[Aeronaut]

JesterX wrote: How is the current passed from the capacitor bank to the cathode/anode through the vacuum chamber? It looks like the whole core is attached to a CF flange, does the flange have pass-through terminals machined into it?

The vacuum chamber is not actually part of the circuit as I understand it. The actual plasma paths are from each of the cathodes to the anode, which conducts all of the plasma’s current during the axial phase rundown. The anode itself is actually shaped more like a circular Tee flange. I know it looks misleading in the gallery 🙂

The base plate and everything that bolt onto it are at the cap bank’s negative (frame ground) potential. The anode is insulated by a pyrex insulator in this case, but that could just as easily be ceramic or a composite.

The pix showing the tops of the caps show the high voltage plates on top with the anode flange as the bolt circle at the center.

[Aeronaut]

Brian H wrote:

Since the DPF design process hinges on how much heat can be removed from how small of an anode radius/area, I decided to verify Eric’s number regarding heat removal ceilings. What I found was an off-the-shelf heat pipe which I think is titanium (melts at a little over 3,000 F) and uses Lithium as the working fluid.

I did a preliminary design drawing (http://energymadecleanly.com/anode.pdf) exploring using this part as well as asking about the preferred berylium/helium construction for FF generators. I just talked with a sales rep and expect some feedback from their engineers tomorrow around this time.

If this works, we’re free to run it at much higher temperatures, decrease anode radius, raise field strength, reduce rundown time, (more energy to the plasmoid), and hopefully slash X-ray production to below 25% of total charged particle output. The X-ray part is a wild hope, since Eric’s tables don’t show field strength affecting it very much.

What think?

Off-the-shelf is very good, of course!
What was the feedback?
And what’s this “LITIUM” stuff mentioned on the drawing? 😉

Sorry about the smelling. Should have been lithium, of course. Haven’t heard back from that division. I’ll call the main company Monday. Biggest question in my mind right now is if they make one that’s electrically insulating. Otherwise my heat exchanger has to use liquid silicone, like Eric recommends in the patent for cooling the onion.

How’re the Olympics going? Looks like you’ve got a ringside seat 🙂

[Aeronaut]

Henning wrote:

After we get fusion up and running, grasslands will be my next environmental pursuit. Restoring the Middle East dustbowls. So much to do.

Yepp. And my taking is, before colonizing Mars, finish colonizing Sahara first. I don’t care if Mars gets settled 1000 years from now, way after my lifespan.

Mars is fine for robotic exploration (with computers outperforming human brain in twenty years anyway, like a recent survey of experts say – or let’s say in fifty years). There is no need for humans on extraterrestical planets, what couldn’t do robots better – giving one or two decades that are required to build stuff for a human expedition.

And no high risk space elevator (yes Aero, that means you).

Start with something useful, i.e. watering Sahara and surroundings.

I fully agree that getting FF up, running, and performing useful work for real people is the first priority. My design strategy is to build thermal products that are designed so the X-ray converter bolts right in during normal scheduled maintenance. Which is going to boil down to a core swap out in the field for economic and regulatory reasons. At some point the net electric output option will make these retrofits irresistible to all FF owners. But I see a steep learning curve for onion makers, at least in the early year(s).

Henning, I see the fusion frontier facing the same perception problem as space travel- most of the world is currently working from a limited resources world view. So the “glass half full” point of view is conspicuously missing, but only if you have the key to pretty much unlimited cheap, clean energy.

Taken a step farther, FF may well need some custom-engineered nano materials to reach its fullest potential by consistently reducing the bulk and mass of the shielding. Capacitors are another area where custom-engineered materials research for FF could cross over into the SE tether’s development.

And the last step is that when we get over the ‘need’ to reach orbit using chemical rockets, a whole new branch of the global economy is going to spring into existence. Returning NASA to its research and engineering roots was an excellent move in that direction, imho.

[Aeronaut]

Progress on the tether is incremental. Much more challenging imo is getting the popular and financial support needed. I have a hunch that FF and the SE are both going to reach the public awareness about the same time. By public awareneness, I mean when most people believe it can be done and then start asking why it hasn’t been done yet.

Now If W had directed NASA to develop the SE as the most cost-effective road to Mars and beyond, $50G would be no major problem.

[Aeronaut]

vansig wrote:

The main problem of getting in space (LEO, at least) is not reaching a certain altitude, it’s reaching a certain velocity (about 7 km/sec) and once you are above an altitude where wings provide lift, you have accelerate to orbital speed within a given time with a given minimal acceleration or else you will simply fall back to Earth.

Yes, space ship 2 reaches its max speed of mach 3.5 after a 70-second burn and coasts up to its 110km max altitude.
This is way short of orbital velocity (~mach 24), requiring (24/3.5)²=47 times as much energy.

Consuming 200kW, one VASIMR VF-200 engine will have 5N thrust, and weigh 300kg. if you’re not already at orbital velocity, this doesn’t get you there.

Yepper. That’s why so many of us are looking forward to a Space Elevator. For some missions, the SE could eliminate or greatly minimize the amount of thrust required by ‘launching’ from near the tether’s end.

[Aeronaut]

vansig wrote: The Aneutronic fusion article on wikipedia indicated that for Boron fusion, this undesirable reaction occurs at >0.1%

B-11 + alpha -> N-14 + n

and that the neutron will carry a large fraction of the alpha energy. seems they’re quoting
Heindler and Kernbichler, Proc. 5th Intl. Conf. on Emerging Nuclear Energy Systems, 1989, pp. 177-82.

is this as bad a problem as they seem to suggest?

No, it’s just a nuisance problem that we work around by shielding the reactor with a 1 meter water jacket covered by 10 cm of boron, covered by 2 cm of lead or boronated polyethylene. The actual reactor is incredibly small and light compared to the shielding and rest of the support equipment. That said, the lower we can get that ratio, the less gross energy we’re going to lose through it.

[Aeronaut]

vansig wrote:

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.

i’m not sure about those ions being relativistic, though. does 0.028 c sound right?

here’s some discussion from last year..
http://answers.yahoo.com/question/index?qid=20090402091850AAAnih4

Here’s what Eric and the Naval Research Lab have to say about using the DPF as a thruster:

ISP: 10^6 (1,000,000 M/second)
With 80% X-ray recovery and 46% efficiency beam recovery, 78% energy to useful thrust.
Thrust-mass ratios of .1N/kg, specific power of 500 kW/kg
6 month transit time to Jupiter. 2:1 total mass/payload ratio.

It also has a slightly more optimistic version of Table 2, showing a scenario where the DPF can show a very slight electrical profit without the X-ray converter. Free heat, anybody?

[Aeronaut]

Methinks funding trumps Q over there.

[Aeronaut]

Combined with the Columbia/MIT experiment, it shows a pattern of bringing government research to the university lab level. At least there it’s accessible to a lot more students and physicists, while costing a lot less.

[Aeronaut]

It’s funded by DOE, and intending to run just deuterium, so my guess is they’re also aiming at steady-state fusion. Btw, doesn’t the D-D cycle also release its energy as HE neutrons?

[Aeronaut]

The airplane is an excellent analogy, Keith. The Wright brothers got their glider technology proven before tacking a drive train onto it. They solved their challenges in the right order. Their big mistake was their paranoid secrecy once they’d done it a few times.

[Aeronaut]

QuantumG,

I found a site today that will blow you away. http://www.myelectricengine.com . This fairly new EE set out to build a reasonably priced MPD, and this site documents his theory, math, and hardware in much easier to understand form than anything else I’ve seen so far. I found the cap bank page while doing a string of searches for how to calculate HV buss inductance. The upshot is that the equivalent circuit of his MHD and our DPF is nearly identical. He doesn’t seem to be aware of the DPF.

The biggest difference is his anode is the outer electrode. The electrode geometries are also different. I did a series of sketches integrating professor Lee’s simplified electrical diagram showing the cap bank as 12 parallel branches, the DPF as 2 more, and the MHD as the last 2, for a total of 16 parallel branches. The DPF and MPD inductances are in series with the spark gaps from Krolak’s diagram. I used 4 SCR banks as current gates. The first 2 divide the HV buss into 3 segments- cap bank, DPF, and MPD, the third gates the MPD’s reverse EMF into the inductive energy recovery system that LLP’s patent reserves for the DPF’s reverse EMF. I’m powering the MPD with the DPF’s reverse EMF. The 4th SCR bank connects the energy conversion and recovery circuits (the cap bank recharger and electrical profit), back to the main cap bank.

Noting the spark gap switch challenges of an expensive part, I got rid of the extra parts (hopefully) by letting the cap bank charge to ~90% of trigger voltage pretty much on it’s own, then delivering the last few thousand volts under control of the ignition timing circuit. Not the ideal MPD theory, but it’s fuel and energy are basically free.

So far it looks good as a current diagram. Haven’t done the math yet, so it may or may not work numerically. But it looks like a promising bolt-on to the drift tube to draw the decelerated He4 ions to the MPD cathode. And in space it shouldn’t need the vacuum pumps.

[Aeronaut]

Do any of the people who are actual physicists here take it seriously? Does it have civilian value or is it just a testbed for nuclear weapons without the weapons?

Big science= big budgets= secure careers for government physicists, staffs, and vendors. It may well turn out to be the Cold War without the obvious weapons focus. I’m not a physicist, or even an engineer. At least not today, and not that I can show the sheepskins to prove. I see NIF, ITER, et al as being potentially useful… in the (unspecified future) as basic materials science research.

The gotcha is the phrase ‘in the unspecified future’, which also serves a second purpose of supporting the status quo by conditioning the general population to consider fusion as something that even the gov a mint, wit all the time and money and talent they’ve been throwing at the problem, can’t do it, it can’t be done.

Only a tiny percentage of the public reads beyond the top 3 results of a search, let alone past the first page or two. And SEO is designed to favor dot gov and dot edu domains, especially when they have thousands of pages about fusion research and related keywords. [end rant]

[Aeronaut]

That’s about the age I was when I came up with the idea. Took my dad about .5 seconds and 0 thought to tell me it wouldn’t work. Maybe a water wheel is what Helion needs to provide the makeup 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.

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