For anyone tuning in now, the event is already over, and German media report that it was a success. I can't find a decent English-language source yet, surely there will be reports on it soon. Most of the German articles have lots of immediately obvious inaccuracies as well right now...
From Wikipedia:
The Wendelstein 7-X (W7-X) reactor is an experimental stellarator (nuclear fusion reactor) built in Greifswald, Germany, by the Max-Planck-Institut für Plasmaphysik (IPP), and completed in October 2015. It is a further development of Wendelstein 7-AS. The purpose of Wendelstein 7-X is to evaluate the main components of a future fusion reactor built using stellarator technology, even if Wendelstein 7-X itself is not an economical fusion power plant.
The Wendelstein 7-X reactor is the largest fusion device created using the stellarator concept which was the brainchild of physicist Lyman Spitzer. It is planned to operate with up to 30 minutes of continuous plasma discharge, demonstrating an essential feature of a future power plant: continuous operation.
The name of the project, referring to the mountain Wendelstein in Bavaria, was decided at the end of the 1950s, referencing the preceding project from Princeton University under the name Project Matterhorn.
The tl;dr of this is that if the Wendelstein works, and works well, we're potentially only a few years away from building a fusion reactor that generates large amounts of clean power at extremely low cost.
If it doesn't work, well, they'll keep trying.
It's like when SpaceX landed that rocket over the ocean (without a barge) then let it crash- if they succeed, the cool stuff comes next.
Between this, and moltex , which claims to have designed an intrinsically safe molten-salt nuclear reactor same capital costs of coal, hence cheaper than coal , the future of clean energy look bright.
The press loves to hype this sort of thing but I think if you talk to most scientists in the field they'll be much more circumspect about getting to commercial fusion. Personally I think it's at least twenty years out, and that's if everything goes well, which it will not.
Can you imagine the chancellor our president coming by for a launch event when you run your software for the very first time that you've never run before not even I an integration test after coding on it for years?!
I suspect they had a very robust testing regime for both the software and the hardware used in this project. As well as more formal mathematical proofs of the physics to back up their engineering.
A better analogy might be for rockets / spaceflight-- where individual systems are rigorously tested independently, but a live launch is the only place that they all come together and have to function as one tightly coupled system.
> A better analogy might be for rockets / spaceflight-- where individual systems are rigorously tested independently, but a live launch is the only place that they all come together and have to function as one tightly coupled system.
I understand the point that you are trying to make, but your analogy is a bit poorly chosen.
Speaking from my days as a sounding rocket telemetry engineer, we performed lots of tests of the individual systems, as you say. But then we also put everything together and performed several "sequence tests" where the entire vehicle (minus the motor) was assembled and tested as if the countdown were real. All events were triggered as if the vehicle were in flight, and experiment systems were tested to ensure they would power on as expected and provide real data. If we had any deployables, the deployment mechanism would be tested to the maximum extent possible. These sequence tests happened off the rail (in special testing facilities) and on the rail (fully assembled in launch configuration, with a motor).
Basically, if you wait until the actual launch to perform integration tests of all of this, you WILL fail. There are too many pieces that need to function in concert to expect them to all work without integration testing.
I've read a lot about the design and construction of the 7-X, but I've never read why there are so many "portholes" all over the thing. There are a comically large number of them, everywhere, of totally different sizes, shapes, and at weird angles. Why are so many holes/ports necessary, and why is there so little homogeneity?
It's a scientific instrument, not a power plant. The portholes are to allow all the measurements and tests that they plan to do over the life of the machine.
Safer has a connotation of safety whereas ungefährlicher has a connotation of danger.
If something that would have killed you before, is less likely to do so now you would call it ungefährlicher or less dangerous but you wouldn't call it safer unless you're intending to be funny.
Not really a good explanation. Ungefärlich is more like "harmless" in English. Yes, it contains the word "harm", but there's a modifier that inverts its meaning.
it's ambiguous in German as well, but both: a fusion reactor has very little radioactive waste (only the components that get hit by neutrons from the fusion reaction are activated, and hard-to-activate materials are being used there), and it's also less radioactive than the waste produced by a fission reactor.
A bit of googling didn't hit on much, but is there a plan for what happens in the future if this continues to go well? In the same way that ITER would be followed by DEMO then hopefully more commercial reactors.
That was a little bit vague. How does the heat actually get out of this thing and into the water? If the plasma is confined in a magnetic field, not in contact with the shell, and the shell is super-cooled to 4K, I'm a little lost on how it would work in practice.
I think only the shells of the superconducting coils are cooled to those temperatures. The rest of the system, including the containment walls, are water-cooled.
In a real system you would also have neutron radiation carrying away energy that could be captured with additional layers of water.
i have absolutely no authority to speculate, but i would guess you'd vent plasma to a heat exchanger by diverting only part of the stream with a controlled EM field, either periodically or continuously. You'd have to do it anyway to remove the helium and inject some fresh tritium and deuterium, right?
The current front-runner seems to be a blanket of water surrounding the reactor vessel, which is heated by the stray neutrons from the fusion reaction.
It has the double-win that if Lithium is added, the high energy neutrons end up breeding more Tritium fuel.
EDIT: There's another post on the front page right now that has a recording of the event: http://www.iflscience.com/physics/watch-germany-switch-their... discussion at https://news.ycombinator.com/item?id=11026559