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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Dean drive | 2/2 | https://en.wikipedia.org/wiki/Dean_drive | reference | science, encyclopedia | 2026-05-05T09:18:34.590638+00:00 | kb-cron |
=== Purported weight loss === Dean made a demonstration for a representative of the magazine Popular Mechanics of one of his "Dean drive" devices. The witness reported that "While suspended above the ground, was able to pull a load to itself without itself being pulled toward the load". Another version of the machine was reported to be "able to apply a force to a hand, without moving—yet when the machine was turned off an equivalent force applied by the hand easily moved the machine". William O. Davis, who witnessed the latter demonstration, wrote in his notebook about Dean's explanation of how the device worked, "... does not strike me as valid ... For this reason I have decided to undertake a theoretical study of dynamic systems to see if a concept can be evolved which will describe a world in which Dean's Drive can exist and yet where other known facts are not contradicted." Davis produced a hypothesis, and it was published in Analog in 1962. Later analysis has revealed that the interactions of vibration, friction, and resonance with the springs of the scale are likely the root cause of the apparent weight loss reported by Campbell and others of apparent "anti-gravity" and "reactionless thruster" effects. In the 1950s Jerry Pournelle, working for an aerospace company, contacted Dean to investigate purchasing the device. Dean refused to demonstrate the device without pre-payment and promise of a Nobel Prize. Pournelle's company were unwilling to pay for the right to examine the device and never saw the purported model. 3M sent representatives about the same time, and obtained similar results. Pournelle eventually was convinced that Dean's device never worked.
== Patents == Dean was granted two U.S. patents on mechanical devices presumably related to his Dean drive claims. His first patent for a "System for converting rotary motion into unidirectional motion" was granted on May 9, 1959. Another patent for a "Variable oscillator system" was granted on May 11, 1965. These two patent designs were the only ones where Dean revealed the design details with an explanation for operation. However, the details were incomplete, and it is not possible to build a Dean drive just from the explanations in the patent. Dean's patents, as well as patents for many other similar devices, have been analyzed and it has been determined that none can produce net directional thrust in free space or operate without violating Newton's third law. Dean also demonstrated other mechanical devices that were clearly different from his patent designs but apparently never sought patents for them nor otherwise revealed their design details or theory of operation. In 1978 physicist Russell Adams wrote an article in Analog. Searching in the US patent office he had found at least 50 patents for similar reactionless drives. After studying the mechanisms, he concluded that they all relied on friction against the floor they were placed on, and they would be useless in space, where there isn't friction against any surface. Dean's patented devices, and his explanation of how his drive was supposed to work, were later shown to develop no net weight loss over time and do not violate Newton's third law of motion. Many other inventors claim to have invented similar devices, and they all still remain unproven, and lacking a solid theoretic basis.
== Later developments == After Dean's death, neither the demonstration devices nor any working devices were found among his experiments. The demonstration devices were clearly different from the devices patented by Dean, and no diagrams were ever found for them. Consequently, it is impossible to test Dean's reported designs or devices to see if they worked as he claimed. In 1997 physicist John G. Cramer mentioned the Dean drive in Analog in his column "Alternate View". He said that the demonstration made to Campbell was faulty, and the drive had turned out to be bogus, like many other claims of antigravity devices. In 2006 a NASA technical memorandum presented the Dean drive as the most famous example of an "oscillation thruster" and examined its theoretical basis and feasibility as a space drive. It said that "Regrettably, such devices are not breakthroughs, since they still require a connection to the ground to create net motion. The ground is the reaction mass and the frictional connection to the ground is a necessary component to its operation." NASA regularly receives proposals of similar devices, and the memo recommended that future reviews of said proposals "should require that submitters meet minimal thresholds of proof before engaging in further correspondence."
== See also == Eric Laithwaite, a UK inventor who made similar claims. Reactionless drive EmDrive
== References ==
== External links == Dean Drive and Other Reactionless Drives, a narrative by Jerry Pournelle describing his brief investigation of the Dean drive. Nicholas Thomas. "'Breakthroughs' commonly submitted to NASA". Archived from the original on 2006-02-11. Explains an Oscillation Thruster.