3 ms·

I have a question. How come the mathematical modeling and simulations haven't yet yielded us the perfect design that will get things right? How come we have to

I have a question. How come the mathematical modeling and simulations haven't yet yielded us the perfect design that will get things right? How come we have to build it and test it to know if it works? Do we lack a mathematical model?

burnt-resistor 1y ago
Putting a bunch of much more viscous radioactive material within proximity of each other is simpler than squishing and maintaining confinement of plasma under extreme conditions. Fission reactors are relatively "easier" to simulate as giant finite element analysis Monte Carlo simulations with roughly voxels of space, i.e., thermal conductivity, heat capacity, etc. I happened to have been involved with one that was 50+ years old that worked just fine because of all of physicists and engineers who carefully crafted model data and code to reflect what would be likely to happen in reality when testing new, conventional reactor designs. The problems with fusion are many orders-of-magnitude more involved and complex with wear, losses, and "fickleness" compared to fission. Thus, experimental physics meeting engineering and manufacturing in new domains is expensive and hard work. Maybe in 200 years there will be a open source, 3D-printable fusion reactor. :D
KingOfCoders 1y ago
The difficulty is in the details. Small differences lead to bigger differences, like in chaos theory [0] What if the model says this coil needs to be 23.1212722 centimeter? Or two coils need to be 37.1441129 centimeters apart? How do you build that? Mathematics is always much more precise than engineering. [0] https://en.wikipedia.org/wiki/Edward_Norton_Lorenz#Chaos_theory https://en.wikipedia.org/wiki/Edward_Norton_Lorenz#Chaos_the...
- HPsquared 1y ago
  You need to think of what happens if it's 0.001 cm too big, small, etc. Manufacturing always involves errors and engineering requires tolerances.
- ninetyninenine 1y ago
  Doesn’t our engineering account for that? We never build things that need that level of detail in our tolerances. Like for example an airplane.
  - KingOfCoders 1y ago
    OP "How come the mathematical modeling and simulations haven't yet yielded us the perfect design that will get things right?"
    - ninetyninenine 1y ago
      Right how come we don't have models that allows to simulate designs with bigger tolerances? That's the perfect design.
padjo 1y ago
We still have wind tunnels and aerodynamics is a pretty simple problem compared to fusion.
regularfry 1y ago
Same question got asked of Bob Bussard when he visited Google to talk about his whiffle-ball design. It's not that we lack models, it's that they're effectively incomputable at the scale we'd need them to be. In a fluid, effects are local: a particle can only directly effect what it is in direct contact with. In a plasma, every particle interacts with every other. One definition of a plasma is that the motion is dominated by electromagnetic effects rather than thermodynamic: by definition, if you have a plasma, the range of interactions isn't bounded by proximity. This doesn't apply quite so much to (e.g.) laser ignition plasmas, partly because they're comparatively tiny, and partly because the timescales you're interested in are very short. So they do get simulated. But bulk simulations the size of a practical reactor are simply impractical.

burnt-resistor 1y ago

Putting a bunch of much more viscous radioactive material within proximity of each other is simpler than squishing and maintaining confinement of plasma under extreme conditions. Fission reactors are relatively "easier" to simulate as giant finite element analysis Monte Carlo simulations with roughly voxels of space, i.e., thermal conductivity, heat capacity, etc. I happened to have been involved with one that was 50+ years old that worked just fine because of all of physicists and engineers who carefully crafted model data and code to reflect what would be likely to happen in reality when testing new, conventional reactor designs. The problems with fusion are many orders-of-magnitude more involved and complex with wear, losses, and "fickleness" compared to fission. Thus, experimental physics meeting engineering and manufacturing in new domains is expensive and hard work. Maybe in 200 years there will be a open source, 3D-printable fusion reactor. :D

KingOfCoders 1y ago

The difficulty is in the details. Small differences lead to bigger differences, like in chaos theory [0] What if the model says this coil needs to be 23.1212722 centimeter? Or two coils need to be 37.1441129 centimeters apart? How do you build that? Mathematics is always much more precise than engineering. [0] https://en.wikipedia.org/wiki/Edward_Norton_Lorenz#Chaos_theory https://en.wikipedia.org/wiki/Edward_Norton_Lorenz#Chaos_the...

HPsquared 1y ago
You need to think of what happens if it's 0.001 cm too big, small, etc. Manufacturing always involves errors and engineering requires tolerances.
ninetyninenine 1y ago
Doesn’t our engineering account for that? We never build things that need that level of detail in our tolerances. Like for example an airplane.
- KingOfCoders 1y ago
  OP "How come the mathematical modeling and simulations haven't yet yielded us the perfect design that will get things right?"
  - ninetyninenine 1y ago
    Right how come we don't have models that allows to simulate designs with bigger tolerances? That's the perfect design.

padjo 1y ago

We still have wind tunnels and aerodynamics is a pretty simple problem compared to fusion.

regularfry 1y ago

Same question got asked of Bob Bussard when he visited Google to talk about his whiffle-ball design. It's not that we lack models, it's that they're effectively incomputable at the scale we'd need them to be. In a fluid, effects are local: a particle can only directly effect what it is in direct contact with. In a plasma, every particle interacts with every other. One definition of a plasma is that the motion is dominated by electromagnetic effects rather than thermodynamic: by definition, if you have a plasma, the range of interactions isn't bounded by proximity. This doesn't apply quite so much to (e.g.) laser ignition plasmas, partly because they're comparatively tiny, and partly because the timescales you're interested in are very short. So they do get simulated. But bulk simulations the size of a practical reactor are simply impractical.