Does the German W7-X 'Stellarator' Fusion reactor stand a chance leading us to fusion power?

What’s the status of this thing?

Are we finally ready for fusion to come alive, or is it still 50 years off? It does seem enormously complicated.

I think the only factual answer is “we’ll see”. It sounds to me like a 19 year experiment that is just as likely to work, or not work, as any other fusion reactor.

The Wendelstein X-7 is an experimental stellarator. It isn’t intended to be a power producing fusion reactor or even necessarily a proof-of-concept for a future commercial power reactor but rather an experiment to assess the controllability and stability of the plasma in a large stellarator design and assess material issues, e.g. thermal and neutron damage, goals that the asinine Gizmodo blurb (I won’t deign to call it a story) doesn’t even touch on.

Controlled nuclear fusion is essentially a scaling problem; that is to say, by making a reactor sufficiently large, most of the problems we currently experience–such as bremsstrahlung losses, high neutron flux, fine control of interacting magnetic fields–are reduced. (If you make it large enough, you don’t even need magnetic or inertial confinement at all; the mass alone will sustain fusion by gravitational pressure.) However, this increases not only the gross size of the reactor but also the initiation energy to get it started and the running energy to maintain stable conditions. We don’t want gigantic, city-sized reactors; we want something small enough to fit into a large office building, or large shipping container, or ideally, within the fuselage of an aircraft. (“Personal” sized nuclear thermal fusion reactors are highly unlikely simply because of the required cooling systems; we’d essentially have to warp the laws of thermodynamics or control fusion directly on a quantum level for that to ever be plausible.) Note that the US once had a similar program in place called the National Compact Stellarator Experiment. It appeared technologically feasible but a number of engineering issues, including maintaining the incredibly high tolerances for reliable function doomed to to cost and schedule overruns and the improbability that it would lead to a commercially viable system. The X-7 is actually a decade behind schedule, which still sets it better than the ITER.

We know fusion is possible because we can look up and see it work every day, but making it work at the current level of technology still has a lot of unknowns, including how to deal with neutron flux and extracting maximal energy. (Both problems may be addressed by lining the reactor with a blanket of fertile material, i.e. “used” fission fuel elements which can then be transmuted into fissile elements; this so-called “hybrid fission-fusion” approach may offer the best of both worlds in providing enough power to operate a stable fusor at sub-unity fusion power output while burning up hazardous waste.) We should keep trying because it offers a fungible form of power that isn’t dependent upon petrochemicals extracted from the ground, uncertain wave power, or ‘limited’ solar, but we shouldn’t make future energy needs dependent upon obtaining working fusion power in the foreseeable future.


One thing that I’d like to take issue with in the article: the reactor is not “at the Max Planck Institute” - that kind of nonsense is, unfortunately, also perpetrated by ignorant German journalists who cover science but are not science journalists.

It’s “at the Max Planck Institute of Plasma Physics”, one of 83 institutes of the Max Planck Society (that are mostly named to the pattern “Max-Planck-Institut für subject” i.e. “Max Planck Institute of subject”).

I suspect that if they worked and generated power on par with current coal, gas and nuclear power plants, we’d eagerly take ones as big or bigger than current power plants of the same capacity.

Then over time, we could reduce the size and replace diesel locomotives with fusion ones, or any nautical engine with fusion ones, and so on, and so-forth.

If fusion is made to work and is reasonably scalable, I could see the initial rollout being mega/gigawatt replacements for our current power plants, with a century-long rolldown to block by block or large-building installations. There is probably some optimal size and distribution and I’d guess it would stabilize at about one plant per thousand people, although there will be things like ranches and wealthy compounds that have their own for one or a few families.

I don’t see micro-fusion much smaller than that for quite some time. But, of course, this is all still pure sf, since we lack that darned actual working reactor thingy.

But I gotta say, “W7-X Stellarator” is pure Doc Smith. :smiley:

Apparently a lot of private ventures are trying a “start-up” business model to achieving fusion, with investors deciding it’s worth a gamble:

I went to a lecture recently by Dr Alan Costley[sup]*[/sup]. Though not the main topic of his presentation he did mention his recent work which strongly suggested that, counter to previous assumptions, the output power/input power ratio of a fusion reactor may be only weakly dependent on the scale of the reactor. He predicted that the best model might be one where a fusion plant would have a number of smaller reactors rather than one big one, and that the current trend towards bigger and bigger reactors may prove to be mistaken. More details here and here.

[sup]*[/sup]Alan Costley is an experienced experimental physicist with 21 years at the National Physical Laboratory, 11 years at JET and 16 years at ITER working on plasma diagnostics, and is now a consultant to Tokamak Energy.
[quoted from article above]

I have to say that’s a truly great parenthetical.

It demonstrates in very few words just how easy, and how insanely difficult, this problem is. At least for critters of our scale.

Bravo good Sir.

He also predicted that larger train locomotives do not increase speed,
and that passengers pedaling the train will be enough to keep it at maximum speed… because like, the engineer will be having to keep the brakes on even then.

Um… I think comments like that are why he retired… Was it a peer reviewed paper with rigorous mathematics ?
Or just a "It might be … " an example of flexible thinking … also perhaps trying to explain failure… “The dog ate my designs”.

Nope, no one is citing Costley’s paper … Costley retired 2009 and this paper is published Jan 2015… only at a self-publishing no peer reviewed required publisher.

I think he might be saying these prototypes could be smaller, and then saying that because there are many small reactors that were faster to build, thats it, job done.

I guess you could read the paper published through the Institute of Physics

:dubious: So modeling implies the physics might not require size…but I’d hazard a guess that the engineering does.