Dean drive
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The Dean drive or Dean device is a hypothetical scheme for spacecraft propulsion. The patent is of a variety known as an oscillation thruster.
It is named after Norman L. Dean, who called it a reactionless drive and who patented an alleged example of such a device. According to Dean, his propulsion device can produce linear acceleration without the use of any reaction mass. If such a device could be physically realized, this would revolutionize space travel, since in conventional rocketry, most of a rocket's launch weight is devoted to carrying mass which is ejected downwards to drive the remaining mass of the rocket and its payload upwards. A reactionless drive would violate Newtonian physics, and is regarded by the scientific mainstream as physically impossible.
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The role of John W. Campbell
Image:Analog Sub in Martian Orbit.jpg The Dean drive obtained a good deal of publicity in the 1950s and 1960s via the columns of John W. Campbell, the longtime editor of Astounding Science Fiction magazine. Campbell apparently believed that the device worked and claimed to have witnessed it operating on a bathroom scale. The weight reading on the scale appeared to decrease when the device was activated. He subsequently published photographs of the scale with the drive stopped and running. The June, 1960, cover of Astounding had a realistic painting of a United States submarine orbiting Mars, supposedly propelled there by a Dean drive.
Dean, who was trying to find potential buyers for his technology, was secretive about the details of how it was supposed to work, but it was said to contain asymmetrical rotating weights and to generate a great deal of vibration.
Campbell and Dean claimed that Newton's laws of motion were only an approximation, and that Dean had discovered a fourth law of motion. This has been described as a nonlinear correction to one of Newton's laws, which, if correct, would allegedly have rendered a reactionless drive feasible after all. Skeptics maintained that there were many possibilities for illusory effects, involving interactions of vibration, friction, resonance with the springs of the scale, instantaneous photographs of an oscillating scale reading, and so forth, to say nothing of outright deception.
Further developments
Purportedly, several groups (including Westinghouse and the U.S. military) became interested in buying the device, if it worked, for sums of half a million dollars or more. Dean's paranoia and insistence upon cash before showing the device, kept interested parties from seeing the device, and Dean never did make any sales.
In 1999, Dean's son, Norman Robert "Bob" Dean, appeared at an anti-gravity conference by invitation of a group of patent holders who had created differing versions of the reactionless drives that referred to N.L. Dean in their patents. He gave a presentation about his father's device. The original drive models, as well as Dean's well-kept and detailed notes, are apparently in the possession of the Dean Family.
The noted science-fiction writer and critic Damon Knight had this to say about the Dean drive in a chapter called "Campbell and his Decade" in his collection of essays about the science-fiction field In Search of Wonder:
- Oh, the Dean Machine, the Dean Machine,
- You put it right in a submarine,
- And it flies so high that it can't be seen--
- The wonderful, wonderful Dean Machine!
More Recent Progress
In a paper entitled "The Challenge To Create The Space Drive" [1] Marc G. Millis argues that a prerequisite to achieving this breakthrough is a description of the specific problems to be solved. Millis suggested studying schemes for realizing a reactionless drive among the concepts to be considered under the aegis of the Breakthrough Propulsion Physics Program, which was funded by NASA from 1996-2002. The program marks the first time an organized scientific effort was mounted by a credible organization to explore some of the "wild ideas" for new propulsion schemes put forward over the years.
Electromagnetic Tethers
It has been claimed that a device called the electromagnetic tether constitutes a reactionless drive but this is technically inaccurate; see for example the description offered at the [Special Projects Group], Harvard-Smithsonian Observatory.
It appears that arguments about "reactionless" drives are as much about linguistics as about science. The fundamental scientific problem is one of momentum transfer. If there is no momentum transfer, the postulated device is classified as a "reactionless" drive and labelled a fraud. If there is a mechanism for momentum transfer, then the device is classed as a reaction drive and therefore by definition, not a "reactionless" drive.
Tethers do have a mechanism for momentum transfer and although they do not expel reaction mass like a rocket, they do transfer momentum and hence can not be a true reactionless drive.
Conceptual Issues
One problem with the Dean patent is that the device the patent described doesn't work as advertised. Some claim that this is because it is not uncommon for patent holders to leave out small, key variations to the basic embodiment to avoid outright theft of their invention by intellectual property predators. This is akin to leaving out the primer in a patent drawing of a rifle cartridge (an idealized analogy to be sure).
The purpose of taking out a patent is supposed to be for the express purpose of preventing such theft. But anyone who has been involved in patent litigation, especially with a large corporation, knows how financially ruinous such actions are. Some patentees seek to avoid expensive litigation by making it appear that their patented device won't work. The idea is that a prospective thief would simply conclude that the device can't work and therefore not bother to infringe.
It is a fact of patent law that one embodiment of a collection of principles for a patentable device applies to all embodiments of the mechanism, the others being merely a change in form. In the above noted example, a primer in a rifle cartridge is merely another embodiment of the basic idea. The rifle cartridge will not work without the primer, but from a legal standpoint there is virtually no difference between an embodiment with a primer and one without. Such differences are merely a change in form.
Another argument against the possibility of physically realizing a reactionless drive is that, according to Newton, such a device could not transfer momentum. This is essentially the point raised above, that such a drive would violate the laws of Newtonian physics. New scientific theories such as SED [2] might eventually provide an explanation for some mechanisms of momentum transfer not currently encompassed by Newtonian physics. It is by no means clear at this point, however, that the Dean Drive is anything but a fraud.
See also
External links
- Dean Space Drive, a website (apparently maintained by the Dean family) detailing additional materials and background information on Norman Dean and his device.
- "Breakthroughs" commonly submitted to NASA - Explains an Oscillation Thruster.