I believe controlled fusion to be the Holy Grail of energy production for the human race given our current understanding of physics. I believe that when we understand physics better that may come with the ability to manipulate gravity, inertia, and time, and those abilities may render hydrogen fusion obsolete.
There are those who believe controlled hydrogen fusion is not possible or practical, I am absolutely not in that camp. I believe if we wanted to throw the resources at it, the type of resources we put towards the Manhattan project or Apollo, that we could have it online feeding power to our electricity grids within five years.
We are not throwing that kind of money at it. The US contribution to ITER, the first magnetic confinement confusion reactor that will operate at commercial power levels, is equal to what we spend on oil imports in two days. Two days worth of oil import money over twelve years for what could be the most important technological development in human history.
At this point, we know how to confine a plasma in a Tokamak good enough, we know the scaling laws, and we can engineer a power plant that will produce power. What we do not know is how some components will hold up under sustained neutron and ion bombardment. ITER will primarily be a materials research experiment to work out material issues and make any necessary refinements to components to operate in a sustained mode.
ITER was also to be the first reactor to use superconductive magnets for plasma confinement allowing longer operation. Current Tokamak’s are limited to one minute or so because they use copper coils which rapidly overheat. However, China built a reactor last year, EAST, using superconductive coils and so ITER will not be the first to do that.
ITER could be built more quickly if it were well funded. It is expected to be the last step between existing research reactors and a true power station reactor. So there is one path that if properly funded could bring us workable fusion soon.
ITER is a conventional Tokamak. There is an improvement on the standard Tokamak design called a Spherical Tokamak. In a normal Tokamak the plasma is donut shaped, short and wide. It was found that Tokamak designs where the plasma was less wide and taller, nearer to a sphere, performed much better, and in fact the idea plasma shape which turned out to be nearly spherical resulted in confinement that was more than three times better for a given magnetic field strength.
An UK based research group first designed a spherical research reactor called START, it out performed it’s design objective but was not designed for high power operation or break even. They then went on to design MAST, again not designed for break even but was designed for higher power operation so that plasma physics could be studied at higher power levels. MAST also outperformed design objectives. This same team then went on to design a commercial power reactor. As designed it would be less expensive to construct than a fission power plant of equal power. Given the track record of this group I find it odd that someone hasn’t offered to provide funding yet. So here is another route to fusion power that is sitting waiting for funding.
Then there is a reactor designed by Dr. Bussard, and I’m not aware of any name given to it yet so for now I’ll just refer to it as the Bussard reactor. Years ago there was a device invented by Dr. Farnsworth called the Farnsworth Fusor. This device used two concentric grids to accelerate deuterium and tritium atoms towards the center of a sphere where some collide and fuse. While useful as a neutron source, this device can not achieve high power levels because ion bombardment of the inner grid melts it.
The Bussard reactor is a very clever design that is based upon the fusor idea but sidesteps the problem of melting grids by creating virtual grids through magnetically steered electrons.
Many people who look at it believe it is an alternate approach to magnetic confinement fusion. It is not. The beauty of the Bussard reactor is that only electrons are magnetically confined. Electrons have a high charge to mass ratio compared to a proton or deuteron, and so a relatively weak magnetic field will suffice. The electrons are used to create a charge gradient that deuterons fall into and out of and oscillate through. This reactor uses electrostatic acceleration and confinement.
Prototypes were built, all performed as expected, scaling laws were understood, but funding ran out before a full scale version could be built. These reactors are super cheap to build compared to Tokamaks. This type of reactor is theoretically capable of reaching much higher collision energy levels making operations with aneutronic fuels possible. This in turn makes possible relatively compact designs because huge neutron shields would no longer be required.
The Levitated Dipole is a relative newcomer that is still highly experimental. It uses a levitated superconductive magnet to create a dipole field similar to the Earth’s. As with Dr. Bussards design, this method of confinement also may be capable of achieving energy levels that would allow the use of aneutronic fuels. This design hasn’t been tested sufficiently to really understand it’s potential yet.
Bogdan Magnich invented another approach referred to as Migma fusion. Two very low power particle accelerators aim two beams of deuterium ions at each other where they collide. The prototype found that the cross-section of the reaction was low and many ions missed each other and escaped. Maglich revised the design to trap deuterium ions in a magnetic trap that caused them to orbit in a circle in such a way that orbits intersected. Funding ran out and so far Dr. Magnich has not been able to find funding. This is yet another potential avenue towards controlled fusion as a power source and like the Bussard reactor and the Levitated Dipole reactor, this method has the potential of achieving the necessary energy levels for aneutronic fuels.
The above are pretty the limit of options that I believe have a short-term chance at being a practical source of electrical energy via fusion. But that’s five different avenues that I think are viable and four of them I believe could be brought online in a short time frame. The Levitated Dipole reactor is too new to really know it’s potential.
Then there is inertial confinement laser initiated fusion which while it keeps a lot of scientists employed around the NOVA laser system, a system of insanely powerful lasers that focus on a tiny pellet containing deuterium and compress it to one third it’s size and heat it to several hundred million degrees initiating fusion. While this approach works for one-shot and might be a way to trigger a nuclear fusion bomb without using a fission device, in terms of providing controlled nuclear fusion for energy generation I do not believe it has a chance in hell. It requires huge capacitor banks be charged which limits the cycle time and it is destructive.
Then there is are low power contenders, cold fusion, I am absolutely convinced it’s a real phenomena, I am absolutely convinced that it can’t be scaled up sufficiently to be a commercial power source for the grid even if reliability issues could be resolved. If reliability issues could be understood and resolved, it might be useful as a power source for small scale apparatus and possibly even vehicles provided it is both aneutronic and does not produce significant quantities of radioactive substances such as tritium.
The most familiar cold fusion experiment involves electrolytic cells in which deuterium ions are driven into a palladium electrode using electric forces. The theory has it that when the loading of deuterium into the metal is sufficient some form of fusion occurs. However, neutrons are not produced but excess heat and and helium are, also it seems some tritium and that may be problematic. This form has not been reproduced reliably but it has been reproduced. Some researchers have identified at least some of the variables so it can be made to happen more reliably but still not 100%.
However there are other cold fusion schemes that produce reactions, deuterium gas pressurized inside of a nickle tank produces neutrons. It is a very low power level howerver.
Bubble fusion, an off-shoot of sonoluminescence. Basically, when certain liquids are excited by ultrasonic sounds, little bubbles glowing blue are produced. This blue glow is caused by the bubbles being compressed and heated by the ultrasound acoustic energy. There is some evidence that fusion can be obtained in this manner. Not at high enough levels to be anything other than a laboratory curiosity, possibly a neutron source, but not a power source.
Crystal fusion.. I have to admit I like the name of this, but no it’s not a new age fusion reactor, it’s a device that uses special pyroelectric crystals which generate a high static charge when heated to produce a high voltage that accelerates deuterium atoms sufficiently to fuse. There is no reason to believe at this point that this would scale to commercial power levels.
This sums up the methods I am presently aware of. I’d welcome input from anybody that knows of others (preferably with pointers to online information).
Of these methods I believe the standard Tokamak, Spherical Tokamak, and the Bussard reactor are all immediately exploitable. On these reactors enough science has been done on the plasma physics and scaling laws to know how to build reactors that will produce power. Of these the Bussard reactor is the least developed but it is at least two orders of magnitude less expensive than the others so it is deserving of funding to produce a power producing prototype. The Spherical Tokamak has not had as much operational experience as standard Tokamaks but the experience with it has been very good. Because it is 3x as efficient at confining a plasma with a given magnetic field, it would be considerably less expensive than a standard Tokamak to build large enough to achieve a burning plasma. The Standard Tokamak is the most well researched, only some material questions remain and ITER will answer those.
Migma fusion is dirt cheap and for that reason alone it should be funded because we don’t have to gamble a lot to complete the research. A high school student with appropriate engineering knowledge could build one of these. This method is light and compact and could be a power source for ships, trains, planes, maybe even large trucks.
Levitated Dipole has the potential for being a useful power source but it is very immature at this time and not ready for prime time just yet, but if adequately funded that could change.