[Tulse]

Technically almost all fusion reactions involve fissioning of the fused nuclei, but the nuclei are very light. What are labelled “fusion-fission hybrids” instead refer to technologies where a fusion reaction is used to produce neutrons to facilitate the fissioning of heavy elements (to, for example, burn waste from fission reactors, or turn it into usable fission fuel).

[Tulse]

There’s a very brief, no-detail report that Tri-Alpha Will Show Off Fusion Technology Next Year. I’m sceptical of such a contentless rumour, but it does suggest the race is heating up.

[Tulse]

The foil captures x-rays, not the alpha particles, which go out in a beam. And there are plenty of other commercially-available x-ray sources around. If one uses deuterium, then the reaction produces neutrons, but there are plenty of other commercially-available neutron sources.

In other words, a FF reactor does not do anything that other, far more easily obtained devices do.

[Tulse]

Utilities are already using wind, solar, geothermal and tidal, so I don’t think they are committed solely to the giant teakettle model of electricity generation. And those boilers, however well understood, come with a lot of overhead, and make the physical plant much more complex relative to the presumed FF design.

The other thing to keep in mind is that, if the price is cheap enough and the modules small enough, there are likely many organizations that would like to produce their own power, and be independent of the grid. This is especially true if they can do so actually cheaper than buying from a major utility. I think this is really the issue, and where the relatively small size of the individual generating units is an advantage — if FF can provide a “right-sized” generator to an office park or hospital or university or skyscraper, and provide power significantly cheaper than from the grid, it really won’t matter what the utilities think. In a way, it is analogous to the sea change in telecommunications, with the rise of small cell providers and ISPs and home phone and long distance companies challenging the monolithic telecoms. Your local telephone company might not want to lower its prices or adopt new technologies, but if the cable company suddenly is offering home phone and long distance service, you bet they will learn to be more nimble. I think the same could apply here.

[Tulse]

Shouldn’t FF modules be much simpler than most other power generation technologies? In other words, will one need as many staff to oversee FF modules? There are very few moving parts (primarily those involved in fuel insertion and the vacuum pump). Unless there is a need for complex waste heat extraction gear, FF modules seem very straightforward compared to boiling water plants.

[Tulse]

My guess is that regulations will demand that each site have at least one person there 24/7, if for no other reason than the decaborane fuel used is highly toxic. But perhaps I’m wrong (or the amounts used will be so small as to be of negligible risk — perhaps someone more knowledgeable can clarify).

[Tulse]

50-100MW may still be too small in terms of maximizing the value of FF — check out Rematog’s amusing example of the importance of labour costs:

https://focusfusion.org/index.php/forums/viewthread/139/P30/#3121

The problem is that as the cost of physical plant and fuel goes toward zero, your biggest cost is going to be operations and maintenance. What is needed is to size plants so that they are most efficient in terms of human resources. Presumably as you scale up there is a point of rapidly diminishing returns, but that point may still be larger than 50-100MW.

Of course, that presumes that the goal is only to produce power at the lowest cost. One might also value distributed generation for other reasons (such as making the grid more robust), in which case having the lowest price per KW-hr may not be the only metric.

[Tulse]

texaslabrat wrote: FF might take care of the scale issue (since it *should* be reasonably economical even in relatively small installations)

I think it depends on what you mean by “relatively small” — the analyses others have posted in the forums here suggest that basic labour overhead costs mitigate against very small installations. There really is value in size, although arguably efficiencies of scale in operating and maintenance costs don’t require installations of the size of modern powerplants.

[Tulse]

texaslabrat wrote: If one just wants to see a general energy out > energy in no matter if it’s heat/x-rays/electrical or whatever…

I’ve always understood “breakeven” to be used in this most basic way for all other fusion projects. It’s also my understanding that none of the multi-billion dollar research projects have accomplished this.

then maybe a series of shots could show that with D-D if instrumented carefully enough in an adiabatic chamber. However, from the pictures I’ve seen so far…I don’t get the impression that such an environment is present so careful heat exchange analysis is not in the cards.

That’s my impression as well. I was just curious as to why this wasn’t an initial goal of the research, since being able to accomplish this would go a very long way toward validating the FF approach — it would be doing for a few million dollars what the huge multi-billion research facilities haven’t been able to achieve over several decades. I would think this would be a hugely impressive milestone, and one that might help to free up further investment money and provide legitimacy to the approach. I’m sure the FF folks have thought of this, and I was just wondering as to why it was ruled out as a goal.

[Tulse]

Does VASIMR have enough thrust to act as a third stage in that manner? Could it go from suborbital to orbital?

[Tulse]

Henning wrote: The D-D reactions are just to clarifying that fusion actually happens.

I understand that — I was just wondering if it was also possible that such reactions could end up at theoretical breakeven. That would seem to me to be a huge validation of the FF approach, even if D-D (and D-T) is not the final intended fuel for a variety of excellent reasons.

[Tulse]

Just to clarify, given that D-D reactions require much less energy and have a greater power density than p-B11 reactions, is it possible that goal 2 will actually involve the generation of net energy (even if that energy is in a form that isn’t practical to capture with the device)?

A more general question (which is perhaps appropriate for a different thread) is how potentially versatile is the FF approach as far as fuels go? I understand the strong desire for aneutronic, direct electrical generation, and that seems like the ideal goal to me. But can the FF system be potentially used successfully (i.e., over unity) with other types of reactions?

[Tulse]

HermannH wrote: I used this calculator to get the blackbody radiation at 300 degrees Celsius. It is a surprising 6 kW / square meter.

That works out to about 833 square meters of radiator, or an area 60 feet by 120 feet. That seems sizable to me for something that has to go into space, but by comparison that’s about the area of two of the ISS solar panels (if I have my figures right), so I suppose that’s easily doable.

[Tulse]

belbear wrote:

Radiating waste heat into deep space isn’t so difficult, on condition you shield your radiator from the sun. After all, space shows us a 3 Kelvin black-body and that’s really cold.

Right, but that is purely radiative cooling, which as I understand it isn’t nearly as efficient as conductive or convective cooling — there’s a reason that thermos bottles use vacuum flasks. As “cold” as space may be, you can cool things far more efficiently on earth by, for example, dumping heat into a lower temperature fluid. (I’m sure that some one with way more technical expertise could clarify what sized radiator would be needed to dump 5MW of heat into space.)

[Tulse]

How much need is there for government involvement in FF? I understand that funding is always tight, but presumably some replicable, demonstrable success (not necessarily even peer-reviewed) should ideally be sufficient to bring in additional private investment. Some of the many huge advantages of FF is that, if it works, it doesn’t need billions in funding to demonstrate that, and its practical implications are immediate.

I suppose what I’m saying is that it seems to me the model for aneutronic fusion isn’t something like the Apollo mission or the Manhattan Project, but more like the Wright brothers or James Watt — these are efforts that can demonstrate success with relatively little in the way of resources, and their success has immediate practical commercial impact. As far as I know, neither Watt or the Wrights published peer-reviewed pieces during their research or required huge government attention — instead, their success was its own proof. I think that if FF or Polywell or Tri-Alpha can demonstrate an over-unity device, the world will (as the saying goes) beat a path to their door. (This is also true for the alt-but-not-aneutronic approaches, such as Helion and General Fusion.)

Is this a hopelessly naive view that is out of touch with funding realities?

[Author]

Posts