EmDrive: Radical New Space Drive

While some may say that nothing is impossible, that is a word that has been frequently used by experts to describe SPR Ltd’s EmDrive. To some, EmDrive is crazy, junk science that will never amount to anything; however, its inventor Roger Shawyer has stuck by it resolutely and insists that this novel spacecraft propulsion system works.

EmDrive is a highly efficient propellant-less propulsion system that converts microwave energy into thrust inside a sealed chamber. Such a system would be a complete game changer in spaceflight; it could dramatically cut the cost of satellites and space stations, extend the lives of spacecrafts and drive deep-space missions. But there’s a problem- it violates Newtonian laws of physics, in particular the law of conservation of momentum. Critics have therefore claimed that any thrust generated by prototype systems tested so far must be coming from another source.

Despite supposedly being impossible, the work has sparked genuine interest in some. For example, Chinese scientists have independently and repeatedly proven the theory of EmDrive. Just last year in fact, a Chinese team built their own EmDrive and confirmed that it produced 720 mN of thrust, which would be sufficient for a satellite thruster. This system could be powered by solar electricity, negating the need for a bulky propellant. However, the work was largely ignored and scientists were still far from convinced.

Now, the big boys in the field, NASA, have swooped in and tested the viability of a microwave thruster built by US scientist Guido Fetta. The results are in, and it seems Shawyer may have been right after all.

After eight days of work, which involved using a highly sensitive low-thrust torsion pendulum within a stainless steel vacuum chamber, the scientists were able to confirm that around 30-50 micro-Newtons of thrust were produced. Furthermore, they were able to verify that the force was not generated by something other than the test system. While the result may be significantly smaller than those obtained by Chinese scientists, it’s still a positive result, which is impressive to say the least.

For physicists out there to fill their boots, the paper states: “Test results indicate that the RF resonant cavity thruster design, which is unique as an electric propulsion device, is producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma.”

According to Wired, that infers it may work by pushing against a cloud of particles and anti-particles that are continuously being produced and disappearing again. NASA has trodden carefully, however, by not addressing the physics of the system and instead solely focusing on whether it works, and that is what they did.

While Fetta’s underlying theory is very different to that of EmDrive, Shawyer claims that the thrusters operate along similar lines. Like Shawyer, Fetta also had a hard time convincing skeptics that the system is valid.
Working microwave thrusters have the potential to revolutionize spaceflight and while this latest research makes no promises, it’s certainly tantalizing.

August 1, 2014 | by Justine Alford.   [Hat tip: Wired]
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EmDrive: Radical new space drive

The prestigious Chinese Academy of Sciences has published a paper by Professor Yang Juan confirming their high power test results. At an input power of 2.5kW, their 2.45GHz EmDrive thruster provides 720mN of thrust. The results have clearly been subject to extensive peer review following the NWPU 2010 paper. The measurements were made on a national standard, thrust measurement device, used for Ion Engine development. Details of the measurement system and calibration data are given in the paper. A professional English translation is given here: Yang Juan 2012 paper

September 2012
A solution to the acceleration limitation of superconducting EmDrive engines has been found. The application of this breakthrough has been described at a recent presentation, where a hybrid spaceplane provides a dramatic reduction in launch cost to geostationary orbit. A reduction factor of 130 compared to Atlas V launch costs is predicted. This will lead to Solar Power Satellites becoming a low cost, baseload, energy source. The presentation can be downloaded here: 2G update

July 2012
An English translation of the 2010 Chinese paper, together with unpublished test results have been obtained. The last line of the paper confirms that experimental thrust measurements have been made at 1kW input power. The unpublished test results show a large number of thrust measurements at input powers up to 2.5kW. The mean specific thrust obtained is close to that measured in the SPR flight thruster tests.

Note that the Chinese thruster, if deployed on the ISS, would easily provide the necessary delta V to compensate for orbital decay, thus eliminating the need for the reboost/refueling missions.
The original 2010 paper, the translation and the unpublished test results are given here:

NWPU 2010 paper
NWPU 2010 paper (English translation)
NWPU 2010 unpublished test results

June 2011
Two papers have been identified, published by Professor Yang Juan of The North Western Polytechnical University, Xi’an, China. These papers provide an independent proof of the theory of EmDrive. Abstracts of these papers are given in Chinese Paper Abstracts.