RF resonant cavity thruster

RF resonant cavity thruster
Controversial invention
Inventor Roger Shawyer (EmDrive), Guido Fetta (Cannae Drive)
Theory violation Conservation of momentum, Newton's Third Law
Prototype resonant cavity thruster built at NASA Eagleworks, 2014

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.

This would be a type of reactionless drive, providing thrust from electricity without consuming a propellant. This appears to violate well-established laws of physics, such as the conservation of momentum;[1] therefore most scientists believe such thrusters to be impossible. Many physicists have labeled them as "pseudoscience".[1][2] Despite this, inventors try to discover such drives, because if they exist they could support long voyages in space, where propellant is a primary limiting factor.[3]

Roger Shawyer published a design with a tapered conical cavity, which he called the EmDrive. Guido Fetta later published a design with a pillbox cavity, which he called the Cannae Drive.[4][5] A few groups of physicists have tried to build and test their own thrusters, based on the designs published by Shawyer and Fetta. Juan Yang at Xi'an's Northwestern Polytechnical University (NWPU) initially reported thrust,[6] but retracted their claims in 2016 after a measurement error was identified and an improved setup measured no significant thrust.[7][8] Harold White's group at NASA's Eagleworks laboratories, which tests unusual rocket designs, has built and tested versions of these designs since 2011. In 2016, they observed thrust from a model they built, with a thrust-to-power ratio of roughly 1 mN/kW, which they wrote up in the Journal of Propulsion and Power.[9]

This concept for a thruster drew attention in the 2000s when a few popular science magazines wrote articles about it as an "impossible" drive.[10][11] There was particular criticism of misleading claims in the media[12] that the drive had been "validated" by NASA following their reports of anomalous thrust in 2014.[11]

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.[13]

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.[3][4][5]

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.[5][14]

John C. Baez, a mathematical physicist at the University of California, and Australian science fiction writer Greg Egan said that as of 2006 the positive results reported by Shawyer were likely misinterpretations of experimental errors.[15]

Physicists Eric W. Davis at the Institute for Advanced Studies in Austin, and Sean Carroll at the California Institute of Technology,[16] have said in 2015 that the thrust measured in both the Dresden University experiments and in earlier Eagleworks publications were indicative of thermal effect errors.

White's 2014 conference paper suggested that resonant cavity thrusters could work by transferring momentum to the "quantum vacuum virtual plasma".[17] Baez and Carroll criticized this explanation, because in the standard description of vacuum fluctuations, virtual particles do not behave as a plasma; Carroll also noted that the quantum vacuum has no "rest frame", providing nothing to push against, so it can't be used for propulsion.[18][19]

White's 2016 peer-reviewed paper[9] invoked an idea called pilot-wave theory to suggest how the quantum vacuum could be used to generate thrust, however the paper noted that such interpretations are “not the dominant view of physics today.”[1]

Designs and prototypes

EmDrive

In 2001, Shawyer founded Satellite Propulsion Research Ltd, in order to work on the EmDrive, a drive that 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.[5] In December 2002, he described 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.[20]

Second device and New Scientist article

In October 2006, Shawyer conducted tests on a new water-cooled prototype and said that it had increased thrust.[21] He planned to have the device ready to use in space by May 2009 and was considering making the resonant cavity a superconductor.[21]

New Scientist magazine[22] 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 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 mathematical physicist John C. Baez and posted on his blog.[15][18]

Egan also recommended[15] that New Scientist publish a refutation penned by John P. Costella (a data scientist with a PhD in theoretical physics).[22][23] 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."[10]

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",[24] 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."[25]

Later work

In 2007, the UK Department of Trade and Industry granted SPR an ITAR export licence to Boeing in the US.[26] 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.[27] 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, stating that "Phantom Works is not working with Mr. Shawyer,” and adding that the company is no longer pursuing this avenue.[4] 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.[28] 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 UK patent application describing a new superconducting EmDrive was published,[29] followed by a first international version.[30] 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.[27]

Cannae and other drives

The Cannae Drive (formerly Q-drive),[31] 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.[31][32][33][34][35] 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.[36] 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.[37]

Researchers working under Yang 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 reported that this had been an experimental error introduced by a power cable. In a revised study with an improved model, they reported that any actual thrust was too small for their setup to measure (less than 1 mN for a 230W power source).[4][38][39]

Device structure

All these devices use microwaves, produced by high power vacuum tubes (like a magnetron or a TWTA) or solid-state field-effect transistor RF generators, 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, for some versions, a dielectric resonator added in front of the narrower end. They require an electrical power source to run the microwave generator, but no actual propellant.

Simulated transverse magnetic modes TM20, (red high, blue low) at the wide and narrow ends of a metallic taperedcavity differ from each other creating an anisotropic interference of electromagnetic waves[40]

The electromagnetic waves associated with the geometry of a truncated cone are very complex, creating a nonlinear anisotropic electromagnetic vacuum. Unlike the geometry of a cylinder, there are no analytical solutions for the resonant modes of a truncated cone and this geometry intrinsically does not suffer from mode degeneration. A sharp distinction between the propagating and evanescent electromagnetic waves can not be achieved and as a result a non-zero power flow runs through truncated cone focusing a portion of energy near the apex. There is no well-defined cutoff wavelength but rather a cutoff radius. Due to the absence of sharp cut off wavelengths the interior of the truncated cone can support inhomogeneous field amplitudes.[41][42][43][44] There are many other situations where the electromagnetic vacuum is believed to be anisotropic for example, doped active centers in anisotropic glasses,[45][46][47] emission of active atoms in a waveguide,[48] spontaneous emission from atoms adsorbed on metallic or dielectric surfaces,[49] emission in a spatially dispersive medium[50] which allows the possibility of longitudinal electromagnetic fields (classically not found in free space but in substances like plasmas) and emission between two conducting plates,[51][52][53] which is a problem of great interest due to the Casimir effect.[54][55][56]

Hypotheses

No mainstream scientific theory explains why such devices should produce thrust, however various attempts have been made to explain reported thrust measurements by the inventors and replicators.

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.[7]

The 2016 Eagleworks paper discusses nine possible sources of experimental error.[1][57] For example, one possible source of error comes from the thermal expansion of the thruster's heat sink, which is offset from the device’s center of gravity; as it expands, it could cause the resonant cavity to move, producing erroneous results.[57]

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]

Radiation pressure

Shawyer describes the drive as not being 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.[38] 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[58] who point out that the standard theory of radiation pressure is more complicated than this simplified analysis suggests.

Vacuum energy

White suggested in 2014 that their model could be an example of a quantum vacuum thruster (QVT). A QVT is a theoretical system that would use magnetohydrodynamics to generate thrust, similar to conventional plasma thrusters, only using the fleeting quantum vacuum fluctuations of the zero-point field as an extremely low-density plasma.[9][59][60]

White's 2016 paper states that pilot-wave theories, non-mainstream interpretations of quantum mechanics, may help explain how QVTs could "push off of the quantum vacuum and preserve the laws of conservation of energy and conservation of momentum.".

Quantized inertia

A paper in EPL by Mike McCulloch, a Lecturer in Geomatics at Plymouth University, describes a possible method in which thrust from resonant cavities can be predicted using McCulloch's controversial theory of quantization of inertia (MiHsC).[61] 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 pointed out possible 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.[62][63][64][65][66] 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.[67] Unlike some 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.[65]

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.[68] 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 cancels their electromagnetic fields but allows continued propagation of the microwave photon pairs, generating net thrust consistent with the impulse-momentum theorem depending on the asymmetric shape of the cavity.[69][70][71]

Dark matter

Most matter is believed to being dark matter, which may permeate everything. Inside this cavity, some photons may interact with a hypothetical particle known as an axion, transfer some of its momentum to this dark matter particle which is emitted out, so pushing the cavity forward in reaction. If so momentum would be conserved because the dark matter goes away in an equal and opposite direction.[72]

True reactionless drive

Main article: Reactionless drive

True reactionless drives are considered impossible for many reasons; for example, 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 that have studied resonant cavity thrusters generally do not believe the drives are reactionless, and are trying to test one of the alternative hypotheses.

Testing and replication

Tests by the inventors

In 2004, Roger Shawyer reported seven independent positive reviews from experts at BAE Systems, EADS Astrium, Siemens and the IEE,[73] 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."[24]

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.[74]

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.[75]

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, said that they had developed a valid electro-magnetic theory behind a microwave resonant cavity thruster.[6][76] 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,[5][38][39] they reported a maximum thrust of 720 mN at 2,500 W of input power.[39] Yang noted that her results were tentative, and said she "[was] not able to discuss her work until more results are published".[5] 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.[7]

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 ±0.7 mN 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 as well as more sensitive pendulums with lower torsional stiffness.[7]

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.[77] 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.[9][78][79][80][81]

In 2011, the group began tests on its first RF resonant cavity thruster prototype.

EmDrive

In July 2014, the group reported tentative positive results for evaluating a tapered RF resonant cavity, similar to the EmDrive.[17] Testing was performed using a low-thrust torsion pendulum capable of detecting force at the µN 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).[17] The experimenters recorded directional thrust immediately upon application of power.

NASA's first tests of this tapered 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.[17] 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, in which their team measured force with a torsional pendulum in a hard vacuum: about 50 µN with 50 W of input power at 5.0×10−6 torr.[82] The new RF power amplifiers were said to be made for hard vacuum, but failed rapidly due to internal corona discharges. Without funding to replace or upgrade them, measurements were scarce for a time.[83]

In 2014, Eagleworks later announced a plan to upgrade their equipment to higher power levels, to use vacuum-capable RF amplifiers with power ranges of up to 125 W, and to design a new tapered cavity that could be in the 0.1 N/kW range. The test article would be subjected to independent verification and validation at Glenn Research Center, the Jet Propulsion Laboratory and the Johns Hopkins University Applied Physics Laboratory.[17][82] As of 2016, this verification and validation has not happened.[84]

In 2015, Eagleworks conducted experiments in vacuum, with up to 80W of input power. They published the results in the American Institute of Aeronautics and Astronautics's peer-reviewed Journal of Propulsion and Power, under the title "Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum". This was released online in November 2016, with print publication in December.[9][79][80][81] In the study, The researchers observed that the system they set up was "consistently performing with a thrust-to-power ratio of 1.2±0.1mN/kW", and enumerated many potential sources of error.[9]

The paper suggested that pilot-wave theory (a controversial, non-mainstream deterministic interpretation of quantum mechanics) could explain how the device produces thrust.[9][80][81] Commenters pointed out that just because a study reporting consistent thrust was published with peer-review does not necessarily mean that the drive functions as claimed.[1][79] Physicist Ethan Siegal commented on the paper, saying that the drive most likely does not violate conservation of momentum as this would "make physics fall apart" but rather that there is something else going on. He said that "Whether it’s new physics [or] the effect’s cause simply hasn’t been determined yet, more and better experiments will be the ultimate arbiter".[85] Physicist Chris Lee was very critical of the work, saying that the paper had a small data set and a number of missing details he described as 'gaping holes'.[86]

Cannae drive

The same NASA test campaign evaluated a Cannae drive in 2014.[17] 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;[32] and a "null" test article lacking those radial slots. Both drives were equipped with an internal dielectric.[17] 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.[18][87][88] In the complete paper, however, Eagleworks concluded that the test results proved that "thrust production was not dependent upon slotting".[17]

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.[89] 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]

See also

References

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  2. ↑ Thomson, Steven (2015-08-09). "Here's why scientists haven't invented an impossible space engine". Ars Technica. Retrieved 2016-09-01.
  3. 1 2 Hambling, David (29 October 2009). "'Impossible' Device Could Propel Flying Cars, Stealth Missiles". WIred. Wired.
  4. 1 2 3 4 Hambling, David (5 November 2012). "Propellentless Space Propulsion Research Continues". Aviation Week & Space Technology.
  5. 1 2 3 4 5 6 Hambling, David (6 February 2013). "EmDrive: China's radical new space drive". Wired UK. Wired UK.
  6. 1 2 Hambling, David (24 September 2008). "Chinese Say They're Building 'Impossible' Space Drive". Wired. Wired.
  7. 1 2 3 4 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.
  8. ↑ "EM Drive Developments, NASA spaceflight forums, discussion of Yang's 2016 paper". forum.nasaspaceflight.com. Retrieved 2016-09-14.
  9. 1 2 3 4 5 6 7 White, Harold; March, Paul; Lawrence, James; Vera, Jerry; Sylvester, Andre; Brady, Davi; 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.B36120.
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  11. 1 2 Powell, Corey S. (Aug 6, 2014). "Did NASA Validate an "Impossible" Space Drive? In a Word, No.". Discover magazine. Retrieved February 16, 2016.
  12. ↑ David Hambling (2014-07-31). "Nasa validates 'impossible' space drive". Wired. Retrieved 2016-09-06.
  13. ↑ 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.
  14. ↑ Tucker, Bill (6 December 2015). "The Power Of The Force; The Curious Case Of The EmDrive". Retrieved 20 February 2016.
  15. 1 2 3 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).
  16. 1 2 3 Dvorsky, George (28 July 2015). "No, German Scientists Have Not Confirmed the "Impossible" EMDrive". io9. Gawker Media.
  17. 1 2 3 4 5 6 7 8 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. Lay summary (PDF) – NASA (30 July 2014).
  18. 1 2 3 Powell, Corey S. (6 August 2014). "Did NASA Validate an "Impossible" Space Drive? In a Word, No.". Discover. Retrieved 2014-08-06.
  19. ↑ Baez, John. "The incredible shrinking force". Google Plus. Retrieved 6 August 2014.
  20. ↑ "Roger SHAWYER -- EM Space Drive -- Articles & Patent".
  21. 1 2 Tom Shelley (14 May 2007). "No-propellant drive prepares for space and beyond". Eureka Magazine. Retrieved 4 May 2015.
  22. 1 2 Shawyer, Roger (September 2006). "A Theory of Microwave Propulsion for Spacecraft (Theory paper v.9.3)" (PDF). New Scientist.
  23. ↑ Costella, John P. (2006). "Why Shawyer's 'electromagnetic relativity drive' is a fraud" (PDF). John Costella’s home page.
  24. 1 2 Alvin Wilby. "Emdrive? No thanks". New Scientist.
  25. ↑ Paul Friedlander. "Emdrive on trial". New Scientist.
  26. ↑ United Kingdom Department of Trade and Industry End User Undertaking
  27. 1 2 Mary-Ann Russon (14 October 2016). "EmDrive exclusive: Roger Shawyer confirms MoD and DoD interested in controversial space propulsion tech". International Business Times.
  28. ↑ Shawyer, Roger (2015-11-01). "Second generation EmDrive propulsion applied to SSTO launcher and interstellar probe". Acta Astronautica. 116: 166–174. doi:10.1016/j.actaastro.2015.07.002.
  29. ↑ Mary-Ann Russon (12 October 2016). "EmDrive: Roger Shawyer is patenting a new design for next-gen superconducting thruster". International Business Times.
  30. ↑ WO application 2016162676, SHAWYER, Roger John & CARDOZO, Gilo, "Superconducting Microwave Radiation Thruster", published 2016-10-16, assigned to Satellite Propulsion Research Ltd.
  31. 1 2 WO application 2007089284, Fetta, Guido Paul, "Resonating cavity propulsion system", published 2007-11-15, assigned to Fetta, Guido Paul
  32. 1 2 "Cannae Drive". Cannae LLC website. Retrieved 31 July 2014.
  33. ↑ US application 2014013724, Fetta, Guido P., "Electromagnetic thruster", published 2014-01-16, assigned to Cannae LLC
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  35. ↑ WO application 2016004044, Fetta, Guido P., "Electromagnetic thrusting system", published 2016-01-07, assigned to Cannae LLC
  36. ↑ Hambling, David (31 July 2014). "Nasa validates 'impossible' space drive". Wired UK. Wired UK. Retrieved 31 July 2014.
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  40. ↑ Grahn, Patrick; Annila, Arto; Kolehmainen, Erkki (2016). "On the exhaust of electromagnetic drive" (PDF). AIP Advances. 6 (6): 065205. doi:10.1063/1.4953807. ISSN 2158-3226.
  41. ↑ Davis, A.M.J.; Scharstein, R.W. (1994). "Electromagnetic plane wave excitation of an open-ended conducting frustum" (PDF). IEEE Transactions on Antennas and Propagation. 42 (5): 699–706. doi:10.1109/8.299569. Therefore real nonzero time-average power flow does occur in a conical waveguide that is smaller in cross section then any cut-on circular wave guide at the same frequency of operation. This observation can be qualitatively explained by considering the oppositely directed evanescent waves that are excited at the cascaded junctions of successively larger but still individually cut off circular waveguides that form a stepped approximation to the cone. Effectively, then, the conical scatterer tends to focus a portion of energy of the incident portion of the radio wave, at least in comparison to the uniform tubular scatterer... In most respects, the scattering by the frustum is a distortion of that by the circular tube. One important difference is the internal focusing effect that is predominantly experienced when the exciting plane wave is incident from the wide end of the frustum. Due to the absence of sharp cut off frequencies from the nonuniform conical waveguide, the interior of the frustum can support nontrivial field amplitudes, even in regions of relatively small electrical cross section.
  42. ↑ Zeng, Xiahui; Fan, Dianyuan (2008). "Electromagnetic fields and transmission properties in tapered hollow metallic waveguides" (PDF). Optics Express. 17 (1): 34. doi:10.1364/OE.17.000034. ISSN 1094-4087. It is shown that all modes run continuously from a propagating through a transition to an evanescent region and the value of the attenuation increases as the distance from the cone vertex and the cone angle decreases. A strict distinction between pure propagating and pure evanescent modes can not be achieved. There is no well-defined cutoff wavelength but rather a cutoff radius. It is interesting to note that the magnitude of the cutoff radius is related to the wavelength and the cone half-angle.
  43. ↑ Mayer, B.; Reccius, A.; Knochel, R. (1992). "Conical cavity for surface resistance measurements of high temperature superconductors". IEEE Transactions on Microwave Theory and Techniques. 40 (2): 228–236. doi:10.1109/22.120094. ISSN 0018-9480. A conical cavity is described. The new cavity is superior to the often used cylindrical cavity, because it intrinsically does not suffer from mode degeneration
  44. ↑ White, Harold; March, Paul; Lawrence, James; Vera, Jerry; Sylvester, Andre; Brady, David; Bailey, Paul (2016). "Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum". Journal of Propulsion and Power. doi:10.2514/1.B36120. A 13.5-mm-diam loop antenna drives the system in the TM212 mode at 1937 MHz. Because there are no analytical solutions for the resonant modes of a truncated cone, the use of the term TM212 describes a mode with two nodes in the axial direction and four nodes in the azimuthal direction
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  52. ↑ Seeley, Fred B. (1993). "Dipole radiators in a cavity: A radio frequency analog for the modification of atomic spontaneous emission rates between mirrors". American Journal of Physics. 61 (6): 545. doi:10.1119/1.17206. ISSN 0002-9505.
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