[vlad]

Formula that links rocket engine power, thrust and its specific impulse is more than simple 🙂
P = I / 2
where P is specific power of rocket engine (in the sense of 1 Watt per 1 N of thrust), without loss of course
and I is a specific impulse of rocket engine, in m/s

specific impulse of the rocket engine in m/s is equal to the speed of exaust velocity
hence for specific impulse of 0.03c (9E6 m/s) and power of 5MWt the thrust would be… about 1 Newton
not too much I believe 🙂

To travel to Mars you definetely should “exchange specific impulse to thrust”
You can (very) roughly estimate optimal specific impulse for some space route as… say equal or – much better – twice to the deltaV of this route.
So if your estimate deltaV for the route from Earth low orbit to Mars low orbit and back to… say 40 km/s (for fast piloted mission with flight time measured by weeks not months) then the optimal specific impulse would start from 4000s, and 8000s would quite nice.

[vlad]

kurtul mehtap wrote:

Two DPFs firing at each other is about 30 years old. The concept evolved into what is known as the hypocycloidal pinch. It has promise for increased pinch lifetime but the energy input is much greater.

The energy cost for PF device to accelerate particles is far greater than a particle accelerator. Medical applications will likely use advanced accelerator technology like plasma wakefield accelerator in the coming decade.

From the dense plasma pinch animation I assumed the direction of the resultant high energy ION Beam as a straight line. While the ION beam is directed outside the anode the electrons are going inside.
So 2 high energy ION beams can collide in the middle and potentially cause fusion.
That was my assumption.if it was so easy to make ions fuse on collision… then there would be no need for two DPF devices firing to each other
you could just just use any simple and cheap proton accelerator (just few kEv’s!) and fire with the proton beam at the boron target

Unfortunately it does not work, because cross-section (or just probability in simple words) of fusion reaction is very low.
You’ll get few fusion reactions, but they’ll give you just a very little part of energy you spend on accelerating the ions.

The problem of fusion is to confine hot ions together for some time so that they could collide many-many times until some significant amount of ions would fuse.

[vlad]

Joeviocoe wrote: Arcing;
Leaking;
Impurities;
OH MY!

It seems that this project has been derailed from the experimental physics portion… because of need of a dedicated Materials and Engineering fabrication department.

like any other experimental physics project 🙂

[vlad]

http://nextbigfuture.com/2013/08/eric-lerner-of-lawrenceville-plamsa.html

AU GU S T 06, 20 13

Eric Lerner of Lawrenceville Plamsa Physics Presented his project to make commercial nuclear fusion with dense plasma focus

On June 11th 2013 Eric Lerner and Lawrenceville Plasma Physics, Inc. were invited to share the latest achievements in the field of nuclear fusion energy research at Google’s Solve for x Brainstorming conference. Eric explains aneutronic fusion, which produces no radioactive waste, and the device, called the Dense Plasma Focus, which could produce eco-safe, green, cheap and unlimited energy for generations to come.

[vlad]

asymmetric_implosion wrote: Vlad: You need to be a bit careful using temperature and ion energy seemingly interchangeably. Temperature is key in thermal fusion devices. In principle, you can have a cold plasma that produces neutrons very well in a pinch. Pinch devices exploit the instabilities to produce non-thermal ions, ions that don’t conform to a thermal distribution. It is of these ions that efficiently produce neutrons. Small PF devices which have temperatures of less than 1 keV can produce neutrons well beyond the expectations of thermal calculations. LPP hypothesizes that their configuration to place a lower limit on the ion energies. If the LPP approach works, energies below 200 keV would not be relevant to the problem. It’s not clear how far the lower limit can be pushed up but the higher the better for p+11B.

you mean that the graph you posted above shows not ion energy, but thermodynamic temperature of thermalized plasma? OK

asymmetric_implosion wrote: As far as the “honest” calculation goes, a great deal of engineering is required to prove that the energy from RLC ring can be recycled.

yes, I see
engineering is much worse than clean pure physics 🙂

Thank you for your explanations!

[vlad]

asymmetric_implosion wrote: D+3He might be an easier path than p+11B at first but you could not claim an aneutronic success. My gut feeling is something like half your yield with very large error bars would be from D+D.

well I think the exact part of D-D reactions in D-3He mix depends on device work temperature, doesn’t it?
according to your graph (cross section vs ion energy) at say 200kEv the cross section of D-D is an order of magnitude more than for D-3He

asymmetric_implosion wrote: LPP is working toward or may have recently reached a 1 J fusion yield. With something like 50 kJ stored in the capacitor bank the Q is 5E-4.

well… yes
to be exact….. this is not an absolutely “honest” calculation
According to LPP significant part of this 50kJ can be returned back to the capacitor bank.
Most part can be returned very easily (like in capacitor – inductor ring), some part – with photo-voltaic effect transformation from X-rays. (I don’t remember exact numbers though..)
So to achieve breakeven DPF device should not generate full capacitor bank energy in each pinch, it is enough if it generates a bit more than energy losses

and yes – even in this case at 1J their Q would be no more than say 1E-3

nevertheless.. I followed their work during last three years, and knowing their history and results…. after they achieve 1J I would seriously think on buying some LPP actions.
Unfortunately as far as I know it’s impossible since I’m not an American citizen or registered investor, just a private person

[vlad]

asymmetric_implosion wrote: D+3He is a little easier to access than p+11B but you are likely to produce a number of neutrons from D+D. 3He is in short supply so not a good long term choice as it is derived from tritium or some lunar digging. p+11B works best above 600 keV.

Attached fig shows the cross sections for the fusion contenders.

Yes you’re right and I understand all these issues

But if someone achieves breakeven on DPF – it would become the BREAKEVEN in capital letters no matter which aneutronic fuel he uses.
And a magic wand that brings funding too 🙂

[vlad]

Is it possible to achieve breakeven with D-He3 fusion on FoFu-1 or similar DPF device?

[vlad]

Thank you, Breakable

Ikanreed, maybe the reason is not in the cost of “fuel” itself, but in the cost of additional devices required. Or maybe in the orders of magnitude higher yield of radiation which would make the experiments more sophisticated ?

P.S. Oops Dr.Lerner answered just while I was writing my message 🙂 and as far as I understand him – he proved my idea
Thanks alot!

[vlad]

“Most people would agree that…” – well I think too many false statements start with these words 🙂
Too many to consider them as a proof of anything

[vlad]

Congratulations!

[vlad]

Joeviocoe wrote:

true…. but the majority of the yield still comes from the fission reaction if I am not mistaken. The hydrogen allows for a more complete burn of the fissile material in each stage. Even Tsar Bomba was mostly fission yield.

afaik you ARE mistaken 🙂
In both issues.

Do explain please.well.. as for real tsar-bomb test, the total power of the explosion was estimated as approximately 58Mt (15% above predicted by design), and only 1.5Mt was from fission “fuse”. So about 96% of power was from fusion.

Most of modern nuclear weapons (except the weakest tactic level ones) are naturally fission- fusion, and usually the more powerful is the warhead the more part of its power is from fusion.

There is a method of increasing the power of fusion bomb – to cover it with U238 shell.
But it is rarely used. E.g. As for the tsar-bomb, it initially contained such a shell in its design, but it was removed and replaced with plumbum beefore the test.

Everything described above is AFAIR and AFAIK 🙂

[vlad]

Joeviocoe wrote: true…. but the majority of the yield still comes from the fission reaction if I am not mistaken. The hydrogen allows for a more complete burn of the fissile material in each stage. Even Tsar Bomba was mostly fission yield.

afaik you ARE mistaken 🙂
In both issues.

[vlad]

vansig wrote: What Focus Fusion is attempting, is aneutronic fusion.

D+3He itself is an aneutronic reaction too.
Hypothetical fusion reactor using this mix would actually produce some neutron flux due to D+D side reactions.
However this flux should be several orders of magnitude lower than D+T, if the reactor keeps the fusion temperature optimal for the best D+3He reaction rate

to topic starter: as for mining Moon for 3He – hmmm, I think it would be worth to return to this idea in… say 20-30 years.
when we have at least working D-T fusion.
or may be never return to it if we have working p-B11 🙂

[Author]

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