[QuantumG]

Random musing: http://selenianboondocks.com/2010/01/fusion-drive/comment-page-1/#comment-7178

[QuantumG]

What a great blog.. Kudos to anyone who makes real hardware.

[QuantumG]

Ok, here’s another one by the same authors, obviously they cleaned it up for public release:

http://quantumg.net/advancements_in_dense_plasma_focus_for_space_propulsion.pdf

It includes pretty pictures. The conclusions are similar, but only the “not wildly optimistic” results are presented 🙂

[QuantumG]

Ahh.. that paper is available from:

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA446973&Location=U2&doc=GetTRDoc.pdf

or, if you prefer:

http://www.quantumg.net/propulsion_and_power_generation_capabilities_of_a_dense_plasma_focus_fusion_system.pdf

This paper does include the numbers I requested. Unfortunately it also includes a lot of “speculative” military technology (estimated 2025 timeframe) like “pulsed-train plasmoid weapons, ultrahigh-power lasers, and gravity devices” which diminishes its credibility somewhat, which really is a shame because the paper is otherwise excellent.

The thrust/weight ratio suggested ranges from 1.0 to 4.5, with 4.5 being considered unreasonably optimistic even with an assumed 20 year development of capacitor density improvement.. more improvements would result in even greater thrust/weight ratios which the paper dares to dream could push the ratio up to 44. The alternative is to dream that the thruster efficiency will dramatically increase, which could also push the ratio up to 44.

The paper suggests that in the 2025 timeframe the technology would exist to build a DPF thruster with a mass in the range of 11.33 tons to 480 tons, and thrust/weight ratios in the range of 2.08 to 44.12.

For reference, the space shuttle main engines have a thrust-to-weight ratio of 73.2, so 44.12 is very respectable.

One thing the paper didn’t do is present numbers for a DPF thruster built with existing capacitor technology, recalculating for available technology and actual demonstrated efficiencies of a real device will be a fun activity once focus fusion has been achieved.

[QuantumG]

Is the use of the focus fusion device as a thruster written up somewhere?

Like.. with actual numbers?

Important numbers being:

* count and velocity of particles emitted per shot
* number of shots per second
* total mass of the device, capacitors, wiring, etc
* total mass of any anticipated shielding (depends on application)

Here I’m imagining an operating mode where just enough net power is generated to do the next shot and the remaining velocity of the high energy ions is used as exhaust to generate thrust. There are other possible operating modes:

* use as an electricity source to power a conventional hall effect thruster, ion thruster, or something exotic like VASIMR
* thermal heating of a traditional propellant like hydrogen.. this would be possible, for example, by using the x-rays, meaning they can’t be captured for net power production.

Estimates of these numbers will allow you to make comparisons with other (typical solar powered) thruster technologies.

Does anyone think a focus fusion thruster (FFT?) could be built with a thrust/weight ratio on par with chemical rockets? Or are we firmly in the domain of high-specific-impulse electric propulsion?

[Author]

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