Reply To: Barack Obama on Energy

[Aeronaut]

QuantumG wrote: 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?

Particle count per shot is a function of plasmoid diameter (how much fuel is contained in the magnetic bubble), plasmoid lifespan, and how many reactions occur as it collapses. Particle speeds are relativistic, afik.

PRF, number of shots per second, is going to depend on mission profile (destination Mars, Pluto, Alpha Centauri and back(?)). power requirements of the entire ship, and the number of reactors on board, just for openers. 2 key limiting factors in the high-energy caps used in FoFu-1 are a design life of only 10,000 shots at rated voltage (improves 1,000-fold @ 40%) and a weight of around 2,820 pounds for 12 caps. http://www.ga-esi.com/EP/capacitors/series-c.php . I’m trying to contact them about another key detail- what are the rise times?

Shielding mass is going to be however you want to enclose a 1 meter water jacket covered by 10cm of boron and 2cm of lead. Haven’t calculated it, myself, but I’m figuring to build under a 5 to 10 ton overhead crane.

The actual vacuum chamber and electrodes will fit in a 5 gallon bucket and probably weigh around 100 to 200 pounds. Another pesky little detail is that a vacuum pump that can evacuate FoFu’s vacuum chamber around 100 times a second or higher is not going to be small, light, or battery-powered. We had a lot of them where I used to work. I’d guess at least 20 HP. They were replaced using a hi-lo rather than a mechanic’s engine puller.

So unity is just the first hurdle.

update- GA just called back. The rise time is less than 1 microsecond, depending on the power buss inductance.