It has always seemed plausible to me that some clever scientist(s) might find a shortcut to fusion that would finally usher in the age of fusion energy, rendering the two “mainstream” approaches, inertial confinement fusion (ICF) and magnetic fusion, obsolete in the process. It would be nice if it happened sooner rather than later, if only to put a stop to the ITER madness. For those unfamiliar with the field, the International Thermonuclear Experimental Reactor, or ITER, is a gigantic, hopeless, and incredibly expensive white elephant and welfare project for fusion scientists currently being built in France. In terms of pure, unabashed wastefulness, think of it as a clone of the International Space Station. It has always been peddled as a future source of inexhaustible energy. Trust me, nothing like ITER will ever be economically competitive with alternative energy sources. Forget all your platitudes about naysayers and “they said it couldn’t be done.” If you don’t believe me, leave a note to your descendants to fact check me 200 years from now. They can write a gloating refutation to my blog if I’m wrong, but I doubt that it will be necessary.
In any case, candidates for the hoped for end run around magnetic and ICF keep turning up, all decked out in the appropriate hype. So far, at least, none of them has ever panned out. Enter two stage laser fusion, the latest pretender, introduced over at NextBigFuture with the assurance that it can achieve “10x higher fusion output than using the laser directly and thousands of times better output than hitting a solid target with a laser.” Not only that, but it actually achieved the fusion of boron and normal hydrogen nuclei, which produces only stable helium atoms. That’s much harder to achieve than the usual deuterium-tritium fusion between two heavy isotopes of hydrogen, one of which, tritium, is radioactive and found only in tiny traces in nature. That means it wouldn’t be necessary to breed tritium from the fusion reactions just to keep them going, one of the reasons that ITER will never be practical.
Well, I’d love to believe this is finally the ONE, but I’m not so sure. The paper describing the results NBF refers to was published by the journal Nature Communications. Even if you don’t subscribe, you can click on the figures in the abstract and get the gist of what’s going on. In the first place, one of the lasers has to accelerate protons to high enough energies to overcome the Coulomb repulsion of the stripped (of electrons) boron nuclei produced by the other laser. Such laser particle accelerators are certainly practical, but they only work at extremely high power levels. In other words, they require what’s known in the business as petawatt lasers, capable of achieving powers in excess of a quadrillion (10 to the 15th power) watts. Power comes in units of energy per unit time, and such lasers generally reach the petawatt threshold by producing a lot of energy in a very, very short time. Often, we’re talking picoseconds (trillionths of a second).
Now, you can do really, really cool things with petawatt lasers, such as pulling electron positron pairs right out of the vacuum. However, their practicality as drivers for fusion power plants, at least in their current incarnation, is virtually nil. The few currently available, for example, at the University of Rochester’s Laboratory for Laser Energetics, the University of Texas at Austin, the University of Nevada at Reno, etc., are glass lasers. There’s no way they could achieve the “rep rates” (shot frequency) necessary for useful energy generation. Achieving lots of fusions, but only for a few picoseconds, isn’t going to solve the world’s energy problems.
As it happens, conventional accelerators can also be used for fusion. As a matter of fact, it’s a common way of generating neutrons for such purposes as neutron radiography. Unfortunately, none of the many fancy accelerator-driven schemes for producing energy that people have come up with over the years has ever worked. There’s a good physical reason for that. Instead of using their energy to overcome the Coulomb repulsion of other nuclei (like charges repel, and atomic nuclei are all positively charged), and fuse with them, the accelerated particles prefer to uselessly dump that energy into the electrons surrounding those nuclei. As a result, it has always taken more energy to drive the accelerators than could be generated in the fusion reactions. That’s where the “clever” part of this scheme comes in. In theory, at least, all those pesky electrons are gone, swept away by the second laser. However, that, too, is an energy drain. So the question becomes, can both lasers be run efficiently enough and with high enough rep rates and with enough energy output to strip enough boron atoms to get enough of energy out to be worth bothering about, in amounts greater than that needed to drive the lasers? I don’t think so. Still, it was a very cool experiment.
An article about fusion just appeared on the Livescience website promisingly entitled “Fusion Experiments Inch Closer to Break-Even Goal” that is unexceptionable hype except for one little detail; the goalpost for fusion ignition has been moved. It hasn’t been nudged. It hasn’t been tweaked. It has been torn up by the roots, carried down the road a few miles, and planted in an entirely new place that bears no resemblance to the original goal. The article in question is about fusion experiments at Lawrence Livermore National Laboratory’s (LLNL’s ) National Ignition Facility, usually referred to by its acronym, as the NIF. The goalpost is that which applies to inertial confinement fusion (ICF), which is the flavor being pursued at LLNL. The other mainstream approach is magnetic fusion, which will be implemented at the ITER facility currently under construction in France. Here’s the money quote from the article:
That got the NIF closer to the “scientific break-even point,” where the amount of energy that comes out of the fusion reaction is equal to that which was put in by the kinetic energy from the implosion. (The energy from the laser isn’t counted in the calculation). Right now, the amount of energy coming out of the NIF setup is about 80 percent of what is put in.
“NIF is built to ignite a fusion pellet,” said Stewart Prager, director of the Princeton Plasma Physics Laboratory. “They didn’t get it by the time they originally stated, but they are making progress.” The NIF was built in 2008; its original mandate was to achieve ignition — the break-even point — in 2012.
What’s wrong with this picture? LLNL explicitly agreed that “ignition” would occur at the point where fusion energy out equals laser energy in. They did so before a committee of prestigious scientists appointed by the National Academy of Sciences’ National Research Council to review the nation’s ICF program. It was entirely fitting and proper that they should do so, because that definition puts them on a level playing field with magnetic fusion. It’s not as if this is a minor point. After all, the very name of the facility in question is the National Ignition Facility. Now, suddenly, “ignition” is being redefined as “fusion energy out equals kinetic energy of the implosion put in!”
Why is this happening? Because, in spite of recent encouraging progress, the NIF is still a long way from achieving real ignition. Politicians are griping because the ignition they were promised hasn’t happened, and there have been dark mutterings about defunding the project. In other words, the NIF’s survival is at stake. I can see the problem. What I can’t see is that gross scientific dishonesty is the answer to the problem. For that strategy to succeed, it is necessary for virtually all the members of Congress to be fools. Although that is certainly a common assumption, it is not necessarily true. There are actually a few scientists in Congress, and I doubt that all of them can be hoodwinked into swallowing this latest redefinition of ignition.
What to do? Try telling it like it is. The NIF hasn’t achieved ignition, and maybe it never will. In spite of that, it remains the finest facility of its kind in the world for accomplishing the mission it was actually funded for; insuring the safety and reliability of our nuclear arsenal. No facility outside the United States can approach so closely the physical conditions that occur in nuclear explosions. No other facility is so precise, or has such a fine suite of diagnostics. The NIF gives us a huge leg up in maintaining our arsenal and avoiding technological surprise as long as nuclear testing is not resumed. As long as we have such facilities and the rest of the world doesn’t, it would be dumb for us to even think about resuming testing. It would be throwing away a massive advantage. Think none of our weaponeers wants to resume testing? Think again! The NIF and facilities like it are the best argument against them. Try pointing that out to Congress. I suspect it would work better than these ham-handed attempts to move the goalposts.
In a recent press release, Lawrence Livermore National Laboratory (LLNL) announced that it had achieved a yield of 3 x 1015 neutrons in the latest round of experiments at its National Ignition Facility, a giant, 192-beam laser facility designed, as its name implies, to achieve fusion ignition. That’s nowhere near “ignition,” but still encouraging as it’s three times better than results achieved in earlier experiments.
The easiest way to achieve fusion is with two heavy isotopes of hydrogen; deuterium, with a nucleus containing one proton and one neutron, and tritium, with a nucleus containing one proton and two neutrons. Deuterium is not radioactive, and occurs naturally as about one atom to every 6400 atoms of “normal” hydrogen, with a nucleus containing only a single proton. Tritium is radioactive, and occurs naturally only in tiny trace amounts. It has a half-life (the time it takes for half of a given amount to undergo radioactive decay) of 12.3 years, and must be produced artificially. When tritium and deuterium fuse, they release a neutron, a helium nucleus, or alpha particle, and lots of energy (17.6 million electron volts).
Fortunately (because otherwise it would be too easy to blow up the planet), or unfortunately (if you want to convert the energy into electricity), fusion is hard. The two atoms don’t like to get too close, because their positively charged nuclei repel each other. Somehow, a way must be found to make the heavy hydrogen fuel material very hot, causing the thermal motion of the atoms to become very large. Once they start moving fast enough, they can smash into each other with enough momentum to overcome the repulsion of the positive nuclei, allowing them to fuse. However, the amount of energy needed per atom is huge, and when atoms get that hot, the last thing they want to do is stay close to each other (think of what happens in the detonation of high explosive.) There are two mainstream approaches to solving this problem; magnetic fusion, in which the atoms are held in place by powerful magnetic fields while they are heated (the approach being pursued at ITER, the International Thermonuclear Experimental Reactor, currently under construction in France), and inertial confinement fusion (ICF), where the idea is to dump energy into the fuel material so fast that its own inertia holds it in place long enough for fusion to occur. The NIF is an ICF facility.
There are various definitions of ICF “ignition,” but, in order to avoid comparisons of apples and oranges between ICF and magnetic fusion experiments, LLNL has explicitly accepted the point at which the fusion energy out equals the laser energy in as the definition of ignition. In the experiment referred to above, the total fusion energy release was about 10,000 joules, give or take. Since the laser energy in was around 1.7 million joules, that’s only a little over one half of one percent of what’s needed for ignition. Paltry, you say? Not really. To understand why, you have to know a little about how ICF experiments work.
Recall that the idea is to heat the fuel material up so fast that its own inertia holds it in place long enough for fusion to occur. The “obvious” way to do that would be to simply dump in enough laser energy to heat all the fuel material to fusion temperatures at once. Unfortunately, this “volumetric heating” approach wouldn’t work. The energy required would be orders of magnitude more than what’s available on the NIF. What to do? Apply lots and lots of finesse. It turns out that if a very small volume or “hot spot” in the fuel material can be brought to fusion conditions, the alpha particles released in the fusion reactions might carry enough energy to heat up the nearby fuel to fusion conditions as well. Ideally, the result would be an alpha “burn wave,” moving out through the fuel, and consuming it all. But wait, it ain’t that easy! An efficient burn wave will occur only if the alphas are slammed to a stop and forced to dump their energy after traveling only a very short distance in the cold fuel material around the hot spot. Their range is too large unless the fuel is first compressed to a tiny fraction of its original volume, causing its density to increase by orders of magnitude.
In other words, to get the fuel to fuse, we need to make it very hot, but we also need to compress it to very high density, which can be done much more easily and efficiently if the material is cold! Somehow, we need to keep the fuel “cold” during the compression process, and then, just at the right moment, suddenly heat up a small volume to fusion conditions. It turns out that shocks are the answer to the problem. If a train of four shocks can be set off in the fuel material as it is being compressed, or “imploded,” by the lasers, precisely timed so that they will all converge at just the right moment, it should be possible, in theory at least, to generate a hot spot. If the nice, spherical symmetry of the fuel target could be maintained during the implosion process, everything should work just fine. The NIF would have more than enough energy to achieve ignition. But there’s the rub. Maintaining the necessary symmetry has turned out to be inordinately hard. Tiny imperfections in the target surface finish, small asymmetries in the laser beams, etc., lead to big deviations from perfect symmetry in the dense, imploded fuel. These asymmetries have been the main reason the NIF has not been able to achieve its ignition goal to date.
And that’s why the results of the latest round of experiments haven’t been as “paltry” as they seem. As noted in the LLNL press release,
Early calculations show that fusion reactions in the hot plasma started to self-heat the burning core and enhanced the yield by nearly 50 percent, pushing close to the margins of alpha burn, where the fusion reactions dominate the process.
“The yield was significantly greater than the energy deposited in the hot spot by the implosion,” said Ed Moses, principle associate director for NIF and Photon Science. “This represents an important advance in establishing a self-sustaining burning target, the next critical step on the path to fusion ignition on NIF.”
That’s not just hype. If the self-heating can be increased in future experiments, it may be possible to reach a threshold at which the alpha heating sets off a burn wave through the rest of the cold fuel, as described above. In other words, ignition is hardly a given, but the guys at LLNL still have a fighting chance. Their main challenge may be to stem the gradual evaporation of political support for NIF while the experiments are underway. Their own Senator, Diane Feinstein, is anything but an avid supporter. She recently turned down appeals to halt NIF budget cuts, and says the project needs to be “reassessed” in light of the failure to achieve ignition.
Such a “reassessment” would be a big mistake. The NIF was never funded as an energy project. Its support comes from the National Nuclear Security Administration (NNSA), a semi-autonomous arm of the Department of Energy charged with maintaining the safety and reliability of the nation’s nuclear arsenal. As a tool for achieving that end, the NIF is without peer in any other country. It has delivered on all of its performance design goals, including laser energy, illumination symmetry, shot rate, the precision and accuracy of its diagnostic instrumentation, etc. The facility is of exceptional value to the weapons program even if ignition is never achieved. It can still generate experimental conditions approaching those present in an exploding nuclear device, and, along with the rest of our suite of “above-ground experimental facilities,” or AGEX, it gives us a major leg up over the competition in maintaining our arsenal and avoiding technological surprise in the post-testing era.
Why is that important? Because the alternative is a return to nuclear testing. Do you think no one at NNSA wants to return to testing, and that the weapon designers at the National Weapons Laboratories wouldn’t jump at the chance? If so, you’re dreaming. It seems to me we should be doing our best to keep the nuclear genie in the bottle, not let it out. Mothballing the NIF would be an excellent start at pulling the cork!
I understand why the guys at LLNL are hyping the NIF’s potential as a source of energy. It’s a lot easier to generate political support for lots of electricity with very little radioactive waste and no greenhouse gases than for maintaining our aging arsenal of nuclear weapons. However, IMHO, ICF is hopeless as a source of electricity, at least for the next few hundred years. I know many excellent scientists will disagree, but many excellent scientists are also prone to extreme wishful thinking when it comes to rationalizing a technology they’ve devoted their careers to. Regardless, energy hype isn’t needed to justify the NIF. It and facilities like it will insure our technological superiority over potential nuclear rivals for years to come, and at the same time provide a potent argument against the resumption of nuclear testing.
According to a German proverb, “Lügen haben kurze Beine” – Lies have short legs. That’s not always true. Some lies have very long ones. One of the most notorious is the assertion, long a staple of anti-nuclear propaganda, that the nuclear industry ever claimed that nuclear power would be “Too cheap to meter.” In fact, according to the New York Times, the phrase did occur in a speech delivered to the National Association of Science Writers by Lewis L. Strauss, then Chairman of the Atomic Energy Commission, in September 1954. Here is the quote, as reported in the NYT on September 17, 1954:
“Our children will enjoy in their homes electrical energy too cheap to meter,” he declared. … “It is not too much to expect that our children will know of great periodic regional famines in the world only as matters of history, will travel effortlessly over the seas and under them and through the air with a minimum of danger and at great speeds, and will experience a lifespan far longer than ours, as disease yields and man comes to understand what causes him to age.”
Note that nowhere in the quote is there any direct reference to nuclear power, or for that matter, to fusion power, although the anti-nuclear Luddites have often attributed it to proponents of that technology as well. According to Wikipedia, Strauss was “really” referring to the latter, but I know of no evidence to that effect. In any case, Strauss had no academic or professional background that would qualify him as an expert in nuclear energy. He was addressing the science writers as a government official, and hardly as a “spokesman” for the nuclear industry. The sort of utopian hyperbole reflected in the above quote is just what one would expect in a talk delivered to such an audience in the era of scientific and technological hubris that followed World War II. There is an excellent and detailed deconstruction of the infamous “Too cheap to meter” lie on the website of the Canadian Nuclear Society. Some lies, however, are just too good to ignore, and anti-nuclear zealots continue to use this one on a regular basis, as, for example, here, here and here. The last link points to a paper by long-time anti-nukers Arjun Makhijani and Scott Saleska. They obviously knew very well the provenance of the quote and the context in which it was given. For example, quoting from the paper:
In 1954, Lewis Strauss, Chairman of the U.S. Atomic Energy Commission, proclaimed that the development of nuclear energy would herald a new age. “It is not too much to expect that our children will enjoy in their homes electrical energy too cheap to meter,” he declared to a science writers’ convention. The speech gave the nuclear power industry a memorable phrase to be identified with, but also it saddled it with a promise that was essentially impossible to fulfill.
In other words, it didn’t matter that they knew very well that Strauss had no intention of “giving the nuclear power industry a memorable phrase to be identified with.” They used the quote in spite of the fact that they knew that claim was a lie. I all fairness, it can be safely assumed that most of those who pass along the “too cheap to meter” lie are not similarly culpable. They are merely ignorant.
ARPA-E, or the Advanced Research Projects Agency – Energy, is supposed to be DOE’s version of DARPA. According to its website, its mission,
…is to fund projects that will develop transformational technologies that reduce America’s dependence on foreign energy imports; reduce U.S. energy related emissions (including greenhouse gasses); improve energy efficiency across all sectors of the U.S. economy and ensure that the U.S. maintains its leadership in developing and deploying advanced energy technologies.
So far, it has not come up with anything quite as “transformational” as the Internet or stealth technology. There is good reason for this. Its source selection people are decidedly weak in the knees. Consider the sort of stuff it’s funded in the latest round of contract awards. The people at DARPA would probably call it “workman like.” H. L. Mencken, the great Sage of Baltimore, would more likely have called it “pure fla fla.” For example, there are “transformational” systems to twiddle with natural gas storage that the industry, not exactly short of cash at the moment, would have been better left to develop on its own, such as,
Liquid-Piston Isothermal Home Natural Gas Compressor
Chilled Natural Gas At-Home Refueling
and,
Superplastic-Formed Gas Storage Tanks
There is the “transformational” university research that is eye-glazingly mundane, and best reserved as filler for the pages of obscure academic journals, such as,
Cell-level Power Management of Large Battery Packs
Health Management System for Reconfigurable Battery Packs
and,
Optimal Operation and Management of Batteries Based on Real Time Predictive Modeling and Adaptive Battery Management Techniques.
There is some “groundbreaking” stuff under the rubric of “build a better magnet, and the world will beat a pathway to your door.”
Manganese-Based Permanent Magnet with 40 MGOe at 200°C
Rare‐Earth‐Free Permanent Magnets for Electrical Vehicle Motors and Wind Turbine Generators: Hexagonal Symmetry Based Materials Systems Mn‐Bi and M‐type Hexaferrite
and,
Discovery and Design of Novel Permanent Magnets using Non-strategic Elements having Secure Supply Chains
…and so on. Far be it for me to claim that any of this research is useless. It is, however, also what the people at DARPA would call “incremental,” rather than transformational. Of course, truly transformational ideas don’t grow on trees, and DARPA also funds its share of “workmanlike” projects, but at least the source selection people there occasionally go out on a limb. In the work funded by ARPA-E, on the other hand, I can find nothing that might induce the bureaucrats on Secretary Chu’s staff to swallow their gum.
If the agency is really serious about fulfilling its mission, it might consider some of the innovative ideas out there for harnessing fusion energy. All of them can be described as “high risk, high payoff,” but isn’t that the kind of work ARPA-E is supposed to be funding? According to a recent article on the Science Magazine website, the White House has proposed cutting domestic fusion research by 16%to help pay for the U.S. contribution to the international fusion experiment, ITER, under construction in Cadarache, France. As I’ve pointed out elsewhere, ITER is second only to the International Space Station as the greatest white elephant of all time, and is similarly vacuuming up funds that might otherwise have supported worthwhile research in several other countries. All the more reason to give a leg up to fusion, a technology that has bedeviled scientists for decades, but that could potentially supply mankind’s energy needs for millennia to come. Ideas being floated at the moment include advanced fusor concepts such as the Bussard polywell, magneto-inertial fusion, focus fusion, etc. None of them look particularly promising to me, but if any of them pan out, the potential payoff is huge. I’ve always been of the opinion that, if we ever do harness fusion energy, it will be by way of some such clever idea rather than by building anything like the current “conventional” inertial or magnetic fusion reactor designs.
When it comes to conventional nuclear energy, we are currently in the process of being left in the dust by countries like India and China. Don’t expect any help from industry here. They are in the business to make a profit. There’s certainly nothing intrinsically wrong with that, but at the moment, profits are best maximized by building light water reactors that consume the world’s limited supply of fissile uranium 235 without breeding more fuel to replace it, and spawn long-lived and highly radioactive transuranic actinides in the process that it will be necessary to find a way to safely store for thousands of years into the future. This may be good for profits, but it’s definitely bad for future generations. Alternative designs exist that would breed as much new fuel as they consume, be intrinsically safe against meltdown, would destroy the actinides along with some of the worst radioactive fission products, and would leave waste that could be potentially less radioactive than the original ore in a matter of a few hundred years. DOE’s Office of Nuclear Energy already funds some research in these areas. Unfortunately, in keeping with the time-honored traditions of government research funding, they like to play it safe, funneling awards to “noted experts” who tend to keep plodding down well-established paths even when they are clearly leading to dead ends. ITER and the International Space Station are costly examples of where that kind of thinking leads. If it were really doing its job, an agency like ARPA-E might really help to shake things up a little.
Finally, we come to that scariest of boogeymen of “noted experts” the world over; cold fusion, or, as some of its advocates more reticently call it, Low Energy Nuclear Reactions (LENR). Following the initial spate of excitement on the heels of the announcement by Pons and Fleischmann of excess heat in their experiments with palladium cells, the scientific establishment agreed that such ideas were to be denounced as heretical. Anathemas and interdicts rained down on their remaining proponents. Now, I must admit that I don’t have much faith in LENR myself. I happened to attend the Cold Fusion Workshop in Sante Fe, NM which was held in 1989, not long after the Pons/Fleischmann bombshell, and saw and heard some memorably whacky posters and talks. I’ve talked to several cold fusion advocates since then, and some appeared perfectly sober, but an unsettlingly large proportion of others seemed to be treading close to the lunatic fringe. Just as fusion energy is always “30 years in the future,” cold fusion proponents have been claiming that their opponents will be “eating crow in six months” ever since 1989. Some very interesting results have been reported. Unfortunately, they haven’t been reproducible.
For all that, LENR keeps hanging around. It continues to find advocates among those who, for one reason or another, aren’t worried about their careers, or lack respect for authority, or are just downright contrarians. The Science of Low Energy Nuclear Reactions by Edmund Storms is a useful source for the history of and evidence for LENR. Websites run by the cold fusion faithful may be found here and here. Recently, stories have begun cropping up again in “respectable” mags, such as Forbes and Wired. Limited government funding has been forthcoming from NASA Langley and, at least until recently, from the Navy at its Space and Naval Warfare Systems Command (SPAWAR). Predictably, such funding is routinely attacked as support for scientific quackery. The proper response to that from the source selection folks at ARPA-E should be, “So what?” After all,
ARPA-E was created to be a catalyst for innovation. ARPA-E’s objective is to tap into the risk-taking American ethos and to identify and support the pioneers of the future. With the best research and development infrastructure in the world, a thriving innovation ecosystem in business and entrepreneurship, and a generation of youth that is willing to engage with fearless intensity, the U.S. has all the ingredients necessary for future success. The goal of ARPA-E is to harness these ingredients and make a full-court press to address the U.S.’s technological gaps and leapfrog over current energy approaches.
The best way to “harness these ingredients and make a full-court press” is not by funding of the next round of incremental improvements in rare earth magnets. Throwing a few dollars to the LENR people, on the other hand, will certainly be “high risk,” but it just might pan out. I hope the people at ARPA-E can work up the minimal level of courage it takes to do so. If the Paris fashions can face down ridicule, so can they. If they lack the nerve, then DOE would probably do better to terminate its bad imitation of DARPA and feed the money back to its existing offices. They can continue funding mediocrity just as well as ARPA-E.
We have passed the end of the fiscal year, and the National Ignition Facility, or NIF, at Lawrence Livermore National Laboratory (LLNL) failed to achieve its goal of ignition (more fusion energy out than laser energy in). As I noted in earlier post about the NIF more than three years ago, this doesn’t surprise me. Ignition using the current indirect drive approach (most of the jargon and buzzwords are explained in the Wiki article on the NIF) requires conversion of the laser energy into an almost perfectly symmetric bath of x-rays. These must implode the target, preserving its spherical shape in the process in spite of a very high convergence ratio (initial radius divided by final radius), and launching a train of four shocks in the process, which must all converge in a tiny volume at the center of the target, heating it to fusion conditions. That will release energetic alpha particles (helium nuclei) which must then dump their energy in the surrounding, cold fuel material, causing a “burn wave” to propagate out from the center, consuming the remaining fuel. It would have been a spectacular achievement if LLNL had pulled it off. Unfortunately, they didn’t, for reasons that are explained in an excellent article that recently appeared in the journal Science. (Unfortunately, it’s behind a subscriber wall, and I haven’t found anything as good on the web at the moment. You can get the gist from this article at Huffpo.) The potential political implications of the failure were addressed in a recent article in the New York Times.
All of which begs the question, “What now?” My opinion, in short, is that the facility should remain operational, at full capacity (not on half shifts, which, for various reasons, would reduce the experimental value of the facility by significantly more than half).
I certainly don’t base that opinion on the potential of inertial confinement fusion (ICF), the technology implemented on the NIF, for supplying our future energy needs. While many scientists would disagree with me, I feel it has virtually none. Although they may well be scientifically feasible, ICF reactors would be engineering nightmares, and far too expensive to compete with alternative energy sources. It would be necessary to fabricate many thousands of delicate, precisely built targets every day and fill them with highly radioactive tritium. Tritium is not a naturally occurring isotope of hydrogen, and its half-life (the time it takes for half of a given quantity to undergo radioactive decay) is just over 12 years, so it can’t be stored indefinitely. It would be necessary to breed and extract the stuff from the reactor on the fly without releasing any into the environment (hydrogen is notoriously slippery stuff, that can easily leak right through several types of metal barriers), load it into the targets, and then cool them to cryogenic temperatures. There is not a reactor design study out there that doesn’t claim that this can be done cheaply enough to make ICF fusion energy cost-competitive. They are all poppycock. The usual procedure in such studies is to pick the cost number you need, and then apply “science” to make it seem plausible.
However, despite all the LLNL hype, the NIF was never funded as an energy project, but as an experimental tool to help maintain the safety and reliability of our nuclear stockpile in the absence of nuclear testing. The idea that it will be useless for that purpose, whether it achieves ignition or not, is nonsense. The facility has met and in some cases exceeded its design goals in terms of energy and precision. Few if any other facilities in the world, whether existing or planned, will be able to rival its ability to explore equations of state, opacities, and other weapons-relevant physics information about materials at conditions approaching those that exist in nuclear detonations. As long as the ban on nuclear testing remains in effect, the NIF will give us a significant advantage over other nuclear states. It seems to me that maintaining the ban is a good thing.
It also seems to me that it would behoove us to maintain a robust nuclear stockpile. Nuclear disarmament sounds nice on paper. In reality it would invite nuclear attack. The fact that nuclear weapons have not been used since 1945 is a tremendous stroke of luck. However, it has also seduced us into assuming they will never be used again. They will. The question is not if, but when. We could continue to be very lucky. We could also suffer a nuclear attack tomorrow, whether by miscalculation, or the actions of terrorists or rogue states. If we continue to have a stockpile, it must be maintained. Highly trained scientists must be available to maintain it. Unfortunately, babysitting a pile of nuclear bombs while they gather dust is not an attractive career path. Access to facilities like the NIF is a powerful incentive to those who would not otherwise consider such a career.
One of the reasons this is true is the “dual use” capability of the NIF. It can be used to study many aspects of high energy density physics that may not be relevant to nuclear weapons, but are of great interest to scientists in academia and elsewhere who are interested in fusion energy, the basic science of matter at extreme conditions, astrophysics, etc. Some of the available time on the facility will be reserved for these outside users.
As for the elusive goal of ignition itself, we know that it is scientifically feasible, just as we know that its magnetic fusion equivalent is scientifically feasible. The only question remaining is how big the lasers have to be to reach it. It may eventually turn out that the ones available on the NIF are not big enough. However, the idea that because we didn’t get ignition in the first attempts somehow proves that ignition is impossible and out of the question is ridiculous. It has not even been “proven” that the current indirect drive approach won’t work. If it doesn’t, there are several alternatives. The NIF is capable of being reconfigured for direct drive, in which the lasers are aimed directly at the fusion target. For various reasons, the beams are currently being frequency-tripled from the original “red” light of the glass lasers to “blue.” Much more energy, up to around four megajoules instead of the current 1.8, would be available if the beams were only frequency-doubled to “green”. It may be that the advantage of the extra energy will outweigh the physics-related disadvantages of green light. An interesting dark horse candidate is the “fast ignitor” scenario, in which the target would be imploded as before, but a separate beam or beams would then be used to heat a small spot on the outer surface to ignition conditions. An alpha particle “burn wave” would then propagate out, igniting the rest of the fuel, just as originally envisioned for the central hot spot approach.
Some of the comments following the Internet posts about NIF’s failure to reach ignition are amusing. For example, following an article on thePhysics Today website we learn to our dismay:
With all due respect to the NIF and its team of well-meaning and enthusiastic researchers here, I am sorry to state hereby that sustainable nuclear fusion is predestined to fail, whether it be in the NIC, the Tokamak or anywhere else in solar space, for fundamentally two simple reasons paramount for fusion: ((1) vibrational synchronism (high-amplitude resonance) of reacting particles; and (2) the overall isotropy of their ambient field.
Obviously the commenter hadn’t heard that the scientific feasibility of both inertial and magnetic fusion has already been established. He reminds me of a learned doctor who predicted that Zadig, the hero of Voltaire’s novel of that name, must inevitably die of an injury. When Zadig promptly recovered, he wrote a thick tome insisting that Zadig must inevitably have died. Voltaire informs us that Zadig did not read the book. In an article on the IEEE Spectrum website, suggestively entitled National Ignition Facility: Mother of All Boondoggles?, another commenter chimes in:
How about we spend the billions on real research that actually has a chance of producing something useful? There are a gazillion ideas out there for research that has a much higher probability of producing useful results. Must be nice to work for LLNL where your ideas don’t need vetting.
In fact, the NIF was “vetted” by a full scale Federal Advisory Committee. Known as the Inertial Confinement Fusion Advisory Committee, or ICFAC, its members included Conrad Longmire, Marshall Rosenbluth, and several other experts in plasma physics and technology of world renown who had nothing whatsoever to gain by serving as shills for LLNL. It heard extensive testimony on plans to build the NIF, both pro and con, in the mid-90’s. Prominent among those who opposed the project was Steve Bodner, head of the ICF Program at the Naval Research Laboratory (NRL) at the time. Steve cited a number of excellent reasons for delaying major new starts like the NIF until some of the outstanding physics issues could be better understood. The Committee certainly didn’t ignore what he and other critics had to say. However, only one of the 15 or so members dissented from the final decision to recommend proceeding with the NIF. I suspect that LLNL’s possession of the biggest, baddest ICF computer code at the time had something to do with it. No one is better at bamboozling himself and others than a computational physicist with a big code. The one dissenter, BTW, was Tim Coffey, Director of NRL at the time, who was convinced that Bodner was right.
There are, of course, the predictable comments by those in the habit of imagining themselves geniuses after the fact, such as,
I am convinced. Garbage research.
and,
Don’t these people feel ashamed telling so many lies?
after the IEEE Spectrum article, and,
It’s amazing to think that you can spout lies to the government to receive $6 billion for a machine that doesn’t come close to performing to spec and there are no consequences for your actions.
Following a post on the NIF at the LLNL – The True Story blog. Fortunately, most of the comments I’ve seen recently have been at a rather more thoughtful level. In any event, I hope Congress doesn’t decide to cut and run on the NIF. Pulling the plug at this point would be penny-wise and pound-foolish.
According to a recent press release from Lawrence Livermore National Laboratory (LLNL) in California, the 192-beam National Ignition Facility (NIF) fired a 500 terawatt shot on July 5. The world record power followed a world record energy shot of 1.89 Megajoules on July 3. As news, this doesn’t rise above the “meh” category. A shot at the NIF’s design energy of 1.8 Megajoules was already recorded back in March. It’s quite true that, as NIF Director Ed Moses puts it, “NIF is becoming everything scientists planned when it was conceived over two decades ago.” The NIF is a remarkable achievement in its own right, capable of achieving energies 50 times greater than any other laboratory facility, with pulses shaped and timed to pinpoint precision. The NIF team in general and Ed Moses in particular deserve great credit, and the nation’s gratitude, for that achievement after turning things around following a very shaky start.
The problem is that, while the facility works as well, and even better than planned, the goal it was built to achieve continues to elude us. As its name implies, the news everyone is actually waiting for is the announcement that ignition (defined as fusion energy out greater than laser energy in) has been achieved. As noted in the article, Moses said back in March that “We have all the capability to make it happen in fiscal year 2012.” At this point, he probably wishes his tone had been a mite less optimistic. To reach their goal in the two months remaining, the NIF team will need to pull a rabbit out of their collective hat. A slim chance remains. Apparently the NIF’s 192 laser beams were aimed at a real ignition target with a depleted uranium capsule and deuterium-tritium fuel on July 5, and not a surrogate. The data from that shot may prove to be a great deal more interesting than the 500 terawatt power announcement.
Meanwhile, the Russians are apparently forging ahead with plans for their own superlaser, to be capable of a whopping 2.8 Megajoules, and the Chinese are planning another about half that size, to be operational at about the same time (around 2020). That, in itself, speaks volumes about the real significance of ignition. It may be huge for the fusion energy community, but not that great as far as the weaponeers who actually fund these projects are concerned. Many weapons designers at LLNL and Los Alamos were notably unenthusiastic about ignition when NIF was still in the planning stages. What attracted them more was the extreme conditions, approaching those in an exploding nuke, that could be achieved by the lasers without ignition. They thought, not without reason, that it would be much easier to collect useful information from such experiments than from chaotic ignition plasmas. Apparently the Russian bomb designers agree. They announced their laser project back in February even though LLNL’s difficulties in achieving ignition were well known at the time.
The same can be said of some of the academic types in the NIF “user community.” It’s noteworthy that two of them, Rick Petrasso of MIT and Ray Jeanloz of UC Berkeley, whose enthusiastic comments about the 500 terawatt shot where quoted in the latest press release, are both key players in the field of high energy density physics. Ignition isn’t a sine qua non for them either. They will be able to harvest scores of papers from the NIF whether it achieves ignition or not.
The greatest liability of not achieving early ignition may be the evaporation of political support for the NIF. The natives are already becoming restless. As noted in the Livermore Independent,
In early May, sounding as if it were discussing an engineering project rather than advanced research, the House Appropriations Committee worried that NIF’s “considerable costs will not have been warranted” if it does not achieve ignition by September 30, the end of the federal fiscal year.
and,
Later that month, in a tone that seemed to demand that research breakthroughs take place according to schedule, the House Armed Services Committee recommended that NIF’s ignition research budget for next year be cut by $30 million from the requested $84 million budget unless NIF achieves ignition by September 30.
Funding cuts at this point, after we have come so far, and are so close to the goal, would be short-sighted indeed. One must hope that a Congress capable of squandering billions on white elephants like the International Space Station will not become penny-wise and pound-foolish about funding a project that really matters.
And you thought I was crazy… Check out this article by Freeman Dyson in the October 1968 issue of Physics Today entitled “Interstellar Transport.” Dyson was an active participant in Project Orion, a program to build interplanetary space vehicles propelled by nuclear bombs. After the program was ended by the 1963 nuclear test ban treaty, he decided to write a paper for a high visibility journal to insure that the idea was kept alive and people were aware of its potential.
People thought big in those days, and Dyson’s notional interstellar transports certainly reflected the fact. The first was designed to absorb the blast of one megaton deuterium fueled bombs in a gigantic copper hemisphere with a radius of 10 kilometers weighing 5 million tons. The fully loaded ship would have weighed 40 million tons, including 30 million of the one megaton bombs. Assuming each bomb would require 10 pounds of plutonium (or about 60 pounds of highly enriched uranium), a total of 150,000 tons of plutonium would be required for the mission.
Dubious assumptions were made, as, for example, that 100% of the bomb’s energy would go into the kinetic energy of debris, even though it was known at the time (and certainly known to Dyson), that the actual fraction is much less than that. The cost was calculated to be one 1968 gross national product, based entirely on the projected cost of the necessary deuterium fuel (3 billion pounds at $200 per pound in 1968 dollars, for a total of $600 billion.) In other words, the cost of the plutonium, copper, and other building material wasn’t even factored in, nor was the cost of getting it all into earth orbit prior to launch. In spite of all this, the massive ship, carrying about 20,000 colonists, would still take about 1300 years to reach the nearest stars. Barring a “Noah’s ark” forlorn hope escape from a dying world, even Dyson considered this impractical for human travel, writing,
As a voyage of colonization a trip as slow as this does not make much sense on a human time scale. A nonhuman species, longer lived or accustomed to thinking in terms of millennia rather than years, might find the conditions acceptable.
To obviate some of the objections of this “conservative” design, Dyson also proposed an “optimistic” design, which allowed some ablation of the surface of the vehicle nearest to the explosions, rather than requiring all the energy to be absorbed in solid material. After removing this energy limitation, the main limitation on the ship’s performance would be imposed by momentum, or, as Dyson put it, “the capacity of shock absorbers to transfer momentum from an impulsively accelerated pusher plate to the smoothly accelerated ship.” Basing his reasoning on the optimum performance of practical shock absorbers, Dyson calculated that such a ship could be accelerated at a constant one g, enabling it to reach the nearest stars in centuries rather than millennia. The cost, again based solely on the value of the deuterium fuel, would be only $60 billion 1968 dollars, or a tenth of the GNP at that time. The weight of the ship would be “only” 400,000 tons, a factor of 100 less than that of the “conservative” design. Dyson concluded,
If we continue our 4% growth rate we will have a GNP a thousand times its present size in about 200 years. When the GNP is multiplied by 1000, the building of a ship for $100B will seem like building a ship for $100M today. We are now building a fleet of Saturn V which cost about $100M each. It may be foolish but we are doing it anyhow. On this basis, I predict that about 200 years from now, barring a catastrophe, the first interstellar voyages will begin.
I suspect Dyson wrote most of this paper “tongue in cheek.” He’s nobody’s fool, has remarkable achievements to his credit in fields such as quantum electrodynamics, solid state physics, and nuclear engineering, and remains highly regarded by his peers. Nobel laureate Steven Weinberg said that the Nobel Committee had “fleeced” Dyson by never awarding him the prize. The objections to his designs are obvious, but for all that, bomb-propelled space vehicles are by no means impractical. I suspect Dyson realized that other scientists would recognize ways they could improve on his “conservative” and “optimistic” designs as soon as they read the paper, and start thinking about their own versions. Project Orion might be dead as a budget line item, but would live on in the minds and imaginations of his peers. And so it did.
Google “interstellar propulsion” and you will find all kinds of speculative schemes for reaching the nearest stars with propulsion systems based on controlled fusion, harnessing of anti-matter, and any number of other speculative technologies that don’t yet exist. Well, actually, fusion technology does exist and is, in fact, quite mature, in the case of thermonuclear explosives, and Project Orion was an entirely practical scheme for harnessing that technology, but that approach is probably ruled out by political considerations for the time being. In any case, all these schemes are based on the assumption that travel times must be measured in decades or, at worst, a few centuries. My question: “What’s the hurry?”
We have already demonstrated the practicality of interstellar travel with Voyagers 1 and 2 and several other probes. Reasonably achievable travel times to nearby stars using chemical rockets and payloads weighing on the order of a ton are around 50,000 years. I suggest such voyages be launched with the purpose of seeding as many planets as possible with earth life forms.
And what of the “ethics” of that endeavor? To answer that question, one must have a clear understanding of what morality is, and why it exists. The British philosopher David Hume discovered what it is centuries ago. As he put it,
Morality is nothing in the abstract nature of things, but is entirely relative to the sentiment or mental taste of each particular being, in the same manner as the distinctions of sweet and bitter, hot and cold arise from the particular feeling of each sense or organ. Moral perceptions, therefore, ought not to be classed with the operations of the understanding, but with the tastes or sentiments.
Cast in more modern terms, that means that the ultimate source of morality, or the perception of objects and actions as good or evil, lies in human emotional traits. Absent those traits, morality and, with it, good and evil, would cease to exist. Like most of our other significant characteristics, moral emotions exist because they evolved. The only reason they evolved is because they happened to increase the chances that creatures bearing those traits would survive and reproduce. In other words, when it comes to ultimate Goods, nothing trumps survival. I propose we seed nearby planets with life in order to survive.
Of course, our species is not capable of surviving a voyage of 50,000 years. Other species, however, are. There are no human beings on the planet identical to me. All of them are more or less related to me. I am somewhat more distantly related to every other life form on the planet. We all share a common ancestor. If my species cannot survive the voyage, let others go. That works for me. My overriding interest is that life survive. How long it will do so on our home planet is uncertain. However, the quality of the environment is deteriorating rapidly, and I prefer not taking chances.
What life forms shall we send? Certain forms of bacteria have survived a dormancy of 250 million years. Tardigrades or “water bears,” far more complicated animals with tens of thousands of cells have survived the vacuum of space, cooling to near absolute zero, and heating to over 150 degrees centigrade. We should choose the life form most closely related to ourselves that is likely to survive the voyage. In the case of tardigrades, the oceans of target planets might first be seeded with plankton before their arrival to serve as a food supply.
At the end of the voyage, it would be necessary to make necessary adjustments to the craft’s trajectory, and then approach and perhaps enter orbit around the target planet in order to choose a favorable landing spot. Sophisticated computers would be necessary to carry out these tasks, and a source of power would be necessary to run them. A pure plutonium reactor might serve as the necessary power source. Of course, plutonium 238 is currently used as a power source for deep space probes, but it only has a half life of 87.7 years, and would have decayed almost completely by the end of the voyage. Plutonium 239, however, has a half life of over 24,000 years, and is fissile, meaning it could also serve as fuel in a very compact nuclear reactor. Its decay heat could be used to power timers and other devices that require minimal power during the voyage, signaling the reactor to turn on during the final stages.
And what of our species? I doubt that it will be possible to send full grown human beings to planets around nearby stars any time in the foreseeable future. The energy requirements are just too great for achieving speeds sufficient for us to survive the journey. Seed ships are another matter. They might be sent with human embryos in suspended animation, to be cared for by robots at their destination, in prefabricated environments constructed in advance. Google “Project Hyperion” to see this idea developed in more detail. All this would require technologies that we have not yet developed. In the meantime, I suggest we get started with the technologies we already have.
As I mentioned in a previous post about fusion progress, signs of life have finally been appearing in scientific journals from the team working to achieve fusion ignition at the National Ignition Facility, or NIF, located at Lawrence Livermore National Laboratory (LLNL) in California. At the moment they are “under the gun,” because the National Ignition Campaign (NIC) is scheduled to end with the end of the current fiscal year on September 30. At that point, presumably, work at the facility will be devoted mainly to investigations of nuclear weapon effects and physics, which do not necessarily require fusion ignition. Based on a paper that recently appeared in Physical Review Letters, chances of reaching the ignition goal before that happens are growing dimmer.
The problem has to do with a seeming contradiction in the physical requirements for fusion to occur in the inertial confinement approach pursued at LLNL. In the first place, it is necessary for the NIF’s 192 powerful laser beams to compress, or implode, a target containing fusion fuel in the form of two heavy isotopes of hydrogen to extremely high densities. It is much easier to compress materials that are cold than those that are hot. Therefore, it is essential to keep the fuel material as cold as possible during the implosion process. In the business, this is referred to as keeping the implosion on a “low adiabat.” However, for fusion ignition to occur, the nuclei of the fuel atoms must come extremely close to each other. Unfortunately, they’re not inclined to do that, because they’re all positively charged, and like charges repel. How to overcome the repulsion? By making the fuel material extremely hot, causing the nuclei to bang into each other at high speed. The whole trick of inertial confinement fusion, then, is to keep the fuel material very cold, and then, in a tiny fraction of a second, while its inertia holds it in place (hence the name, “inertial” confinement fusion), raise it, or at least a small bit of it, to the extreme temperatures necessary for the fusion process to begin.
The proposed technique for creating the necessary hot spot was always somewhat speculative, and more than one fusion expert at the national laboratories were dubious that it would succeed. It consisted of creating a train of four shocks during the implosion process, which were to overtake one another all at the same time precisely at the moment of maximum compression, thereby creating the necessary hot spot. Four shocks are needed because of well-known theoretical limits on the increase in temperature that can be achieved with a single shock. Which brings us back to the paper in Physical Review Letters.
The paper, entitled Precision Shock Tuning on the National Ignition Facility, describes the status of efforts to get the four shocks to jump through the hoops described above. One cannot help but be impressed by the elegant diagnostic tools used to observe and measure the shocks. They are capable of peering through materials under the extreme conditions in the NIF target chamber, focusing on the tiny, imploded target core, and measuring the progress of a train of shocks over a period that only lasts for a few billionths of a second! These diagnostics, developed with the help of another team of brilliant scientists at the OMEGA laser facility at the University of Rochester’s Laboratory for Laser Energetics, are a triumph of human ingenuity. They reveal that the NIF is close to achieving the ignition goal, but not quite close enough. As noted in the paper, “The experiments also clearly reveal an issue with the 4th shock velocity, which is observed to be 20% slower than predictions from numerical simulation.”
It will be a neat trick indeed if the NIF team can overcome this problem before the end of the National Ignition Campaign. In the event that they don’t, one must hope that the current administration is not so short-sighted as to conclude that the facility is a failure, and severely reduce its funding. There is too much at stake. I have always been dubious about the possibility that either the inertial or magnetic approach to fusion will become a viable source of energy any time in the foreseeable future. However, I may be wrong, and even if I’m not, achieving inertial fusion ignition in the laboratory may well point the way to as yet undiscovered paths to the fusion energy goal. Ignition in the laboratory will also give us a significant advantage over other nuclear weapons states in maintaining our arsenal without nuclear testing.
Based on the progress reported to date, there is no basis for the conclusion that ignition is unachievable on the NIF. Even if the central hot spot approach currently being pursued proves too difficult, there are alternatives, such as polar direct drive and fast ignition. However, pursuing these alternatives will take time and resources. They will become a great deal more difficult to realize if funding for NIF operations is severely cut. It will also be important to maintain the ancillary capability provided by the OMEGA laser. OMEGA is much less powerful but also a good deal more flexible and nimble than the gigantic NIF, and has already proved its value in testing and developing diagnostics, investigating novel experimental approaches to fusion, developing advanced target technology, etc.
We have built world-class facilities. Let us persevere in the quest for fusion. We cannot afford to let this chance slip.
