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What a cynical response to a genuine scientific advance. Getting net power from fusion is an incredibly difficult task, and scientific breakeven (and ignition,

What a cynical response to a genuine scientific advance. Getting net power from fusion is an incredibly difficult task, and scientific breakeven (and ignition, i.e. where the fusion energy contributes to heating further fusion reactions) is the first step, and this hasn’t been done before. Why not celebrate that? Why such cynicism? We are developing literally a new way of making nuclear fire, a method which previously required an atomic bomb to produce. The first small kindled flame is definitely a triumph, even if we haven’t yet built a power plant for it.

nutate 4y ago
The concern over startup energy is like saying we can't have internal combustion engines until the engine can start itself with gasoline. Turns out we've gotten along fine starting cars with electricity for about 100 years, including a long while where we had to hand crank them ourselves. Surplus is just a matter of runtime once you're getting more than you put in to maintain it.
- scythe 4y ago
  In this case, it's not clear how the analogy could apply, because you can't realistically deliver more fuel to the "reactor" while it's "running". An ultrafast laser pulse hits a target and it undergoes fusion for a few nanoseconds, maybe less, generating a huge explosion. You can't operate a fuel injector on that timeframe. So you need a big gain in terms of efficiency. You can hopefully make a bigger fuel pellet, but that kind of scaling hasn't been demonstrated and isn't guaranteed, because it begins to disperse as soon as fusion initiates in this inertial confinement scheme. So "just" a matter of runtime is harder than it might seem at first. I'm curious if you could power boats like this, though. It might not be economical for electricity. But the power-to-weight ratio is probably pretty good.
  - noobermin 4y ago
    You do not need a continuous stream injecting at every nano second...you can operate much slower than that. If you watched the stream, they said a few hertz is enough. A milisecond is an eternity compared to a nanosecond, you remove the neutrons away from the interaction site well before the next start of the rep-rate when you inject the next pellet / holhraum. You just need to have something to capture the neutrons and convert that into heat to boil water, which will accumulate over various repetitions of course (water boils much slower than a GHz), and that thing need not be where the pellets are blasted. That said, I'd need to think about it the design, I just don't think it's impossible.
    - scythe 4y ago
      From the PDF (page 15): https://suli.pppl.gov/2018/course/Ma.pdf https://suli.pppl.gov/2018/course/Ma.pdf typical confinement time for ICF is on the order of a tenth of a nanosecond. I don't expect they have made a factor-of-millions improvement on this. I generally avoid watching videos whenever possible, but I think you are referring to the frequency at which the fuel pellets can be repeatedly ignited by a laser — there are no plans to use the output of one fuel pellet to directly ignite the next. In fact not even the "magneto-inertial" techniques with putative confinement times in the microseconds have a roadmap to achieve this.
      - noobermin 4y ago
        You don't use the ignition of one pellet for the next...each pellet ignites itself. It isn't a nuclear fission reaction where it is a chain reaction between pellets. Each pellet interaction produces energy, and you capture that energy. It is ignition for the pellet, not other pellets in the machine. The boiling of water thankfully happens on a much longer timescale, being accumulationf of energy of many pellets over a few cycles.
        scythe 4y ago
        The pellets produce a net energy release larger than the energy used by the laser. This energy gain is called "ignition" in fusion parlance. A fuel pellet does not ignite itself — otherwise, they would be destroyed as soon as they are produced, like the critical ball in a nuclear warhead. That's what I was saying from the beginning: the laser does not function like the spark plug on a car engine; it is required for every ignition. It's pretty clear if you go back and read the analogy I initially responded to.
- DennisP 4y ago
  "Getting more than you put in to maintain it" is the whole point for all these net power discussions. In this particular case, it's a quick laser pulse and an exploding fuel pellet, so there's no lengthy runtime possible.
  - noobermin 4y ago
    The next step is rep-rate, which a lot of the field has neglected, while some people (tooting my horn, my lab) were amongst the few pushing it. The thing is people couldn't even achieve the result with one shot, but now that it seems feasible now, hopefully scientists (and more importantly funders) will start to care about increasing rep-rate.
    - Robotbeat 4y ago
      Yes, although they need to still leverage this ignition/scientific-breakeven achievement to get the higher energy gains needed for a practical power plant. Not just 1.5x but 25-50x. With ignition now being repeatable, that should be a doable proposition.
      - noobermin 4y ago
        So, one of the things that I probably shouldn't say is the NIF design is not really optimized for fusion specifically (I won't say too much but you can guess why). There are schemes out there that can be more efficient, for example, not even bothering to convert to UV and then x-rays (start at UV in fact, or crank up the intensity of light, the light in NIF is very intense but modern high intensity systems are orders of magnitude more intense, they are however dramatically lower in pulse energy). That plus using modern laser tech when you realize NIF was designed in the 80s, we can definitely make it much more efficient eventually.
        Robotbeat 4y ago
        Don’t need to be too coy about the fact that NIF was built to recreate the processes inside an H-bomb after underground nuclear testing was banned. They literally use the same concept of a “Hohlraum” (here in miniature) where heat and light (from a fission trigger in the case on an H-bomb, lasers in the case of NIF) convert to x-rays on the outer casing and evenly illuminate the fuel pellet casing which ablates a bit to drive implosion which triggers the actual compression heating of the fuel pellet. Heck, some previous tests even used a uranium tamper (because in part, uranium has high inertia due its density thus prolonging the period of high pressure), just like a real H-bomb.
moloch-hai 4y ago
It was a cynical announcement. There is no "triumph" here, just an improved $10M container that, blasted with 50 kWh of the highest-grade energy, electric power, produced 0.7 kWh of the lowest-grade energy, fast neutrons. Check the value of a kWh on your electric bill.
- Robotbeat 4y ago
  This is a scientific and technological advancement, not a practical commercial engineering one. It is the necessary precursor to any future commercial one. To call that cynical is just ignorance.
- ludsan 4y ago
  Goodness gracious. This is the definition of cynical -- an argumentation of "why hasn't this solved everything?" and an appeal to an electric bill. I don't know why these fusion energy discussions seems to attract the worst of our impatience and edge-lord cynicism. At least we haven't had a smarmy "always 5 decades away" post yet. Science and engineering is made of hundreds of unsung triumphs with incremental decades-long payoffs. Like it or not, the "Q>1" mark has been a target for decades. I am glad to see it finally surpassed, and look forward to the order-of-magnitude increase we need to make the economics work.
  - moloch-hai 4y ago
    You wholly miss the point. What improvements are available? Get more neutron kinesis from each target, say 10 kWh? Bring the input energy down, through more efficient lasers, maybe even to 1 kWh? Bring the cost of the target down, from $10M each to, what, $10? Let us assume further that tritium is free, and that collecting the neutrons and driving a steam turbine (the major cost of operating a nuke) is also free. But 10 kWh of hot neutrons translates to, at best, 4 kWh of electrical energy, and $2.50 per kWh is an order of magnitude more than we pay now. So, even in the best of all conceivable outcomes, this turkey does not fly. We get "breakthroughs" of greater magnitude on a regular schedule in solar panel and wind turbine manufacture, that do not get trumpeted by the DoE. This is a weapons program, operated by weapons researchers, pursuing weapons goals. The announcement is an attempt by the US DoE to help secure funding by making it look like they are involved in something besides nuclear weapons. How cynical do you need for it to be?
vesinisa 4y ago
So what was the advance here really? The experiment generated a bit more energy than usually, going over a certain purely theoretical threshold where it's "ignition" only if you ignore all the externalities required for driving the experiment? It was advertised like the Higgs boson while it was really more like Elon Musk announcing that a fully autonomous Tesla had completed the first full circuit on a test track.
- Robotbeat 4y ago
  This is not just more than usual, but actual ignition. They reportedly achieved ignition last year as well, but not a confirmed and repeatable scientific breakeven so they didn’t have a big announcement until today. Ignition is critical as it means that, to use an analogy, a flame has been kindled. The heat of fusion is driving significantly more fusion, no longer just the laser alone. In other words, a sort of chain reaction. That is THE key to eventually scaling this efficaciously to higher gains, like the 25-50 needed for useful electricity production.
- woeirua 4y ago
  It's a big deal because no fusion experiment to date has achieved ignition. It's a validation of our modeling and engineering capability and it means that we probably can build a commercial reactor down the road. Let me put it this way, if NIF failed to achieve ignition then it would be a very ominous sign. No one ever seriously thought that NIF would ever lead directly to a commercial reactor, LCF is far too finicky to ever reliably be used in a commercial setting.

nutate 4y ago

The concern over startup energy is like saying we can't have internal combustion engines until the engine can start itself with gasoline. Turns out we've gotten along fine starting cars with electricity for about 100 years, including a long while where we had to hand crank them ourselves. Surplus is just a matter of runtime once you're getting more than you put in to maintain it.

scythe 4y ago
In this case, it's not clear how the analogy could apply, because you can't realistically deliver more fuel to the "reactor" while it's "running". An ultrafast laser pulse hits a target and it undergoes fusion for a few nanoseconds, maybe less, generating a huge explosion. You can't operate a fuel injector on that timeframe. So you need a big gain in terms of efficiency. You can hopefully make a bigger fuel pellet, but that kind of scaling hasn't been demonstrated and isn't guaranteed, because it begins to disperse as soon as fusion initiates in this inertial confinement scheme. So "just" a matter of runtime is harder than it might seem at first. I'm curious if you could power boats like this, though. It might not be economical for electricity. But the power-to-weight ratio is probably pretty good.
- noobermin 4y ago
  You do not need a continuous stream injecting at every nano second...you can operate much slower than that. If you watched the stream, they said a few hertz is enough. A milisecond is an eternity compared to a nanosecond, you remove the neutrons away from the interaction site well before the next start of the rep-rate when you inject the next pellet / holhraum. You just need to have something to capture the neutrons and convert that into heat to boil water, which will accumulate over various repetitions of course (water boils much slower than a GHz), and that thing need not be where the pellets are blasted. That said, I'd need to think about it the design, I just don't think it's impossible.
  - scythe 4y ago
    From the PDF (page 15): https://suli.pppl.gov/2018/course/Ma.pdf https://suli.pppl.gov/2018/course/Ma.pdf typical confinement time for ICF is on the order of a tenth of a nanosecond. I don't expect they have made a factor-of-millions improvement on this. I generally avoid watching videos whenever possible, but I think you are referring to the frequency at which the fuel pellets can be repeatedly ignited by a laser — there are no plans to use the output of one fuel pellet to directly ignite the next. In fact not even the "magneto-inertial" techniques with putative confinement times in the microseconds have a roadmap to achieve this.
    - noobermin 4y ago
      You don't use the ignition of one pellet for the next...each pellet ignites itself. It isn't a nuclear fission reaction where it is a chain reaction between pellets. Each pellet interaction produces energy, and you capture that energy. It is ignition for the pellet, not other pellets in the machine. The boiling of water thankfully happens on a much longer timescale, being accumulationf of energy of many pellets over a few cycles.
      - scythe 4y ago
        The pellets produce a net energy release larger than the energy used by the laser. This energy gain is called "ignition" in fusion parlance. A fuel pellet does not ignite itself — otherwise, they would be destroyed as soon as they are produced, like the critical ball in a nuclear warhead. That's what I was saying from the beginning: the laser does not function like the spark plug on a car engine; it is required for every ignition. It's pretty clear if you go back and read the analogy I initially responded to.
DennisP 4y ago
"Getting more than you put in to maintain it" is the whole point for all these net power discussions. In this particular case, it's a quick laser pulse and an exploding fuel pellet, so there's no lengthy runtime possible.
- noobermin 4y ago
  The next step is rep-rate, which a lot of the field has neglected, while some people (tooting my horn, my lab) were amongst the few pushing it. The thing is people couldn't even achieve the result with one shot, but now that it seems feasible now, hopefully scientists (and more importantly funders) will start to care about increasing rep-rate.
  - Robotbeat 4y ago
    Yes, although they need to still leverage this ignition/scientific-breakeven achievement to get the higher energy gains needed for a practical power plant. Not just 1.5x but 25-50x. With ignition now being repeatable, that should be a doable proposition.
    - noobermin 4y ago
      So, one of the things that I probably shouldn't say is the NIF design is not really optimized for fusion specifically (I won't say too much but you can guess why). There are schemes out there that can be more efficient, for example, not even bothering to convert to UV and then x-rays (start at UV in fact, or crank up the intensity of light, the light in NIF is very intense but modern high intensity systems are orders of magnitude more intense, they are however dramatically lower in pulse energy). That plus using modern laser tech when you realize NIF was designed in the 80s, we can definitely make it much more efficient eventually.
      - Robotbeat 4y ago
        Don’t need to be too coy about the fact that NIF was built to recreate the processes inside an H-bomb after underground nuclear testing was banned. They literally use the same concept of a “Hohlraum” (here in miniature) where heat and light (from a fission trigger in the case on an H-bomb, lasers in the case of NIF) convert to x-rays on the outer casing and evenly illuminate the fuel pellet casing which ablates a bit to drive implosion which triggers the actual compression heating of the fuel pellet. Heck, some previous tests even used a uranium tamper (because in part, uranium has high inertia due its density thus prolonging the period of high pressure), just like a real H-bomb.

moloch-hai 4y ago

It was a cynical announcement. There is no "triumph" here, just an improved $10M container that, blasted with 50 kWh of the highest-grade energy, electric power, produced 0.7 kWh of the lowest-grade energy, fast neutrons. Check the value of a kWh on your electric bill.

Robotbeat 4y ago
This is a scientific and technological advancement, not a practical commercial engineering one. It is the necessary precursor to any future commercial one. To call that cynical is just ignorance.
ludsan 4y ago
Goodness gracious. This is the definition of cynical -- an argumentation of "why hasn't this solved everything?" and an appeal to an electric bill. I don't know why these fusion energy discussions seems to attract the worst of our impatience and edge-lord cynicism. At least we haven't had a smarmy "always 5 decades away" post yet. Science and engineering is made of hundreds of unsung triumphs with incremental decades-long payoffs. Like it or not, the "Q>1" mark has been a target for decades. I am glad to see it finally surpassed, and look forward to the order-of-magnitude increase we need to make the economics work.
- moloch-hai 4y ago
  You wholly miss the point. What improvements are available? Get more neutron kinesis from each target, say 10 kWh? Bring the input energy down, through more efficient lasers, maybe even to 1 kWh? Bring the cost of the target down, from $10M each to, what, $10? Let us assume further that tritium is free, and that collecting the neutrons and driving a steam turbine (the major cost of operating a nuke) is also free. But 10 kWh of hot neutrons translates to, at best, 4 kWh of electrical energy, and $2.50 per kWh is an order of magnitude more than we pay now. So, even in the best of all conceivable outcomes, this turkey does not fly. We get "breakthroughs" of greater magnitude on a regular schedule in solar panel and wind turbine manufacture, that do not get trumpeted by the DoE. This is a weapons program, operated by weapons researchers, pursuing weapons goals. The announcement is an attempt by the US DoE to help secure funding by making it look like they are involved in something besides nuclear weapons. How cynical do you need for it to be?

vesinisa 4y ago

So what was the advance here really? The experiment generated a bit more energy than usually, going over a certain purely theoretical threshold where it's "ignition" only if you ignore all the externalities required for driving the experiment? It was advertised like the Higgs boson while it was really more like Elon Musk announcing that a fully autonomous Tesla had completed the first full circuit on a test track.

Robotbeat 4y ago
This is not just more than usual, but actual ignition. They reportedly achieved ignition last year as well, but not a confirmed and repeatable scientific breakeven so they didn’t have a big announcement until today. Ignition is critical as it means that, to use an analogy, a flame has been kindled. The heat of fusion is driving significantly more fusion, no longer just the laser alone. In other words, a sort of chain reaction. That is THE key to eventually scaling this efficaciously to higher gains, like the 25-50 needed for useful electricity production.
woeirua 4y ago
It's a big deal because no fusion experiment to date has achieved ignition. It's a validation of our modeling and engineering capability and it means that we probably can build a commercial reactor down the road. Let me put it this way, if NIF failed to achieve ignition then it would be a very ominous sign. No one ever seriously thought that NIF would ever lead directly to a commercial reactor, LCF is far too finicky to ever reliably be used in a commercial setting.