Casimir Effect Space Propulsion Part II

My own look at Casimir Effect

Nearly a quarter-century ago, after reading Hal Puthoff's article (Ref 5 below) I decided to look further into the possibility of adapting Casimir Effect into a perpetual force generator for spacecraft propulsion. At that time I wrote the following:—

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Casimir Effect as a possible method of spacecraft propulsion.

1. Casimir — brief biography.

    Hendrik B. G. Casimir, one of the foremost theoretical physicists of the 1930's and 1940's, later became Technical Head of the Philips Research Laboratories. He first wrote in 1948 on the effect that now bears his name (Ref 1 & Fig 1). Briefly, this states that if you take two flat parallel metal plates and place them very close together, a force of attraction will occur between them. The origin of the force is of interest — it arises as predicted by quantum theory from fluctuations in the very fabric of space-time itself, which permeate the whole universe.

Fig 1.  Brief explanation of Casimir Effect, and force calculation for plates separated by 100 nm

2. "Reality" of Casimir Effect.

    In experiments starting in 1957, Casimir Effect has been verified beyond doubt (Ref 2 p235) yet it is still dealt with poorly, if at all, in physics courses. Also for a long time after Ref 1 was published, even specialists seemed unaware of it. Thus Bryce DeWitt wrote in 1989 (Ref 2 P247):—

"This made me sit up and take notice. I knew nothing of Casimir's original work (1948,1949) and had not heard of Sparnaay's experiments (1957).... I had always been taught that the zero - point energy of a quantized field was unphysical, and Casimir was saying that this view was wrong.... Just how deep the Casimir effect goes has become apparent in the years since 1960. I can think of hardly anything today more pertinent to quantum gravity."

3. Using Casimir Effect to generate a permanent net force.

    The "classical" Casimir Effect occurs because conducting plates placed close together exclude certain zero - point fluctuations from the region between the plates. Note the
important difference between this and, for example, the attraction between two magnets. The fluctuations are truly ubiquitous throughout the universe and are external to the plates, whereas the magnets attract because of localised currents (electron movements) within the magnets.

    The crucial question now is, can Casimir Effect cause a net force on just a single metal plate? I say yes, if one side of the plate is covered with tapered, blind holes. See Fig 2. (Note the extremely small hole size).

Fig 2.  A thin metal plate (shown in cross-section) covered with tapered holes on one side only,
as a possible Casimir force generator

4. Why a net force should be generated.

4.1 Equivalence Principle

    The device of Fig 2 is a microscopic analogue of the acoustic or radar energy absorbing surface used in anechoic chambers etc, so possibly the equivalence principle can be cited in its support. (But note that the details of energy absorption are not quite equivalent).

4.2 Analogy with "classical" Casimir Effect.

    Provided the sides of the tapered holes are sufficiently smooth, most fluctuations will reflect in a specular rather than a diffuse manner, and the notes on Fig 2 will apply.

4.3 Support from the theoretical literature.

    Equation 1.8 of Ref 3 shows that the energy density near a plane conductor deformed by curvature differs from that near a flat one, and the sharper the curvature, the greater the difference. So the device of Fig 2 which has one side flat and the other with many sharp curves should experience different energy densities at the two sides, and hence a net force.

5. Practical details.

    See Fig 3.

6. References.

Ref 1. H.B.G. Casimir, 1948, Proc. Kon. Ned. Akad. Wetenschap 51 p793

Ref 2. A. Sarlemijn & M.J. Sparnaay eds 1989 Physics in the Making, Elsevier Science Pub. Co.

Ref 3. P. Candelas, 1982, Annals of Physics (N.Y.) 143, p241

Ref 4. H.B.G. Casimir, 1983 Haphazard Reality: Half a Century of Science, Harper & Row

Ref 5. H. Puthoff, 1990, "Everything for Nothing", New Scientist 28 July 1990 p36

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I'll give Fig 3 mentioned above, and discuss it in detail, next time.


UPDATE, end of 2016:—

I have found two other references predicting that a single plate should experience a strong permanent net Casimir force as I have suggested above, provided one side is left flat, and the other is covered with extremely small indentations. The shape of the indentations is probably less critical than their size. One option suggests a cylindrical shape; and the other trapezoidal, see the Russian (English-language) references http://vixra.org/pdf/1512.0276v1.pdf and http://vixra.org/pdf/1404.0097v1.pdf.