Theoretical physicists are one step closer to explaining how NASA’s ‘impossible’ EmDrive works

Julien Prisco is a futurist, theoretical physicist and computer scientist. He writes about science, technology and the future. He is also co-founder of Space cooperative.

An attempt theoretical explanation for the mysterious and “impossible” EmDrive propulsion system was published in the International Journal of Applied Physical Sciences in August. First proposal by British engineer Roger Shawyer, the EmDrive is an asymmetrical box resembling a truncated cone, with a permanent microwave field within it which, apparently in violation of known physical laws, appears capable of generating thrust and propel the device.

Meanwhile, Chinese state media complaints that the country’s scientists have developed a working EmDrive prototype and are preparing to test it in space. NASA is also funding a feasibility study for an interstellar mission powered by a related exotic method of propulsion.

In September 2016, propulsion researchers gathered for an invitation-only workshop at a secluded retreat in Estes Park, Colorado. Proceedings and videos from the workshop, sponsored by the Space Studies Institute, are available online.

Later that year, a NASA article eagleworks team, titled “Measurement of the impulse thrust of a closed radiofrequency cavity in vacuum“, published in the American Institute of Aeronautics and Astronautics (AIAA) Propulsion and Power Log, describes promising experimental results and hints at possible theoretical EmDrive models.

Publication of the NASA paper silenced some objections to EmDrive research based on the lack of peer-reviewed publications in top scientific journals. But a more serious debate continues, based on something much more important: the fundamental laws of physics. Some scientists think EmDrive technology is impossible because it doesn’t seem to adhere to our current understanding of how the universe is supposed to work.

The Law of Conservation of Momentum says that there is no way electromagnetic waves bouncing inside a box can push a box forward. Unless, that is, some other physical effect takes the momentum away.

Today’s jet-powered spacecraft works like this: the thruster exhaust carries away momentum and generates forward thrust. But the need to carry enough propellant is a strong limit for space travel, making long-distance space missions expensive to the point of infeasibility.

If the zero-reaction EmDrive works, it would open the door to zero-reaction space missions that could reach planets in weeks instead of months, and at a much lower cost. This could eventually open a path to the stars. Therefore, it’s no surprise that visionary engineers continue to pursue experimental and theoretical research into EmDrive, despite the controversial nature of the technology.

In the lab, EmDrive researchers attempt to demonstrate conclusively that the push is there. The 2016 NASA paper reports a modest push beyond experimental margins of error. But that thrust would work much better, especially for long-range missions, than higher thrust on heavier thruster-based spacecraft. Indeed, according to NASA researchers, the EmDrive would outperform other “zero thruster” propulsion systems studied to date, such as light sail.

Theoretical scientists are trying to figure out why and how EmDrive propulsion works. The NASA paper suggests a tentative explanation based on a theory from quantum physics, “a theory of nonlocal hidden variables, or pilot wave theory for short.”

A new research paper from a Portuguese scientist, titled “A possible explanation of the Em drive based on a pilot wave theory” is now all the rage among EmDrive enthusiasts in the NASA Spaceflight Forum. Paid paper offers a model similar to NASA’s (here’s a open access preprint you can read.)

Pilot wave theories have been proposed since the 1920s by quantum physicists, including Louis de Broglie and David Bohm, to make sense of the strange behavior of quantum matter. Recently, pilot wave quantum theories have gained popularity after the discovery that the quantum-like behavior of the pilot wave can be reproduced in classical fluids and explained by classical (non-quantum) fluid dynamics.

The EmDrive prototype. Image: Mario Solera/Flickr

It appears that fluid droplets bouncing off a vibrating fluid bath generate a pilot wave field which, in turn, guides the movement of the droplets themselves to startling effect. similarity to quantum behavior. The local non”remote scary action“, which baffled Einstein, has yet to be invoked to explain the dynamics of the pilot wave field.

However, the EmDrive doesn’t sound very quantum: it’s just a macroscopic device with good old electromagnetic microwaves inside. Therefore, there is a belief among scientists that the anomalous surge (if, again, it really is there) should have a classical (non-quantum) explanation based on Maxwell’s theory. electromagnetism and Einstein general relativity.

Mach’s Principle– the idea that local inertia is determined by distant masses and the structure of the universe as a whole – could be a starting point. Physicist James F. Woodward speculated about “Mach effects” or “Woodward Effects,” based on Hoyle-Narlikar theory of gravity, a version of Machian’s general relativity which includes “advanced waves“time-traveling from the distant universe.

The simplest Woodward effect, which has been proposed as the theoretical basis for EmDrive and other reactionless propulsion methods, predicts local mass fluctuations that can be exploited for propulsion without requiring reaction.

“Towards the woods [devised] a method to use these mass fluctuations for a new propulsion system: push the mass when it is heavy and withdraw it when it is lighter”, explains the physicist Martin Tajmar in a recent article. Tajmar leads a groundbreaking propulsion physics group at TU Dresden, focused on testing “the latest EMDrive and Mach-Effect thruster designs, the two most promising breakthrough thruster concepts that are currently being investigated in various laboratories”.

The Woodward effects could open the door to other, more exotic, sci-fi-like methods of propulsion, alluded to in the title of Woodward’s book” Crafting Spaceships and Stargates: The Science of Interstellar Transportation and Absurdly Benign Wormholes.”

A method of reactionless propulsion based on the Woodward effect, first dubbed Mach effect thruster (MET) then renamed Mach Effect Gravitational Assist (MEGA), was financed by the NIAC (Nasa Innovative Advanced Concepts) program and is described as a “technically credible and advanced tool [concept] it could one day “change the possible” in aerospace.”

Earlier this month, the project’s lead researcher, Heidi Fearn, gave a presentation titled “Mach effects for propulsion in space: an interstellar missionat the 2017 NIAC Symposium in Denver.

Fearn’s proposed interstellar mission would involve accelerating a robotic ship to 40% of the speed of light, slowing it down, spinning around the recently discovered exoplanet Proxima b in the Alpha Centauri system, collecting data and eventually, transmitting it to Earth within 25 years. The MEGA interstellar mission would be cheaper and at the same time more ambitious than another proposed interstellar mission, Revolutionary Starshot. Fearn pointed out that the mission’s feasibility is supported by credible physics and encouraging preliminary experimental results.

“Woodward’s mass fluctuation has been shown to fit well within the framework of gravitational absorber theory, of the type described by Fearn, based on the theory of Hoyle and Narlikar using advanced waves,” the authors note. conclusions of the proceedings of the Estes Park workshop. The lecture notes also indicated that many attendees believe that Woodward effects could also be derived from conventional, classical general relativity without advanced waves.

Other scientists disagree, and the jury is still out on whether EmDrive is ultimately bullshit. Exotic propulsion research needs more precise testing in the lab, testing in space, and theoretical studies that can be funded by small grants before we really know if it can help us reach for the stars.

Some exotic propulsion research is now inexpensive “garage science” that does not require multi-billion dollar investment and can even be self-funded. EmDrive enthusiasts can now 3D Printed EmDrive Parts and start doing independent experimental research.

In fact, many independent scientists participated in the Estes Park workshop. Of course, some critics take advantage of the artisanal nature of some of these experiments to deny the scientific value of the research. But in 1905, a young independent “amateur scientist”, taking time out from his daily job at the patent office, wrote three papers that changed the course of physics. His name was Albert Einstein.

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