Viewing 15 posts - 1 through 15 (of 67 total)
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  • #417
    Duke Leto
    Participant

    Hi there, 2nd time poster long time FF interest.

    These are going to be some technical spec questions about the DPF and the proposed the DPF reactor. Bonus points to any one who can glean from the questions what I’m thinking.

    1) On the page, the proposed $500,000 1st generation reactor is stated to have a capacity of 20 MW. In the investor prospectus for LPP, it’s 2 MW. Which is correct? (Pesky powers of ten.)

    2) What’s the anticipated Rem (radiation) output of the X-Ray/Gamma-Ray emissions that are not captured for power generation?

    3) What is the anticipated lead shielding thickness to dissipate this radiation?

    4) Will the Rem output and shielding decrease in direct proportion to the decrease in wattage if miniturazation of the device can take place?

    5) What are the approximate dimensions of the proposed reactor?

    6) Some discussion has been made about filtering out the helium “ash” to maintain fuel purity. I assume there will be reservoirs of pure fuel and spent helium, and that a gauge determining teh levels of each would be all that is needed to determine when to “Fill Up”.

    #2076
    Lerner
    Participant

    1) On the page, the proposed $500,000 1st generation reactor is stated to have a capacity of 20 MW. In the investor prospectus for LPP, it

    #2079
    Duke Leto
    Participant

    So barring some miracle discovery in radiation containment, there’s an asymptotal lower limit on unit size of about a cubic meter.

    Ergo no fusion-electric car or propellor airplane, even if the system can be scaled down to about 500 KW. Rail Gun equipped 5 MW M1A1 Tanks, sure, but no way to mass produce the little lovelies and retrofit all the existing oil guzzling cars.

    On the brighter side, you can slap one of those babies into an SD40 locomotive without too much trouble, gutting the diesel in the diesel electric locomotive. Can probably just leave the old engine in place and dump the reactor into the empty fuel tank.

    The absorbtive capability of water for catching neutrons has to be a function of density as well as depth. (—- remembers distance between nuclei outside neutron stars.) Scratch that thought about increasing the water density. What about cadmium or (gods forgive me) graphite?

    #2080
    Jolly Roger
    Participant

    Borated polyethylene may be a viable substitute for water as neutron shielding.

    http://ds.dial.pipex.com/johncaunt/shielding/html/neutshort.html

    Coming from a commercial fission background, I was thinking of borated water for neutron shielding instead of/in addition to solid boron.

    One advantage of water, borated or not, as neutron shielding is that it is also a coolant, removing the heat of the low-energy neutrons. The particle decelerators and capacitor banks will need cooling too.

    I know we are trying to stay away from the steam cycle. It doesn’t sound like we are talking about a lot of excess heat anyway. There are many ways to extract energy from heated water.

    #2122
    Jolly Roger
    Participant

    Lerner wrote: Reactor plus shielding is 2 meters across but whole thing, including capacitor bank may be more like 3x2x2 meters.

    Duke Leto wrote: So barring some miracle discovery in radiation containment, there’s an asymptotal lower limit on unit size of about a cubic meter. Ergo no fusion-electric car or propellor airplane…

    It may be possible to design a semi-tractor or bus around a Focus Fusion reactor, but I wouldn’t be too comfortable being stuck in rush hour traffic next to an active gamma and x-ray source. But then again, I have been involved in shipping low-level fission waste down the road, so there is not much difference.

    Trains and ships will not be a problem fitting an FF reactor aboard. A large plane could carry one under each wing or in its belly to power electric ducted fans.

    1 Watt = 1 Newton-meter/second, therefore 5 MW = 5,000 kN-m/s. The engines of a Boeing 747 develop ~280 kN of thrust. (The units aren’t quite right, so this might be mixing “apples-and-oranges”.)

    Does this mean that if a reactor/engine system had an efficiency higher than ~6% a Focus-Fusion-powered 747 could fly? If not, why not?

    #2129
    Duke Leto
    Participant

    Jolly Roger wrote:
    Does this mean that if a reactor/engine system had an efficiency higher than ~6% a Focus-Fusion-powered 747 could fly? If not, why not?

    Oh that’s easy. Just use the electricity to run high voltage/high temperature electrolysis of a saline solution at or close to the point near the jet engines that are going to burn the Hydrogen/Oxygen mix. About the same overall weight, a little more thrust and the fuel isn’t explosive outside the engines.

    #2133
    Jolly Roger
    Participant

    Duke Leto wrote: … use the electricity to run high voltage/high temperature electrolysis of a saline solution at or close to the point near the jet engines that are going to burn the Hydrogen/Oxygen mix. About the same overall weight, a little more thrust and the fuel isn’t explosive outside the engines.

    An interesting idea, but not what I had in mind.

    Most of the thrust from a turbofan jet engine is from the bypass air. (see diagram http://en.wikipedia.org/wiki/Image:Turbofan_operation.png )

    In the aircraft engine I propose, an electric motor to drive the fan replaces the compressor. A Focus Fusion reactor replaces the combustion chamber. A particle decelerator/generator replaces the high and low speed turbines. Placing the reactor and generator aft of the motor reduces power losses and cable weight. Total aircraft weight is reduced, as only decaborane fusion fuel is required.

    The helium ion exhaust provides some rocket thrust. If mixed with the bypass air to heat it, additional thrust may be obtained.

    By changing how much energy is extracted from the exhaust and routed to the electric motor, this engine may be able to function in a space plane both within and above the atmosphere, and perhaps even under water. (Remember the flying submarine from “Voyage to the Bottom of the Sea”?)

    #2135
    Duke Leto
    Participant

    1) I’m not sure that the Helium stream would provide thrust with anything close to the efficiency that it provides deceleration electricity, since ion drives provde minimal constant acceleration over long distances.

    2) I also gather from your description that the alpha stream would be going through the fan system, that would mean that the reactor must be located in the center. I think this would mean that:

    a) It would be much more difficult to maintain the needed pressure of the Hydrogen-Boron fuel.
    b) You would be pouring unspent fuel into the atmosphere or whereever at an alarming rate, and thus wasting Boron.
    c) You’d be shooting fully energized ionizing alpha particles into the environment, which I believe is nastier then Gamma.

    I’ll defer to your judgement on these points, since I don’t have a Nuclear background.

    Keep in mind I’m looking to have engines that fit into existing vehicles without too much fuss, not next generation machines.

    Man this looks terrible without list tags.

    #2136
    Jolly Roger
    Participant

    Duke Leto wrote: 1) I’m not sure that the Helium stream would provide thrust with anything close to the efficiency that it provides deceleration electricity, since ion drives provide minimal constant acceleration over long distances.

    You are right about the Helium exhaust not providing very much thrust. It just does not put through much mass. It is more effective powering a motorized fan/propeller to move large masses of air.

    An FF rocket will not be a typical ion drive, however. It will have ~1,000 times more power. It may more closely resemble a plasma rocket like VASIMR.

    To get out of Earth’s gravity well we need high thrust, and that means moving a lot of mass quickly. Maybe we could boil water with microwaves, or squirt salt water through a linear accelerator, or even a compressed air/water rocket.

    2) I also gather from your description that the alpha stream would be going through the fan system, that would mean that the reactor must be located in the center.

    I did not make myself clear. The reactor is located behind the motor, but only so that the electrical cable from the generator to the motor is short. The reactor and generator could just as easily be located somewhere else in the plane. The airflow from the fan does not go through the reactor. It goes around it, to provide cooling.

    As the Helium exhaust will provide negligible thrust, we will now minimize it, turn the reactor around and place the decelerator/generator immediately behind the motor, and the reactor at the rear. The reactor, fuel and exhaust will be self-contained and separated from the environment.

    I think this would mean that: …
    c) You’d be shooting fully energized ionizing alpha particles into the environment, which I believe is nastier then Gamma.

    We will now extract as much energy as possible from the Alpha stream and neutralize it with electrons. It may be worthwhile to save the helium and sell it. Unreacted fuel will be recycled back to the reactor.

    Alpha particles are only hazardous if taken internally, as they steal electrons and break chemical bonds. Exposure to Alpha gas would damage the mouth, nose, throat and lungs.

    Keep in mind I’m looking to have engines that fit into existing vehicles without too much fuss, not next generation machines.

    To retrofit existing aircraft, reactor/motor/fan pods can be made to replace wing-mounted turbofan engines on the larger planes. Tail-mounted engines will be more complicated to replace, but possible. The existing fuel tanks will be drained, cleaned, dried and removed if possible. Reactor fuel tanks will be small enough to include in the engine pods.

    Medium-sized aircraft will have the reactor/generator placed in the fuselage, with electrical cables to the replacement motor/fan pods on the wings.

    Aircraft too small for a reactor will be converted to fuel cell or electric vehicles.

    Next generation aircraft will be more efficient than retrofitted ones.

    #2137
    Transmute
    Participant

    I doubt that DPF fusion reactors are going to have a high enough power to weight ratio to compete with a jet engine, a jet engine is power and thrust all in one package, a DPF fusion reactor would need somekind of amazing electic motor and fans capable of propelling a plane to speeds beyond 800kph, and forget about supersonic travel with a electic pusher! Why not just make oil out of waste using fusion power to provide heat and hydrogen and run conventional aircraft off of it with no infrastructure change?

    #2139
    Duke Leto
    Participant

    Transmute wrote: Why not just make oil out of waste using fusion power to provide heat and hydrogen and run conventional aircraft off of it with no infrastructure change?

    Emissions is my worry.

    #2140
    Duke Leto
    Participant

    You raise an interesting question though, how much WOULD it cost to synthesize Oil and Gasoline with a DPF running the energy conversion?

    #2141
    Duke Leto
    Participant

    Duke Leto wrote: You raise an interesting question though, how much WOULD it cost to synthesize Oil and Gasoline with a DPF running the energy conversion?

    And could it be done using only carbon taken from the existing biological cycle?

    #2143
    Duke Leto
    Participant

    Or better still, just atmospheric CO2 and water?

    #2144
    Rezwan
    Participant

    Duke Leto wrote:

    Why not just make oil out of waste using fusion power to provide heat and hydrogen and run conventional aircraft off of it with no infrastructure change?

    Emissions is my worry.

    Don’t have the numbers or a handy pie chart, but it seems to me this isn’t that big of a concern. If the DPF works, and we go through and replace coal and oil burning power plants, and a majority of cars switch to electric, we’ll pretty much reduce the bulk of emissions. Then with tree planting schemes, or other carbon-fixing ventures, I’m sure we could balance the rest. Our net impact could be very small. Or no bigger than cows and the methane they emit (and cows get a bad rap. A lot of this is because of their industrial diet – gives ’em extra gas).

    So, there will be room in the emissions balance sheet to keep old-fashioned airplanes going.

    This in no way is meant to limit innovation in aero-propulsion.

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