EmDrive
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| − | The '''EmDrive''' is an experimental spacecraft propulsion device first invented and developed by Roger Shawyer. The design and concept is currently under investigation by various independent parties. The inventor claims that the device (engine) works by saturating a resonant cavity with microwave radiation; the radiation exerts pressure on the walls of the cavity, and due to "relativistic effects," the cavity (shaped like a truncated cone) will experience a larger force against the large end than the small end, due to the group velocity of the waves changing as the local diameter of the cavity varies. This would create a net thrust from the large end toward the small end of the device. <ref>The calculations in question are found [http://www.newscientist.com/data/images/ns/av/shawyertheory.pdf here]</ref> The inventor claims that this will cause the engine to be propelled through space. Just a small force if continuously applied over a period of time could propel a spacecraft to great speeds only limited by resistance forces, if it encounters any. Although different research groups who have tested similar devices have observed positive results, all seem to have their own hypothesis concerning how these microwave resonance devices might work. <ref>Wired.uk [http://www.wired.co.uk/news/archive/2014-08/07/10-qs-about-nasa-impossible-drive/ article] about the NASA experiments</ref> - Shawyer's "theory" is based on Special Relativity, the Chinese hypothesis is based on Electro-magnetism and Maxwell's Law, and NASA is talking about the microwaves pushing against "quantum vacuum virtual particles" in the resonance chamber. On the other hand, Dr. Fernando Minotti, a researcher at CONICET, in a 2013 paper titled "Scalar-tensor theories and asymmetric resonant cavities" noted that the alleged thrust produced by the Emdrive may be explained by certain scalar tensor theories of gravity. | + | The '''EmDrive''' is an experimental spacecraft propulsion device first invented and developed by Roger Shawyer. The design and concept is currently under investigation by various independent parties. The inventor claims that the device (engine) works by saturating a resonant cavity with microwave radiation; the radiation exerts pressure on the walls of the cavity, and due to "relativistic effects," the cavity (shaped like a truncated cone) will experience a larger force against the large end than the small end, due to the group velocity of the waves changing as the local diameter of the cavity varies. This would create a net thrust from the large end toward the small end of the device. <ref>The calculations in question are found [http://www.newscientist.com/data/images/ns/av/shawyertheory.pdf here]</ref> The inventor claims that this will cause the engine to be propelled through space. Just a small force if continuously applied over a period of time could propel a spacecraft to great speeds only limited by resistance forces, if it encounters any. Although different research groups who have tested similar devices have observed positive results, all seem to have their own hypothesis concerning how these microwave resonance devices might work. <ref>Wired.uk [http://www.wired.co.uk/news/archive/2014-08/07/10-qs-about-nasa-impossible-drive/ article] about the NASA experiments</ref> - Shawyer's "theory" is based on Special Relativity, the Chinese hypothesis is based on Electro-magnetism and Maxwell's Law, and NASA is talking about the microwaves pushing against "quantum vacuum virtual particles" in the resonance chamber. On the other hand, Dr. Fernando Minotti, a researcher at CONICET, in a 2013 paper titled "Scalar-tensor theories and asymmetric resonant cavities" noted that the alleged thrust produced by the Emdrive may be explained by certain scalar tensor theories of gravity. Also, Dr. Michael McCulloch in a paper titled "Can the Emdrive Be Explained by Quantised Inertia?" noted that the thrust produced by the EmDrive may be explained by Unruh radiation which causes the photons in the wide end of the cavity to have greater inertial mass that the photons in the narrow end, causing the cavity to exhibit thrust towards the narrow end. |
Shawyer also claims that the device (engine) is not reactionless and does not violate any laws of physics, even though it appears to do so. Specifically, if it is a "reactionless" drive (as it appears to be), it would violate the conservation of momentum; as every action has an equal, but opposite reaction. To propel a craft normally ''requires'' something to shoot off in the other direction, a fuel of some kind, which the Emdrive does not use. The device also has no moving parts. Several prominent physicists have said that the concept is impossible. <ref>{{wayback|http://www.assassinationscience.com/johncostella/shawyerfraud.pdf}}</ref> A PhD physicist John Costella, in his related paper explained why, but that claim didn't stop China from building a better functional prototype than Shawyer had tested. | Shawyer also claims that the device (engine) is not reactionless and does not violate any laws of physics, even though it appears to do so. Specifically, if it is a "reactionless" drive (as it appears to be), it would violate the conservation of momentum; as every action has an equal, but opposite reaction. To propel a craft normally ''requires'' something to shoot off in the other direction, a fuel of some kind, which the Emdrive does not use. The device also has no moving parts. Several prominent physicists have said that the concept is impossible. <ref>{{wayback|http://www.assassinationscience.com/johncostella/shawyerfraud.pdf}}</ref> A PhD physicist John Costella, in his related paper explained why, but that claim didn't stop China from building a better functional prototype than Shawyer had tested. | ||
Revision as of 19:55, 15 January 2015
The EmDrive is an experimental spacecraft propulsion device first invented and developed by Roger Shawyer. The design and concept is currently under investigation by various independent parties. The inventor claims that the device (engine) works by saturating a resonant cavity with microwave radiation; the radiation exerts pressure on the walls of the cavity, and due to "relativistic effects," the cavity (shaped like a truncated cone) will experience a larger force against the large end than the small end, due to the group velocity of the waves changing as the local diameter of the cavity varies. This would create a net thrust from the large end toward the small end of the device. [1] The inventor claims that this will cause the engine to be propelled through space. Just a small force if continuously applied over a period of time could propel a spacecraft to great speeds only limited by resistance forces, if it encounters any. Although different research groups who have tested similar devices have observed positive results, all seem to have their own hypothesis concerning how these microwave resonance devices might work. [2] - Shawyer's "theory" is based on Special Relativity, the Chinese hypothesis is based on Electro-magnetism and Maxwell's Law, and NASA is talking about the microwaves pushing against "quantum vacuum virtual particles" in the resonance chamber. On the other hand, Dr. Fernando Minotti, a researcher at CONICET, in a 2013 paper titled "Scalar-tensor theories and asymmetric resonant cavities" noted that the alleged thrust produced by the Emdrive may be explained by certain scalar tensor theories of gravity. Also, Dr. Michael McCulloch in a paper titled "Can the Emdrive Be Explained by Quantised Inertia?" noted that the thrust produced by the EmDrive may be explained by Unruh radiation which causes the photons in the wide end of the cavity to have greater inertial mass that the photons in the narrow end, causing the cavity to exhibit thrust towards the narrow end.
Shawyer also claims that the device (engine) is not reactionless and does not violate any laws of physics, even though it appears to do so. Specifically, if it is a "reactionless" drive (as it appears to be), it would violate the conservation of momentum; as every action has an equal, but opposite reaction. To propel a craft normally requires something to shoot off in the other direction, a fuel of some kind, which the Emdrive does not use. The device also has no moving parts. Several prominent physicists have said that the concept is impossible. [3] A PhD physicist John Costella, in his related paper explained why, but that claim didn't stop China from building a better functional prototype than Shawyer had tested.
Chinese researchers from the Northwestern Polytechnical University led by Yang Juan claimed to have verified the theory behind EmDrive independently in 2008[4] and constructed a kilowatt-capable device in 2010[5] that produced 750 mN of measured thrust given 2500 W of input power.
New Scientist wrote a rather favourable article on it in 2006, although after complaints they later made a note on the New Scientist blog that they should have more thoroughly covered the criticism of the drive.[6]
There is a video supposedly showing it in action.
In July 2014, a NASA team at the Advanced Propulsion Physics Laboratory under the guidance of physicist Harold G. White investigated the EmDrive[7]. The NASA experiments observed an average output of 91.2 µN at 17 W of input power over five runs, with a net peak thrust of 116 µN. Note that NASA's related paper was careful not to discuss details regarding the device's theoretical principle of operation, for good reason: Nobody knows for sure how it works, or at least there is no consensus agreement concerning how it might work.
On a related note, the same NASA team investigated a similar device called the Cannae Drive, which was also shown to produce thrust - again, it's principle of operation is similar to Emdrive, but somewhat less efficient according to Shawyer. The inventor of Cannae Drive, Guido G. Fetta, postulated that the drive produced thrust partly via radial slots engraved along the bottom rim of the resonant cavity interior. However, the NASA team proved this idea false by testing a "null" drive that had no slots along the bottom. Both drives produced about the same amount of thrust indicating that slotting did not effect the thrust. A third control device was also tested with an RF load but without using a resonant cavity, which resulted in no thrust as expected.
NASA plans to upgrade their equipment to higher power levels, use vacuum-capable RF amplifiers with power ranges of up to 125 W, and design a new tapered cavity analytically expected to produce thrust in the 0.1 N/kW range. Then, the test article will be shipped to other laboratories for independent verification and continued evaluations of the technology, at Glenn Research Center, the Jet Propulsion Laboratory and the Johns Hopkins University Applied Physics Laboratory.
Footnotes
- ↑ The calculations in question are found here
- ↑ Wired.uk article about the NASA experiments
- ↑ Archive copy at the Wayback Machine
- ↑ Chinese EmDrive
- ↑ Chinese researchpaper
- ↑ New Scientist - Emdrive on trial
- ↑ [1] Anomalous Thrust Production from a low-power RF Test Device, similar to Emdrive, which measured positive results on a Low-Thrust Torsion Pendulum