EmDrive

Rocket engines operate by expelling propellant, which acts as a reaction mass and which produces thrust per Newton's third law of motion. All designs for electromagnetic propulsion operate on the principle of reaction mass. A hypothetical drive which did not expel propellant in order to produce a reaction force, providing thrust while being a closed system with no external interaction, would be a reactionless drive, violating the conservation of momentum and Newton's third law.{{cite magazine|last=Hambling|first=David|date=6 February 2013|title=EmDrive: China's radical new space drive|url=https://www.wired.co.uk/news/archive/2013-02/06/emdrive-and-cold-fusion|magazine=Wired UK}} Reactionless drives, like other forms of perpetual motion, do not exist in nature, and claims that a drive is reactionless are considered by physicists to be pseudoscience.

The first design of a resonant cavity thruster claiming to be a reactionless drive was by Roger Shawyer in 2001. He called his conical design an "EmDrive", and claimed that it produced thrust in the direction of the base of the cone. Guido Fetta later built a "Cannae Drive", based in part on Shawyer's concept,{{cite web|url=http://aviationweek.com/awin/propellentless-space-propulsion-research-continues|title=Propellentless Space Propulsion Research Continues|last=Hambling|first=David|date=5 November 2012|work=Aviation Week & Space Technology}} using a pillbox-shaped cavity.

Since 2008, a few physicists have tested their own models, trying to reproduce the results claimed by Shawyer and Fetta. Juan Yang at Xi'an's Northwestern Polytechnical University (NWPU) was unable to reproducibly measure thrust from their models, over the course of 4 years.{{cite magazine|last=Hambling|first=David|date=24 September 2008|title=Chinese Say They're Building 'Impossible' Space Drive|url=https://www.wired.com/2008/09/chinese-buildin/|magazine=Wired}}{{cite journal|last1=Yang|first1=J.|last2=Liu|first2=X.-C.|last3=Wang|first3=Y.-G.|last4=Tang|first4=M.-J.|last5=Luo|first5=L.-T.|last6=Jin|first6=Y.-Z.|last7=Ning|first7=Z.-X.|date=February 2016|script-title=zh:微波推力器独立系统的三丝扭摆推力测量|trans-title=Thrust Measurement of an Independent Microwave Thruster Propulsion Device with Three-Wire Torsion Pendulum Thrust Measurement System|url=http://www.tjjs.casic.cn/ch/reader/create_pdf.aspx?file_no=20160220&flag=1&journal_id=tjjs&year_id=2016|script-journal=zh:推进技术 |journal=Journal of Propulsion Technology|language=zh|volume=37|issue=2|pages=362–371|access-date=1 May 2016|archive-date=28 January 2018|archive-url=https://web.archive.org/web/20180128115752/http://www.tjjs.casic.cn/ch/reader/create_pdf.aspx?file_no=20160220&flag=1&journal_id=tjjs&year_id=2016|url-status=dead}} In 2016, Harold White's group at NASA's Advanced Propulsion Physics Laboratory reported in the Journal of Propulsion and Power that a test of their own model had observed a small thrust.{{cite journal|last1=White|first1=Harold|last2=March|first2=Paul|last3=Lawrence|first3=James|last4=Vera|first4=Jerry|last5=Sylvester|first5=Andre|last6=Brady|first6=Davi|last7=Bailey|first7=Paul|date=17 November 2016|title=Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum|journal=Journal of Propulsion and Power|volume=33|issue=4|pages=830–841|doi=10.2514/1.B36120|hdl=2060/20170000277|s2cid=126303009 |hdl-access=free}} In late 2016, Yue Chen of the communication satellite division of the China Academy of Space Technology (CAST), said his team had tested prototypes, and would conduct in-orbit tests to determine if they could observe thrust.{{cite web|url=http://www.ibtimes.co.uk/emdrive-chinese-space-agency-put-controversial-tech-onto-satellites-soon-possible-1596328|title=EmDrive: Chinese space agency to put controversial tech onto satellites 'as soon as possible'|last1=Russon|first1=Mary-Ann|date=13 December 2016|work=International Business Times|access-date=15 December 2016}}{{cite web|url=http://www.ibtimes.co.uk/emdrive-these-are-problems-china-must-fix-make-microwave-thrusters-work-satellites-1596487|title=EmDrive: These are the problems China must fix to make microwave thrusters work on satellites|last1=Russon|first1=Mary-Ann|date=14 December 2016|work=International Business Times|access-date=15 December 2016}}{{cite web|url=http://digitalpaper.stdaily.com/http_www.kjrb.com/kjrb/html/2016-12/11/content_357004.htm|title=电磁驱动：天方夜谭还是重大突破 我国正开展关键技术攻关，争取5年内实现工程应用|author1=操秀英|date=11 December 2016|website=Science and Technology Daily|publisher=Ministry of Science and Technology of the People's Republic of China|language=zh|trans-title=EmDrive: Fantasy or major breakthrough|access-date=15 December 2016|archive-date=16 December 2016|archive-url=https://web.archive.org/web/20161216144000/http://digitalpaper.stdaily.com/http_www.kjrb.com/kjrb/html/2016-12/11/content_357004.htm|url-status=dead}}{{Cite web|url=http://www.techtimes.com/articles/190067/20161226/china-confirms-emdrive-research-plans-to-use-the-technology-on-chinese-satellites-as-soon-as-possible.htm|title=China Confirms EmDrive Research, Plans To Use The Technology On Chinese Satellites As Soon As Possible|last=Kumar|first=Kalyan|date=26 December 2016|access-date=28 December 2016}}{{cite news|url=http://www.huffingtonpost.co.uk/entry/china-built-em-engine-nasa-mars-in-ten-weeks_uk_59b8efb9e4b0edff971798cf|title=China Claims To Have Built A Version Of NASA's 'Impossible Engine' That Uses NO Fuel|last1=Gallagher|first1=Sophie|date=13 September 2017|website=The Huffington Post UK}} Martin Tajmar's group at the Dresden University of Technology started testing prototypes in 2015, and by 2021 concluded that observations of thrust were false positives, reporting in the CEAS Space Journal they had refuted all EmDrive claims by "at least 3 orders of magnitude".{{Cite journal |last1=Tajmar |first1=M. |last2=Neunzig |first2=O. |last3=Weikert |first3=M. |date=2022-01-01 |title=High-accuracy thrust measurements of the EMDrive and elimination of false-positive effects |journal=CEAS Space Journal |language=en |volume=14 |issue=1 |pages=31–44 |doi=10.1007/s12567-021-00385-1 |bibcode=2022CEAS...14...31T |s2cid=237650091 |issn=1868-2510|doi-access=free }}

Media coverage of experiments using these designs has been polarized. The EmDrive first drew attention, both credulous and dismissive, when New Scientist wrote about it as an "impossible" drive in 2006. Media outlets were later criticized for misleading claims that a resonant cavity thruster had been "validated by NASA"{{cite magazine

| url = https://www.wired.co.uk/article/nasa-validates-impossible-space-drive

| title = Nasa validates 'impossible' space drive

| date = 31 July 2014

| magazine = Wired

| author = David Hambling

| access-date = 6 September 2016

}} following White's first tentative test reports in 2014.{{cite news

|url = http://blogs.discovermagazine.com/outthere/2014/08/06/nasa-validate-imposible-space-drive-word/

|title = Did NASA Validate an "Impossible" Space Drive? In a Word, No.

|work = Discover magazine

|date = 6 August 2014

|access-date = 16 February 2016

|author = Powell, Corey S.

|archive-date = 8 August 2014

|archive-url = https://web.archive.org/web/20140808210746/http://blogs.discovermagazine.com/outthere/2014/08/06/nasa-validate-imposible-space-drive-word/

|url-status = dead

}} Scientists have continued to note the lack of unbiased coverage.{{Cite web

| url = http://www.centauri-dreams.org/?p=36830

| title = Uncertain Propulsion Breakthroughs?

| date = 30 December 2016

| last1 = Millis

| first1 = Marc

| last2 = Hathaway

| first2 = George

| editor-last = Gilster

| editor-first = Paul

| website = Centauri Dreams

| last3 = Tajmar

| first3 = Martin

| last4 = Davis

| first4 = Eric

| last5 = Maclay

| first5 = Jordan

}}

In 2006, responding to the New Scientist piece, mathematical physicist John C. Baez at the University of California, Riverside, and Australian science-fiction writer Greg Egan, said the positive results reported by Shawyer were likely misinterpretations of experimental errors.

In 2014, White's first conference paper suggested that resonant cavity thrusters could work by transferring momentum to the "quantum vacuum virtual plasma", a new term he coined.{{cite conference

|last1 = Brady

|first1 = David A.

|last2 = White

|first2 = Harold G.

|last3 = March

|first3 = Paul

|last4 = Lawrence

|first4 = James T.

|last5 = Davies

|first5 = Franck J.

|title = 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

|chapter = Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum

|conference = 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

|publisher = American Institute of Aeronautics and Astronautics

|date = 30 July 2014

|chapter-url = http://www.libertariannews.org/wp-content/uploads/2014/07/AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf

|doi = 10.2514/6.2014-4029

|access-date = 31 July 2014

|hdl = 2060/20140009930

|isbn = 978-1-62410-303-2

|hdl-access = free

|archive-date = 18 February 2015

|archive-url = https://web.archive.org/web/20150218162819/http://www.libertariannews.org/wp-content/uploads/2014/07/AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf

|url-status = dead

}} 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 cannot be used for propulsion.{{cite web

| last1 = Baez

| first1 = John

| title = The incredible shrinking force

| url = https://plus.google.com/117663015413546257905/posts/WfFtJ8bYVya

| website = Google Plus

| access-date = 6 August 2014

}} In the same way, physicists James F. Woodward and Heidi Fearn published two papers showing that electron−positron virtual pairs of the quantum vacuum, discussed by White as a potential virtual plasma propellant, could not account for thrust in any isolated, closed electromagnetic system such as a quantum vacuum thruster.{{cite journal

|last1 = Fearn

|first1 = H.

|last2 = Woodward

|first2 = J. F.

|title = Breakthrough Propulsion I: The Quantum Vacuum

|date = May 2016

|journal = Journal of the British Interplanetary Society

|volume = 59

|issue = 5

|pages = 155–162

|url = http://www.ayuba.fr/images/emdrive/JBIS-69-05.pdf

|bibcode = 2016JBIS...69..155F

|access-date = 12 February 2017

|archive-date = 29 December 2016

|archive-url = https://web.archive.org/web/20161229032249/http://www.ayuba.fr/images/emdrive/JBIS-69-05.pdf

|url-status = dead

}}{{cite journal

|last1 = Fearn

|first1 = H.

|last2 = Woodward

|first2 = J. F.

|title = Breakthrough Propulsion II: A Mass Change Experiment

|date = October 2016

|journal = Journal of the British Interplanetary Society

|volume = 59

|issue = 10

|pages = 331–339

|url = http://www.jbis.org.uk/paper.php?p=2016.69.331

|bibcode = 2016JBIS...69..331F

|access-date = 13 September 2017

|archive-date = 10 September 2017

|archive-url = https://web.archive.org/web/20170910173944/http://www.jbis.org.uk/paper.php?p=2016.69.331

|url-status = dead

}}

In 2015, physicists Eric W. Davis at the Institute for Advanced Studies in Austin and Sean M. Carroll at the California Institute of Technology concluded that the thrust measurements reported in papers by both Tajmar and White were indicative of thermal effect errors.{{cite web

| last = Dvorsky

| first = George

| title = No, German Scientists Have Not Confirmed the "Impossible" EMDrive

| date = 28 July 2015

| website = io9

| url = http://io9.com/no-german-scientists-have-not-confirmed-the-impossibl-1720573809

}}

In May 2018, researchers from the Institute of Aerospace Engineering at Technische Universität Dresden, Germany, concluded that the dominant effect underlying the apparent thrust could be clearly identified as an artifact caused by Earth's magnetic field interacting with power cables in the chamber, a result that other experts agree with.[https://web.archive.org/web/20180522215338/https://news.nationalgeographic.com/2018/05/nasa-emdrive-impossible-physics-independent-tests-magnetic-space-science/ NASA's 'Impossible' Space Engine Tested—Here Are the Results]. Nadia Drake, National Geographic. 22 May 2018.[https://www.space.com/40682-em-drive-impossible-space-thruster-test.html 'Impossible' EmDrive Space Thruster May Really Be Impossible]. Mike Wall, Space.com. May 23, 2018,[https://www.researchgate.net/publication/325177082_The_SpaceDrive_Project_-_First_Results_on_EMDrive_and_Mach-Effect_Thrusters The SpaceDrive Project - First Results on EMDrive and Mach-Effect Thrusters]. (PDF) Martin Tajmar, Matthias Kößling, Marcel Weikert, and Maxime Monette. Technische Universität Dresden, Germany. Presented at Barcelo Renacimiento Hotel, Seville, Spain 14 – 18 MAY 2018.

In March 2021, Tajmar's group published a definitive analysis of their own past experiments and those of others, showing that all could be explained by and reproduced via outside forces, refuting all EmDrive claims.

When power flows into the EmDrive, the engine warms up. This also causes the fastening elements on the scale to warp, causing the scale to move to a new zero point. We were able to prevent that in an improved structure. Our measurements refute all EmDrive claims by at least 3 orders of magnitude.

File:Emdrive schematic.svg

In 2001, Shawyer founded Satellite Propulsion Research Ltd, to work on the EmDrive, which he said used a resonant cavity to produce thrust without propellant. The company was backed by a SMART award grant from the UK Department of Trade and Industry.{{cite news

| last = Margaret

| first = Hodge

| title = Answer about the Electromagnetic Relativity Drive

| department = Column 346W

| date = 5 December 2006

| journal = Daily Hansard Official Report

| publisher = House of Commons of the United Kingdom

| location = London

| url = https://publications.parliament.uk/pa/cm200607/cmhansrd/cm061205/text/61205w0031.htm

}} In December 2002, he loosely described a prototype which he alleged had produced a thrust of {{convert|0.02|N|ozf|lk=on}} powered by an 850 W cavity magnetron. He reported that the device could operate for only a few dozen seconds before the magnetron failed from overheating,{{cite web

| url = http://rexresearch.com/shawyer/shawyer.htm

| title = Roger Shawyer – EM Space Drive – Articles & Patent

}} however details were never published or replicated.

In October 2006, Shawyer claimed to have conducted tests on a new water-cooled prototype with increased thrust.{{cite web

| url = http://www.eurekamagazine.co.uk/design-engineering-features/technology/no-propellant-drive-prepares-for-space-and-beyond/9657/

| title = No-propellant drive prepares for space and beyond

| work = Eureka Magazine

| author = Tom Shelley

| date = 14 May 2007

| access-date = 4 May 2015

}} He reported plans to have the device ready to use in space by May 2009 and to make the resonant cavity a superconductor, neither of which materialized.

New Scientist magazine{{cite journal

| last = Shawyer

| first = Roger

| title = A Theory of Microwave Propulsion for Spacecraft (Theory paper v.9.3)

| journal = New Scientist

| date = September 2006

| url = https://www.newscientist.com/data/images/ns/av/shawyertheory.pdf

| url-status = dead

| archive-url = https://web.archive.org/web/20180526051221/https://www.newscientist.com/data/images/ns/av/shawyertheory.pdf

| archive-date = 26 May 2018

}} featured the EmDrive on the cover of 8 September 2006 issue. The article portrayed the device as plausible and emphasized the arguments of those who held that point of view. Egan, a popular science fiction author, distributed a public letter stating that "a sensationalist bent and a lack of basic knowledge by its writers" made the magazine's coverage unreliable, sufficient "to constitute a real threat to the public understanding of science". Especially, Egan said he was "gobsmacked by the level of scientific illiteracy" in the magazine's coverage, alleging that it used "meaningless double-talk" to obfuscate the problem of conservation of momentum. The letter was endorsed by Baez and posted on his blog.{{cite web

| last = Egan

| first = Greg

| editor-last = Baez

| editor-first = John C.

| title = A Plea to Save New Scientist

| date = 19 September 2006

| url = http://golem.ph.utexas.edu/category/2006/09/a_plea_to_save_new_scientist.html

| publisher = The n-Category Café (a group blog on math, physics and philosophy)

}}{{cite web

|url = http://blogs.discovermagazine.com/outthere/2014/08/06/nasa-validate-imposible-space-drive-word/

|title = Did NASA Validate an "Impossible" Space Drive? In a Word, No.

|publisher = Discover

|date = 6 August 2014

|access-date = 6 August 2014

|author = Powell, Corey S.

|archive-date = 8 August 2014

|archive-url = https://web.archive.org/web/20140808210746/http://blogs.discovermagazine.com/outthere/2014/08/06/nasa-validate-imposible-space-drive-word/

|url-status = dead

}} New Scientist editor Jeremy Webb responded to critics:{{quote|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{{nbsp}}... 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.{{cite web

| title = Emdrive on trial

| last = Webb

| first = Jeremy

| date = 3 October 2006

| website = New Scientist Publisher's blog

| url = https://www.newscientist.com/blog/fromthepublisher/2006/10/emdrive-on-trial.html

}}}} New Scientist also published a letter from the former technical director of EADS Astrium: {{quote|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.{{cite web

| url = https://www.newscientist.com/letter/mg19225740-300-emdrive-no-thanks/

| title = Emdrive? No thanks

| author = Alvin Wilby

| work = New Scientist

}}}} A letter from physicist Paul Friedlander: {{quote|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{{nbsp}}... 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.{{cite web

| url = https://www.newscientist.com/letter/mg19225720-700-emdrive-on-trial/

| title = Emdrive on trial

| author = Paul Friedlander

| work = New Scientist

}}}}

In 2007, the UK Department of Trade and Industry granted SPR an export license to Boeing in the US.{{cite web

| url = https://drive.google.com/file/d/0B7kgKijo-p0idV9tcmVIVzZrdTQ/view

| title = End User Undertaking.pdf

| access-date = 9 October 2017

}} According to Shawyer, in December 2008 he was invited to present on the EmDrive, and in 2009 Boeing expressed interest in it,{{cite journal

| last = Shawyer

| first = Roger

| date = November–December 2015

| title = Second generation EmDrive propulsion applied to SSTO launcher and interstellar probe

| url = http://www.emdrive.com/IAC14publishedpaper.pdf

| journal = Acta Astronautica

| volume = 116

| pages = 166–174

| doi = 10.1016/j.actaastro.2015.07.002

}} at which point he stated that SPR built a thruster which produced 18 grams{{val}} of thrust, and sent it to Boeing. Boeing did not license the technology and communication stopped.{{cite web

| title = EmDrive exclusive: Roger Shawyer confirms MoD and DoD interested in controversial space propulsion tech

| first = Mary-Ann

| last = Russon

| date = 14 October 2016

| website = International Business Times

| url = http://www.ibtimes.co.uk/emdrive-exclusive-roger-shawyer-confirms-mod-dod-interested-controversial-space-propulsion-tech-1586392

}} In 2012, a Boeing representative confirmed that Boeing Phantom Works used to explore exotic forms of space propulsion, including Shawyer's drive, but such work later ceased. They confirmed that "Phantom Works is not working with Mr. Shawyer", nor pursuing those explorations.

In 2014, Shawyer presented ideas for 'second-generation' EmDrive designs and applications at the annual International Astronautical Congress. A paper based on his presentation was published in Acta Astronautica in 2015.{{Cite journal

| title = Second generation EmDrive propulsion applied to SSTO launcher and interstellar probe

| url = http://www.emdrive.com/IAC14publishedpaper.pdf

| journal = Acta Astronautica

| date = 1 November 2015

| pages = 166–174

| volume = 116

| doi = 10.1016/j.actaastro.2015.07.002

| first = Roger

| last = Shawyer

}} While no functional prototype of the first-generation drive had yet been produced, and no detailed schematic of a new device was provided, it loosely described models for a superconducting resonant cavity and for thrusters with multiple cavities.

In 2016, Shawyer filed further patents{{cite web

| title = EmDrive: Roger Shawyer is patenting a new design for next-gen superconducting thruster

| first = Mary-Ann

| last = Russon

| date = 12 October 2016

| website = International Business Times

| url = http://www.ibtimes.co.uk/emdrive-roger-shawyer-patenting-new-design-next-gen-superconducting-thruster-1585982

}}{{cite patent

| country = WO

| number = 2016162676

| status = application

| title = Superconducting Microwave Radiation Thruster

| pubdate = 2016-10-16

| fdate = 2016-04-07

| pridate = 2015-04-07

| invent1 = Shawyer, Roger John

| invent2 = Cardozo, Gilo

| assign1 = Satellite Propulsion Research Ltd.

| class =

| url = https://patentscope.wipo.int/search/docs2/pct/WO2016162676/pdf/9QlGacH5MJpLQJQJ-gyiXGgRe1afnNfBcRKPtF0irvY

}} and launched a new company, Universal Propulsion Ltd., as a joint venture with Gilo Industries Group, a small UK aerospace company.

The Cannae Drive (formerly Q-drive) is another implementation of this idea, with a relatively flat cavity. It was designed by Guido Fetta in 2006 and promoted within the US through his company, Cannae LLC, since 2011.{{cite patent

| country = WO

| number = 2007089284

| status = application

| url = http://www.freepatentsonline.com/WO2007089284.pdf

| title = Resonating cavity propulsion system

| pubdate = 2007-11-15

| fdate = 2006-09-12

| pridate = 2005-09-12

| invent1 = Fetta, Guido Paul

| assign1 = Fetta, Guido Paul

}}{{cite patent

| country = US

| number = 2014013724

| status = application

| url = http://patentimages.storage.googleapis.com/pdfs/US20140013724.pdf

| title = Electromagnetic thruster

| pubdate = 2014-01-16

| fdate = 2012-03-22

| pridate = 2011-03-25

| invent1 = Fetta, Guido P.

| assign1 = Cannae LLC

}}{{cite conference

| last1 = Fetta

| first1 = Guido P.

| title = 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

| chapter = Numerical and Experimental Results for a Novel Propulsion Technology Requiring no On-Board Propellant

| conference = 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

| publisher = American Institute of Aeronautics and Astronautics

| date = 30 August 2014

| doi = 10.2514/6.2014-3853

| isbn = 978-1-62410-303-2

}}{{cite patent

| country = WO

| number = 2016004044

| status = application

| url = https://patentscope.wipo.int/search/docs2/pct/WO2016004044/pdf/gmjkS1jLXUE9TztaNQeRtY8ZO8xZd8hQPV2OOcQvifU

| title = Electromagnetic thrusting system

| pubdate = 2016-01-07

| fdate = 2015-06-30

| pridate = 2014-06-30

| invent1 = Fetta, Guido P.

| assign1 = Cannae LLC

}} In 2016, Fetta announced plans to eventually launch a CubeSat satellite containing a version of the Cannae Drive, which would run for 6 months to observe how it functions in space.{{Cite web

| url = https://www.popularmechanics.com/science/energy/a22678/em-drive-cannae-cubesat-reactionless/

| title = The Impossible Propulsion Drive Is Heading to Space

| first = David

| last = Hambling

| work = Popular Mechanics

| date = 2 September 2016

| access-date = 14 September 2016

}} No followup was published.

In China, researchers working under Yang at NWPU built a resonant cavity thruster in 2008, and tested it for a number of years. A 2012 report claimed they had observed thrust, but in 2014 they found it to have been an experimental error. A second, improved prototype did not produce any measured thrust.

At the China Academy of Space Technology, Yue Chen filed several patent applications in 2016 describing various radio frequency (RF) resonant cavity thruster designs. These included a method for stacking several short resonant cavities to improve thrust,{{cite patent

| country = CN

| number = 105781921A

| status = application

| title = Electromagnetic thruster cavity based on periodic structure

| pubdate = 2016-07-20

| fdate = 2016-03-16

| pridate = 2016-03-16

| invent1 = Chen, Yue

| invent2 = Peng Weifeng

| invent3 = Bai Guangming

| invent4 = Yaxing Cai, Liu Yang, Yin Jiacong, Zhang Faren

| assign1 = China Academy of Space Technology

| url = https://www.google.com/patents/CN105781921A?cl=en

}} and a design with a cavity that was a semicylinder instead of a frustum.{{cite patent

| country = CN

| number = 105947224A

| status = application

| title = An electromagnetic propulsion system and method

| pubdate = 2016-09-21

| fdate = 2016-06-20

| pridate = 2016-06-20

| invent1 = Chen, Yue

| invent2 = Peng Weifeng

| invent3 = Bai Guangming

| assign1 = China Academy of Space Technology

| url = https://www.google.com/patents/CN105947224A?cl=en

}} That December, Chen announced that CAST would conduct tests on a resonant cavity thruster in orbit, without specifying what design was used. In an interview on CCTV in September 2017, Chen showed some testing of a flat cylindrical device, corresponding to the patent describing stacked short cavities with internal diaphragms.{{YouTube|id=Mdcer1QQLrA|title=Propellantless propulsion: The Chinese EmDrive by CAST scientist Dr Chen Yue, China's Space Agency}}

All proposed theories for how the EmDrive works violate the conservation of momentum, which states any interaction cannot have a net force; a consequence of the conservation of momentum is Newton's third law, where for every action there is an equal and opposite reaction. Also, because force × velocity = power, any such device would violate conservation of energy when moving at a high enough velocity. The conservation of momentum is a symmetry of nature.{{cite web

| last1 = Lee

| first1 = C.

| title = Generating Thrust Without Fuel Relies on Missing Details

| url = https://arstechnica.com/science/2013/02/generating-thrust-without-fuel-relies-on-missing-details/

| website = Ars Technica

| archive-url = https://archive.today/20170511132235/https://arstechnica.com/science/2013/02/generating-thrust-without-fuel-relies-on-missing-details/

| archive-date = 11 May 2017

| date = 8 February 2013

| url-status = live

| access-date = 26 February 2025

}}

An often-cited example of apparent nonconservation of momentum is the Casimir effect,{{cite web

| last1 = Maxey

| first1 = K.

| title = Propulsion on an Interstellar Scale – the Quantum Vacuum Plasma Thruster

| url = https://www.engineering.com/propulsion-on-an-interstellar-scale-the-quantum-vacuum-plasma-thruster/

| website = engineering.com

| archive-url = https://archive.today/20130215224220/http://www.engineering.com/DesignerEdge/DesignerEdgeArticles/ArticleID/5058/Propulsion-on-an-Interstellar-Scale-the-Quantum-Vacuum-Plasma-Thruster.aspx

| archive-date = 15 February 2013

| url-status = live

| access-date = 26 February 2025

}} in the standard case where two parallel plates are attracted to each other. However the plates move in opposite directions, so no net momentum is extracted from the vacuum and, moreover, energy must be put into the system to take the plates apart again.

Assuming homogeneous electric and magnetic fields, it is impossible for the EmDrive, or any other device, to extract a net momentum transfer from either a classical or quantum vacuum.

Extraction of a net momentum "from nothing"{{cite magazine

| last1 = Cho

| first1 = A.

| title = Momentum From Nothing

| magazine = Physical Review Focus

| volume = 13

| date = 23 January 2004

| issn = 1539-0748

| doi = 10.1103/PhysRevFocus.13.3

}}{{cite journal

| last1 = Ball

| first1 = P.

| title = Movement From Nothing

| url = https://www.nature.com/articles/news040126-19

| journal = Nature

| archive-url = https://archive.today/20170201170321/http://www.nature.com/news/2003/030202/full/news040126-19.html

| archive-date = 1 February 2017

| doi = 10.1038/news040126-19

| date = 2 February 2003

| url-status = live

| access-date = 26 February 2025

| url-access= subscription

}} has been postulated in an inhomogeneous vacuum, but this remains highly controversial as it will violate Lorentz invariance.{{cite arXiv

| last1 = Lafleur

| first1 = T.

| title = Can the Quantum Vacuum be Used as a Reaction Medium to Generate Thrust?

| year = 2014

| eprint = 1411.5359

| class = quant-ph

}}

Both Harold White's{{cite web

| last1 = White

| first1 = H.

| last2 = March

| first2 = P.

| last3 = Williams

| first3 = N.

| last4 = O'Neill

| first4 = W.

| url = https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110023492_2011024705.pdf

| title = Eagleworks Laboratories: Advanced Propulsion Physics Research

| year = 2011

| publisher = NASA

}}{{cite journal

| last1 = White

| first1 = H.

| last2 = March

| first2 = P.

| title = Advanced Propulsion Physics: Harnessing the Quantum Vacuum

| journal = Nuclear and Emerging Technologies for Space

| year = 2012

| url = http://www.lpi.usra.edu/meetings/nets2012/pdf/3082.pdf

}}{{cite AV media

| last1 = White

| first1 = H.

| title = NASA Ames Research Director's Colloquium: Eagleworks Laboratories: Advanced Propulsion

| url = https://www.youtube.com/watch?v=Wokn7crjBbA&t=55m45s

| via = YouTube

| publisher = NASA's Ames Research Center

| date = 5 November 2014

| time = 56m:21s

| quote = That test article is trying to establish more accurately the requirements as required by the mathematics – working with negative vacuum energy – the Casimir force.

}}

and Mike McCulloch's{{cite journal

| last1 = McCulloch

| first1 = M. E.

| title = Inertia From an Asymmetric Casimir Effect

| journal = EPL

| volume = 101

| issue = 5

| year = 2013

| pages = 59001

| issn = 0295-5075

| doi = 10.1209/0295-5075/101/59001

| bibcode = 2013EL....10159001M

| arxiv = 1302.2775

| s2cid = 118357836

}} theories of how the EmDrive could work rely on these asymmetric or dynamical Casimir effects. However, if these vacuum forces are present, they are expected to be exceptionally tiny based on our current understanding, too small to explain the level of observed thrust.{{cite web

| last1 = Freeman

| first1 = D.

| title = Warp Drives and Science Fictions

| url = http://berkeleysciencereview.com/warp-drives-and-science-fictions/

| website = Berkeley Science Review

| publisher = University of California Berkeley

| archive-url = https://archive.today/20170612124308/http://berkeleysciencereview.com/warp-drives-and-science-fictions/

| archive-date = 12 June 2017

| year = 2015

}}{{cite web

| last1 = Marcus

| first1 = A.

| title = Research in a Vacuum: DARPA Tries to Tap Elusive Casimir Effect for Breakthrough Technology

| url = https://www.scientificamerican.com/article/darpa-casimir-effect-research/

| work = Scientific American

| archive-url = https://archive.today/20150302015744/http://www.scientificamerican.com/article/darpa-casimir-effect-research/

| archive-date = 2 March 2015

| date = 12 October 2009

| url-status = live

| access-date = 26 February 2025

}} In the event that observed thrust is not due to experimental error, a positive result could indicate new physics.{{cite web

| url = https://www.centauri-dreams.org/2016/12/30/uncertain-propulsion-breakthroughs/

| title = Uncertain Propulsion Breakthroughs?

| last2 = Hathaway

| first2 = G.

| date = 30 December 2016

| website = Centauri Dreams

| publisher = Tau Zero Foundation

| last3 = Tajmar

| first3 = M.

| last4 = Davis

| first4 = E.

| last5 = Maclay

| first5 = J.

| last1 = Millis

| first1 = M.

| archive-url = https://archive.today/20161230172536/http://www.centauri-dreams.org/?p=36830

| archive-date = 30 December 2016

| url-status = live

}}{{cite web|url=http://today.uconn.edu/2016/12/the-em-drive-science-fact-or-science-fiction/|title=To Mars in 70 Days. Science Fiction or Fact?|last1=Poitras|first1=C.|date=6 December 2016|website=UConn Today|publisher=University of Connecticut|url-status=dead|archive-url=https://archive.today/20170305105905/http://today.uconn.edu/2016/12/the-em-drive-science-fact-or-science-fiction/|archive-date=5 March 2017}}

In 2004, Shawyer claimed to have received seven independent positive reviews from experts at BAE Systems, EADS Astrium, Siemens and the IEE.{{cite journal

|title = Defying gravity: UK team claims engine based on microwaves could revolutionise spacecraft propulsion

|last = Fisher

|first = Richard

|journal = The Engineer

|volume = 293

|issue = 7663

|page = 8

|date = 5 November 2004

|url = http://www.theengineer.co.uk/news/defying-gravity/266633.article

|access-date = 9 July 2014

|archive-date = 9 January 2015

|archive-url = https://web.archive.org/web/20150109002553/http://www.theengineer.co.uk/news/defying-gravity/266633.article

|url-status = dead

}} The technical director of EADS Astrium (Shawyer's former employer) denied this in the strongest terms, stating:

{{quote|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.}}

In 2011, Fetta claimed to have tested a superconducting version of the Cannae drive, suspended inside a liquid-helium-filled dewar, with inconclusive results.

None of these results were published in the scientific literature, replicated by independent researchers, or replicated consistently by the inventors. In a few cases details were posted for a time on the inventors' websites, but no such documents remained online as of 2019.Fetta's experimental notes are no longer available, but an archived version as of 2 November 2012 is on archive.org: [https://web.archive.org/web/20121102082714/http://www.cannae.com/proof-of-concept/experimental-results EXPERIMENTAL RESULTS] (retrieved 11 February 2015)

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

| last = Shawyer

| first = Roger

| date = 1 November 2015

| title = Second generation EmDrive propulsion applied to SSTO launcher and interstellar probe

| journal = Acta Astronautica

| volume = 116

| pages = 166–174

| doi = 10.1016/j.actaastro.2015.07.002

}}

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, China, said that they had developed a valid electro-magnetic theory behind a microwave resonant cavity thruster.{{cite journal

|last1 = ZHU

|first1 = Yu

|last2 = YANG

|first2 = Juan

|last3 = MA

|first3 = Nan

|title = The Performance Analysis of Microwave Thrust Without Propellant Based on the Quantum Theory

|date = September 2008

|journal = Journal of Astronautics

|volume = 29

|issue = 5

|pages = 1612–1615

|language = zh

|url = http://en.cnki.com.cn/Article_en/CJFDTOTAL-YHXB200805027.htm

|access-date = 4 July 2014

|archive-date = 14 July 2014

|archive-url = https://web.archive.org/web/20140714225420/http://en.cnki.com.cn/Article_en/CJFDTOTAL-YHXB200805027.htm

|url-status = dead

}} 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,{{Cite journal

| last1 = Yang

| first1 = Juan

| last2 = Wang

| first2 = Yu-Quan

| last3 = Ma

| first3 = Yan-Jie

| last4 = Li

| first4 = Peng-Fei

| last5 = Yang

| first5 = Le

| last6 = Wang

| first6 = Yang

| last7 = He

| first7 = Guo-Qiang

| date = May 2013

| title = Prediction and experimental measurement of the electromagnetic thrust generated by a microwave thruster system

| journal = Chinese Physics B

| volume = 22

| issue = 5

| pages = 050301

| doi = 10.1088/1674-1056/22/5/050301

| url = http://cpb.iphy.ac.cn/EN/article/downloadArticleFile.do?attachType=PDF&id=53411

| format = PDF

| bibcode = 2013ChPhB..22e0301Y

| s2cid = 250763558

| url-access= subscription

}}{{Cite journal

| last1 = Shi

| first1 = Feng

| last2 = Yang

| first2 = Juan

| last3 = Tang

| first3 = Ming-Jie

| last4 = Luo

| first4 = Li-Tao

| last5 = Wang

| first5 = Yu-Quan

| date = September 2014

| title = Resonance experiment on a microwave resonator system

| journal = Acta Physica Sinica

| volume = 63

| issue = 15

| page = 154103

| doi = 10.7498/aps.63.154103

| url = http://wulixb.iphy.ac.cn/CN/article/downloadArticleFile.do?attachType=PDF&id=60316

| format = PDF

| language = zh

| doi-access= free

}} they reported a maximum thrust of 720 mN at 2,500 W of input power. Yang noted that her results were tentative, and said she "[was] not able to discuss her work until more results are published".

In a 2014 follow-up experiment (published in 2016), Yang could not reproduce the 2010 observation and suggested it was due to experimental error. They had refined their experimental setup, using a three-wire torsion pendulum to measure thrust, and tested two different power setups. They concluded that they were unable to measure significant thrust; that "thrust" measured when using external power sources (as in their 2010 experiment) could be noise; and that it was important to use self-contained power systems for these experiments, and more sensitive pendulums with lower torsional stiffness.

Since 2011, White had a team at NASA known as the Advanced Propulsion Physics Laboratory, or Eagleworks Laboratories, devoted to studying exotic propulsion concepts.{{cite tech report

| last1 = White

| first1 = Harold

| last2 = March

| first2 = Paul

| last3 = Nehemiah

| first3 = Williams

| last4 = O'Neill

| first4 = William

| title = Eagleworks Laboratories: Advanced Propulsion Physics Research

| url = https://ntrs.nasa.gov/search.jsp?R=20110023492

| website = NASA Technical Reports Server (NTRS)

| publisher = NASA

| number = JSC-CN-25207

| date = 5 December 2011

}} The group investigated ideas for a wide range of untested and fringe proposals, including Alcubierre drives, drives that interact with the quantum vacuum, and RF resonant cavity thrusters. In 2014, the group began testing resonant cavity thrusters, and in November 2016 they published a peer-reviewed paper on this work, in the Journal of Propulsion and Power.{{Cite magazine

| url = https://www.wired.co.uk/article/emdrive-peer-review-paper-science

| title = Nasa's 'impossible' EmDrive could work, study says

| last = Burgess

| first = Matt

| magazine = Wired

| location = Wired.com

| date = 21 November 2016

| access-date = 22 November 2016

}}{{Cite web

| url = https://www.vice.com/en/article/nasas-peer-reviewed-paper-on-the-emdrive-is-now-online/

| title = NASA's Peer-Reviewed Paper on the EmDrive Is Now Online

| last = Johnson

| first = Lief

| date = 19 November 2016

| website = Motherboard.com

| publication-date = 19 November 2016

| access-date = 22 November 2016

}}

In July 2014, White reported tentative positive results for evaluating a tapered RF resonant cavity. Their first tests of this tapered cavity were conducted at very low power (2% of Shawyer's 2002 experiment). A net mean thrust over five runs was measured at 91.2 μN at 17 W of input power. The experiment was criticized for its low power, small data set, and for not having been conducted in vacuum, to eliminate thermal air currents.

The group announced a plan to upgrade their equipment to higher power levels, and to use a test framework subject to independent verification and validation at one or more major research centers.

{{cite web|author=Wang, Brian|date=6 February 2015|title=Update on EMDrive work at NASA Eagleworks|url=http://nextbigfuture.com/2015/02/update-on-emdrive-work-at-nasa.html|url-status=dead|archive-url=https://web.archive.org/web/20160315230923/http://nextbigfuture.com/2015/02/update-on-emdrive-work-at-nasa.html|archive-date=15 March 2016|access-date=8 February 2015|website=NextBigFuture|df=dmy-all}}

This did not happen.[https://forum.nasaspaceflight.com/index.php?topic=40959.3320 Topic: EM Drive Developments – related to space flight applications – Thread 8], Nasa Spaceflight Forum, posts by Paul March, 26 November 2016.

They later conducted experiments in vacuum at 40-80W of input power, publishing the results in 2016 in the Journal of Propulsion and Power, under the title "Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum". The study said their system was "consistently performing with a thrust-to-power ratio of 1.2±0.1mN/kW", but also enumerated many potential sources of error. This was the first such paper published in a peer-reviewed journal, however the experiment was again criticized for its small dataset and missing details about the experimental setup, which was again not independently validated.{{Cite web

| url = http://news.nationalgeographic.com/2016/11/nasa-impossible-emdrive-physics-peer-review-space-science/

| archive-url = https://web.archive.org/web/20161122020601/http://news.nationalgeographic.com/2016/11/nasa%2Dimpossible%2Demdrive%2Dphysics%2Dpeer%2Dreview%2Dspace%2Dscience/

| url-status = dead

| archive-date = 22 November 2016

| title = NASA Team Claims 'Impossible' Space Engine Works—Get the Facts

| last1 = Drake

| first1 = Nadia

| author1-link = Nadia Drake

| last2 = Greshko

| first2 = Michael

| work = National Geographic

| location = Nationalgeographic.com

| date = 21 November 2016

| access-date = 23 November 2016

}}{{Cite web

| url = http://arstechnica.co.uk/science/2016/11/nasas-em-drive-still-a-wtf-thruster/

| title = NASA's EM-drive still a WTF-thruster

| last = Lee

| first = Chris

| website = arstechnica.co.uk

| date = 23 November 2016

| access-date = 23 November 2016

}}{{Cite web

| url = http://www.centauri-dreams.org/?p=36890

| title = Close Look at Recent EmDrive Paper

| date = 3 January 2017

| last = Hathaway

| first = George

| editor-last = Gilster

| editor-first = Paul

| website = Centauri Dreams

}}

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.{{cite conference|last1=Tajmar|first1=Martin|last2=Fiedler|first2=Georg|date=July 2015|title=Direct Thrust Measurements of an EM Drive and Evaluation of Possible Side-Effects|chapter=Direct Thrust Measurements of an EMDrive and Evaluation of Possible Side-Effects |url=http://tu-dresden.de/die_tu_dresden/fakultaeten/fakultaet_maschinenwesen/ilr/rfs/forschung/folder.2007-08-21.5231434330/ag_raumfahrtantriebe/JPC%20-%20Direct%20Thrust%20Measurements%20of%20an%20EM%20Drive%20and%20Evaluation%20of%20Possible%20Side-Effects.pdf|conference=51st AIAA/SAE/ASEE Joint Propulsion Conference|publisher=American Institute of Aeronautics and Astronautics|doi=10.2514/6.2015-4083|isbn=978-1-62410-321-6 |access-date=26 July 2015}} Testing was performed first on a knife-edge beam balance able to detect force at the micronewton level, atop an antivibration 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 {{convert|4e-6|mbar|uPa|abbr=on|order=flip}}.

They used a conventional ISM band 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 micronewtons, much larger than the expected result of zero thrust. 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 the device.

In 2018, they published results from an improved test rig, which showed that their measured thrust had been a result of experimental error from insufficiently shielded components interacting with the Earth's magnetic field.{{cite news

| title = 'Impossible' EM drive doesn't seem to work after all

| url = https://www.newscientist.com/article/2169809-impossible-em-drive-doesnt-seem-to-work-after-all/

| access-date = 25 May 2018

| work = New Scientist

}} In new experiments, they measured thrust values consistent with previous experiments and again measured thrust perpendicular to the expected direction when the thruster was rotated by 90°. Moreover, they did not measure a reduction in thrust when an attenuator was used to reduce the power that actually entered the resonant cavity by a factor of 10,000, which they said "clearly indicates that the "thrust" is not coming from the EMDrive but from some electromagnetic interaction." They concluded that "magnetic interaction from not sufficiently shielded cables or thrusters are a major factor that needs to be taken into account for proper μN thrust measurements for these type of devices," and they planned on conducting future tests at higher power and at different frequencies, and with improved shielding and cavity geometry.{{Cite conference

| last1 = Tajmar

| first1 = Martin

| last2 = Kößling

| first2 = Matthias

| last3 = Weikert

| first3 = Marcel

| last4 = Monette

| first4 = Maxime

| date = 16 May 2018

| title = The SpaceDrive Project – First Results on EMDrive and Mach-Effect Thrusters

| url = https://www.researchgate.net/publication/325177082

| conference = Space Propulsion Conference, at Seville, Spain

}}

In 2021, they revisited these experiments again and ran more precise tests. They reported with high confidence that the forces previously measured could be completely explained by experimental error, and that there was no evidence for any measurable thrust once these errors were taken into account.{{Cite web

|date = 2021-03-21

|title = Latest EmDrive tests at Dresden University shows "impossible Engine" does not develop any thrust

|url = https://www.grenzwissenschaft-aktuell.de/latest-emdrive-tests-at-dresden-university-shows-impossible-engine-does-not-develop-any-thrust20210321/

|access-date = 2021-04-01

|website = grenzwissenschaft-aktuell.de

}}{{Cite web|last=Delbert|first=Caroline|date=2021-03-31|title=Scientists Just Killed the EmDrive|url=https://www.popularmechanics.com/science/a35991457/emdrive-thruster-fails-tests/|access-date=2021-04-01|website=Popular Mechanics|language=en-US}}{{Cite web

|title = High-Accuracy Thrust Measurements of the EMDrive and Elimination of False-Positive Effects

|last1= Tajmar |first1=Martin |last2=Neunzig |first2=Oliver|last3=Weikert |first3=Marcel

|url = https://www.researchgate.net/publication/350108418

|access-date = 2021-04-01

|website = ResearchGate

|language=en}} They were able to run the experiment and show no thrust in any direction, and to reintroduce the previous sources of experimental error to replicate the earlier results. They also replicated White's setup, showing that thermal effects could replicate the apparent thrust his team had observed, and that this thrust went away when measured with a more precise suspension. They went on to publish two further papers, showing similar negative results for the laser-based LemDrive variant and Woodward's Mach-Effect thruster.{{Cite web

|title = Thrust Measurements and Evaluation of Asymmetric Infrared Laser Resonators for Space Propulsion

|url=https://www.researchgate.net/publication/350108417

|access-date = 2021-04-01|website=ResearchGate

|language = en}}{{Cite web

|title = The SpaceDrive Project – Mach-Effect Thruster Experiments on High-Precision Balances in Vacuum

|url = https://www.researchgate.net/publication/350108329

|access-date = 2021-04-01

|website = ResearchGate

|language = en}}

Since 2016, a few groups have raise funds for planned tests of EM drives or similar devices in space. As of 2025, there is no independent confirmation that any such device as gone to space, as none of the groups have published updates or technical details about the tests.

In August 2016, Cannae announced plans to launch a thruster on a cubesat which they would run for 6 months to observe how it functions in space. As of 2025, no launch details had been announced.

In December 2016, Yue Chen told a reporter at China's Science and Technology Daily that his team would test an EmDrive in orbit. Chen claimed their prototype's thrust was at the "micronewton to millinewton level", which would have to be scaled up to at least 100–1000 millinewtons for a chance of conclusive experimental results..{{cite news

| url = http://www.ibtimes.co.uk/emdrive-chinese-space-agency-put-controversial-tech-onto-satellites-soon-possible-1596328

| title = EmDrive: Chinese space agency to put controversial tech onto satellites 'as soon as possible'

| work = International Business Times

| first = Mary-Ann

| last = Russon

| date = 13 December 2016

| access-date = 15 December 2016

}}{{cite news

| url = http://www.ibtimes.co.uk/emdrive-these-are-problems-china-must-fix-make-microwave-thrusters-work-satellites-1596487

| title = EmDrive: These are the problems China must fix to make microwave thrusters work on satellites

| work = International Business Times

| first = Mary-Ann

| last = Russon

| date = 14 December 2016

| access-date = 15 December 2016

}}{{citation |url=http://digitalpaper.stdaily.com/http_www.kjrb.com/kjrb/html/2016-12/11/content_357004.htm |title=电磁驱动：天方夜谭还是重大突破 我国正开展关键技术攻关，争取5年内实现工程应用 |trans-title=EmDrive: Fantasy or major breakthrough |work=Science and Technology Daily |language=zh |author=操秀英 |date=11 December 2016 |access-date=15 December 2016 |archive-date=16 December 2016 |archive-url=https://web.archive.org/web/20161216144000/http://digitalpaper.stdaily.com/http_www.kjrb.com/kjrb/html/2016-12/11/content_357004.htm |url-status=dead }}{{cite news

| last1 = Yan

| first1 = Li

| title = Mars could be getting closer and closer, if this science isn't m

| url = http://www.ecns.cn/2016/12-21/238503.shtml

| access-date = 21 December 2016

| agency = China News Service (中国新闻社)

| date = 21 December 2016

}}{{cite web

| last1 = Lin

| first1 = Jeffrey

| last2 = Singer

| first2 = P. W.

| title = EmDrive: China Claims Success With This "Reactionless" Engine for Space Travel

| url = http://www.popsci.com/emdrive-engine-space-travel-china-success

| website = popsci.com

| publisher = Popular Science

| access-date = 21 December 2016

| date = 20 December 2016

}} After 2017, no further updates were announced.

In 2023, a new company, IVO Limited, claimed to be developing a similar drive, which they would test in space later that year on a cubesat,{{cite web |last1=Hambling |first1=David |date=17 November 2023 |title=Controversial Quantum Space Drive In Orbital Test, Others To Follow |url=https://www.forbes.com/sites/davidhambling/2023/11/17/controversial-quantum-space-drive-in-orbital-test-others-to-follow/ |accessdate=19 January 2024 |work=Forbes}} but in the end did not do so.{{cite web |date=9 February 2024 |title=Rogue Space Systems operations team is announcing the suspension of the active phase of a partially successful mission. |url=https://rogue.space/suspension_of_barry1_operations/ |accessdate=20 March 2024 |website=Rogue Space Systems}}

The strongest early result, from Yang's group in China, was later reported to be caused by an experimental error. Tajmar published an explanation of how all reports of apparent thrust could have been caused entirely by failing to account for all sources of error or noise.

Experimental errors in the testing of the prototypes generally fall into four categories{{cite news|url=http://blogs.discovermagazine.com/d-brief/2016/11/21/impossible-emdrive-thruster-cleared-first-hurdle/#.WDUr2R_6zCI|title=The Impossible' EmDrive Thruster Has Cleared Its First Credibility Hurdle |first=Nathaniel |last=Scharping |date=21 November 2016|department=D-Brief |magazine=Discover|access-date=23 November 2016|archive-date=22 November 2016|archive-url=https://web.archive.org/web/20161122110859/http://blogs.discovermagazine.com/d-brief/2016/11/21/impossible-emdrive-thruster-cleared-first-hurdle/#.WDUr2R_6zCI|url-status=dead}}

• Measurement error and noise. Most theoretical scientists who have looked at the EmDrive believe this to be the likely case.
• Thermal effects.
• Electromagnetic effects, including interaction with ambient magnetic fields and Lorentz forces from power leads.

Other potential sources of error include confirmation bias and publication bias (discarding negative results).

{{Main|Observational error}}

The simplest and most likely 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 goes into generating a tiny amount of thrust. When attempting to measure a small signal superimposed on a large signal, the noise from the large signal can obscure the small signal and give incorrect results.

File:IR imagery of RF amplifier and heat sink.png

The largest error source is believed to come from the thermal expansion of the thruster's heat sink; as it expands this would lead to a change in the centre of gravity causing the resonant cavity to move. White's team attempted to model the thermal effect on the overall displacement by using a superposition of the displacements caused by "thermal effects" and "impulsive thrust" with White saying "That was the thing we worked the hardest to understand and put in a box". Despite these efforts, White's team were unable to fully account for the thermal expansion. In an interview with Aerospace America, White comments that "although maybe we put a little bit of a pencil mark through [thermal errors] ... they are certainly not black-Sharpie-crossed-out."{{cite journal|last1=Hadhazy|first1=A.|year=2016|title=Fuel Free Space Travel|url=https://aerospaceamerica.aiaa.org/features/fuel-free-space-travel/|journal=Aerospace America|volume=February 2017|access-date=January 11, 2023}}

Their method of accounting for thermal effects has been criticized by Millis and Davies, who highlight that there is a lack of both mathematical and empirical detail to justify the assumptions made about those effects. For example, they do not provide data on temperature measurement over time compared to device displacement. The paper includes a graphical chart, but it is based on a priori assumptions about what the shapes of the "impulsive thrust" and "thermal effects" should be, and how those signals will superimpose. The model further assumes all noise to be thermal and does not include other effects such as interaction with the chamber wall, power lead forces, and tilting. Because the Eagleworks paper has no explicit model for thrust to compare with the observations, it is ultimately subjective, and its data can be interpreted in more than one way. The Eagleworks test, therefore, does not conclusively show a thrust effect, but cannot rule it out either.

White suggested future experiments could run on a Cavendish balance. In such a setup, the thruster could rotate out to much larger angular displacements, letting a thrust (if present) dominate any possible thermal effects. Testing a device in space would also eliminate the center-of-gravity issue. Tajmar's team later used such a setup to show that past results had all been artefacts of thermal effects.

These experiments used relatively large electromagnetic inputs to generate small amounts of thrust. As a result, electromagnetic interactions between power leads, between power lines and ambient magnetic fields, or between the apparatus and walls of a test chamber, could all have significant effects.

Yang reported in 2016 that an interaction with the Earth's magnetic field had caused the fairly large apparent thrust in their 2012 paper. Tajmar looked for potential Lorentz force interactions between power leads in trying to replicate White's experimental setup. Another source of error could have arisen from electromagnetic interaction with the walls of the vacuum chamber. White argued that any wall interaction could only be the result of a well-formed resonance coupling between the device and wall and that the high frequency used imply the chances of this would be highly dependent on the device's geometry. As components get warmer due to thermal expansion, the device's geometry changes, shifting the resonance of the cavity. In order to counter this effect and keep the system in optimal resonance conditions, White used a phase-locked loop system (PLL). Their analysis assumed that using a PLL ruled out significant electromagnetic interaction with the wall.

{{Columns-list|colwidth=22em|

• Abraham–Minkowski controversy
• Beam-powered propulsion § Direct impulse
• Casimir effect
• Crookes radiometer
• Dean drive
• Helical engine
• Quantum vacuum thruster
• Reactionless drive
• Unruh effect
• White–Juday interferometer experiment
• Woodward effect

}}

{{Reflist}}

• {{Official website|cannae.com}}, Cannae
• {{Official website|emdrive.com}}, EmDrive
• {{cite magazine |last=Oberhaus |first=Daniel|title=A Mythical Form of Space Propulsion Finally Gets a Real Test |magazine=WIRED |date=2019-06-05 |url=https://www.wired.com/story/a-mythical-form-of-space-propulsion-finally-gets-a-real-test/ |access-date=2019-06-07}}
• [http://www.thespaceshow.com/show/17-jun-2016/broadcast-2722-em-drive Broadcast 2722 EM Drive] @ The Space Show
• [https://www.youtube.com/playlist?list=PL_YvUODKu7Ct45wRbvvM7ZLAr180Wmjct Videos of presentations on EM Drive, Mach Effect, Cannae by March, Woodward, Tajmar and others at the 2016 Breakthrough Propulsion Workshop] @ Space Studies Institute YouTube Playlist
• [https://www.tmro.tv/2016/05/09/the-empossibledrive/ TMRO video podcast #EMPossibleDrive 9.16 with builder Dave Distler] {{Webarchive|url=https://web.archive.org/web/20161008202307/https://www.tmro.tv/2016/05/09/the-empossibledrive/ |date=8 October 2016 }} @25 minutes in
• [https://www.popularmechanics.com/science/a35991457/emdrive-thruster-fails-tests/ EmDrive fails tests]

{{Pseudoscience}}

{{Spacecraft propulsion}}

Category:Discovery and invention controversies

Category:Fringe physics

Category:Hypothetical technology

Category:Pseudoscience

Category:Spacecraft propulsion