6.2 KiB
| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| EmDrive | 2/5 | https://en.wikipedia.org/wiki/EmDrive | reference | science, encyclopedia | 2026-05-05T09:19:20.530876+00:00 | kb-cron |
=== EmDrive === In 2001, Shawyer founded Satellite Propulsion Research Ltd, to work on the EmDrive, which he said used a resonant cavity to produce thrust without propellant. The company was backed by a SMART award grant from the UK Department of Trade and Industry. In December 2002, he loosely described a prototype which he alleged had produced a thrust of 0.02 newtons (0.072 ozf) powered by an 850 W cavity magnetron. He reported that the device could operate for only a few dozen seconds before the magnetron failed from overheating, however details were never published or replicated.
==== Second device and New Scientist article ==== In October 2006, Shawyer claimed to have conducted tests on a new water-cooled prototype with increased thrust. He reported plans to have the device ready to use in space by May 2009 and to make the resonant cavity a superconductor, neither of which materialized.
New Scientist magazine featured the EmDrive on the cover of 8 September 2006 issue. The article portrayed the device as plausible and emphasized the arguments of those who held that point of view. Egan, a popular science fiction author, distributed a public letter stating that "a sensationalist bent and a lack of basic knowledge by its writers" made the magazine's coverage unreliable, sufficient "to constitute a real threat to the public understanding of science". Especially, Egan said he was "gobsmacked by the level of scientific illiteracy" in the magazine's coverage, alleging that it used "meaningless double-talk" to obfuscate the problem of conservation of momentum. The letter was endorsed by Baez and posted on his blog. New Scientist editor Jeremy Webb responded to critics:It is a fair criticism that New Scientist did not make clear enough how controversial Roger Shawyer's engine is. We should have made more explicit where it apparently contravenes the laws of nature and reported that several physicists declined to comment on the device because they thought it too contentious ... The great thing is that Shawyer's ideas are testable. If he succeeds in getting his machine flown in space, we will know soon enough if it is ground-breaking device or a mere flight of fancy. New Scientist also published a letter from the former technical director of EADS Astrium: I reviewed Roger's work and concluded that both theory and experiment were fatally flawed. Roger was advised that the company had no interest in the device, did not wish to seek patent coverage and in fact did not wish to be associated with it in any way. A letter from physicist Paul Friedlander: As I read it, I, like the thousands of other physicists who will have read it, immediately realised that this was impossible as described. Physicists are trained to use certain fundamental principles to analyse a problem and this claim clearly flouted one of them ... The Shawyer drive is as impossible as perpetual motion. Relativistic conservation of momentum has been understood for a century and dictates that if nothing emerges from Shawyer's device then its centre of mass will not accelerate. It is likely that Shawyer has used an approximation somewhere in his calculations that would have been reasonable if he hadn't then multiplied the result by 50,000. The reason physicists value principles such as conservation of momentum is that they act as a reality check against errors of this kind.
==== Later work ==== In 2007, the UK Department of Trade and Industry granted SPR an export license to Boeing in the US. According to Shawyer, in December 2008 he was invited to present on the EmDrive, and in 2009 Boeing expressed interest in it, at which point he stated that SPR built a thruster which produced 18 grams of thrust, and sent it to Boeing. Boeing did not license the technology and communication stopped. In 2012, a Boeing representative confirmed that Boeing Phantom Works used to explore exotic forms of space propulsion, including Shawyer's drive, but such work later ceased. They confirmed that "Phantom Works is not working with Mr. Shawyer", nor pursuing those explorations. In 2014, Shawyer presented ideas for 'second-generation' EmDrive designs and applications at the annual International Astronautical Congress. A paper based on his presentation was published in Acta Astronautica in 2015. While no functional prototype of the first-generation drive had yet been produced, and no detailed schematic of a new device was provided, it loosely described models for a superconducting resonant cavity and for thrusters with multiple cavities. In 2016, Shawyer filed further patents and launched a new company, Universal Propulsion Ltd., as a joint venture with Gilo Industries Group, a small UK aerospace company.
=== Cannae and other drives === The Cannae Drive (formerly Q-drive) is another implementation of this idea, with a relatively flat cavity. It was designed by Guido Fetta in 2006 and promoted within the US through his company, Cannae LLC, since 2011. In 2016, Fetta announced plans to eventually launch a CubeSat satellite containing a version of the Cannae Drive, which would run for 6 months to observe how it functions in space. No followup was published. In China, researchers working under Yang at NWPU built a resonant cavity thruster in 2008, and tested it for a number of years. A 2012 report claimed they had observed thrust, but in 2014 they found it to have been an experimental error. A second, improved prototype did not produce any measured thrust. At the China Academy of Space Technology, Yue Chen filed several patent applications in 2016 describing various radio frequency (RF) resonant cavity thruster designs. These included a method for stacking several short resonant cavities to improve thrust, and a design with a cavity that was a semicylinder instead of a frustum. That December, Chen announced that CAST would conduct tests on a resonant cavity thruster in orbit, without specifying what design was used. In an interview on CCTV in September 2017, Chen showed some testing of a flat cylindrical device, corresponding to the patent describing stacked short cavities with internal diaphragms.