Look what's been written:"but the Navy provided a reported $1.8 million for Nebel and his colleagues to carry on Bussard's work."http://cosmiclog.msnbc.msn.com/archive/2008/08/28/1301440.aspxHhahaahahahahaaa, that kind of investment for such important project is laughable for the capacity of the US Navy. They've got tens of billions of dollars, but can't give a reasonable sum of money for it.... Quote from: intlibber on 09/30/2008 07:33 pmWhat is NASA doing to investigate polywell fusion as a path to SSTO and manned interplanetary ships?Right now all of the space agencies are wasting money from taxes to highly expensive and dangerous fire show, called chemical rockets and shuttles. No one ever cares that a Polywell fusor, or several Fusors, could provide the necessary energy for a Space Elevator , a Lightcraft, or WEAV.
What is NASA doing to investigate polywell fusion as a path to SSTO and manned interplanetary ships?
I think the problem may be a little different than you suspect. NASA has many commitments that run back decades. As I asked recently, isn't NASA funding Blended Wing Body research for more than 25 years now? That's amazing especially considering it's Boeing who stands to benefit here, not NASA.
QuoteI'm lost as to what you're referring to with regards gains as high as 12. If we're talking about Q, what we're talking is fusion power out/power in. Don't Poly people count X-Ray as part of fusion power out? What I'm getting with Nebel's 1.7-12 Q depending upon how the physics breaks is that either way, he expects to do more than break even with B11. Or was he talking about X-rays?I think those are probably ultimate Q values - useful power out versus total power in. I don't know if X-ray capture is included in those numbers, but even if it is, a gain of 12 is probably unreachably high for a reactor with the commonly-calculated thermal bremsstrahlung yield. Most discussion on talk-polywell assumes bremsstrahlung is a total loss, but we've been wrong before (witness the 'first wall problem' that recently evaporated after a casual comment from rnebel)...I suspect that the bremsstrahlung problem, subject to their proposed mitigation techniques, is the source of most of the uncertainty in the quoted values of Q.
I'm lost as to what you're referring to with regards gains as high as 12. If we're talking about Q, what we're talking is fusion power out/power in. Don't Poly people count X-Ray as part of fusion power out? What I'm getting with Nebel's 1.7-12 Q depending upon how the physics breaks is that either way, he expects to do more than break even with B11. Or was he talking about X-rays?
Yes but look back on the history of flying wings. Northrup didn't take 3 decades to fly. They had troubles. When these things stall, they flip head over heals and sometimes don't recover. But this is stuff we've known about for 6 decades. If Boeing wants to build a BWB, they should build it. There is no onus upon the taxpayer to provide tech support for this research on ad infinitum. I think it's just silly.This sort of thing only happens when people are spending other people's money. You'd never see this in private industry.
Bremsstrahlung is a function of the average atomic number of the isotopes involved. With D-D fusion, you have an average number of 1 so bremsstrahlung is as low as possible. With straight p-B11 fusion, you have 1+5/2 or an average of 3, so bremsstrahlung will be significantly higher.What Bussard found, however, was if the reactor ran in a proton-rich regime, this would bring the average down and he could reduce the bremsstrahlung to 5%. Another factor is that where the ions intersect, they are at a very low electrical potential. Bremsstrahlung is an issue in tokamaks because they operate at over 150 kEv or more, while Bussards WB-6 was running at only 12.5 kEv peak electrical potential, however the core of the reactor, where the magnetic fields are balanced, is at a very low electrical potential. So the particles are at high velocity and low electrical potential when they intersect, which also greatly minimizes bremsstrahlung and thermalization issues.
Quote from: mlorrey on 05/26/2009 12:49 amBremsstrahlung is a function of the average atomic number of the isotopes involved. With D-D fusion, you have an average number of 1 so bremsstrahlung is as low as possible. With straight p-B11 fusion, you have 1+5/2 or an average of 3, so bremsstrahlung will be significantly higher.What Bussard found, however, was if the reactor ran in a proton-rich regime, this would bring the average down and he could reduce the bremsstrahlung to 5%. Another factor is that where the ions intersect, they are at a very low electrical potential. Bremsstrahlung is an issue in tokamaks because they operate at over 150 kEv or more, while Bussards WB-6 was running at only 12.5 kEv peak electrical potential, however the core of the reactor, where the magnetic fields are balanced, is at a very low electrical potential. So the particles are at high velocity and low electrical potential when they intersect, which also greatly minimizes bremsstrahlung and thermalization issues.It's standard procedure to run hydrogen-rich, so as to reduce Z. That alone isn't enough; a thermal reactor will still not break even unless a large fraction of the X-ray power can be recovered.Bussard's reactor, on the other hand, has high-density fast ions at the core, along with slow, lower-density electrons. The electrons are fast at the edge, where their density is at a minimum. The density of the electrons has a maximum (and their speed a minimum) at some finite radius, due to the virtual cathode potential bottoming out and starting to climb again towards the virtual anode generated by the ion focus. One of the things you have to fiddle with to optimize bremsstrahlung is the height of that virtual anode, because it affects the speed of the electrons through the core.Tokamaks typically don't run as hot as fusors and Polywells. I am unaware of anyone ever managing to get a tokamak up to 150 keV (I thought it was usually about a 30th of that), although Hirsch did run fusors that hot. Besides, that's temperature, not potential. Potential has nothing to do with any of this; as far as fusion calculations are concerned it's just a mathematical construct, the gradient of which is the electric field.Now, tokamaks do have a wide spread of particle energies, whereas Polywells are supposed to be nonequilibrium machines with a much narrower distribution. So there is a high-energy tail on the tokamak particle energy distribution that results in the bulk of the bremsstrahlung. It also results in the bulk of the fusion, so...
All I can say is Tom Ryder tried to make your arguments and Bussard showed that Tom was trying to apply tokamak conditions to a polywell to get those numbers, and the real numbers were much much lower. Evidently Nebel and the Navy think so too. EMC2 now has another 2 million in funding.
Also in the comments, Nebel mentioned that we should have a yes or no answer on this technology in 1.5 to 2 years.
Please somebody explain to me how to channel alpha particles from a polywell reactor to form a jet without forming any instabilities at the bottom of the "well"?Until somebody explains to me how to do that, I remain convinced that there is no clear way to make a thruster from a polywell reactor.
Actually the alpha particle fusion products have far more energy than the fuel ions. That is the whole point. So they leave both the potential well and the magnetic confinement PDQ.For direct power generation, they would be slowed down by charged grids, outside the confinement. For a Direct Fusion Product rocket engine, their paths would be bent by magnetic fields until they all head in the same direction.
The fuel ions are moving fast. The fusion products, though, are still faster. That is how energy gain is achieved. You put some energy in, you get more out.
Really? The alpha particle fusion products have more energy then fuel ions? Then explain to me how do the fuel ions get hot enough to ignite?