[vansig]

Breakable wrote:

The units are wrong – it’s 6.4 kj not mj. See the “how_will_we_get_there_from_here” doc. Also, I think in Eric’s google tech talk, he mentioned 330 hz.

Nothing seems to add up
6.4 kj * 330 hz = 2.112 MW
Lets just say the generator will produce from a few kilowatts to a few gigawatt’s. I fully understand that there can be great uncertainty ATM.
Probably much will be cleared up at the end of this year or next when unity is achieved.

5 MWe / 50% efficiency = 10MW(e+t); divide by ~300 shots/second = 33.3 kJ / shot. (this is the 33 kJ Eric mentions).
Note that this is what we get after some otherwise usable electrical energy was carved off to fire up the next shot, which costs 70 kJ. (that’s 100 kJ from the capacitor bank, 70 kJ consumed, 30 kJ recovered in the mirror bank). So really, there’s 70+33=103 kJ in a shot.

The 6.4 kJ above is a part of the picture, that ignores the onion. It is very sensitive to actual recovery efficiencies.

[vansig]

vansig wrote: A 5MW Focus fusion generator, operating at 50% efficiency, will generate 5MW heat. Use that in your “jet” engine.

By the way, a nuclear powered ramjet engine was invented in 1957. The only thing i don’t like about it, is that fission can melt down and make a mess.

http://en.wikipedia.org/wiki/Project_Pluto

[vansig]

Aeronaut wrote: Can several FF cores share the same shielding envelope? I believe this is the 5th time I’ve asked.

Yes, I believe so. A shot is on the order of about a microsecond, total time. AFAIK, the only thing preventing 100,000 shots/second or more is thermal management. Sharing the same onion and the same water and other shielding, and even the same capacitors, could well enable the reactor’s total mass to scale up sub-linearly.

[vansig]

i don’t have specifics, but if leakage resistance were as low as 1 MΩ, (generally considered poor quality for a capacitor, some having leakage resistance as high as 10^12 Ω),
this would yield self-discharge current of 45 mA at 45kV. If τ0 = RC is the time constant, then a 33,000 μF cap would have τ0 = 33,000.

With these parameters i think we could run a pinch every few minutes without significant loss.

http://en.wikipedia.org/wiki/Types_of_capacitor

[vansig]

Breakable wrote: Just to clarify FF module output is MW and not MWH?

yes.

[vansig]

okay, let’s scale this up by tesselating a spherical onion ~3m diameter with up to 60 anodes, and immersing the entire assembly in water, at the tail of the aircraft. i will bet that the capacitor bank scales sub-linearly. even if we must completely surround the reactor with shielding, i’m getting < 100 tonnes for the whole thing. that's 27..50 tonnes of water, alone; and the rest is equipment.

now i know this ignores failsafe mechanisms, which you’d likely want to do, so maybe we can split this into two reactor compartments, and place them in the shoulders of the wings. this would increase the share of the water shielding somewhat; but in the event of failures, you can run your 5 MW anodes at 10..15MW if you like.

the result is quite a massive increase in payload capacity, ~50..150 tonnes

[vansig]

Glenn Millam wrote: OK, let me get this straight. There are a lot of unknowns to me here.
[…]
Does anyone have these answers? I know that the current plan for FF is to be housed in garage-sized power plants. Thats very small for a power plant but kind of big on a jetliner. But where there is a will there is a way….

Some of these answers are readily available. Some can be calculated.

Let’s use the Boeing 747-400 series as a baseline. it has a cruising speed of Mach 0.85; and 282 kN thrust per engine, x4 engines…
http://en.wikipedia.org/wiki/Boeing_747-400#Specifications

by the way, i think the onion is aluminum foil, not lead, and it captures 100% of the xrays. the neutron shielding is 1m thick water and a boron jacket; the gamma ray shielding is lead.

[vansig]

KeithPickering wrote: About half of the energy from FF derives from capture of the X-rays using the onion-skin. So the space issue is real, as each FF must have its own onion-skin. Twenty of those would easily fill a 747, leaving no room for payload.

and i thought the onion was about the size of a large pumpkin, say ~1 m diameter

[vansig]

zapkitty wrote: I can haz sub-MW FFs?

the lower bound is about capacitor leakage rate; the upper bound, about cooling.

[vansig]

Aeronaut wrote: Here’s the direct link, Rezwan. http://www.legion.org/magazine/2529/power-power-domestic-dilemma . Only problem is that it’s a tease to get subscribers. Here’s the Google search results for Jay Stuller, the author. We can learn a lot from him and maybe get mentioned in the reprint of the book he wrote the article to promote. http://www.google.com/#hl=en&q=jay+stuller&btnG=Google+Search&aq=f&oq=jay+stuller&fp=Li-R6mbKWrc

the author is mixing his terms. he writes,
“any attempt to phase out fossil fuels runs smack into a dilemma: electric motor technology simply can’t produce enough energy to move heavy trucks and aircraft, which need diesel and jet fuel.”

it is not the electric motor technology, but the battery energy density that is the problem.

[vansig]

zapkitty wrote:
And part of the economic “fuel” for DPF propagation will be the
selling of excess power over transmission lines.
[…]
As the situation develops the existing lines that are judged to to be no longer
needed will be allowed to lapse.

do remember that focus fusion power is entirely dispatchable: there need be no excess power, at all,
since you can adjust number of pinches/second as demand requires.

so, really, the question becomes
whether it is cheaper, or safer, to deliver a fusion generator, and install it, than to distribute power to a needy neighbour over wires.

returning to the topic,
a lot of waste heat really should be made a resource rather than be waste, at all.

[vansig]

dennisp wrote:
are you proposing heating via electric resistance? I think we just invented the flying toaster! 🙂

No. A 5MW Focus fusion generator, operating at 50% efficiency, will generate 5MW heat. Use that in your “jet” engine.

[vansig]

Breakable wrote:
Would be interesting if some reaction-less drive would come online
http://en.wikipedia.org/wiki/Reactionless_drive

According to that article,
“The underlying problem [with reactionless drives] is that breaking the law of conservation of momentum shatters the entire mathematical framework [of physics].” These devices by their very nature violate the law of conservation of momentum

Let’s propose a reactionless drive that does not break conservation of momentum. All we need to do is to find a way to make weakly-interacting particles interact a little more strongly, and then find, among them, a favoured direction.

[vansig]

so we’re talking ~ 1m thickness of water times the cross-sectional area of the rear of the cabin, call it ~7..20 tonnes. compare this to the weight of jet fuel in a 747, ~230..240 tonnes.

aircraft will both carry more payload and extend their range enormously.

[vansig]

zapkitty wrote:
I thought that the production DPFs, boron-fueled, were to have a low radiation
footprint?… That is, once you’re outside of the x-ray converter shell.

yes, though ~0.1% of reactions do generate some slow neutrons:
11B + α → 14N + n + 157 keV;
11B + p → 11C + n − 2.8 MeV;

and ~.01% produce a gamma:
11B + p → 12C + γ + 16.0 MeV.

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