The Focus Fusion Society Forums Focus Fusion Cafe FF for Jet Engines?

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  • #838
    nemmart
    Participant

    Why not just power the airplane with FF’s? Just checked some numbers. A 747 burns on average a gallon a second during flight. Jet A has roughly the same energy per weight as gasoline which has 121 MJ per gallon. Therefore a 747 uses 121 MW/hr, which means 20 FFs to produce the juice.

    My second thought is that so many of these posts read like FF is an all but done deal. But we should all be a bit more realistic — it isn’t a done deal. So many things could go wrong – from the fusion physics, to the engineering to the economics.

    Another aspect that particularly troubles to me: if FF was as close as it sometimes appears, I’d think funding would be pouring in. Think of it this way — what would be more beneficial, FF working or say a malaria vaccine? Organizations like the Gates foundation throw tons of money at long shot, big payoff efforts, like a malaria vaccine. So why hasn’t someone or some organization with deep pockets decided to fund this?

    #7007
    Glenn Millam
    Participant

    nemmart wrote: Why not just power the airplane with FF’s? Just checked some numbers. A 747 burns on average a gallon a second during flight. Jet A has roughly the same energy per weight as gasoline which has 121 MJ per gallon. Therefore a 747 uses 121 MW/hr, which means 20 FFs to produce the juice.

    You wouldn’t want to put FFs on an airplane. X-ray shielding alone will make the weight prohibitive.

    Also, don’t confuse joules and watts.

    As for your numbers… are you sure you are factoring in the jet engine’s efficiency? When using any fuel to power an engine, it is not just the total amount of potential energy in the fuel that matters, but the efficiency of the engine in extracting useful energy from the fuel.

    Jet engines are not terribly efficient at extracting energy from fuel. In fact, most fossil fuel based engines aren’t. Car engines get about 20% efficiency. So if you put a gallon of gas in a car, with a total energy of 130 MJ, you end up only getting 26MJ of useful energy out of it. The rest is wasted.

    In terms of cars, the efficiency and local nature of FF would make it a great solution for powering electric cars. Part of the argument about electric cars is that the sources we currently have of producing and transmitting electricity gives only about 33% efficiency, thus making an electric car about 25% fuel efficient. If we had FF, with its potential 80%+ efficiency and ability to have the plant closer to the end user, you could see a dramatic increase in the efficiency of the drive to work. This, of course, depends on a lot of problems to be overcome. Not only does FF have to work, but you need a better battery than current technology.

    And that’s just cars. With planes, you need to have weight in consideration. To make a good electric airliner, you would need a phenominal battery technology that is light, stable, incredibly energy-dense, and won’t randomly catch on fire or arc lightning about the cabin. I think carbon-based fuels will be used in airplanes for a long time. But that’s OK, because if the only thing we are using fossil fuels for are airplanes, then the oil reserves of the planet will last a long, long time.

    And, you could always take one of these instead.

    #7008
    Henning
    Participant

    Glenn Millam wrote: You wouldn’t want to put FFs on an airplane. X-ray shielding alone will make the weight prohibitive.

    That’s the neutron shielding that requires that heavy water (1 ton per m^3), but that compensates the tons of fuel required.

    See also here in the forums: Space and Aerospace Design in a Focus Fusion World

    #7010
    Dr_Barnowl
    Participant

    Henning wrote:
    That’s the neutron shielding that requires that heavy water (1 ton per m^3), but that compensates the tons of fuel required.

    A lot of that weight is in the wings – but you can’t put shielding in the wings for a reactor in the body. The space consumed by the reactor and shielding would displace passengers which is a non-economic prospect.

    An FF powered fuel reformer is a far more likely solution to the aviation issue.

    Not only does FF have to work, but you need a better battery than current technology.

    The two energy techs I have my eye on are FF and EESTOR (a high density capacitor technology company), although I find FF a lot more credible than EESTOR, I’d be fairly cheery if either of them were to come to fruition. If LPP meet their goals this year then I will throw a hell of a party. Really, FF is my source of hope for the future – my instinct tells me that there are hard times ahead without a solution to the energy crisis. EESTOR would be nice, but the existing pool of ICE powered cars are not going to vanish overnight. With the predicted break-even on a DPF reactor somewhere less than a year, you can bet that as soon as they are viable, the rush to build and install them won’t end until all the coal powered stations are offline.

    #7014
    vansig
    Participant

    or place the reactors in the tail section, then have just a single shield for the bunch

    #7015
    zapkitty
    Participant

    Hmmm?

    I thought that the production DPFs, boron-fueled, were to have a low radiation
    footprint?… That is, once you’re outside of the x-ray converter shell.

    #7017
    vansig
    Participant

    zapkitty wrote:
    I thought that the production DPFs, boron-fueled, were to have a low radiation
    footprint?… That is, once you’re outside of the x-ray converter shell.

    yes, though ~0.1% of reactions do generate some slow neutrons:
    11B + α → 14N + n + 157 keV;
    11B + p → 11C + n − 2.8 MeV;

    and ~.01% produce a gamma:
    11B + p → 12C + γ + 16.0 MeV.

    #7019
    Phil’s Dad
    Participant

    Did you mean – 2.8MeV?
    Bit of a downer :ohh:

    #7022
    vansig
    Participant

    so we’re talking ~ 1m thickness of water times the cross-sectional area of the rear of the cabin, call it ~7..20 tonnes. compare this to the weight of jet fuel in a 747, ~230..240 tonnes.

    aircraft will both carry more payload and extend their range enormously.

    #7028
    dennisp
    Participant

    Hmph. Ok maybe I should retract my “too bulky” comment.

    How would the jet work? Propeller plane is easy, just electric motors, but we’ve got no burning fuel to inject into a jet engine.

    #7029
    Breakable
    Keymaster

    dennisp wrote: Hmph. Ok maybe I should retract my “too bulky” comment.

    How would the jet work? Propeller plane is easy, just electric motors, but we’ve got no burning fuel to inject into a jet engine.

    Just another engineering problem. Would be interesting if some reaction-less drive would come online
    http://en.wikipedia.org/wiki/Reactionless_drive

    still even if not, then:
    1) propellers,
    2) turbines,
    3) or just heating the air can be substituted as a reactive drive

    #7030
    dennisp
    Participant

    I’ve been following the Woodward drive…that’d be an even bigger breakthrough than fusion. Wish it had more funding but they are doing some experiments at least.

    Short of that though, are you proposing heating via electric resistance? I think we just invented the flying toaster! 🙂

    #7033
    Brian H
    Participant

    Hi, zapkitty. Your posts are most welcome and on-point!

    As for airplanes, Elon Musk, of SpaceX/TeslaMotors fame, has his next goal as the design and production of VTOL electric airliners capable of 12,000 mile flights. I personally think the near-future improvements in battery tech (5-10X current energy density, plus much reduced internal heating and charging problems) will answer. For the same weight of battery, that would extrapolate to a 2-3,000-mi. range for TeslaMotors current and near-future models, e.g. It would probably also suffice for airliners.

    #7034
    Brian H
    Participant

    dennisp wrote: I’ve been following the Woodward drive…that’d be an even bigger breakthrough than fusion. Wish it had more funding but they are doing some experiments at least.

    Short of that though, are you proposing heating via electric resistance? I think we just invented the flying toaster! 🙂

    One commenter had a great response: “There Ain’t No Such Thing As A Free Launch!”
    :cheese:

    #7035
    Brian H
    Participant

    As far as flying toasters, anything that heats air will do for a propulsion source. That’s all a jet engine does, in the end.

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