Jump to content

EmDrive

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by BookWormHR (talk | contribs) at 18:38, 20 November 2016 (→Mechanism and hypotheses: Added photon leakage subsection). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Template:Infobox controversial invention

Prototype Em drive built at NASA Eagleworks laboratory

A radio frequency (RF) resonant cavity thruster is a proposed type of electromagnetic thruster in which electromagnetic radiation is confined to a microwave cavity, and provides thrust to the cavity in a particular direction as the radiation reflects within the cavity.

Such a thruster would be a type of reactionless drive, providing thrust from electricity without consuming a propellant. This would apparently violate Newton's Third Law and the conservation of momentum,[1] leading most physicists and propulsion experts who look at such devices to dismiss them as impossible.[2][3] Despite this, inventors try to discover such drives, because if they existed they could support long voyages in space, where propellant is a primary limiting factor.[4]

RF resonant cavity thrusters in particular have been promoted by two inventors who say they have designed such devices: Roger Shawyer designed a thruster he called the EmDrive, and Guido Fetta designed a thruster he called the Cannae Drive.[5][6]

A few groups of physicists have tried to build and test their own resonant cavity thrusters, based on the designs published by Shawyer and Fetta. Juan Yang at Xi'an's Northwestern Polytechnical University (NWPU) built and tested three thrusters from 2008 to 2014. Initial observations of thrust[7] were later retracted after a measurement error was identified;[8] with an improved setup they did not measure any significant thrust.[8][9] Sonny White's group at NASA's Eagleworks laboratories, which tests unusual rocket designs, has built and tested versions of both the EmDrive and the Cannae drive. In 2014, they reported observing a small thrust,[10] close to their margin of error.

This concept for a thruster drew attention in the 2000s when a few popular science magazines wrote articles about it as an "impossible" drive.[11][12] There has been particular criticism of misleading claims in the US media[13] that the drive had been "validated" by NASA.[12]

History and context

Electromagnetic propulsion designs which operate on the principle of reaction mass have been around since the start of the 20th century. In the 1960s, extensive research was conducted on designs from ion thrusters that convert propellant to ions and accelerate and eject them; to plasma thrusters that eject plasma ions in a similar way using plasma currents. The plasma in a plasma thruster can be generated from an intense source of microwave or other radio-frequency (RF) energy and in combination with a resonant cavity, can be tuned to resonate at a particular frequency.[14]

A low-propellant space drive has long been a goal of space exploration, since the propellant is dead weight that must be lifted and accelerated with the ship all the way from launch until the moment it is used (see Tsiolkovsky rocket equation). Solar sails, gravity assists, and propulsion by beams from the ground are useful specifically because they allow a ship to gain speed without propellant. However, these techniques do not work in deep space. Shining a light out of the ship provides a small force from radiation pressure, i.e. using photons as a kind of propellant, but the force is far too weak (for a given amount of electrical power) to be useful in practice.

A true zero-propellant drive is widely believed to be impossible, but if it existed, it could potentially be used for travel in many environments including deep space. As a result such drives are a popular concept in science fiction, and their very improbability contributes to enthusiasm for exploring such designs.[4][5][6]

Controversy

The design of such thrusters and the theories that attempt to explain how they might work are all matters of controversy, particularly the claims that it is an example of a reactionless drive, in violation of conservation of momentum.[6][15]

The concept has been criticised by physicists including Eric W. Davis, at the Institute for Advanced Studies in Austin and Sean Carroll at the California Institute of Technology,[16] who have said that the thrust measured in the original Eagleworks publication is indicative of thermal effects. John C. Baez, a mathematical physicist at the University of California and Australian science fiction writer Greg Egan have also said that positive results are misinterpretations of experimental errors.[17] Since those criticisms were written, the significant positive results, primarily the work at Northwestern Polytechnic University, have indeed been identified as experimental errors.

The initial results claimed by Shawyer in selling the idea to potential investors, have never been replicated. Even the most optimistic replication yielded far less thrust than he initially claimed. Moreover, Shawyer repeatedly claimed that his successive models were getting better, and would soon be ready to use in space, none of which turned out to be the case. After a brief burst of publicity for these claims, the hyperbole contributed to general controversy around the possibility that such thrusters could work at all.

To the extent that there are theories that could explain thrust from such devices, the predicted thrusts are tiny for significant input energy, and the experiments designed so far have had many sources of noise. So even when respected labs have tried to experiment with such a thruster, the results have been difficult to evaluate or replicate.

Designs and prototypes

EmDrive

In 2001, Shawyer founded Satellite Propulsion Research Ltd, in order to work on the EmDrive. He thought he could produce a drive that 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.[6] In December 2002, he claimed a working prototype with a total thrust of about 0.02 newtons powered by an 850 W magnetron. The device could operate for only a few dozen seconds before the magnetron failed, due to overheating.[18]

Second device and New Scientist article

In October 2006, Shawyer conducted tests on a new water-cooled prototype and claimed increased thrust.[1] He planned to have the device ready to use in space by May 2009 and was considering making the resonant cavity a superconductor.[1]

New Scientist magazine[19] featured the EmDrive on the cover of the 8 September 2006 issue. The article portrayed the device as plausible and emphasized the arguments of those who held that point of view.

Science fiction author Greg Egan 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". In particular, Egan found himself "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 mathematical physicist John C. Baez and posted on his blog.[17][20]

Egan also recommended[17] that New Scientist publish a refutation penned by John P. Costella (a data scientist with a PhD in theoretical physics).[19][21] New Scientist editor Jeremy Webb responded to critics, stating,

"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."[11]

New Scientist also published a letter from the former technical director of EADS Astrium, who stated: "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",[22] and a letter from physicist Paul Friedlander, who stated

"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."[23]

Later work

In 2007, the UK Department of Trade and Industry granted SPR an ITAR export licence to Boeing in the US.[24] In December 2008, Shawyer was invited to The Pentagon to make a presentation on the EmDrive, then Boeing confirmed they wanted to licence the technology. The UK Ministry of Defence agreed to a technology transfer, and SPR designed, built and tested a Flight Thruster for use on a test satellite. According to Shawyer, the 10-month contract was completed by July 2010 and the Flight Thruster, giving 18 grams of thrust, transferred to Boeing. Afterwards, SPR never received a licence agreement and communication with Boeing stopped.[25] Questioned on that matter in 2012, a Boeing representative confirmed Boeing Phantom Works used to explore exotic forms of space propulsion including Shawyer's EmDrive some years ago, but such work has since ceased, claiming that "Phantom Works is not working with Mr. Shawyer,” and adding that the company is no longer pursuing this avenue.[5] No further details of Boeing's Flight Thruster have been made public.

In 2013 and 2014, Shawyer presented ideas for 'second-generation' EmDrive designs and applications, at the annual International Astronautical Congress. A paper based on his 2014 presentation was published in Acta Astronautica in 2015.[26] It describes a model for a superconducting resonant cavity and three models for thrusters with multiple cavities, with hypothetical applications for launching space probes.

In October 2016, a new UK patent application describing a new superconducting EmDrive was published,[27] followed by a first international version.[28] Shortly thereafter Shawyer unveiled the creation of Universal Propulsion Ltd., a new company aimed to develop and commercialise such thrusters, as a joint venture with Gilo Industries Group, a small UK aerospace company designing and selling paramotors and the Parajet Skycar.[25]

Cannae and other drives

The Cannae Drive (formerly Q-drive),[29] another engine designed to generate propulsion from a resonant cavity without propellant, is another implementation of this idea. Its cavity is also asymmetric, but is flatter than that of the EmDrive. It was designed by Fetta in 2006 and has been promoted within the US through his company, Cannae LLC, since 2011.[29][30][31][32][33] Shawyer has said the Cannae drive "operates along similar lines to EmDrive, except that its thrust is derived from a reduced reflection coefficient at one end plate," which he says would reduce its thrust.[34] In 2016, Fetta announced plans to eventually launch a cubesat satellite containing a version of the Cannae Drive, which they would run for 6 months to observe how it functions in space.[35]

Researchers working under Juan Yang (杨涓) at the Northwestern Polytechnical University (NWPU) in Xi'an developed their own prototype resonant cavity thruster in 2008, publishing a report in their university's journal on the theory behind such devices. In 2012-2014 they reported measuring net thrust in a series of preliminary tests, however in 2014 they found that this had been an experimental error introduced by a power cable. In a revised study with an improved model, they found that any actual thrust was too small for their setup to measure (less than 1mN for a 230W power source).[5][36][37]

Replication efforts

Three science labs have tried to build and test at least one such thruster: at NWPU, at the Dresden University of Technology, and at NASA's Eagleworks research group. There has been debate whether the experiments were successful in measuring thrust since the data was often dominated by noise. [citation needed]

Mechanism and hypotheses

There are no known physical mechanisms for such thrusters to work. They have been studied because two inventors claimed to have working models, however those models have not worked in public and those inventors have also no proposed physical mechanisms for their function. Various attempts have been made to explain theoretically why some experiments might conceivably detect thrust.

Device structure

All these devices use a magnetron to produce microwaves that are directed into a metallic, fully enclosed conically tapered high Q resonant cavity. They have a greater area at one end of the device and a dielectric resonator in front of the narrower end. They require an electrical power source to run the magnetron, but no actual propellant.

Hypotheses

Noise and experimental error

The simplest explanation is that any thrust detected is due to experimental error or noise. In all of the experiments set up, a very large amount of energy is going into generating a tiny amount of thrust. Even the smallest stray signal – for instance from thermal or magnetic effects – could produce what looks like a thrust of that size. These experiments require more shielding from their environment than any of the experiments as of 2015 were able to provide, as each of those experimenters has noted. The strongest early result, from Yang's group in Xian, was later reported to be caused by a large experimental error.[8]

Measurement error

A similar explanation is that imprecisions in measurement, variation in measurement, or publication bias, have led to occasional positive observations with no statistical significance.[16] For instance, those who have tried running such experiments have only written up in detail the experimental runs where they believe to have at least some positive result. This is often a factor with experiments that have large variation, small studies and sample sizes, and few replications.[38]

Radiation pressure

Shawyer claims that the drive is not reactionless, and instead that thrust is caused by a radiation pressure imbalance between the two faces of the cavity caused by the action of group velocity in different frames of reference within the framework of special relativity.[36] He has self-published non-peer-reviewed papers describing how he believes the drive works: "[t]his force difference is supported by inspection of the classical Lorentz force equation F = q(E + νB). (1) If ν is replaced with the group velocity νg of the electromagnetic wave, then equation 1 illustrates that if vg1 is greater than vg2, then Fg1 should be expected to be greater than Fg2." This statement makes two assumptions that Shawyer does not substantiate and that may explain the discrepancy between his predictions and those of conventional physics. For example he assumes that radiation pressure is the result of the Lorentz force acting on charged particles in the reflecting material. This is analyzed by Rothman and Boughn[39] who point out that the standard theory of radiation pressure is more complicated than this simplified analysis suggests.

Virtual plasma

Harold G. "Sonny" White, who investigates field propulsion at Eagleworks, NASA's Advanced Propulsion Physics Laboratory, speculated that such resonant cavities may operate by creating a virtual plasma toroid that could realize net thrust using magnetohydrodynamic forces acting upon quantum vacuum fluctuations.[40] Likewise, the paper describing the Eagleworks tests refer to a possible interaction with a so-called "quantum vacuum virtual plasma".[41]

This reference has been criticized by mathematical physicists John Baez and Sean M. Carroll because in the standard description of vacuum fluctuations, virtual particles do not behave as a plasma; furthermore, because the quantum vacuum has no "rest frame", there is nothing to push against, so it can't be used for propulsion.[20][42][43]

Quantized inertia

A paper in EPL by Mike McCulloch, a Lecturer in Geomatics at Plymouth University, claims that the EmDrive's thrust can be predicted using McCulloch's controversial theory of quantization of inertia (MiHsC).[44] McCulloch hypothesizes that inertia arises from an effect predicted by general relativity called Unruh radiation, that an accelerating object experiences black body radiation. Thus inertia is the pressure the Unruh radiation exerts on an accelerating body. At very small accelerations, Unruh wavelengths become so large they can no longer fit in the observable universe. When this happens, inertia is quantized. He claimed observational evidence for this in the form of the otherwise unexplained jumps in momentum observed in some spacecraft as they fly past Earth toward other planets.[45][46][47][48][49] While this model allows the device to create thrust without breaking Newton's third law, it assumes that Unruh radiation is real, and requires the speed of light to change within the microwave cavity. This change in the speed of light is contrary to the central tenet of special relativity.[50] Unlike other hypotheses used to explain the device, McCulloch's hypothesis is testable and McCulloch has suggested building a cavity where the length of the cavity is the same as the diameter of the small end, to cause the Unruh radiation to fit better in the small end, resulting in a reversal of thrust.[48]

Photon leakage

Scientists in Finland have proposed a possible explanation of this phenomenon involving the propagation of microwave photons leaking from the closed metal cavity and thereby producing an exhaust momentum, satisfying the classical action-reaction principle.[51] This explanation relies on the wave-particle duality of electromagnetic radiation, postulating that the stochastic phases of the microwaves will (with some probability) result in destructive interference between microwaves which cancel their electromagnetic fields but allow continued propagation of the microwave photon pairs, generating net thrust consistent with the impulse-momentum theorem depending on the asymmetric shape of the cavity. This mechanism is controversial because the explanation is predicated on an understanding of vacuum energy that is inconsistent with the prevailing framework of quantum mechanics.

True reactionless drive

This would be the most unlikely result of all. These are considered impossible for many reasons; most reactionless drives are a form of perpetual motion machine. If thrust were produced without expelling momentum from the system in the opposite direction, the lack of momentum expulsion would make the device not only propellant-free, but a "reactionless" drive in the sense that it violates Newton's Third Law and the conservation of momentum. Any such drive would require a new undiscovered physical law, which somehow had not been observed under any other conditions. The experimenters listed above do not believe the drives are reactionless, and are trying to test one of the previous hypotheses.

Testing and replication claims

Tests by the inventors

In 2004, Roger Shawyer reported seven independent positive reviews from experts at BAE Systems, EADS Astrium, Siemens and the IEE,[52] however these are disputed. In a letter to New Scientist, the then-technical director of EADS Astrium (Shawyer's former employer) denied this, stating

"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."[22]

In 2011, Fetta tested a superconducting version of the Cannae drive. The RF resonant cavity was suspended inside a liquid helium-filled dewar. The weight of the cavity was monitored by load cells. Fetta theorized that when the device was activated and produced upward thrust, the load cells would detect the thrust as change in weight. When the drive was energized by sending 10.5 watt power pulses of RF power into the resonant cavity, there was, as predicted, a reduction in compressive force on the load cells consistent with thrust of 8-10 mN.

None of these results have been published in the scientific literature, or replicated by independent researchers. They have been posted on their inventors' websites.[53]

In 2015, Shawyer published an article in Acta Astronautica, summarising existing tests on the EmDrive. Of seven tests, four produced a measured force in the intended direction and three produced thrust in the opposite direction. Furthermore, in one test, thrust could be produced in either direction by varying the spring constants in the measuring apparatus.[54]

Northwestern Polytechnical University

In 2008, a team of Chinese researchers led by Juan Yang (杨涓), professor of propulsion theory and engineering of aeronautics and astronautics at Northwestern Polytechnical University (NWPU) in Xi'an, Shaanxi, China, claimed to have developed a valid electro-magnetic theory behind a microwave resonant cavity thruster.[7][55] A demonstration version of the drive was built and tested with different cavity shapes and at higher power levels in 2010. Using an aerospace engine test stand usually used to precisely test spacecraft engines like ion drives,[6][36][37] they reported a maximum thrust of 720 mN at 2,500 W of input power.[37] Yang noted that her results were tentative, and said she "[was] not able to discuss her work until more results are published".[6] This positive result was over 100x more thrust per input power than any other experiment, and inspired other groups to try to replicate their work. However in a followup paper, Yang could not reproduce the 2010 observation and suggested it was due to experimental error.[8]

In 2016, Yang's team published a paper, in which they refined their experimental setup, using a three-wire torsion pendulum to measure thrust. They tested two different power setups. In one trial, the power system was outside the cavity: in this case, they observed a "thrust" of 8-10 mN. In a second trial, the power system was within the cavity, and they measured no such thrust. Instead they observed an insignificant thrust below their noise threshold of 3 mN, fluctuating between ±0.7mN with a measurement uncertainty of 80%. They concluded that they were unable to measure significant thrust; that "thrust" measured when using external power sources (such as in their 2010 experiment) could be noise; and that it was important to use self-contained power systems for these experiments.[8]

NASA/JSC Advanced Propulsion Physics Laboratory

White's team at the NASA/JSC Advanced Propulsion Physics Laboratory, also known as "Eagleworks", is devoted to studying advanced propulsion systems that they hope to develop using quantum vacuum and spacetime engineering.[56] The group has investigated a wide range of untested and fringe proposals, including RF resonant cavity thrusters and related concepts. In November 2016, A peer-reviewed paper summarising Eagleworks test campaign was published by the Journal of Propulsion and Power.[57][58]

EmDrive

In 2011, the group built an RF resonant cavity thruster prototype for testing. In July 2014, the group reported tentative positive results for evaluating an RF resonant tapered cavity similar to the EmDrive.[41] Testing was performed using a low-thrust torsion pendulum capable of detecting force at the micronewton level within a sealed but not evacuated vacuum chamber (the RF power amplifier used an electrolytic capacitor not capable of operating in a hard vacuum).[41] The experimenters recorded directional thrust immediately upon application of power.

NASA's first tests of this tapered RF resonant cavity were conducted at very low power (2% of Shawyer's 2002 experiment), but a net mean thrust over five runs was measured at 91.2 µN at 17 W of input power. A net peak thrust was recorded at 116 µN (about 0.0004 ounces, or approximately the same weight as a grain of rice) at the same power level.[41] The experiment was criticized for among other things not having been conducted in a vacuum, to eliminate thermal air currents.

In early 2015, Paul March from Eagleworks made new results public, claiming positive experimental force measurements with a torsional pendulum in a hard vacuum: about 50 µN with 50 W of input power at 5.0×10−6 torr and new null-thrust tests.[59] The new RF power amplifiers were said to be made for hard vacuum, but still fail rapidly due to internal corona discharges. With not enough funding to replace or upgrade them, measurements are still scarce and need improvement before a new report can be published.[60] In Eagleworks' 2016 peer-reviewed paper, the team declares the anomalous thrust remains in a hard vacuum, while any spurious causes investigated (thermal expansion, air currents, outgassing, RF leakage, vibrations and RF, magnetic or electrostatic interactions) are ruled out.[58]

Glenn Research Center offered to replicate the experiment in a hard vacuum if Eagleworks manages to reach 100 µN of thrust, because the GRC thrust stand cannot measure forces lower than 50 µN.[59]

Eagleworks later announced a plan to upgrade their equipment to higher power levels, use vacuum-capable RF amplifiers with power ranges of up to 125 W and to design a new tapered cavity analytically determined to be in the 0.1 N/kW range. The test article will be subjected to independent verification and validation at Glenn Research Center, the Jet Propulsion Laboratory and the Johns Hopkins University Applied Physics Laboratory.[41]

Cannae drive

The same NASA test campaign evaluated a Cannae drive.[41] They tested two versions: one device with radial slots engraved along the bottom rim of the resonant cavity interior, as required by Fetta's theory to produce thrust;[30] and a "null" test article lacking those radial slots. Both drives were equipped with an internal dielectric.[41] The null test device was not intended to be the experimental control. The control device was a third test article involving an RF load but without the resonant cavity interior. Like the EmDrive tests, the Cannae drive tests took place at atmospheric pressure, not in a vacuum.

About the same net thrust was reported for both the device with radial slots and the null test device without slots. The experimental control without a resonant cavity interior measured zero thrust, as expected. Some considered the positive result for the non-slotted device a possible flaw in the experiment, as the null test device had been expected to produce less or no thrust based upon Fetta's theory of how thrust was produced by the device.[20][61][62] In the complete paper, however, Eagleworks concluded that the test results proved that "thrust production was not dependent upon slotting".[41]

Dresden University of Technology

In July 2015 an aerospace research group at the Dresden University of Technology (TUD) under Martin Tajmar reported results for an evaluation of an RF resonant tapered cavity similar to the EmDrive.[63] Testing was performed first on a knife-edge beam balance capable of detecting force at the micronewton level, on top of an anti-vibration granite table at ambient air pressure; then on a torsion pendulum with a force resolution of 0.1 mN, inside a vacuum chamber at ambient air pressure and in a hard vacuum at 4×10−6 mbar (3×10−6 torr).

They used a conventional 2.45 GHz 700 W oven magnetron, and a small cavity with a low Q factor (20 in vacuum tests). They observed small positive thrusts in the positive direction and negative thrusts in the negative direction, of about 20 µN in a hard vacuum. However when they rotated the cavity upwards as a "null" configuration, they observed an anomalous thrust of hundreds of µN, significantly larger than the observed results. This indicated a strong source of noise which they could not identify. This led them to conclude that they could not confirm or refute claims about such a thruster. They plan future experiments with better magnetic shielding, other vacuum tests and improved cavities with higher Q factors to increase thrust.

Eric W. Davis, a physicist at the Institute for Advanced Studies at Austin, noted "The experiment is quite detailed but no theoretical account for momentum violation is given by Tajmar, which will cause peer reviews and technical journal editors to reject his paper should it be submitted to any of the peer-review physics and aerospace journals."[16]

The first Peer-reviewed EM Drive paper

The first peer-reviewed paper titled "Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum" has been published online as an open access 'article in advance' in the American Institute of Aeronautics and Astronautics (AIAA)’s Journal of Propulsion and Power. It'll appear in the December print edition.

Its claim is that the drive did produce consistently 1.2 ± 0.1 mN/kW The team made it clear as they were not attempting to optimise the performance it's likely that the EM Drive could get a lot more efficient still.[64]

The report states that further testing will be required to rule out other possible causes, e.g. center of gravity (CG) shifts and thermal expansion. [65]

See also

3

References

  1. ^ a b c Tom Shelley (14 May 2007). "No-propellant drive prepares for space and beyond". Eureka Magazine. Retrieved 4 May 2015.
  2. ^ Thomson, Steven (9 August 2015). "Here's why scientists haven't invented an impossible space engine". Ars Technica. Retrieved 1 September 2016.
  3. ^ Brian Koberlein (21 April 2016). "The Theoretical Model For This Impossible Space Drive Doesn't Prove Anything". Forbes. Retrieved 6 September 2016.
  4. ^ a b Hambling, David (29 October 2009). "'Impossible' Device Could Propel Flying Cars, Stealth Missiles". WIred. Wired.
  5. ^ a b c d Hambling, David (5 November 2012). "Propellentless Space Propulsion Research Continues". Aviation Week & Space Technology.
  6. ^ a b c d e f Hambling, David (6 February 2013). "EmDrive: China's radical new space drive". Wired UK. Wired UK.
  7. ^ a b Hambling, David (24 September 2008). "Chinese Say They're Building 'Impossible' Space Drive". Wired. Wired.
  8. ^ a b c d e Yang, Juan; Liu, Xian-chuang; Wang, Yu-quan; Tang, Ming-jie; Luo, Li-tao; Jin, Yi-zhou; Ning, Zhong-xi (February 2016). "Thrust Measurement of an Independent Microwave Thruster Propulsion Device with Three-Wire Torsion Pendulum Thrust Measurement System". Journal of Propulsion Technology (in Chinese). 37 (2): 362–371.
  9. ^ "EM Drive Developments, NASA spaceflight forums, discussion of Yang's 2016 paper". forum.nasaspaceflight.com. Retrieved 14 September 2016.
  10. ^ "NASA Downplays 'Impossible' EM Drive Space Engine". Retrieved 14 September 2016.
  11. ^ a b Webb, Jeremy (3 October 2006). "Emdrive on trial". New Scientist Publisher's blog.
  12. ^ a b Powell, Corey S. (6 August 2014). "Did NASA Validate an "Impossible" Space Drive? In a Word, No". Discover magazine. Retrieved 16 February 2016.
  13. ^ David Hambling (31 July 2014). "Nasa validates 'impossible' space drive". Wired. Retrieved 6 September 2016.
  14. ^ Balaam, Philip; Micci, Michael M. (1995). "Investigation of stabilized resonant cavity microwave plasmas for propulsion". Journal of Propulsion and Power. 11 (5): 1021–1027. doi:10.2514/3.23932. ISSN 0748-4658.
  15. ^ Tucker, Bill (6 December 2015). "The Power Of The Force; The Curious Case Of The EmDrive". Retrieved 20 February 2016.
  16. ^ a b c Dvorsky, George (28 July 2015). "No, German Scientists Have Not Confirmed the "Impossible" EMDrive". io9. Gawker Media.
  17. ^ a b c Egan, Greg (19 September 2006). Baez, John C. (ed.). "A Plea to Save New Scientist". The n-Category Café (a group blog on math, physics and philosophy).
  18. ^ "Roger SHAWYER -- EM Space Drive -- Articles & Patent".
  19. ^ a b Shawyer, Roger (September 2006). "A Theory of Microwave Propulsion for Spacecraft (Theory paper v.9.3)" (PDF). New Scientist.
  20. ^ a b c Powell, Corey S. (6 August 2014). "Did NASA Validate an "Impossible" Space Drive? In a Word, No". Discover. Retrieved 6 August 2014. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  21. ^ Costella, John P. (2006). "Why Shawyer's 'electromagnetic relativity drive' is a fraud" (PDF). John Costella’s home page.
  22. ^ a b Alvin Wilby. "Emdrive? No thanks". New Scientist.
  23. ^ Paul Friedlander. "Emdrive on trial". New Scientist.
  24. ^ United Kingdom Department of Trade and Industry End User Undertaking
  25. ^ a b Mary-Ann Russon (14 October 2016). "EmDrive exclusive: Roger Shawyer confirms MoD and DoD interested in controversial space propulsion tech". International Business Times.
  26. ^ Shawyer, Roger (1 November 2015). "Second generation EmDrive propulsion applied to SSTO launcher and interstellar probe". Acta Astronautica. 116: 166–174. doi:10.1016/j.actaastro.2015.07.002.
  27. ^ Mary-Ann Russon (12 October 2016). "EmDrive: Roger Shawyer is patenting a new design for next-gen superconducting thruster". International Business Times.
  28. ^ WO application 2016162676, SHAWYER, Roger John & CARDOZO, Gilo, "Superconducting Microwave Radiation Thruster", published 2016-10-16, assigned to Satellite Propulsion Research Ltd. 
  29. ^ a b WO application 2007089284, Fetta, Guido Paul, "Resonating cavity propulsion system", published 2007-11-15, assigned to Fetta, Guido Paul 
  30. ^ a b "Cannae Drive". Cannae LLC website. Retrieved 31 July 2014.
  31. ^ US application 2014013724, Fetta, Guido P., "Electromagnetic thruster", published 2014-01-16, assigned to Cannae LLC 
  32. ^ Fetta, Guido P. (30 August 2014). Numerical and Experimental Results for a Novel Propulsion Technology Requiring no On-Board Propellant. 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference. American Institute of Aeronautics and Astronautics. doi:10.2514/6.2014-3853. Retrieved 31 July 2014.
  33. ^ WO application 2016004044, Fetta, Guido P., "Electromagnetic thrusting system", published 2016-01-07, assigned to Cannae LLC 
  34. ^ Hambling, David (31 July 2014). "Nasa validates 'impossible' space drive". Wired UK. Wired UK. Retrieved 31 July 2014.
  35. ^ "The Impossible Propulsion Drive Is Heading to Space". 2 September 2016. Retrieved 14 September 2016.
  36. ^ a b c Yang, Juan; Wang, Yu-Quan; Ma, Yan-Jie; Li, Peng-Fei; Yang, Le; Wang, Yang; He, Guo-Qiang (May 2013). "Prediction and experimental measurement of the electromagnetic thrust generated by a microwave thruster system" (PDF). Chinese Physics B. 22 (5). IOP Publishing: 050301. Bibcode:2013ChPhB..22e0301Y. doi:10.1088/1674-1056/22/5/050301.
  37. ^ a b c Shi, Feng; Yang, Juan; Tang, Ming-Jie; Luo, Li-Tao; Wang, Yu-Quan (September 2014). "Resonance experiment on a microwave resonator system" (PDF). Chinese Physics B (in Chinese). 63 (15). Chinese Physical Society: 154103. doi:10.7498/aps.63.154103.
  38. ^ False Positives, p-Hacking, Stastical Power and Evidential Value. Leif Nelson, 2015.
  39. ^ Rothman, Tony; Boughn, Stephen. "The Lorentz force and the radiation pressure of light". arXiv:0807.1310.
  40. ^ Harold "Sonny" White (2013). "Eagleworks Laboratories WARP FIELD PHYSICS" (PDF). NASA Technical Reports Server (NTRS). NASA.
  41. ^ a b c d e f g h Brady, David A.; White, Harold G.; March, Paul; Lawrence, James T.; Davies, Franck J. (30 July 2014). Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum (PDF). 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference. American Institute of Aeronautics and Astronautics. doi:10.2514/6.2014-4029. Retrieved 31 July 2014. {{cite conference}}: Unknown parameter |laydate= ignored (help); Unknown parameter |laysource= ignored (help); Unknown parameter |layurl= ignored (help)
  42. ^ Baez, John. "The incredible shrinking force". Google Plus. Retrieved 6 August 2014.
  43. ^ Gonzalez, Robert T. "Don't Get Too Excited About NASA's New Miracle Engine". io9. Gawker Media. Retrieved 6 August 2014. The business about "quantum vacuum virtual plasma" (the physics of which they "won't address" in this paper) is complete bullshit. There is a quantum vacuum, but it's nothing like a plasma.
  44. ^ M.E. McCulloch (2015), "Testing quantised inertia on the emdrive", EPL, 111 (6), arXiv:1604.03449, Bibcode:2015EL....11160005M, doi:10.1209/0295-5075/111/60005
  45. ^ Knight, Will (20 April 2016). "The Curious Link Between the Fly-By Anomaly and the "Impossible" EmDrive Thruster". MIT Technology Review. Retrieved 21 April 2016.
  46. ^ "Interstellar EmDrive gets boost from new theory of inertia".
  47. ^ "A new theory of inertia could explain the EM Drive's anomalous thrust".
  48. ^ a b "EmDrive: the mysterious propulsion technology that seems to defy physics".
  49. ^ Russon, Mary-Ann (26 April 2016). "EmDrive: British scientist's 'new physics' theory accidentally proves controversial space propulsion works". International Business Times UK.
  50. ^ Koberlein, Brian (21 April 2016). "The Theoretical Model For This Impossible Space Drive Doesn't Prove Anything". Retrieved 24 April 2016.
  51. ^ Grahn, Patrick (2016). "On the exhaust of electromagnetic drive" (PDF).
  52. ^ Fisher, Richard (5 November 2004). "Defying gravity: UK team claims engine based on microwaves could revolutionise spacecraft propulsion". The Engineer. 293 (7663). London: 8.
  53. ^ Page is no longer available, but an archived version as of 2 November 2012 is available at archive.org: www.cannae.com/proof-of-concept/experimental-results (retrieved 11 February 2015)
  54. ^ Shawyer, Roger (1 November 2015). "Second generation EmDrive propulsion applied to SSTO launcher and interstellar probe". Acta Astronautica. 116: 166–174. doi:10.1016/j.actaastro.2015.07.002.
  55. ^ ZHU, Yu; YANG, Juan; MA, Nan (September 2008). "The Performance Analysis of Microwave Thrust Without Propellant Based On The Quantum Theory". Journal of Astronautics (in Chinese). 29 (5): 1612–1615.
  56. ^ White, Harold; March, Paul; Nehemiah, Williams; O'Neill, William (5 December 2011). Eagleworks Laboratories: Advanced Propulsion Physics Research. NASA Technical Reports Server (NTRS) (Technical report). NASA. JSC-CN-25207.
  57. ^ Prisco, Giulio (18 November 2016). "Final Nasa Eagleworks paper confirms promising EmDrive results, proposes theoretical model". Hacked.
  58. ^ a b White, Harold; March, Paul; Lawrence, James; Vera, Jerry; Sylvester, Andre; Brady, David; Bailey, Paul (17 November 2016). "Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum" (PDF). Journal of Propulsion and Power. doi:10.2514/1.B3612.
  59. ^ a b Wang, Brian (6 February 2015). "Update on EMDrive work at NASA Eagleworks". NextBigFuture.
  60. ^ Wang, Brian (7 February 2015). "NASA Emdrive experiments have force measurements while the device is in a hard vacuum". NextBigFuture.
  61. ^ Timmer, John (1 August 2014). "Don't buy stock in impossible space drives just yet". Ars Technica. Ars Technica. Retrieved 2 August 2014.
  62. ^ Nelsen, Eleanor (31 July 2014). "Improbable Thruster Seems to Work by Violating Known Laws of Physics". Nova. PBS. Retrieved 1 August 2014.
  63. ^ Tajmar, Martin; Fiedler, Georg (July 2015). Direct Thrust Measurements of an EM Drive and Evaluation of Possible Side-Effects (PDF). 51st AIAA/SAE/ASEE Joint Propulsion Conference. American Institute of Aeronautics and Astronautics. doi:10.2514/6.2015-4083. Retrieved 26 July 2015.
  64. ^ http://arc.aiaa.org/doi/10.2514/1.B36120
  65. ^ http://phys.org/news/2016-11-physics-violated-em-leaked-nasa.html
Retrieved from "https://en.wikipedia.org/enwiki/w/index.php?title=EmDrive&oldid=750592204"