactor to start up the fusion reactor.


Good point, reminds me of the shut down/start up probs in the Thresher/Scorpion era.


Ultracapacitors for the initial pulse?

Duane
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drmike
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Postby drmike » Tue Jun 10, 2008 1:05 pm

Ultracaps don't have good instant current peaking. A gasoline engine with a generator will work fine to charge up regular capacitors. If a few gallons of gas is all you need to start up an air craft carrier nobody will mind.

Mumbles
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Why shut them down? (except for maintenance)

Postby Mumbles » Tue Jun 10, 2008 2:58 pm

Tom Ligon wrote:Truckers would rather let their motors idle than shut 'em down.

Why shut them down at all? If the "fuel" (hydrogen and boron - roughly available at any mud-puddle, right?) is so plentiful and inexpensive, why shut them down at all?

Instead, invest in a small piece of infrastructure and have a plug that inserts into the stationary transport (truck, train, plane, boat) and push power into the grid. Get paid to sit still, provide power to the massess, and avoid the whole start-up/shut down issue.

That, or back to a question I asked before about having a BFR at "idle." Throttle that engine back to idle, just enough to keep it going while maintaining it's own reaction. Minimalize the heat output, fuel input (even though it is cheap), radiation issues, maximize the structural lifetime of the BFR... And when you need it, throttle it back up to design output power...

Be Safe
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MSimon
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Postby MSimon » Tue Jun 10, 2008 3:20 pm

I have been thinking that a modest 180 Hz modulation of the proper waveform of BFR current output might reduce the necessary size of some of the high voltage components.
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blaisepascal
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Postby blaisepascal » Tue Jun 10, 2008 3:41 pm

MSimon wrote:I have been thinking that a modest 180 Hz modulation of the proper waveform of BFR current output might reduce the necessary size of some of the high voltage components.


If I recall correctly, there is a large amount of investment already in engineering and equipment that works at 400Hz, usually used for maritime and aerospace applications (where size is more critical than standardization with landline mains).

Would that frequency and those components work as well as 180Hz?

MSimon
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Postby MSimon » Tue Jun 10, 2008 5:38 pm

blaisepascal wrote:
MSimon wrote:I have been thinking that a modest 180 Hz modulation of the proper waveform of BFR current output might reduce the necessary size of some of the high voltage components.


If I recall correctly, there is a large amount of investment already in engineering and equipment that works at 400Hz, usually used for maritime and aerospace applications (where size is more critical than standardization with landline mains).

Would that frequency and those components work as well as 180Hz?


Of course for aircraft 3 phase at 1200 Hz would do the trick. However, I think future aircraft will be going to a DC bus for weight considerations now that converter technology is well in hand.
Engineering is the art of making what you want from what you can get at a profit.

kunkmiester
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Postby kunkmiester » Tue Jun 09, 2009 3:36 am

I was under the impression that there was a minimum size needed. That's the main reason they're looking at the 100MW machine.

You'd probably need to get it 1 meter or less to put in a current truck. Otherwise you'd be looking at something like this:
http://www.darkroastedblend.com/2008/02 ... rains.html (the first one, big and yellow, though the second one might work too)
Evil is evil, no matter how small

Heath_h49008
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Postby Heath_h49008 » Sat Jan 30, 2010 6:42 am

If we have the electricity, cracking alcohol for long distance fuel becomes cheap and clean. Add to that the use of nanotube capacitor/batteries for a series-hybrid driveline, and the case for putting an entire reactor in a truck or car becomes a bit hard for me to make.

But, an aircraft that can produce maximum thrust virtually forever, holds some interesting options.

What I'm more concerned with, is mass. You need a vacuum plant, the energy conversion hardware, and the control systems. How small can we make those systems?

An F-14 wasn't exactly small. In fact, two f110 turbofans occupy about the same space as a shipping container... probably more... and each made about 25k lbs of thrust.

If we can beat that with a reactor that doesn't have to lug all that fuel, and can actually maintain that thrust for more than 2 minutes or so before running dry... I think we have changed the game.

If the size is right, airliners, fighters, and even corp. sized aircraft could be users.

But not if the reactor needs 50k lbs of support mass, and can only produce 100Mw.

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Postby 93143 » Sat Jan 30, 2010 7:12 pm

Too big for fighters. I doubt you could get net power from p-11B with less than a 10' magrid even with very strong magnets, so very optimistically that's a 14' vacuum chamber. 20' or more is likely, but let's go with 14'.

Now, the neutronicity of a p-11B core is too low to have much effect on the materials, but it does require shielding. Say 6" of water, a bit of 10B, and 1½" of lead. That's 75,000 lbs right there. Then there's the bremsstrahlung, 5% of net power by some estimates. Say 2-5" of lead, so bump the weight to 100,000-200,000 lbs. Then there's the gammas given off by the secondary branch of the main reaction. There aren't that many of them (0.01%) but they're high-energy. Say a foot of lead. (You can forget the water and 10B at this point.) Now your shield weight is up to 450,000 lbs.

You could shadow-shield the pilot's seat, requiring only a few tons of lead, but now the ground crew has to be behind heavy shielding barriers before the reactor is turned on, and no one can be allowed nearby while it's running. Kinda complicates carrier operations, not to mention formation flying, or airshows...

A shadow shield at the reactor would be about 50,000-80,000 lbs, allowing passengers and payload to be safely carried, but this doesn't solve the other problems.

...

Now, you might be able to get a 6 GW core into a 35' sphere. This gives you a complete shielding mass of about 3 million lbs.

Fortunately, at the thrust-to-power ratio achieved by a modern high-bypass turbofan, 6 GW can lift more than twice that weight straight up...

I say use a heat exchanger to dump reactor waste heat into the engine upstream of the main heating element, so as not to have to dump coolant overboard. Range is now limited by how much isotopically-pure protium and boron-11 you can carry...

Heath_h49008
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Postby Heath_h49008 » Sat Jan 30, 2010 7:23 pm

So, while it has to be the size of a Los Angeles class sub... we can make that sub fly. (Fly, orbit, and take lunar weekend jaunts)

6Gw... The possibilities are inspiring.

Heath_h49008
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Postby Heath_h49008 » Sat Jan 30, 2010 7:44 pm

In an air breathing cycle, I'm curious if we could get efficient thrust from gas expansion heating in a jet form. (Plasma heating and expanding gas instead of burning fuel) It seems like a whole lot of energy being dumped as heat at relatively low speed. From an efficiency standpoint, an electric motor, or a Magnetoplasmadynamic thruster would seem more efficient without the conversion losses.

MSimon
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Postby MSimon » Sat Jan 30, 2010 7:48 pm

Heath_h49008 wrote:So, while it has to be the size of a Los Angeles class sub... we can make that sub fly. (Fly, orbit, and take lunar weekend jaunts)

6Gw... The possibilities are inspiring.


That is kind of what I was thinking. Aircraft carriers in the sky.
Engineering is the art of making what you want from what you can get at a profit.


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