Reply To: Where are Japan and China in funding Focus?

[Steve Ivy]

4

jamesr wrote: OK so maybe I didn’t explain myself very clearly… So here’s another way of looking at it:

If your oscillations in density & temperature grow in amplitude, at some point the radial gradient from a region of high to low density will grow beyond the point where the simple linear equations cease to fit, and non-linear interactions become important.

Generally there are only two classes of instability involving gradients: Rayleigh-Taylor; where the driving force is parallel to the gradient, and Kelvin-Helmholtz; where the driving force is perpendicular to the gradient (anything else is just a mix of the two). So although it is not exactly the same scenario as the classical Rayleigh-Taylor description, characteristics such as equation of the growth rate is the same.

If you want the peak density/temperature to be in the range for fusion then the gradient away from that peak must be very steep – too steep to be stable.

James, I am really not trying to be difficult (I am trying to defend how this could work, not quite the same thing as being difficult I hope) but I looked at the Kelvin-Helmholtz equation as well and found this…

http://en.wikipedia.org/wiki/Kelvin–Helmholtz_instability
“two fluids in parallel motion with different velocities and densities will yield an interface that is unstable for all speeds.”

In my case the motion appears to be all perpendicular, not parallel.

So the turbulence source if there is any would appear to me to a special case formula for RT turbulence used in cases of highly converging highly dense fluids pushing extremely light fluids at extreme speeds.

All the examples of Kelvin-Helmholtz I have seen apply to two fluids in parallel motion (like the initial parallel laminar flows of two fluids in contact say oil and water, one dense, and the other less so ) and with one of the layers traveling faster than the other.

Assuming forces involved are large enough that surface tension is insignificant, in such a case the flow is unstable for all speeds.

So things don’t look good (if there is a parallel flow in this system) and assuming that there is sufficient time available for that turbulence to propagate?

The thing is I still don’t see where there is a parallel flow of two different fluids with differing densities at different speeds in this system?

All I see is a system (at the encroaching wave front) where you have a very dense substance traveling inward (with all points along the imploding shell having the same velocity vector r and same density and all pointed directly towards the center)

And at the interface of contact on the inner wall you have (an inner sphere of extremely sparse gas that due to the recently passed adiabatic expansion in a near vacuum) is by definition very cold.

I think it safe to make the assumption of adiabatic expansion because of the short time scale of the expansion…

http://en.wikipedia.org/wiki/Adiabatic_process
“Such a process can occur if the container of the system has thermally-insulated walls or the process happens in an extremely short time, so that there is no opportunity for significant heat exchange[1].”

So whatever velocity vector that stuff in the center might have before it is effectively zero just prior to being struck by the incoming shock wave.

Since that wave is encroaching from all directions inward, the material inside the shell when struck will either become adhered to the wall in the manner of a classical inelastic collision or become part of much smaller mass that will be projected even faster inward to form a leading shock wave as some portion of the light mass inside it will be driven ahead in a m1*v1=m2*v2 manner of an elastic collision.

So that implies there will be not just one incoming shock wave for very long but instead there would be many onion skin layers of (at turns converging and diverging) lower energy but faster concentric spheres of waves that will lead the main incoming shock wave in and follow it out.

All of these concentric spherical waves arriving and leaving in extremely short succession.

These layers of masses in excited states and with various radii would create an interesting time variant trap for any light emitted at the center so when the primary mass arrives there will likely already be an intense flash of photons trapped there at the center perhaps even gamma radiation? Just the sort of thing you would want to trigger a fusion event.

I do see points of time when this system would be unconditionally unstable that is the time when the main wave has just passed center and is back on it’s way out. At that point (at some point some distance from the center) you would have a universally diverging vector. But it doesn’t matter then because hopefully by then you already got your tiny little H-Bomb to go off. And then you get to do it over and over again.

I think the existing form of fusion reactor that most closely resembles the system I am proposing is not the controversial method of sonoluminescence but rather the Fransworth Fusor and we know that device works!

It’s just that the Fusor isn’t very efficient due to the collisions of the ions with the grids used to create the radial oscillations in the plasma. BTW, we know those grids are not even remotely close to a true sphere! Yet they seem to work.

So I would think that if we restricted the consideration of the system to a plasma instead of a gas that the potential for this system should seem obvious, it just isn’t all that different from a system we already know works. Well with the single exception that the driving method I propose completely eliminates the primary loss mechanism of the Fusor.

Thank You Again for your time – Steve

Maybe someone else can help me to see the source of turbulence James talked about?

I say if you want a symmetric compression, drive the system symmetrically, most systems don’t really try.