Space and Aerospace Design in a Focus Fusion World

[Phil’s Dad]

Aeronaut wrote: Looks like your chicken gun, PD 🙂

Some chicken…

Attached files

[QuantumDot]

to solve the thrust problem with the focus fusion you just need to add some material in front of the ion beam and let the beam heat and then eject the material, it would basically function like a pulse detonation rocket engine with the FF acting as a ignition source. so there would still be a lot of engineering problems but it would be possible for a single stage craft. using a deep cooling precooler and then the ff to ignite and then when it gets too high use some stored fuel as a rocket and then when in space just use the pure ion beam or when you need more thrust revert it back to a rocket. adding in optical and magnetic refrigeration would reduce the weight add simplify the design and be useful at all stages of the vehicles life.

[Augustine]

QuantumDot wrote: to solve the thrust problem with the focus fusion you just need to add some material in front of the ion beam and let the beam heat and then eject the material, it would basically function like a pulse detonation rocket engine with the FF acting as a ignition source. so there would still be a lot of engineering problems but it would be possible for a single stage craft. using a deep cooling precooler and then the ff to ignite and then when it gets too high use some stored fuel as a rocket and then when in space just use the pure ion beam or when you need more thrust revert it back to a rocket. adding in optical and magnetic refrigeration would reduce the weight add simplify the design and be useful at all stages of the vehicles life.

I think that you violated the law of conservation of energy. If for example a FF pulse imparts 10 Joules of energy then you can’t make it 100 Joules of energy by putting something in the way of the blast unless you put something in the way that explodes (releases additional energy by breaking chemical bonds) when hit with by an ion beam.

[Augustine]

Do we have any idea what kind of thrust a FF pulse can produce? I recall that JPL funded FF to work in deep space which would imply that it isn’t capable of getting anything to LEO. Maybe if we are lucky you could get to LLO.

I’d love anyone who could give a reference to what kind of thrust a FF engine would produce. Does it produce 1N of thrust per pulse? If it pulsed 100 times a second then you would have 100N which is actually quite respectable.

[Lerner]

Actually, what counts for thrust is momentum change, not energy alone, so if you impart the energy to a greater mass, you can get greater thrust.
Can’t remember the exact figures, but I’ll leave it to you guys to calculate the thrust–it is not high:
beam energy per pulse 10kJ
beam velocity 1.6 x10^4km/sec
pulse rate–500 Hz
You would need many DPFs for substantial thrust but in theory 250 sets of elcetrodes could be fed from a single set of capacitors.

[Aeronaut]

Lerner wrote: Actually, what counts for thrust is momentum change, not energy alone, so if you impart the energy to a greater mass, you can get greater thrust.
Can’t remember the exact figures, but I’ll leave it to you guys to calculate the thrust–it is not high:
beam energy per pulse 10kJ
beam velocity 1.6 x10^4km/sec
pulse rate–500 Hz
You would need many DPFs for substantial thrust but in theory 250 sets of elcetrodes could be fed from a single set of capacitors.

Can they share the same water jacket? Iow, do they need to be shielded from each other? Something like the after torpedo room in a sub, with that wall of tubes?

[QuantumDot]

Augustine wrote:

to solve the thrust problem with the focus fusion you just need to add some material in front of the ion beam and let the beam heat and then eject the material, it would basically function like a pulse detonation rocket engine with the FF acting as a ignition source. so there would still be a lot of engineering problems but it would be possible for a single stage craft. using a deep cooling precooler and then the ff to ignite and then when it gets too high use some stored fuel as a rocket and then when in space just use the pure ion beam or when you need more thrust revert it back to a rocket. adding in optical and magnetic refrigeration would reduce the weight add simplify the design and be useful at all stages of the vehicles life.

I think that you violated the law of conservation of energy. If for example a FF pulse imparts 10 Joules of energy then you can’t make it 100 Joules of energy by putting something in the way of the blast unless you put something in the way that explodes (releases additional energy by breaking chemical bonds) when hit with by an ion beam.

You seem to have misunderstood something. since what i am trying to describe is basically a form of afterburner for the DPF, since thrust is the velocity time the change is mass divided by the change in time, now since you are increasing the mass from what i think is a few micro grams to say a few kilograms in the same amount of time thrust should go up quite a lot now since you are slowing down the beam since it will hit the fuel and heat it up to a few thousand degrees C it won’t have the same exit velocity or the same ISP but when you need thrust it should work quite well.

[Dr_Barnowl]

You seem to have misunderstood something. since what i am trying to describe is basically a form of afterburner for the DPF

Energy is conserved – you can’t buy additional kinetic energy by adding inert mass. Afterburners only work because the mass that’s added to the exhaust stream is more fuel, which combusts, adding energy and mass to the exhaust gases, causing greater expansion of the gases and higher exhaust velocity.

You may be able to increase momentary thrust (by releasing superheated bursts of inert propellant), but you now have a much, much, much, larger propellant tank to haul, you lost energy in the preheat chamber due to thermal leakage, and the average thrust you’ll manage will be less than just venting the ion stream out of the back.

[vansig]

Dr_Barnowl wrote:

You seem to have misunderstood something. since what i am trying to describe is basically a form of afterburner for the DPF

Energy is conserved – you can’t buy additional kinetic energy by adding inert mass.

kinetic energy, E[k] = .5 mv²; so with constant E[k], if you double the m leaving the nozzle, then v is necessarily reduced (factor .707). but under conservation of momentum, mv has therefore increased by 1.414. so adding inert mass increases thrust, but costs a lot more propellant.

[QuantumDot]

George Miley design for a p-b11 dpf says for a 500kN 2000isp
power 800mw
w = 80mj
vo = 400kv
Q = 3.07
and about 10um per day of ablative material at 10 hz
thrust to weight of 20 – 44 kN/MT
http://nextbigfuture.com/2010/03/dense-plasma-focus-dpf-fusion-systems.html

QED engines are described elsewhere in this and previ

[Author]

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