Skunk Works Reveals Compact Fusion Reactor Details • Hacker News Board

Re: Skunk Works Reveals Compact Fusion Reactor Details

#231

Post by rayiner » Wed, Oct 15, 2014, 7:21 PM UTC

waterlesscloud wrote: post #226

rayiner wrote: post #213

Earlier quoted context omitted.

That's hardly ever true. In my experience, Hacker News is full of people from the software field; folks whose professions are often unconstrained by physics,[1] and who have a generally optimistic "this can happen" mentality. That's why everyone here believes we'll have fully self-driving cars in 5-6 years. In the rest of the engineering world, the answer to any question is: it'll be harder than you think it'll be (p…

Did you know computer chips are infinitely more efficient than they were a century ago? They too are a product of applying new discoveries and then engineering around the constraints of physics. Things change. Progress is made.

Sure, but in any given field, the low-hanging fruit gets eaten quickly.

Re: Skunk Works Reveals Compact Fusion Reactor Details

#232

Post by avian » Wed, Oct 15, 2014, 7:34 PM UTC

anigbrowl wrote: post #224

On a tangent, is there any fundamental reason that reactors are always built to drive turbines rather thermocouples - do they simply not scale up to the amount of heat a typical reactor puts out, or what?

Steam turbine plus a conventional generator is vastly more efficient than thermocouples - 30-40% for steam versus I suspect they are also much, much cheaper when you are talking about powers in the hundreds-of-megawatts range. I don't have specific data at hand to back that though. I never heard of any grid-level power generation being done with thermocouples.

Re: Skunk Works Reveals Compact Fusion Reactor Details

#233

Post by FiatLuxDave » Wed, Oct 15, 2014, 7:36 PM UTC

hendler wrote: post #205

Osmium wrote: post #191

Earlier quoted context omitted.

> I suspect this effect means that, for reactors, the wear and tear is more localized, but of a larger amplitude. Not exactly. The initial collisions do indeed cause localised damage cascades, but the overall effect of a large neutron flux is embrittlement of the material. This is a problem already in fission reactor vessels, but the neutron fluxes are a whole order of magnitude larger in fusion reactors, and it's a…

http://www.thomasnet.com/products/neutron-shielding-74851395...

The majority of those suppliers provide boron-impregnated plastic, which is fine for e.g. shielding spallation neutrons from a medical linac head. Reactor shielding is orders of magnitude higher, so material damage is a real concern. Not to say that people can't or don't use that material, but it is not the most cost effective stuff.

Frankly, the best neutron shielding in the world, on a per-cost basis, is water with borax. I don't know why people don't use this more. We used to use stacked bags of borax as neutron shielding when I built a fusion reactor (non-self sustaining, of course), and we had more than enough shielding to handle 2.45 MeV neutrons for under $1000.

Re: Skunk Works Reveals Compact Fusion Reactor Details

#234

Post by jsmthrowaway » Wed, Oct 15, 2014, 7:45 PM UTC

rayiner wrote: post #213

jsmthrowaway wrote: post #194

Earlier quoted context omitted.

It's always a safe bet that the top Hacker News comment will always be "won't work, it's too hard." It's like sitting around for a year trying to sell a project at my current employer, with everybody and their lead telling you "that'll never work," then you implement in a weekend and those same people start nitpicking what you've come up with. (What happened to it'll never work? "Well, your CSS isn't great.") Honestl…

That's hardly ever true. In my experience, Hacker News is full of people from the software field; folks whose professions are often unconstrained by physics,[1] and who have a generally optimistic "this can happen" mentality. That's why everyone here believes we'll have fully self-driving cars in 5-6 years. In the rest of the engineering world, the answer to any question is: it'll be harder than you think it'll be (p…

> That's hardly ever true.

Even pg discussed the phenomenon, as you undoubtedly know. There's a good idea, or a news article hailing progress, or some other kind of optimism, then the first comment is a mid-brow dismissal. They are the lowest-effort comments to make; "that won't work because X isn't well-respected and Y often happens to similar teams" requires almost no research and cannot really be refuted.

The only way to refute it is by calling a spade a spade, and look what I get for doing so: having my comment twisted to be fuzzy feel-good smarm crap, when really I'm just saying "shut up and get out of the way if you don't think it'll work."

Re: Skunk Works Reveals Compact Fusion Reactor Details

#235

Post by chisophugis » Wed, Oct 15, 2014, 7:46 PM UTC

wcoenen wrote: post #57

> 100-megawatt reactor measuring seven feet by 10 feet, which could fit on the back of a large truck A typical thermal power station has an efficiency below 50% for electricity generation, so the plant dissipates at least as much heat as it generates electrical power. I wonder how you could get rid of 100MW of waste heat from a volume small enough to fit on a truck. That's a heat flux of more than a megawatt per squa…

FWIW, a single Boeing 747 engine does about 100MW. Such an engine can be considered to "fit on a truck" for some definition of truck.

Also consider that much of the size is due to the fan on the front (which is not part of the actual engine power plant), which makes the engine's area in the plane transverse to the axis of rotation seem larger.

However, jet engines have the advantage of burning their fuel directly in the air that is flowing through the engine, which results in an extremely rapid transfer of heat to the air compared to other (this is why 10 Boeing 747 engines == 1 GW coal/nuclear plant which is "buildings" in size).

See slide 25 (page 13) of http://ronney.usc.edu/AME436S13/Lecture1files/AME436-S13-lec...

Re: Skunk Works Reveals Compact Fusion Reactor Details

#236

Post by nutjob123 » Wed, Oct 15, 2014, 7:48 PM UTC

jsmthrowaway wrote: post #194

nabla9 wrote: post #164

I'm not seeing any top physicists working in this program (McGuire is not one). I would be willing to bet 1000 EUR that their math and modeling does not add up, or they have skipped some details. Problem with fusion research like this is that the closer you get self sustainment or energy generation, the harder it gets and problems pile up. This project looks like many other similar projects that have gone bust. They…

It's always a safe bet that the top Hacker News comment will always be "won't work, it's too hard." It's like sitting around for a year trying to sell a project at my current employer, with everybody and their lead telling you "that'll never work," then you implement in a weekend and those same people start nitpicking what you've come up with. (What happened to it'll never work? "Well, your CSS isn't great.") Honestl…

I dislike negativity as much as the other guy but fusion specifically has been "10 years away" for the last 60 years. I'm not convinced, especially without any specifics about what improvements they made. Probably just another grab for funding.

Re: Skunk Works Reveals Compact Fusion Reactor Details

#237

Post by jsmthrowaway » Wed, Oct 15, 2014, 7:50 PM UTC

protonfish wrote: post #207

jsmthrowaway wrote: post #194

Earlier quoted context omitted.

It's always a safe bet that the top Hacker News comment will always be "won't work, it's too hard." It's like sitting around for a year trying to sell a project at my current employer, with everybody and their lead telling you "that'll never work," then you implement in a weekend and those same people start nitpicking what you've come up with. (What happened to it'll never work? "Well, your CSS isn't great.") Honestl…

And it's always a safe bet the top response to that comment will be somebody criticizing it without any solid facts or reason but with fuzzy "you just need to believe harder!" kind of nonsense.

Actually, I subtly said "get the hell out of the way if you don't think it'll work," not warm and fuzzy smarminess. But it's much easier for you to mock if you read warm and fuzzies out of it, and I get that.

What I said, reworded, was the people who sit on the sidelines of anything and tell you, while you are trying something, that it won't work are among the worst people in the profession. I didn't say believe harder. I don't give a damn what you believe and don't need you reminding me, constantly, that my project has a chance of failure. Keep it to yourself or get on board. That's my point.

I am not a kind person, so that you'd ascribe feel-good nonsense to me is downright hilarious. I can handle it but a lot of people can't, and it's really, really tiring to keep a team from becoming demoralized when there's a naysayer popcorn gallery in every thread and watercooler discussion.

Re: Skunk Works Reveals Compact Fusion Reactor Details

#238

Post by mikeyouse » Wed, Oct 15, 2014, 8:02 PM UTC

mrisse wrote: post #100

From the article: Lockheed shares fell 0.6 percent to $175.02 amid a broad market selloff. Shouldn't the market be a little more excited about this?

Quick and dirty;

Lockheed has a market beta of 0.7 -- So it's correlated with the general market fairly strongly. On aggregate, if the market increases or decreases by 1%, you'd expect Lockheed to follow the market by 0.7%.

Today most of the major indices are down ~1%, Lockheed is down 0.4%, so you could attribute that 0.3% deviation from the expected number as reactor news. 0.3% of Lockheed's market cap represents about $170M today.

It's obviously not this straightforward, but if I were a shitty journalist, I could make the case that this is actually a pretty good result since commercialization will likely be a decade away, it will take a ton of resources and investment to get there, and there's a high chance of failure.

A shitty DCF with a ramp to $500M/year in R&D, 75% margins on sales, and a $10B/year business in perpetuity comes out to $170M NPV with a ~31% discount rate --- Not too unrealistic.

Re: Skunk Works Reveals Compact Fusion Reactor Details

#239

Post by ninkendo » Wed, Oct 15, 2014, 8:02 PM UTC

Animats wrote: post #183

This might work. It's from Lockheed's Skunk Works, which has a very good track record and tremendous respect in the aerospace community. With the basic physics laid out, this is mostly an engineering and construction problem. Their plan is to build and test a new prototype every year. The Skunk Works can do that; they've been doing it for decades. They're a manufacturer of prototypes, and have in-house capabilities f…

> With the basic physics laid out, this is mostly an engineering and construction problem.

That phrase has been accurate for nuclear fusion in general for more than 50 years. The engineering and construction problems are immense.

Re: Skunk Works Reveals Compact Fusion Reactor Details

#240

Post by rayiner » Wed, Oct 15, 2014, 8:08 PM UTC

jsmthrowaway wrote: post #234

rayiner wrote: post #213

Earlier quoted context omitted.

That's hardly ever true. In my experience, Hacker News is full of people from the software field; folks whose professions are often unconstrained by physics,[1] and who have a generally optimistic "this can happen" mentality. That's why everyone here believes we'll have fully self-driving cars in 5-6 years. In the rest of the engineering world, the answer to any question is: it'll be harder than you think it'll be (p…

> That's hardly ever true. Even pg discussed the phenomenon, as you undoubtedly know. There's a good idea, or a news article hailing progress, or some other kind of optimism, then the first comment is a mid-brow dismissal. They are the lowest-effort comments to make; "that won't work because X isn't well-respected and Y often happens to similar teams" requires almost no research and cannot really be refuted. The only…

I don't think of such comments as being "mid-brow" dismissals. Indeed, the people most knowledgable about the field are the ones who are most likely to tell you it won't work. And 97% of the time they'll be right.

As for "shut up and get out of the way"--whose way exactly? Unless you're a nuclear physicist, comments expressing hopeful optimism aren't very useful.