> A series of 50-kiloton bombs would be dropped into the cavern and exploded to heat the water and create steam. The steam would then power a secondary cooling loop for power extraction using a steam turbine. Dropping about two bombs a day would cause the system to reach thermal equilibrium, allowing the continual extraction of about 2 GW of electrical power
For some reason (that I haven’t figured out yet) thermonuclear bombs are just so much more efficient than any other proposed fission or fusion reaction.
It’s strange that controlled fusion is an energy sink, but whatever black magic is happening inside an H-bomb manages to unlock so much “free” energy.
Fusion is ridiculously efficient and effective power source. The problem with it is that it is very hard to created conditions where fusion can happen. The one reliable way we have that doesn't take more energy in than it outputs, is to detonate a fission bomb and use the x-rays to compress a fusion secondary.
The history of fusion research for the past 70 years is trying to figure out a cost-effective way to trigger enough fusion to make net energy without a nuke. So far, we've got bupkis. (The magnetic containment approaches using high-temperature superconductors seem promising, but we won't know they actually work until we've built them.)
We orbit a giant fusion energy source and capturing its energy has gotten pretty cheap. Not very efficient per se, but there's so much energy and it's free, so it doesn't matter.
> It’s strange that controlled fusion is an energy sink, but whatever black magic is happening inside an H-bomb manages to unlock so much “free” energy.
E=mc^2. The proportion of the original mass converted to energy in fusion is higher than it is for fission.
The trouble with fusion is that you need really high temperatures and pressures to sustain it. You can easily sustain a fission reaction at a few hundred degrees C, or even lower than that if you wanted to (but the general goal is to boil water to run a steam turbine so >100°C is what you want).
Fusion requires millions of degrees, which would vaporize most things you might want to use as a container, so instead they use strong magnetic fields and then you spend a lot of energy maintaining the magnetic field. A bomb doesn't care about that because sustained operation isn't required and vaporizing everything in the vicinity is kind of the idea.
Moreover, efficiency isn't really the issue. The efficiency of fission is already absurd. Fission of a given mass of uranium generates the same amount of energy as burning 2.7 million times that amount coal -- by mass, it's even more by volume.
The main advantages of fusion are that hydrogen is a lot more common than uranium (though uranium is still pretty available) and that the byproduct of fusion is helium (a non-radioactive noble gas with general usefulness), whereas some of the fission byproducts are variously radioactive or have limited known commercial applications.
Fusion is all about the 'triple product': pressure x temperature x time. The sun and nuclear bombs have plenty of pressure, but nuclear bombs don't operate for very long. Fusion reactors actually have a much lower pressure than the sun but correspondingly operate at much higher temperatures (about 10x what's in the core of the sun!).
The efficiency is higher because the device is bigger. To oversimplify a bit, the surface area through which energy is radiated away grows slower than the volume containing the fuel. So heavier fuel "pellets" in bombs (ones in the kilogram to ton range) have a much easier time burning efficiently than the tiny milligram scale fuel pellets at NIF. Tiny fuel pellets cool down too fast. Likewise, multi-megaton fusion bombs are more efficient than the "little" sub-megaton bombs that the US favors (for reasons of compactness/deliverability) in its nuclear weapons stockpile.
Even the cleanest bombs (97%+ fusion rather than fission) turned out to be too dirty for basically everything civilian (unlocking gas reservoirs - too radioactive; landscaping to replace enormous amounts of conventional explosives - too radioactive).
Not really making nukes take a ridiculous amount of energy and you only get to use it once where the energy to create ITER gets split across its operating lifespan.
Further fission here requires a fission first stage which represents a huge additional energy input.
I really don’t trust that LLM estimate, they are really bad at that kind of thing but for the sake of argument let’s take that as a baseline.
ITER is supposed to be a 10-20x return on energy provided (10x being a basically guaranteed minimum) which means it may or may not be better depending on the specific bomb design, but it’s not massively better.
People talk about fusion as useless and slow but the current record holder in steady state was first turned on in 1983 and hit 0.67 in 1997. It’s not a failure of the underlying technology, it’s a near total lack of investment that’s stalled progress. ITER was started under the first Bush presidency and scaled back to a minimum design. It could have easily been built 20+ years ago if it was an actual priority.
> It could have easily been built 20+ years ago if it was an actual priority.
That is a bad thing to do. We diversified bets, and we end up finding a couple of pretty good energy sources, plus making some of the existing ones cleaner and safer.
Had we put all our money in fusion, today we might be drowning in cheap clean energy... or still living in a dirty coal-fuel environment, with a few old and dangerous fision reactors for lack of investment in development. A very risky bet.
I agree diversifying bets is a good idea, but building ITER 20 years ago wouldn’t have been a particularly significant investment.
Spend 1 billion/year (in today’s money) from 1987 and by 2006 you’re well past ITER’s projected cost back then there was little advantage to waiting. JET’s first plasma was 1983 so that’s another 10 years for design and 12 years for construction.
By comparison the US was spending ~12 Billion / year in energy R&D in 1978 (2026) dollars. That fell over time, but it’s not like total energy R&D spending couldn’t have increased vs historic levels. https://www.congress.gov/crs-product/RS22858
> but building ITER 20 years ago wouldn’t have been a particularly significant investment.
We don't know this. There are a number of investments that fail and the investors need to let go or you get into the phallacy of sunken costs. E.g. wave energy was a failure, thermo-solar under delivered, algae based fuels never scaled up, and ethanol fuels from waste proved very difficult to engineer, syngas was a ecological nightmare... All of them received significant investment, and they were abandoned, pivoted or relegated to niche applications. I personally would throw fusion in that same group of failed investments.
Luckily for us, solar PV (paired with batteries) is a huge win that justifies all the above failures: for decades it was a dream for the 25th century, but some people make it true in the 21st.
Not every spending/investment ends up in success! Fusion is one hurdle after another, yet it advocates still believe that is just a throw-more-money-at-it problem. I am not so convinced. Of all the failed (for now) energy sources, fusion is the biggest money sink. France spent 25 billion, plus 7 billion in private funds. It is not like they are working with peanuts, at those quantities you have to show some serious results, maybe facing scaling problems rather than basic development problems (e.g. ethanol failed at scaling, when it already proved viable on smaller scale. Fusion is not even in "we have this toy reactor that works we are fighting to scale" phase).
Except we do know this because people built similar systems at similar scales and temperatures before.
> All of them received significant investment
Not compared to Nuclear, Fossil Fuel, or PV R&D + subsidies. For scale in the US alone “From FY 2016 to FY 2022, federal subsidies for renewable energy totaled $183.3 billion” That’s more than 1 ITER per year, and splitting that budget across multiple countries and 2 decades is a very different proposition. Especially as there was ITER funding in this time period so the delta is less than the full cost of the project.
Further look at the timeline, I’m suggesting the project should have finished long before PV became cheap.
> Except we do know this because people built similar systems at similar scales and temperatures before.
Did we? Where are those fusion plants installed?
> Not compared to Nuclear, Fossil Fuel, or PV R&D + subsidies
You are probably referring to this document: https://www.eia.gov/analysis/requests/subsidy/pdf/subsidy.pd... . A huge share of the $183.3 billion are tax expenditures, which is to say they reduce taxes on activities related with energy (e.g. nuclear decommissioning is tax free). That is not the same as throwing money at those technologies R&D, but it counts as subsides because they can operate more cheaply. Only $11 billion of the $183.3 is true expending. But they mix R&D with other direct expending, like guaranteed loans. In Figure 11 we can see that R&D for all renewable energies is less than $300 million.
Fusion energy don't want tax expenditures, they want cash and lots of it.
> Did we? Where are those fusion plants installed?
Oxfordshire etc but most of the cost is stuff you’d see at any nuclear power plant.
> Only $11 billion of the $183.3 is true expending
That’s not how money works, there’s zero difference between a tax break and handing out money because money is fungible. The IRS will write you a check on a “tax” break.
If you want on of many direct quotes from them “DT-2 phase with the target to complete all project goals including the Q=10 project specification”. Guarantee may be a good little overstated, but Q=10 is a very pessimistic estimate.
Really the actual science bits are focused on the breeding blanket, remote operation, material science, etc hitting a high Q on DT doesn’t matter with the world’s supply of tritium so minimal. DEMO might be targeting Q=100, but that’s only useful if the tritium supply is sufficient and the timeline ends up way faster than starting in 1978 to only see a ~2033 first plasma.
Fission reactions shut down when the core expands enough to become subcritical. Boosting can help some, but most of the fissionable material will still fail to fission.
Thermonuclear assemblies don't have a chain reaction, so they can burn most of their fuel, once they get hot enough.
Not one of them... But were you talking about explosive assemblies or reactor assemblies? Cuz fission "reactor assemblies" going subcritical has very little to do with expansion in the long term, but rather with consumption of excess reactivity and buildup of poisons.
Also, you interestingly reminded me that fusion is unlike fission, the latter being a chain or cascading reaction (the self-sustaining kind), while former isn't (or is it? :M.Stevens face:)
The person I was responding to said "bombs", so I was talking about that. A fission bomb's chain reaction shuts down as soon as the assembly expands enough to become a bit subcritical. The thermonuclear bomb's hot burning fuel, on the other hand, continues to react (albeit at a slower rate) as it expands; there is no such sharp cutoff. The latter fact can be used to improve fission bombs some by "boosting": including a small amount of DT gas in the fission bomb, to provide a source of neutrons that induce some fission even after k drops below 1. If k is (say) 0.9, then each DT neutron will produce 10 fission events, for a large energy return, roughly 100x the energy from the fusion itself.
I'll add another observation: the secondary in a thermonuclear bomb is a lot like the target in inertial confinement fusion, only much larger. The expansion time of these systems is proportional to their radius, so if (say) the bomb has a million times the fuel, it takes 100 times longer to expand. So for a given density and temperature of fuel, there is 100x as much time for the fusion reactions to occur. In a real sense, thermonuclear bombs become easier to build as they get bigger.
Fission fragment rocket engines are also (theoretically) extremely efficient.. using the particles that come out of the reaction directly as a high-velocity exhaust stream.
Practical for many missions, just not for sending humans in person to other planets. For example, consider a mission to deliver a telescope out past 550AU so that it can use the whole sun as a gravitational lens. That’s more than 11× further than Pluto, but a fission fragment drive could get the telescope out there in about the amount of time it took New Horizons to fly past Pluto.
Yeah, thrust is thrust, there is no difference, really.
Only issue that I can think of is landing on a body with an atmosphere. In this case you might need to adjust for the bomb veing slowed by atmospheric on entry.
And also possibly adjust for any inhabitants trying to shoot you down before you try to land there with an Orion drive. ;-)
I actually like their implementation.
I'm curious if it will be enough for governments, but it is nice that they are trying to persue a path without id checks
I think it's interesting they limit the types of content they use to determine your age. I'd guess they don't impose those same limitations when it comes to other uses (including targeted ads)
This proposed solution does however allow quite liberal access to discord without confirming the age. If the implementation is as worded; then i would not see a reason to confirm my age at all.
The issue comes down to if governments accept such a (urgh) comparatively lax implementation. It's pretty clear to me that the primary purpose of these laws are entirely to... force all citizens to identify themselves across the internet for the purpose of profile building, and nothing to do with child safety.
So as implementations go; this one is pretty decent. We should stop governments from passing these darn laws though.
I can imagine a few more. Here's one that is 100% effective:
* Wait until your account was created > 18 years ago.
That may not be enough for you, and that's fine, this is not a governmental service or site, with a mandate to serve everyone. You can chose not to use discord, and discord can choose not to have you as a customer. YMMV.
I guess it falls in the same category of burglars that enter from the unlocked main door.
It is still illegal even if there were no security measures to overcome by the attacker.
That being said using an API does require a minimum of computer knowledge
>None of the dietary studies that I have seen has provided any conclusive evidence that meat per se is the harmful ingredient
This is innacurate if not simply false; according to the WHO red meat is a class 2 carcinogenic and sausages are class 1 carcinogenic. This leaves only white meat as non cancerogenic
If you look at the data vegan (and vegetarian to a lesser extent) diets over various studies consitently perform better in cardiovascular health and cancer rate (colon in particular) compared to the omnivorous conterpart
Those mentioned by you are very specific kinds of meat, and there were doubts about how healthy they are long before the last century.
There is absolutely no evidence that any data about red meat or sausages also applies to other kinds of meat, e.g. those that have negligible content of myoglobin and saturated fat, like poultry breast or white fish.
I agree with what you said, that almost any study about vegan or vegetarian diets shows positive effects, but it is never clear which are the differences from the comparison diets that really mattered, because the compositional differences between diets were too many and too variable.
The OP is actually talking about the studies that the WHO was using to classify meat as a class 2 carginogen. For meat preserves the evidence is clear and known mechanistically, but for meat in general it's inconclusive at best and badly-designed at worst.
Correct, but the link for "super jupiter" also goes to something that astronomers are fairly sure is 1.38x the diameter of Jupiter. Much less massive of course. Meaning Jupiter's diameter is not an absolute hard limit nothing can be larger than.
I guess it is more of a derivative of the question: "in which bucket should we put the brown dwarf? Is it a star or a planet?".
The answer is neither of course; but since it is more closely related to stars than to planets, I'm more inclined to call this satellite an exoplanet (instead of exomoon).
That being said it is still a nice finding, way more difficult to discover than "normal" exopanets.
'Planet' comes from the Greek word for 'wanderer' which was very useful for labeling the handful of bright stars that moved through the heavens in a pattern. Then we got to the Space Age and kept calling them (and similar new additions) 'planets' even as we learned far more about them. And immediately there's a problem. Setting aside Pluto (and the Sun), you've still got Mercury on one end (5% of Earth's mass, and smaller than several moons) and Jupiter on the other end (320% of Earth's mass - more than everything else in the solar system put together, and over 1000 times Earth's volume). "Planet" stops being a word you can use with any sort of detail. (Thus the IAU definition battle and Pluto's "demotion".) Astronomers have pretty good terminology for stars, but once you go sub-stellar, the labeling rapidly gets difficult, and for good reason.
> Astronomers have pretty good terminology for stars,
...do they though?
The "proper" terminology says all main sequence stars are dwarves, but nobody calls them all that in practice.
Some astronomers insist on saying "yellow dwarf", but some don't really bother.
In general having the only two kinds of star be "giant" or "dwarf" is contentious, but it's also contentious that there isn't a name for whatever is in the "middle". "Main-sequence star" is a broader category and doesn't apply. They're all "stars", obviously, so that isn't specific enough.
The only decent terminology is for the spectral classes, but those only work as long as you look at spectra. The moment you try to figure out what the theory says those stars would look like as proper 3D objects, things get very messy. You also immediately get the issue that star size and brightness goes O>B>A>F>G>K>M. So... it's alphabetic except it isn't. And C is something completely different and doesn't fit the brightness classification at all.
As far as I'm concerned, CD-35 2722 B can self identify however they want.
If they want to identify as a planet, however, they can claim the almost unique distinction of having a gas giant as their moon. I wonder if the gas giant itself has their own small rocky and potentially habitable moons.
