Power distribution cables at intervals longitudinally could produce a magnetic field and provide power to other colonies. We have the tech now, it'd just be expensive.

Zubrin's book "The Case for Mars" removed a lot of my skepticism. He details how terraforming might work.

In the article they mention it's to aid scientists in determining how the painting ages.

Yeah, you're right, shouldn't have lumped education in with science spending. Amazing we spend so much per capita and get so little in return.

I understand the military has its place, but imagine the world we'd live in if the Afghanistan blunder budget (~2.3 trillion!) was spent on science and education.

Haha, you've done quite a bit of research here. Neon looks interesting, the only thing I would caution is any activation has to be brought through the lines through the entire cryogenic setup. For hydrogen and helium this isn't an issue. It might just mean a neon setup has to be in the radiation boundary. It's outside my area so I don't know how feasible this would be, but possible from an engineering perspective and maybe it could make sense economically.

Hydrogen is certainly cheaper and on paper I can see why some graduate students would choose it over helium. In reality it presents a new hazard to the reactor and regulators may not like having an explosion hazard coupled with activated material.

Quite a bit of the cryogenics fluids are subjected to nuclear heating - both the toroidal field coils and central solenoid coils are mere cm away from the plasma wall even in the ITER design, shrinking the size of the reactor with the MIT design even more so. The spherical tokamaks are even more extreme. It's a funny environment to go from millions of K to 4 K in such a sharp gradient.

ARC is just a paper design, I would bet that once it hits the real design phase they will switch to helium for the extra field and stability. On top of critical current / field you have related quench stability. It's not as expensive as you think, virtually every accelerator or superconducting facility has a 4K helium setup. There are other "real" considerations like taking into account nuclear heating meaning you need a dense fluid rather than a gas for the extra capacity. I'm not sure if neon has neutron activation issues. We will see...

The parasitic losses largely disappear with more advanced designs. Once ignition is achieved you can theoretically turn off RF and neutral beam heating and your return factor Q becomes infinity. For now no one really wants to push this area because (from my limited understanding) they are still trying to figure out the physics, and while boostrapped or ignition designs might seem great they inevitably mean less tunability and control. Once the physics is more understood we might very well have high bootstrapped tokamaks that only require power in for start / ignition.

I agree with you we're not here yet, but it appears to be very close. The Lawson criteria triple product metric of reactors has been doubling at a rate faster than Moore's law, even with the abysmal funding fusion has gotten to date. These startups should be able to demonstrate Q>1 physics and likely Q>1 eng.

The "no radioactive waste" I agree tends to be oversold, but it is true that an incident is almost impossible and if vacuum was breached a tiny bit of tritium would go into the atmosphere, and nearly instantly disperse. Not much tritium needs to be in the reactor at any time, unlike fission designs (grams of tritium vs. tons of uranium). End of life you still have a radioactive first wall which needs to be decommissioned, but with proper material selection this would be radioactive for tens to hundreds of years in a cask compared to fission's millennia.

In practice HTS still requires liquid helium to get to the higher magnetic fields that drive the advantage. While some of these might be superconducting ~77K the critical current and field is quite low. Otherwise you're correct, power roughly scales with B^2 so size overall shrinks tremendously. There are additional challenges with this route, for example mechanical stress also goes up with B^2, and overall heat concentration as well (tough to design divertors and neutron capture blankets). These appear to be solvable but are difficult problems.

Having worked in the field, I'm convinced several technologies (tokamak, stellerator) will demonstrate Q>1 this decade. It's a long leap from going from this to a working reliable low maintenance reactor, and I'm not convinced technology like a tokamak is ready for a "build and leave it alone" type tech required for commercial operation. We'll get there someday for sure, but it might take more time than these startups are suggesting -- it's a very hard problem. TAE, Helion, and Zap Energy all have technologies that at least from the engineering perspective appear to be much simpler and cheaper, but still have to prove the physics. I'd like to be pleasantly surprised and see one of them demonstrate a far superior tech compared to tokamaks, but fusion history hasn't been kind to new concepts.

They are complete game changers, but they still require helium to get to the high magnetic fields. At the transition temperature the magnetic field and current carrying capabilities are tiny, getting to large currents and fields requires cooling. Since you want to maximize field for the benefit of the reactor this means minimizing T - so helium is still in. For superconducting electronics and chips you don't need to lower T as much.

https://encrypted-tbn0.gstatic...

Yes, you're right. HTS allows the Tokamak design to be shrunk proportionally to the square of the magnetic field. With this SPARC becomes 1/10 the size of ITER with the same power output. It's not exactly perfect, the heat becomes far more concentrated so the divertor design becomes very challenging, but there are many paths forward here.

If the initial costs of reductions are reduced the economics of fusion are clear. Unlike fission the inputs are essentially free compared to power out (lithium, deuterium, tritium, even beryllium molten salt blankets are all a tiny fraction of construction and a rounding error in operational costs). There's no hazardous waste. The activated first wall does not require expensive decommissioning at the end of the reactor's life.

Biggest challenges for an operational reactor IMO are reliability related. You can't have them stall during operation, but unlike fission they will be very sensitive to things like plasma disruptions and instabilities. If anything "breaks" you may not have a disaster as with fission, but you still can't access the reactor until the radiation cools down (and cities go without power). Radiation damage over time might require swappable walls. To me the solution might be redundancy on site, but this would require the total construction cost to be reduced substantially.

The other approaches like Helion and TAE would be far better costs and maintenance, but the physics is still unproven. If either demonstrate Q>1 before SPARC/MIT, Tokamaks might be dead.

The allies did a good deal to sabotage the nazi attempts. Notably the sabotage of the Norwegian heavy water site sticks out, Operation Gunnerside reads like something out of James Bond: https://en.wikipedia.org/wiki/...

Some of the work out of ORNL looks promising for uranium extraction which has been an interest of mine. Polymer strands would have a good surface area for binding. My thought is it would be cool to make a stand-alone ocean plant which uses the thermal differences between deep water and surface to drive an ammonia turbine loop, use the power to flow water past the polymers and complete the turbine cycle, excess power to grid.

https://www.ornl.gov/news/bio-...
https://www.ornl.gov/news/ornl...

Would love to see similar fibers be developed for other materials of interest: vanadium, gold, lithium, etc. The Chinese are building pilot plants to extract uranium as presently they have to rely on outside countries for energy sources and this would be a way to ensure energy security regardless of cost.

Yes, and not the first time it's been done before either. C60 when under "modest" pressure of ~20 GPa will cross link and make a substance that will indent diamond:

https://science.sciencemag.org...

This was done ~2012. It's all very interesting but until someone finds a way to mass produce the material it's just a curiosity. You can't really make quantities of this stuff if you need a diamond anvil cell.

Ah, sorry for spreading misinformation. I knew it was molten salt but my faulty memory told me it was thorium.