The 'impossible' EmDrive could reach Pluto in 18 months
Nasa's Eagleworks Lab wastesting a copy of the EmDrive, a propulsion device frequently labelled as "impossible" because it appears to violate the law of conservation of momentum. Against all expectation they found it produced thrust. The response from the scientific community was dramatic, and generally sceptical -- but the "anomalous thrust" stubbornly refuses to disappear as more research zeroes in on it.
The situation is not helped by garbled media reports like"British scientist who says he's found the secret of Star Trek's 'warp speed'". But the subject is attracting serious examination from scientists who want to know if a sealed cavity filled with resonating microwaves can really produce net thrust. Previously the effect has been measured by British scientist Roger Shawyer, who invented the EmDrive, and a Chinese team, as well as Nasa.
Martin Tajmar, professor and chair for Space Systems at the Dresden University of Technology, is perhaps uniquely well qualified to evaluate the EmDrive. His research interests include "Breakthrough Propulsion Physics," space drives which do not rely on the variations on rocket thrust but which draw on more exotic science.
Tajmar has looked at the possibility of space propulsion using "negative matter" from a theoretical perspective -- theoretical because of the difficulty of producing such a substance, which is not as easy as simple antimatter. More practically he has investigated claims of "electrostatic torque," a twisting force meant to occur between charged spheres, and found the supposed anomaly was due to a slight asymmetry in the experimental setup. His work on claims of gravitational shielding with spinning superconductors had led to a better understanding of sources of error in high-precision gyroscope measurements. These are cases where an apparatus apparently producing small anomalous forces needed to be examined closely.
The same applies to the EmDrive. The obvious sources of error -- air currents, leaking microwaves, ionisation -- have long ago been ruled out. But this is the first time that someone with a well-equipped lab and a strong background in tracking experimental error has been involved, rather than engineers who may be unconsciously influenced by a desire to see it work.
Tajmar will be presenting his results at the American Institute for Aeronautics and Astronautics' Propulsion and Energy Forum and Exposition in Orlando on 27 July, in a paper called "Direct Thrust Measurements of an EmDrive and Evaluation of Possible Side-Effects". By side-effects, he is referring to the electric and magnetic fields that may cause false readings.
Tajmar prefers his results not to be shared in advance, but told WIRED that his paper will not close the EmDrive story and that it merits further research.
Roger Shawyer is encouraged by Tajmar's work, which he says validates his own theoretical predictions as well as his experimental results. Shawyer has often been dismissed because of his own lack of peer-reviewed scientific publications. That looks to be changing very soon; a paper Shawyer presented at the International Astronautical Conference in Toronto in 2014 is in the final stages for peer-review for publication. This describes an advanced EmDrive-powered spaceplane.
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There has been a tremendous upwelling of amateur scientific interest in the EmDrive. Although the microwave cavity needs to be made very precisely, and tuning microwave resonance is not simple, building one does not require great resources. As well as a lively technical discussion onNasaSpaceflight.com, there is now an EmDrive wiki, listing more than a dozen projects to replicate Shawyer's drive. At least one experimenter, Romanian electrical engineer Berca Iulian, has posted positive results online and invited comment.
Things have also been moving in the larger scientific world. WIRED understands that there are multiple labs around the world working on their own EmDrives, although Tajmar's is the only new one willing to go public so far.
Guido Fetta, inventor of the Cannae Drive which closely resembles the EmDrive and which was successfully tested by Nasa at the same time, continues to develop his drive and is now testing a new version.
"Cannae will have additional results from advanced prototype tests later this year," says Fetta, adding that this will be in the fourth quarter.
Cannae's previous plans have included superconducting drives with a much higher Q-factor (a measurement of the effectiveness of a resonator) than those tested previously. According to the theory, this should produce far greater thrust than earlier devices.
In spite of the Daily Mail's over-excited reporting, the EmDrive is not a Star Trek Warp Drive which will travel faster than light. However, if it does work as Shawyer and others claim, it will revolutionise the space industry, and make possible new developments like solar power via satellite.
It could also make a big difference to space exploration. The New Horizons mission took over nine years to get to Pluto, and scooted past the dwarf planet at over 36,000 mph in a fleeting encounter. An EmDrive with modest performance (0.4 N/kilowatt, a figure used by Nasa in its EmDrive calculations) could get there in less than 18 months, go into orbit around Pluto and take close-ups, or drop a lander on to the surface. More ambitious ideas include a manned trip to the moons of Saturn with a three-year mission time.
Many will still dismiss the EmDrive as impossible. Given an anomaly, the scientific view -- as shown by professor Tajmar -- is to ask exactly what is causing the anomaly and whether it can be reliably replicated. Some damage to our theories of physics is an acceptable payoff if we get a working space drive.
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