Capturing Imagination – Spaceship angle

[Aeronaut]

[Hi Folks, we split this off from this post. It feels like a new topic. – Admin]

I hear you, Kyle. The only reason I found this forum is that I was determined to find a space flight-weight reactor, despite what the search engines were telling me was ‘state of the art’. Because I dug long enough, I found one with propulsion potential as well. (the ion stream moves at relativistic speeds).

Rezwan, I don’t get how a cheap power plant can be sexy. I do clearly remember the awe of some of my first few searches for fusion power, when I saw the pix of tokamok reaction chambers. But they weren’t going to fly. Just shiny toys designed to look good and do nothing practical for the average citizen.

One of our credibility problems is that since we don’t use superconducting magnets, we have neither the budget nor the bigger than life pix to capture the average person or average investor’s imagination, unless we can get FoFu into the engine room and/or life support system in the next Star Trek movie. Remember all those stubby silos in the engine room’s background? Who’s to say those aren’t water jackets shielding the fusion reactors?

Another credibility issue springs from publicly aiming at over-unity. Same problem fission must have had until Nautilus sailed in 1957. Even if we had thermal unity today, with enough ion conversion to recharge the caps and run the pumps, we’d look like a long road to commercial amounts of electrical power. I spent a few hours this week trying to lay out even one slice of the “onion” like a glorified solar cell using CVD machinery to deposit the foils and insulator/cooling system. And the patent reads ~150 to 180 of these slices.

Then there’s always the nagging doubt about public support-> political support->NRC regulatory support. I’d guess that a potential investor’s going to look at that and probably understand nothing other than a 3-5 year ROI in the best case, where everything ends up on schedule as of 1-1-2015.

BUT- optimize for 125J/btu (sub-unity), and you might be able to get an industrial oven or furnace maker to buy a license, since it will be a proven way for the end users to cut their gas bills in half. Even if the first license sells for $10M (early mover’s special deal), that funds the rest of Phase I and all of Phase II and the rest is the history of the investment that got away.

The best deals are the ones that you have go out and get 3 rows of callouses digging for in order to find. Maybe we’re going at this bass-ackwards and should be talking in ‘whispers’ about this ‘secret’.

[Rezwan]

Aeronaut wrote: One of our credibility problems is that since we don’t use superconducting magnets, we have neither the budget nor the bigger than life pix to capture the average person or average investor’s imagination, unless we can get FoFu into the engine room and/or life support system in the next Star Trek movie. Remember all those stubby silos in the engine room’s background? Who’s to say those aren’t water jackets shielding the fusion reactors?

Or get it on a Firefly transport. The engine room on that show looks a lot like LPP’s experimental space. It’s supposed to be a fusion engine. And Firefly is definitely “sexy”. Plus it appeals to the rugged individualist. The show’s been canceled, but the fans and stars live on. And they’re known to be dedicated. Do we have any Firefly fans here who also post to Firefly blogs? Has that show slipped off the radar? Not possible.

[Phil’s Dad]

It’s the bit that goes up and down in the middle of the TARDIS.

Attached files

[Aeronaut]

Ironman had fusion plants all over the place. And a prototyping system to die for.

[DerekShannon]

yeah, I had to suppress my urge to scream “Who cares about the stupid suits when you have all those tiny fusion reactors?!?” during IronMan.

Anywhoozle, I envision my focus fusion-powered space yacht as a mock-up of the NCC-1701 Enterprise with the generators jutting out as the warp nacelles. Center of gravity be damned!

[Aeronaut]

DerekShannon wrote: yeah, I had to suppress my urge to scream “Who cares about the stupid suits when you have all those tiny fusion reactors?!?” during IronMan.

Anywhoozle, I envision my focus fusion-powered space yacht as a mock-up of the NCC-1701 Enterprise with the generators jutting out as the warp nacelles. Center of gravity be damned!

Mine is more along the lines of the Lost In Space series’ Jupiter II. There’s a flight simulator for it online somewhere with a screenshot looking in the flight deck’s window. The fusion reactor is clearly visible on the centerline, using roughly 1/3 of the ship’s volume.

Brian, I was wondering when somebody was going to catch that unity detail and call me on it. Long as we’re on the subject of details, I’m thinking Eric’s going to prove unity and beyond using the neutron tof detectors to prove that this many Joules in resulted in that many Joules out. Joules convert to almost anything, while eliminating the confusion of thermal vs electrical unity without the hassle and expense of a ‘regulation’ test chamber.

Long as you’re ok with letting decaborane vaporization temp/pressure tables specify your electrode and chamber temperatures (to keep decaborane a gas), you’re required to highly engineer your cooling system or vary your PRF to favor cooling at the cost of electrical output stability. It’s in the patent’s fine print (para 144) that using pentaborane frees the designer to optimize for cooling system efficiency by providing a much wider operating temperature range.

[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?

[Rezwan]

My understanding is that ion propulsion is orders of magnitude better than chemical propulsion, but now that you mention it, I can’t put my hands on the numbers. Here is a post on DPFs and Space Propulsion.

[Brian H]

Rezwan wrote: My understanding is that ion propulsion is orders of magnitude better than chemical propulsion, but now that you mention it, I can’t put my hands on the numbers. Here is a post on DPFs and Space Propulsion.

One issue is boost phase (getting out of atmosphere and the gravity well). Ion drives have been low-thrust long-duration winners in long journeys; it’s the “halfway to anywhere” achievement of orbit that’s critical. I believe using DPF for MHD thrust supposedly solves that.

IIRC, wasn’t Eric’s funding in the mid-90s from the DOE under the banner of Advanced Propulsion systems, until that whole area was de-funded by penny-wise pound-foolish Congresscritters?

[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]

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 🙂

[Aeronaut]

QuantumG wrote: 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 🙂

Eric estimated 2 ton mass (I’m pretty sure it was unshielded) in his Google talk video. A 360 degree water jacket 1 meter thick is the single largest and heaviest component. But I’m sure you can pretty much eliminate the shielding mass if the reactor’s on the end of a 100 foot long boom. Could be tough getting a net reduction of mass…

Eric’s first 2 experiments were funded by NASA’s Jet Propulsion Lab. The incoming Bush Administration defunded the program that JPL was using to fund FF.

[Brian H]

Aeronaut wrote:

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 🙂

Eric estimated 2 ton mass (I’m pretty sure it was unshielded) in his Google talk video. A 360 degree water jacket 1 meter thick is the single largest and heaviest component. But I’m sure you can pretty much eliminate the shielding mass if the reactor’s on the end of a 100 foot long boom. Could be tough getting a net reduction of mass…

Eric’s first 2 experiments were funded by NASA’s Jet Propulsion Lab. The incoming Bush Administration defunded the program that JPL was using to fund FF.
Net FF mass reduction isn’t a big deal, compared to the fuel load necessary for a chemical thrust rocket. Fuel weight would be negligible for FF, even at non-stop full thrust. Reaction mass would maybe be the largest requirement, unless the alpha beam itself would serve. A small ion engine would be much lighter, but would have much lower specific impulse, too.

[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.

[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.

[Author]

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