MHD

...What is Magnetohydrodynamics, MHD for short? It is the art and the manner of acting on a fluid, liquid or gas, by making electromagnetic forces act on it, provided that it is sufficiently conductive to electricity. We will then speak of an MHD accelerator. It is also the art and the manner of transforming the kinetic energy of a fluid into electrical energy. We will then speak of an MHD generator. More generally, insofar as a direct conversion of one form of energy into another form of energy (kinetic, electromagnetic) takes place, we will speak of an MHD converter.

... To get an introduction to MHD, see my comic strip "Le Mur du Silence" (well named) in the "cd-Lanturlu".

...In the sixties, France found itself quite at the forefront in this field. One could say: by sheer chance. A major MHD research effort had been initiated at the beginning of the sixties, in many countries: England, the USSR, the USA, France. Countries like Germany, then Japan joined this pack later. The goal then was to develop MHD generators which could in principle have efficiencies far superior to those of thermal machines (up to 60%). The energy sources were of two kinds: combustion of hydrocarbons or nuclear energy. For the process to be profitable it was essential that the fluid from which one proposed to extract as much kinetic energy as possible have sufficient electrical conductivity. Now in principle all gases are very poor conductors of electricity. They are even downright... insulators. So everything that seemed possible was done to endow these gases with a significant electrical conductivity, by "seeding" them with alkali elements, with a low "ionization potential" (essentially cesium). But the results proved disappointing, despite the very large sums invested in this research, at a time of strong economic growth. It was then envisaged to operate these generators "with two temperatures, by endowing "the free-electron gas" with a higher temperature than that of the gas itself, made up of atoms. But a fearsome instability, discovered theoretically in 1964 by E. Velikhov (who later became vice-president of the Academy of Sciences of the USSR) ruined all these plans, from the end of the sixties. In the mid-seventies, most countries had given up, with the exception of the USSR which maintained, until its economic collapse, a significant effort in this sector of research.

... When I was assigned to the Institute of Fluid Mechanics of Marseille, in 1965, I found there a small team, gathered around a researcher: Georges Inglesakis, who had carried out, inspired by work done in the USA by a researcher of Swiss origin, Bert Zauderer, experiments in direct conversion using as a source of gas burst what was called a "shock tube". The experiments were of very brief duration (less than a hundred microseconds) but all the interest lay in the fact that the gas expelled at very high speed (more than 2500 m/s), under significant pressure (one bar) was also very hot (ten thousand degrees), therefore very strongly conductive to electricity. Under these conditions it became possible to simulate these MHD generators of which one dreamed by compressing, therefore heating and expelling through a nozzle gases as poorly conductive to electricity under ordinary conditions as argon, but which became so at the temperature to which they were brought. Of course, these experiments had no interest on the strictly industrial level. What to do with a generator that can operate, every hour, only for a tenth of a millionth of a second, even if it spews several megawatts during that time? At the time no one realized (except the Soviets) that these pulsed generators would one day find their reuse in what was to be called much later the "star wars" and of which I will speak in the site.

...The reader will learn, subsequently, and perhaps with surprise, that the father of Soviet MHD was none other than the brilliant Andrei Sakharov (also father of the first Russian H-bomb). Sakharov was not a researcher, he was a finder and a visionary. No one, at this Marseille Institute where I had landed, suspected the real possibilities of MHD. Some spectacular results were nevertheless obtained. In 1967, two years after my entry into the laboratory, thanks to a trick, rediscovered fifteen years later by a Japanese, I succeeded in operating for the first time a two-temperature generator (still during these brief bursts), by outrunning Velikhov's instability (which developed in a millionth of a second). Plasma acceleration experiments were also successfully carried out, with speed gains of 5 km/s over only ten centimeters of nozzle length. But all this went completely unnoticed, against the backdrop of general collapse.

... In France, research is in principle "directed". Organizations like the CNRS or others therefore equip themselves with "programs". the problem is that the people who establish these programs and those who have the ideas, carry out the research, are not the same people. I don't know if you have ever cut off a duck's head with a blow of a chopper. Everyone knows that the beast is then capable of running briskly. French research is a bit like this headless duck, the situation being aggravated by the fact that the French research authorities depend closely on:

• The army

• The polytechnicians

... When one has understood all that, most often after long years of setbacks, there remains nothing but to turn to the only field of research where one can envisage long-term work: theoretical research.

... I abandoned all research in MHD in 1987, after having insisted ten years after the French research programs had been officially closed. I abandoned because I was constrained and forced to. I explained myself in various books. I will take up all this again in this section of my MHD site. At the heart of this research there was a fascinating idea: is it possible to make a craft move through the air at supersonic, and even hypersonic, speed, in dense air, without creating a "Bang", a shock wave? A student, Bertrand Lebrun, wrote a doctoral thesis under my direction, in this vein. Our theoretical work, accompanied by numerous scientific publications in top-level journals and communications at international congresses, answered in the affirmative (see the list at the end of the document accessible via the link). In the mid-eighties I succeeded in convincing the Director General of the CNRS, Papon, to help us set up an experiment. Funds were released. The idea was to work once again in short-duration experiments, using the "shock tube" as a hot-burst blower. A laboratory in Rouen still possessed one of these... antiquities. We had moreover recovered important equipment, a vestige of the first "tokamak" of Fontenay-aux-Roses. Papon was delighted, seeing "that we were going to do cutting-edge research with scrap equipment". At the end of the eighties, we were within two fingers of succeeding. But the army deliberately scuppered the project. We had proof of it subsequently, which I published in a book.

... The army, by definition, has all the rights, insofar as it bases itself on the criterion of defense confidentiality. One easily imagines the strategic asset that an "MHD cruise missile" could represent, the only one capable of playing leapfrog with the hills, in hypersonic flight (for the uninitiated: all current cruise missiles are subsonic). The fact that the army at that time wanted to forbid such research being carried out in a civil context could have been, at the limit, understandable, insofar as it would have pursued this research in its own sanctuaries, far from indiscreet eyes. Yet, thirteen years later, it turned out that the French military had simply been incapable of pursuing this research and that it had quite simply been abandoned, rather quickly moreover, for lack of... skills. The investigation that was carried out simply brought the following conclusion:

There is no French military MHD

...This at a time when a group of military men originating from the IHEDN (Institute of Higher National Defense Studies) launches an alarm cry, in a booklet published in July 99. They evoke a fantastic lead of the Americans in the field, sound the tocsin. We will see subsequently that these concerns could be founded. I am even convinced that they have them and I will explain myself. But what is grotesque is that among those who worry about this situation are many of those who were, between 1976 and 987, the great leaders of the bankruptcy of the French effort in matters of MHD. Shortsightedness, incompetence. What is more extraordinary is that it is these same people who hold out the begging bowl, demand "a response in terms of action", energetic, ask that they be given in fact carte blanche, whereas they are the main persons responsible for our delay in this field. Putting on conspiratorial airs they strive to suggest that their spokesmen are seconded by strong technico-scientific skills. Yet it is nothing of the sort. All this is alas only a rather lamentable and moreover useless gesticulation, for it is... too late.

... What is hardly bearable for the researcher that I am is to see moreover a character devoid of all scientific competence pontificating on television while declaring "we now know how to make a machine move at supersonic speed without creating a Bang". I then thought that it was good that the student, the teacher, the engineer, the taxpayer, the man in the street, and even .. the politician be warned, have elements of appreciation so that these people not be taken, a second time, twenty-three years later, for imbeciles.

... As an appetizer, the reader will find by clicking on the link below, a rather popularized presentation of this famous MHD manipulation, the one we dreamed of doing, which we had entirely calculated and which would have (like all the manipulations I did in this field) worked on the first try. A manipulation that the soldierly rabble was incapable of carrying through.

.. How is that possible? Do not overestimate the military (and the polytechnicians). Remember Clemenceau's phrase, at the turn of the 14-18 war: "The best way to defeat Germany is to create a Polytechnic School there".

... Before passing to this presentation of the manipulation, in the style "one hundred microseconds that could change our vision of the world", a tasty anecdote in support of my words. After the first French nuclear tests, at Regane, the military learned that the Americans henceforth carried out their tests underground. They asked them how they proceeded. The answer arrived quickly:

• Listen, you little frog-eaters, you are very kind, but on the one hand you have withdrawn from NATO, on the other hand we do not care so much about seeing nuclear know-how spread across this planet. So, figure it out....

... The polytechnician military engineers, the "gunpowder engineers", made learned calculations. They concluded that it was necessary to drill a tunnel, in a mountain, place the nuclear device at the very bottom, then pack the rest with concrete and scrap iron. Thus it was done. A firing command post was installed practically facing the thus-obturated tunnel, then the Minister of the Armed Forces, Pierre Messmer, was invited to come to this corner of the Sahara, to attend the test. It is moreover he himself who recounted this affair to the newspaper Paris-Match, which was then trying, vainly (in our country one willingly cultivates secrecy) to write the history of the French bomb. One will see right away why he made this confidence. The Minister, even after all these years, was still seething.

... When the device was fired, the pressure immediately ejected the hundreds of meters of reinforced concrete and the tunnel behaved like a shotgun. Stupefied, the Minister saw these debris pass at close distance. Everyone was irradiated, of course. The evaluation of the doses received proved difficult: the films (including the Minister's) had been completely fogged. Messmer was beside himself. That a legionnaire or the inhabitants of a village be irradiated, fine, but ... the minister of the armed forces, all the same!

... In fact, and our military engineers ended up understanding it, it was not in a hard rock that the device had to be lodged, but on the contrary under hundreds of meters of ground soft enough to absorb the shock. Think about it. If you want to explode a grenade, then analyze the products of the explosion, it is perhaps more logical to place it on sandbags than to cast it in concrete. Today one knows how to operate. When the bomb explodes, a cavity is created in the compressible ground (as was the substratum of the Mururoa atoll). The energy is thus absorbed by inelastic compression. At the same time a shock wave rises toward the surface, which slightly lifts the ground, and the trick is done.

... All this to say that military sanctuaries are perhaps not the be-all and end-all in matters of fundamental research. I sometimes hear people say to me:

• But, don't you believe that all that is shown to us, all these televised gesticulations are there "only to amuse the gallery", but that, behind this screen, much more serious research could be carried out?

... Sorry to disappoint you. Behind this screen, there is nothing. Otherwise the report mentioned above would not contain so many blunders revealing the scientific nullity of its authors.

I do not have the power to change the world, but I do not like people being taken for imbeciles.

One hundred microseconds to change our vision of the universe