2011 IEC Confrence slide presentations are now up

[Mike_P]

The 6.6m break even radius size would seem indicate that the building needed to house the reaction chamber would be aprox. 90 foot on a side minimum. What throws me a little is the scaling of his diagram on page 2. Does anyone know how big that object is?

[Mike_P]

SOrry for the nubie question, but when the presentation talks about "Bremsstrahlung losses ≈ 1/3 fusion output power", is this effectively x-ray energy?

[Enginerd]

SOrry for the nubie question, but when the presentation talks about "Bremsstrahlung losses ≈ 1/3 fusion output power", is this effectively x-ray energy?

Yup. The ions undergoing fusion are mixed with electrons of roughly the same temperature. When these electrons collide with the ions, they emit x-ray radiation of 10–30 keV energy range. This x-ray energy tends to be radiated away and lost, where it is (hopefully) wastefully absorbed into shielding rather than frying the workers.

[Enginerd]

The 6.6m break even radius size would seem indicate that the building needed to house the reaction chamber would be aprox. 90 foot on a side minimum. What throws me a little is the scaling of his diagram on page 2. Does anyone know how big that object is?

So for useful power we need a reaction chamber roughly 14 meters across. That is way too large for use in a fusion powered rocket... Perhaps using D-D (and dealing with the neutronic mess) rather than pB11 would allow for a small enough reaction chamber to use in an interplanetary rocket.

[D Tibbets]

IIRC he did mention some cusp-plugging effects in past presentations.

Yes, but cusp plugging didn't work. Not the same thing as the wiffleball.

I think the Wiffleball is implied in all of the EMC2 conclusions. It is hopeless without it. I think the cusp plugging with it's set of benefits and problems relates mostly to what happens to electrons that escape magnetic confinement. A repeller generally operate by electrostatic means, and is not magnetically shielded (?). Recirculation is not a repeller in this sense, though the magrid could be considered as a magnetic shielded repeller (negative repeller (attractor) from an external electrons perspective. Inside the magrid Gauss's law mutes the issue. Whether magnetically shielded independant repellers have any advantage over the incorporated 'repellers' of the magrid, is a question. Reported failure of the repellers in WB5 would seem to be discouraging. Perhaps placing the independant repellers further out would not have the problems that the WB5 had (were the repellers inside or outside of the midplane of the magnets (past the narrowest part of the cusps) where the magrid charge starts acting due to Gauss law considerations)?

Dan Tibbets

[D Tibbets]

SOrry for the nubie question, but when the presentation talks about "Bremsstrahlung losses ≈ 1/3 fusion output power", is this effectively x-ray energy?

Yup. The ions undergoing fusion are mixed with electrons of roughly the same temperature. When these electrons collide with the ions, they emit x-ray radiation of 10–30 keV energy range. This x-ray energy tends to be radiated away and lost, where it is (hopefully) wastefully absorbed into shielding rather than frying the workers.

Sort of. The electron temperature may vary inversly with the ion temperature. With a central focus, the ions are densest in the center, the hottest, and contribute most to the fusion rate. The electronsin this area are traveling slower (cooler) and this will decrease the Bremsstrulung radiation magnitude. To some degree this may be essential for positive Q with P-B11.

X ray losses are losses only if the energy is not recovered. Just as with neutrons or non direct converted fast fusion ions, the energy ends up as heat in the walls. This is carried away by a coolent, and runs a steam turbine to harvest this heat (both from fusion, x-rays, fuel ion and electron losses). The problem is that this thermal energy can be converted to electricity at only ~ 25-30% efficiency. An alternative method of harvesting the X-ray energy at higher efficiencies could be a game changer. E. Lenier's (sp?) patent for direct conversion of X- ray energies at ~ 80% efficiency may be of profound importance.

Dan Tibbets

[happyjack27]

as far as wiffleballs go, it seems from simulations and math, as well as the results of real experiments, that its established that the field configurations at least _approach_ a wiffleball formation. i believe the asymptotic behavior is real the sticking point. for instance, how <i>stable</i> is it? how narrow is the "good" regime? etc.

also i'm still a little skeptical about how you can maintain a small excess of electrons in the plasma at high confinement. you can get net neutral plasma through neutral gas puffs, sure. but magnetic electron confinement is a two-way street: it keeps electrons out just as well as it keeps them in.

[D Tibbets]

The 6.6m break even radius size would seem indicate that the building needed to house the reaction chamber would be aprox. 90 foot on a side minimum. What throws me a little is the scaling of his diagram on page 2. Does anyone know how big that object is?

So for useful power we need a reaction chamber roughly 14 meters across. That is way too large for use in a fusion powered rocket... Perhaps using D-D (and dealing with the neutronic mess) rather than pB11 would allow for a small enough reaction chamber to use in an interplanetary rocket.

D-He3 is another possibly smaller (and less neutronic) option. The He3 would come from terrestrial grid D-D Polywells. The He3 would be harvested and used in the rocket D-He3 reactors. It should be extremely cheaper than lunar mining of He3(the He3 is essentially a wast product of the D-D reactor).

Dan Tibbets

[D Tibbets]

as far as wiffleballs go, it seems from simulations and math, as well as the results of real experiments, that its established that the field configurations at least _approach_ a wiffleball formation. i believe the asymptotic behavior is real the sticking point. for instance, how <i>stable</i> is it? how narrow is the "good" regime? etc.

also i'm still a little skeptical about how you can maintain a small excess of electrons in the plasma at high confinement. you can get net neutral plasma through neutral gas puffs, sure. but magnetic electron confinement is a two-way street: it keeps electrons out just as well as it keeps them in.

Of course excess electrons internally will impead introduction of new electrons. The key is of course the Wiffleball and the magnitude of the excess electrons. The Coulomb charge quickly builds to tremendous repulsions (voltage necessary to overcome). Apparently the 1 ppm excess is low enough that the repulsion cal be overcome with modest excess voltage. Note that the potential well is less than the drive voltage. The Wiffleball is an effective barrier that allows only a small leak. Within limits, the comparison to an air tank is reasonable. So long as there is only a small leaking hole, you can force a little more air into the tank so long as the pump provides a little excess pressure. If the leakage is too great, you can still maintain a pressure near the pump pressure, but you have to use progressively greater pump capacity (current) . The Wiffleball does not change the rules. It just reduces the leakage so that the current needed to maintain the pressure is much less. The drive voltage is is a constant in this comparison. As a side issue, normal cusp confinement is different in that the leackage is high enough, that the current needed to not only maintain the pressure (potential well) it makes the attainment of high pressures exponentially more difficult. That is why experiments without a Wiffleball have difficulty building past small potential wells (as a percentage of the drive voltage).

Some head scratching is needed when considering WB5. Bussard, etel apparently had a Wiffleball, but the potential well was low. He tried increasing the current ~ 10 fold, but only obtained only ~ a 2 X increase in the potential well. The recirculation is important beyond the Wiffleball. Also, the ion losses to the repellers and this effect on the PPM alowable electron excess plays a role.

Dan Tibbets

[kurt9]

The 6.6m break even radius size would seem indicate that the building needed to house the reaction chamber would be aprox. 90 foot on a side minimum. What throws me a little is the scaling of his diagram on page 2. Does anyone know how big that object is?

So for useful power we need a reaction chamber roughly 14 meters across. That is way too large for use in a fusion powered rocket...

Not necessarily. Ships for deep space transportation are likely to be built in orbit. A 14 meter chamber can certainly be built in orbit with the proper manufacturing capability. Of course, such a fusion rocket will not work for Earth-LEO launch. This will remain with chemical propulsion (or LENR, if it turns out to be real) or laser launch.

[MSimon]

D Tibbets,

It is not just the low efficiency of thermal conversion. The cost of the machinery is significant (80% of plant cost for a Uranium Nuke).

[MSimon]

D T, heh

That 1 ppm number is misleading - i.e. it is quite significant. It is roughly the ratio of "free" electrons to "bound" electrons in a conducting conductor.

It doesn't take a lot of electrons bunched together to make a very high voltage.

So to call it a "small" excess is both true and misleading.

[Carl White]

(deleted)

[Mike_P]

SOrry for the nubie question, but when the presentation talks about "Bremsstrahlung losses ≈ 1/3 fusion output power", is this effectively x-ray energy?

Yup. The ions undergoing fusion are mixed with electrons of roughly the same temperature. When these electrons collide with the ions, they emit x-ray radiation of 10–30 keV energy range. This x-ray energy tends to be radiated away and lost, where it is (hopefully) wastefully absorbed into shielding rather than frying the workers.

Sort of. The electron temperature may vary inversly with the ion temperature. With a central focus, the ions are densest in the center, the hottest, and contribute most to the fusion rate. The electronsin this area are traveling slower (cooler) and this will decrease the Bremsstrulung radiation magnitude. To some degree this may be essential for positive Q with P-B11.

X ray losses are losses only if the energy is not recovered. Just as with neutrons or non direct converted fast fusion ions, the energy ends up as heat in the walls. This is carried away by a coolent, and runs a steam turbine to harvest this heat (both from fusion, x-rays, fuel ion and electron losses). The problem is that this thermal energy can be converted to electricity at only ~ 25-30% efficiency. An alternative method of harvesting the X-ray energy at higher efficiencies could be a game changer. E. Lenier's (sp?) patent for direct conversion of X- ray energies at ~ 80% efficiency may be of profound importance.

Dan Tibbets

If the loss is reduced to 5% (as was suggested in the presentation) would this reduce the break-even radius?

[RobL]

So for useful power we need a reaction chamber roughly 14 meters across. That is way too large for use in a fusion powered rocket... Perhaps using D-D (and dealing with the neutronic mess) rather than pB11 would allow for a small enough reaction chamber to use in an interplanetary rocket.

Why would you need a reaction chamber in the vacuum of space? though a frame to hold the magnets and circulate power and coolant sure.

I like your idea of using He3 from a simpler DD reactor for applications needing aneutronic fuels, but in space you are already in a nasty radiation environment and engines will only run for a few months or years but not for decades. Is neutron radiation and activation really that much more of a burden?