Comment by sbierwagen | Hacker News Reader

Comment by sbierwagen | Hacker News Reader

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  Also, what happens if the mechanisms that contain the "Star 
  in a Bottle" fail? Will the French Alps suddenly and 
  catastrophically acquire a new valley?

This is a reasonable concern, but your intuitions on the physical processes involved are off by a couple orders of magnitude.

From a previous comment on another fusion story, two years ago: http://news.ycombinator.com/item?id=2839722

  Fusion reactors are fundamentally different from fission 
  reactors. You have to get a tenuous wisp of hydrogen (the 
  reactor in this particular experiment was running at 10 
  mTorr, or 0.0013% atmospheric pressure) very, very hot, and 
  keep it away from solid matter, which is millions of 
  degrees of colder than the fuel plasma, and will suck all 
  of the energy out of the reaction.

  You shut off the containment coils, and tremendously hot 
  plasma ions leap away from each other, instantly stopping 
  the reaction. If the reaction somehow "runs away", which it 
  absolutely can't, then it brushes the walls of the vacuum 
  chamber, poisoning it with cold metal ions, like injecting 
  lead shavings that have been chilled to absolute zero 
  directly into your heart.

  If our magical "runaway reaction" somehow overcomes this, 
  and melts a hole in the vacuum chamber, then the atmosphere 
  rushes in, both freezing cold and at intolerably high 
  pressure, like the North Sea flooding into the hull of a 
  submarine resting on the ocean floor.

  Fusion reactors don't melt down, or explode. At all. It 
  just can't happen, much like how a Yugo rear-ending a 
  garbage truck in Brooklyn doesn't instantly consume all of 
  New York City in a gasoline fireball.

"a Yugo rear-ending a garbage truck in Brooklyn doesn't instantly consume all of New York City in a gasoline fireball."

My new favorite metaphor.

The metaphors that arise to describe worrying about things that can't actually happen are also my favorite. The one most memorable to me:

"Putting a speed limiter on a Zamboni just in case the accelerator gets stuck"

I'd just like to point out that the Yugo metaphor is invalid because the article specifically states that the experiment involves "beams of uncharged particles — the energy in them so great it could vaporize a car in seconds".

So there.

Similarly, the YUGO (825kg curb weight) contains about 7.4e19 joules of energy, when converted purely.

Which comes out to 17.7 billion tons of tnt, or 1.1 million times the force unleashed on Hiroshima.

If we're being pedantic.

How much energy is there in a Ferrari?

1735 kilograms (Ferrari California curb weight) * (the speed of light^2) = 1.55934024 × 1020 joules

How many Hiroshimas is that?

Well, that turns out to be a unit of energy which GNU unit (my favorite shell utility) doesn't have, nor does it have kilotons (or tons) of TNT).

However I've found a calculator that does do kilotons of TNT:

http://lectureonline.cl.msu.edu/~mmp/conversions/conv_energy...

So one Ferrari is 37.13 * 10^6 kilotons. Hiroshima was 15 kt, so one Ferrari contains the energy released in 2,475,333.3 Hiroshima atomic bombs.

And for reference, 1 kilotonTNT is:

4.200e+12 joule

1.003e+12 calorie

1.003e+9 kilocalorie

At 3600 kcal/lb fat, one kilotonTNT is equivalent to 278,611.11 lb of fat. Which is to say, if everyone (313 million people) in the US lost 1/5 of an ounce each, the energy released would be equivalent to one Hiroshima bomb.

3.978e+9 BTU

1,167 MWh, or 1.2 GWh. Roughly the energy a large generating plant produces in an hour. Which is to say that the time over which you release energy matters.

And you've also inspired me to figure out how to add my own units definitions, so now I have kttnt:

686 barrels of oil, almost exactly 100 tons of oil, 1.16 GWh, 143 toncoal, 154 tons of charcoal, or about 51 grams of pure uranium.

And checking: 100 tons / 51 grams is 1,778,793, which is to say, atomic energy has roughly 1 million times the energy storage density of our best chemical energy sources.

You'll note that 100 tons of oil is a lot less than a kiloton (1000 tons) of TNT. Turns out that what makes TNT so special isn't its energy content but the rate of release of that energy. Oil (or aviation fuel as the occupants of 120 Cortlandt St., NYC, discovered a few years back) has about 10 times the energy content of explosives, it just delivers it over a longer period of time.

It's possible. Albeit the Yugo needs to move at the speed of light.

Which might sound plausible for anyone that never heard of Yugo, or the speed of light.

That addresses the concern about the fusion reaction. But when the plasma melts a hole in a building-sized vacuum chamber and air suddenly rushes in, I expect that you'll get a big implosion, which will ricochet off itself and become an explosion, like if you punched a hole in a CRT with a nail. The article talks about a solenoid that exerts more force than the Space Shuttle does to lift itself to orbit. When the vacuum chamber deforms the solenoid, that energy is going to go somewhere. Plus, they mention gigajoules of electricity going through superconducting wires. I expect that the vacuum chamber implosion would destroy them before they heated up and no longer became superconducting. So instead of gigajoules going through essentially giant resistors and heating up something fierce, that energy will do something else, not sure what.

I don't think this will destroy a mountain, but I would expect the reactor and building to be catastrophically destroyed by the vacuum chamber implosion, along with some, shall we say, interesting, but certainly powerful, effects from the solenoid and other magnets.

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