4 ms·

Ok, so then someone should start a company that iterates on fission (proven tech like Merlin) and gets the cost of that way down and safety way up, then uses th

Ok, so then someone should start a company that iterates on fission (proven tech like Merlin) and gets the cost of that way down and safety way up, then uses that momentum to work on fusion, which (like the Raptor engine) is a whole 'nother ball game, but you can still use some of the expertise from fission for fusion. The analogy holds!

ubercore 6y ago
I think fission to fusion is more like steam engine to jet engine. Fission can happen by _accident_ if you have the right materials at energy levels of just dropping something on something else [0]. Starting fusion isn't easy, but as I understand it, that's not even the hard part. Containment is the big deal, because of the energy needed. [0] https://en.wikipedia.org/wiki/Demon_core https://en.wikipedia.org/wiki/Demon_core
- fastball 6y ago
  Isn't the Sun fusion happening by accident?
  - JoshuaDavid 6y ago
    Sure, and solar power is cheap fusion energy. Getting fusion energy without gravitational confinement is the tricky bit.
  - semi-extrinsic 6y ago
    Yeah, but the Sun only works because of its unfathomably massive size, compared to anything we can do on Earth. If you take 800 cubic meters of plasma from the core of the Sun, about the same volume as ITER, it only produces 216 kW - comparable to the engine in your car. And in that volume, you will have an average rate of 1500 hydrogen fusion reactions per second. Compared to ITER, this is something like twelve orders of magnitude slower. That is why ITER needs to go to much higher temperatures than the sun.
    - pfdietz 6y ago
      You have made an error somewhere. 1500 fusion reactions per second is maybe 10^10 eV per second, which would be around a nanowatt.
      - semi-extrinsic 6y ago
        Yeah, you are right there is a mistake. I made a typo in Avogadro's number. Sorry about that! The power density is correct, but the number of reactions is too low by a factor of 10^10...
- jabl 6y ago
  There's a saying that fission is like playing a mini-golf course where you have a flat surface peppered with holes, and every time you hit a hole you get ~2 new balls. Fusion is like a mini-golf course which is a volcano mountain with a tiny hole on the top.
sudosysgen 6y ago
Fission and fusion is a quantum leap. It's like going from the Babbage Differential Engine to a Ryzen 7 1700X. You can't iterate your way from fission to fusion, but you can iterate your way from the Merlin to the Raptor. The Raptor which, by the way, is not even that far ahead of what came before it.
- fastball 6y ago
  Don't actually think you can iterate from Merlin to Raptor.
  - avmich 6y ago
    > Don't actually think you can iterate from Merlin to Raptor. In some sense Earth science had practically do that - from Goddard's 1926 pressure-fed/piston pumps feed via von Braun's open loop of 1944, via Isayev-Melnikov staged combustion of 1949-1959 to Glushko's full-flow combustion of 1967. Slow, and engines were designed from scratch. But still some iterations and evolution.

ubercore 6y ago

I think fission to fusion is more like steam engine to jet engine. Fission can happen by _accident_ if you have the right materials at energy levels of just dropping something on something else [0]. Starting fusion isn't easy, but as I understand it, that's not even the hard part. Containment is the big deal, because of the energy needed. [0] https://en.wikipedia.org/wiki/Demon_core https://en.wikipedia.org/wiki/Demon_core

fastball 6y ago
Isn't the Sun fusion happening by accident?
- JoshuaDavid 6y ago
  Sure, and solar power is cheap fusion energy. Getting fusion energy without gravitational confinement is the tricky bit.
- semi-extrinsic 6y ago
  Yeah, but the Sun only works because of its unfathomably massive size, compared to anything we can do on Earth. If you take 800 cubic meters of plasma from the core of the Sun, about the same volume as ITER, it only produces 216 kW - comparable to the engine in your car. And in that volume, you will have an average rate of 1500 hydrogen fusion reactions per second. Compared to ITER, this is something like twelve orders of magnitude slower. That is why ITER needs to go to much higher temperatures than the sun.
  - pfdietz 6y ago
    You have made an error somewhere. 1500 fusion reactions per second is maybe 10^10 eV per second, which would be around a nanowatt.
    - semi-extrinsic 6y ago
      Yeah, you are right there is a mistake. I made a typo in Avogadro's number. Sorry about that! The power density is correct, but the number of reactions is too low by a factor of 10^10...
jabl 6y ago
There's a saying that fission is like playing a mini-golf course where you have a flat surface peppered with holes, and every time you hit a hole you get ~2 new balls. Fusion is like a mini-golf course which is a volcano mountain with a tiny hole on the top.

sudosysgen 6y ago

Fission and fusion is a quantum leap. It's like going from the Babbage Differential Engine to a Ryzen 7 1700X. You can't iterate your way from fission to fusion, but you can iterate your way from the Merlin to the Raptor. The Raptor which, by the way, is not even that far ahead of what came before it.

fastball 6y ago
Don't actually think you can iterate from Merlin to Raptor.
- avmich 6y ago
  > Don't actually think you can iterate from Merlin to Raptor. In some sense Earth science had practically do that - from Goddard's 1926 pressure-fed/piston pumps feed via von Braun's open loop of 1944, via Isayev-Melnikov staged combustion of 1949-1959 to Glushko's full-flow combustion of 1967. Slow, and engines were designed from scratch. But still some iterations and evolution.