Cold Fusion

My second post-doc. was at Southampton University, and one of the leading physical chemists there was Martin Fleischmann, who had an excellent record for clever and careful work. There would be no doubt that if he measured something, it would be accurate and very well done. In the academic world he was a rising star until he scored a career “own goal”. In 1989, he and Stanley Pons claimed to have observed nuclear fusion through a remarkably simple experiment: they passed electricity through samples of deuterium oxide (heavy water) using palladium electrodes. They reported the generation of net heat in significant excess of what would be expected from the power loss due to the resistance of the solution. Whatever else happened, I have no doubt that Fleischmann correctly measured and accounted for the heat. From then on, the story gets murky. Pons and Fleischmann claimed the heat had to come from nuclear fusion, but obviously there was not very much of it. According to “Physics World”, they also claimed the production of neutrons and tritium. I do not recall any actual detection of neutrons, and I doubt the equipment they had would have been at all suitable for that. Tritium might seem to imply neutron production, thus a neutron hitting deuterium might well make tritium, but tritium (even heavier hydrogen) could well have been a contaminant in their deuterium, or maybe they never detected it.

The significance, of course, was that deuterium fusion would be an inexhaustible source of clean energy. You may notice that the Earth has plenty of water, and while the fraction that is deuterium is small, it is nevertheless a very large amount in total, and the energy in going to 4-helium is huge. The physicists, quite rightly, did not believe this. The problem is the nuclei strongly repel each other due to the positive electric fields until they get to about 1,000 – 10,000 times closer than they are in molecules. Nuclear fusion usually works by either extreme pressure squeezing the nuclei together, or extreme temperature giving the nuclei sufficient energy that they overcome the repulsion, or both.

What happened next was that many people tried to reproduce the experiment, and failed, with the result this became considered an example of pathological science. Of course, the problem always was that if anything happened, it happened only very slightly, and while heat was supposedly obtained and measured by a calorimeter, that could happen from extremely minute amounts of fusion. Equally, if it were that minute, it might seem to be useless, however, experimental science doesn’t work that way either. As a general rule, if you can find an effect that occurs, quite often once you work out why, you can alter conditions and boost the effect. The problem occurs when you cannot get an effect.

The criticisms included there were no signs of neutrons. That in itself is, in my opinion, meaningless. In the usual high energy, and more importantly, high momentum reactions, if you react two deuterium nuclei, some of the time the energy is such that the helium isotope 3He is formed, plus a neutron. If you believe the catalyst is squeezing the atoms closer together in a matrix of metal, that neutron might strike another deuterium nucleus before it can get out and form tritium. Another reason might be that the mechanism in the catalyst was that the metal brought the nuclei together in some form of metal hydride complex, and the fusion occurred through quantum tunnelling, which, being a low momentum event, might not eject a neutron. 4He is very stable. True, getting the deuterium atoms close enough is highly improbable, but until you know the structure of the hydride complex, you cannot be absolutely sure. As it was, it was claimed that tritium was found, but it might well have been that the tritium was always there. As to why it was not reproducible, normally palladium absorbs about 0.7 hydrogen atoms per palladium atom in the metal lattice. The claim was that fusion required a minimum of 0.875 deuterium atoms per palladium atom. The defensive argument was the surface of the catalyst was not adequate, and the original claim included the warning that not all electrodes worked, and they only worked for so long. We now see a problem. If the electrode does not absorb and react with sufficient deuterium, you do not expect an effect. Worse, if a special form of palladium is required, that rectifying itself during hydridization could be the source of the heat, i.e.the heat is real, but it is of chemical origin and not nuclear.

I should add at this point I am not advocating that this worked, but merely that the criticisms aimed at it were not exactly valid. Very soon the debate degenerated into scoffing and personal insults rather than facts. Science was not working at all well then. Further, if we accept that there was heat generated, and I am convinced that Martin Fleischmann, whatever his other faults, was a very careful and honest chemist and would have measured that heat properly, then there is something we don’t understand. What it was is another matter, and it is an unfortunate human characteristic that the scientific community, rather than try to work out what had happened, preferred to scoff.

However, the issue is not entirely dead. It appears that Google put $10 million of its money to clear the issue up. Now, the research team that has been using that money still have not found fusion, but they have discovered that the absorption of hydrogen by palladium works in a way thus far unrecognised. At first that may not seem very exciting, nevertheless getting hydrogen in and out of metals could be an important aspect of a hydrogen fuel system as the hydrogen is stored at more moderate pressures than in a high-pressure vessel. The point here, of course, is that understanding what has happened, even in a failed experiment, can be critically important. Sure, the actual initial objective might never be reached, but sometimes it is the something else that leads to real benefits. Quite frequently, in science, success stories actually started out as something else although, through embarrassment, it is seldom admitted.

Finally, there is another form of cold fusion that really works. If the electrons around deuterium and tritium are replaced with muons, the nuclei in a molecule come very much closer together, and nuclear fusion does occur through quantum tunnelling and the full fusion energy is generated. There are, unfortunately, three problems. The first is to maintain a decent number of muons. These are made through the decay of pions, which in turn are made in colliders. This means very considerable amounts of energy are spent getting your muons. The second is that muons have a very short life – about 2 microseconds. The third is if they lose some energy they fall into the helium atom and stay there, thus taking themselves out of play. Apparently a muon can catalyse up to 150 fusions, which looks good, but the best so far is that to get 1 MW of net energy, you have to put 4 MW in to make the muons. Thus to get really large amounts of energy, extremely huge generators are required just to drive the generation. Yes, you get net power but the cost is far too great. For the moment, that is not a productive source.

Processing Minerals in Space

I have seen some recent items on the web that state that asteroids are full of minerals and fortunes await. My warning is, look deeper. The reason is, most asteroids have impact craters, and from basic physics but some rather difficult calculations you can show these were formed from very energetic collisions. That the asteroid did not fly to bits indicates it is a solid with considerable mechanical strength. That implies the original dust either melted to form a solid, or a significant chemical reaction took place. For those who have read my “Planetary Formation and Biogenesis” you will know why they melted, assuming I am right. So what has that got to do with things? Quite simply, leaving aside metals like gold, the metal oxides in molten silica form the olivine or pyroxene families, or aluminosilicates. That is they form rocks. To give an example of the issue, I recently read a paper where various chondrites were analysed, and the method of analysis recorded the elements separately. The authors were making much of the fact that the chondrites contained 19% iron. Yikes! But wait. Fayalite contains almost 55% iron by weight, but it is useless as an ore. The olivine and pyroxene structures have tetrahedral silicon oxides (the pyroxene as a strand polymer) where the other valence of the oxygen is bound to a divalent cation, mostly magnesium because magnesium is the most common divalent element in the supernova dust. What these authors had done was to analyse rock.

If you read my previous post you will see that I have uncovered yet another problem with science: the authors were very specialized but they went outside their sphere of competency, quite accidentally. They cited numbers because so much in science depends on numbers. But it is also imperative to know what the numbers mean.

On Earth, most of the metals we obtain come from ores, which have formed through various forms of geochemical processing. Thus to get iron, we usually process haematite, which is an iron oxide, but the iron almost certainly started as an average piece of basalt that got weathered. It is most unlikely that good deposits of haematite will be found on asteroids, although it is possible on Mars where small amounts have been found. If Mars is to be settled, processing rocks will be mandatory for survival but the problems are different from those of asteroids. For this post, I wish to restrict myself to discussing asteroids as a source of metals. Let us suppose an asteroid is collected and brought to a processing site, the question is, what next?

The first problem is size-reduction, i.e.breaking it down to more manageable pieces. How do you do that? If you hit it with something, you immediately separate, following Newton’s third law. If you want to see the difficulties, stand on a small raft and try to keep on hitting something. Ah, you say, anchor yourself. How? You have to put something like a piton into solid rock, and how do you do that without some sort of impact? Of course it can be done, but it is not easy. Now you start smashing it. What happens next is bits of asteroid fly off into space. Can you collect all of the pieces? If not, you are a menace because the asteroid’s velocity v, which will be in the vicinity of 30 km/s if near Earth, has to be added to whatever is given to the fragments. Worse, they take on the asteroid’s eccentricity ε(how much difference there is between closest and farthest distance from the sun) and whatever eccentricity has been added by the fragmentation. This is important because the relative velocity of impact assuming the target is on a circular orbit is proportional to εv. Getting hit by a rock at these sort of velocities is no joke.

However, suppose you collect all the rock, you have two choices: you can process the rock as is, or you can try to refine it. If you adopt the latter idea, how do you do it? On Earth, such processing arises through millions of years of action with fluids, or through superheated fluids passing through high temperature rock. That does not sound attractive. Now some asteroids are argued to have iron cores so the geochemical processing has been done for you. Of course you still have to work your way through the rock, and then you have to size reduce the iron, which again raises the question, how? There is also a little less good news awaiting you: iron cores are almost certainly not pure iron. The most likely composition is iron with iron silicide, iron phosphide, iron carbide and a lot of iron sulphide. There will also be some nickel, together with corresponding compounds, and (at last joy?) certain high value metals that dissolve in iron. So what do you do with this mess?

Then, supposing you separate out a pure chemical compound, how do you get the metal out? The energy input required can be very large. Currently, there is a lot of effort being put into removing CO2from the atmosphere. The reason we do not pull it apart and dump the carbon is that all the energy liberated from burning it has to be replaced, i.e.a little under 400 kJ/mol. and that is such a lot of energy. Consider that as a reference unit. It takes roughly two such units to get iron from iron oxide, although you do get two iron atoms. It takes about five units to break forsterite into two magnesium atoms and one silicon. It takes ten such units to break down kaolinite to get two aluminium atoms and two silicon atoms. Breaking down rock is very energy intensive.

People say, electrolysis. The problem with electrolysis is the material has to dissolve in some sort of solvent and then be separated into ions. Thus when making aluminium, bauxite, an aluminium oxide is used. Clays, which are aluminosilicates such as kaolinite or montmorillinite, are not used, despite being much cheaper and more easily obtained. In asteroids any aluminium will almost certainly be in far more complicated aluminosilicates. Then there is the problem of finding a solvent for electrolysis. For the least active metals, such as copper, water is fine, but that will not work for the more active ones, such as aluminium. Titanium would be even more difficult to make, as it is made from the reduction of titanium tetrachloride with magnesium. You have to make all the starting materials!

On Earth, many oxides are reduced to metal by heating with carbon (usually very pure coal) and allow the carbon to take the oxygen and disappear as a gas. The problem with that, in space, is there is no readily available source of suitable carbon. Carbonaceous chondrites have quite complicated molecules. The ancients used charcoal, and while this is NOT pure carbon, it is satisfactory because the only other element there in volume tends to be oxygen. (Most charcoal is about 35% oxygen.) The iron in meteors could certainly be useful, but for some other valuable elements, such as platinum, while it may be there as the element, it will probably be scattered through the matrix and be very dilute.

Undoubtedly there will be ways to isolate such elements, but such methods will probably be somewhat different from what we use. In some of my novels I have had fusion power tear the molecules to atoms, ionise them, and separate out the elements in a similar way to how a mass spectrometer works, that is they are accelerated and then bent with powerful electromagnetic fields. The “bend” in the subsequent trajectory depends on the mass of the ions, so each isotope is separated. Yes, that is fiction, but whatever is used would probably seem like fiction now. Care should be taken with any investment!