Emdrive Latest News: What is Emdrive Thruster Technology, and Can It Really Work?

[Image: NASA]

In November 2015, NASA’s Eagleworks Laboratories revealed that it had carried out a series of tests on Roger Shawyer’s controversial electromagnetic (EM) propulsion drive thruster, suggesting that the controversial EMdrive thruster technology can actually work.

Eagleworks Laboratories is the experimental lab at NASA’s Johnson Space Center, and was set up to investigate far-out propulsion claims. The Eagleworks holds the same significance to NASA what the Google X “moonshot” R&D lab holds for Google/Alphabet.

EM Drive: The Concept

First designed in 2001 by British aerospace engineer Roger Shawyer, the EMdrive is actually a propellantless, propulsion system, which is claimed to produce thrust without requiring any fuel. EM Drive is a hypothetical machine which uses an RF resonant cavity thruster model. According to Shawyer, his EM Drive will use solar power to produce multiple microwaves that will move to and fro in an enclosed chamber to generate a vast amount of thrust.

The principle of operation of an EM Drive is based on the phenomenon of radiation pressure. According to Shawyer, any EM wave, traveling at the speed of light will have some momentum which when transferred to a reflector, will result in a small force. If the EM wave moving within a conical waveguide is bounced between two reflectors and the velocity difference at the reflector surfaces is large, the difference between forces will produce a resultant thrust to the waveguide linking the two reflectors.

Theoretically, absence of a fuel would make a craft significantly lighter, easier to move, and much cheaper to create. The engine would be able to work continuously without using any rocket fuel until some part of the engine fails or wears out. In addition, the drive would be able to achieve extremely high speeds and reach to distant planets like Pluto within a period of just a few months. It is also claimed that with EMdrive, it would be possible to reach moon in just 4 hours.

However, Shawyer’s idea was rejected by most scientists for being unfeasible. Scientists said the entire concept of a reactionless drive is inconsistent with Newton’s law of conservation of momentum, which states that the linear and angular momentum within a closed system always remains constant irrespective of changes taking place within the system. Moreover, as reactionless drives are based on the concept that no reaction is produced even when an action happens, many scientists said this concept is against Newton’s third law of motion which states that for every action, there is an equal and opposite reaction, and if an EM-Drive really works, that means an as-yet-undefined phenomenon is taking place.

EMdrive: Tests Performed

In 2001, British Government gave Shawyer a £45,000 grant for testing the EMdrive. These tests used 850 watts of power and reportedly achieved 0.016 Newton of force.

In 2009, another series of tests were performed by a team of Chinese researchers at the Northwestern Polytechnical University that confirmed the correctness of the theory behind EM Drive and RF resonant cavity thrusters. These researchers built their own EM Drive and performed multiple tests on that drive between 2012 and 2014. The tests demonstrated a modest amount of thrust being generated towards the wider end of a conical, closed container when the container was filled with resonating microwaves. The tests required 2,500 watts of power for the 2.45 GHz EM Drive thruster to produce 720 mN (millinewtons) of thrust. The measurements were done using a national standard, thrust measurement device, which is also used for Ion Engine development.

In August 2013, NASA carried out an official study of EM Drive and published the findings in June 2014. The results were also presented at the 50th Joint Propulsion Conference in Ohio. NASA scientists built their own version of an EM Drive, and performed tests in a variety of conditions including a hard vacuum. The team confirmed that the RF resonant cavity thruster design does generate thrust. Researchers reported achieving a thrust about 1/1,000 of what Shawyer had claimed.

Roger Shawyer, while addressing the IAC 2014 conference in Toronto, stated that EM-drive theory has been verified by 8 sets of test data, and these data sets were obtained from measurements on seven different thrusters by four organizations in three different countries.

In 2015, a NASA group tested engineer Guido Fetta’s Cannae Drive and reported that positive net thrust was achieved. Same year, Dresden University of Technology’s research group carried out tests on EM Drive and reported generated of thrust—both predicted as well as unexpected.

In 2016, engineer Paul March used NASA Spaceflight forum to reveal some of the findings of new tests conducted on EM Drive. According to March, researchers at Eagleworks Lab utilized an improved experimental procedure and were able to mitigate some errors from prior tests. March explained that the lab created and installed a 2nd generation magnetic damper which helped in reducing the stray magnetic fields in a vacuum chamber. The magnetic fields were reduced by an order of magnitude inside the chamber, and researchers were also able to decrease Lorentz force interactions. A contamination was however noticed, which was caused by thermal expansion. The contamination proved even worse in a vacuum (outer space conditions). Researchers then tried to develop an analytics tool that would allow separating the contamination and performing an integrated test to mitigate thermally induced errors completely.

March also revealed that despite these issues, the machine still produced “anomalous thrust signals”—the single biggest discovery of these tests. According to some researchers, the recurring phenomenon of direction-based momentum could make EMdrive a legitimate answer to interstellar travel.

The American space agency then planned to carry out another series of tests on a quantum vacuum plasma thruster for independent validation of the thruster. Some low-thrust torsion pendulum tests were also carried out at NASA’s Jet Propulsion Laboratory and the results obtained from both tests were compared.

Why So Much Interest in EM Drive

 Scientists and researchers have been watching every new development in EM-drive thruster technology with great interest. According to experts, this technology could find application in atmospheric temperature-controlling satellites, space travel, and development of more efficient automobiles.

Some Clarifications Regarding EM Drive

Shawyer’s Space Company Satellite Propulsion Research Ltd states that :

  • The thrust produced by the EMdrive is not a reactionless force, but is produced due to the reaction between the end plates of the waveguide and the Electromagnetic wave propagated within it.

 

  • The EM Drive doesn’t violate established laws of physics. Newton’s laws are applied when deriving the basic static thrust equation. Newton’s laws, including the law of conservation of momentum, have also been demonstrated to apply to the EM Drive experimentally. The dynamic thrust equation is based on the law of conservation of energy, and the equation applies to the EM-drive under acceleration. The basic design equations are derived using the principles of electromagnetic theory.

 

  • EM Drive will not violate the law of conservation of momentum while operating in free space. The EM wave momentum gets developed and increases in the resonating cavity, and then transferred to the end walls upon reflection. The gain of momentum by EMdrive added to the momentum lost by the EM wave is equal to zero. The direction and acceleration measured also comply with Newton’s laws.

 

  • The axial component of the sidewall force doesn’t balance out the net force in the EM thruster because of non-linear relationship between the group velocity and waveguide diameter.

 

  • The EM Drive is not a perpetual motion machine because it obeys the law of conservation of energy. Acceleration of the EM-drive requires that energy is spent. After switching off of the EM Drive, motion remains constant unless the drive is acted upon by some other force.

 

  • Convection currents were not found to affect the results, as measurements for EMdrive thruster were taken with the thrust vector horizontal, up, and down.

 

  • Acceleration and deceleration tests were performed in both clockwise and anti-clockwise directions, and it was observed that acceleration from rest starts when the output frequency of the magnetron matches the resonant frequency of the engine, following a warm-up period.

 

  • For terrestrial transport applications, it is expected that the second generation engines will be able to produce a specific thrust of 30kN/kW. For 1 kilowatt, a static thrust of 3 tonnes can be obtained, which is sufficient to support terrestrial transport applications.

In April 2016, a report published in the IBTimes stated that EMdrive is undergoing peer review This report was based on a comment from Paul March—member of the EM Drive team at NASA’s Englaworks lab—who said that the people should have patience about publishing of the EW paper as peer review is a very slow process.

Paul March wrote on the NASA Spaceflight forum on 17 March:

“The Eagleworks Lab is NOT dead and we continue down the path set by our NASA management. Past that I can’t say more other than to listen to Dr Rodal on this topic, and please have patience about when our next EW paper is going to be published. Peer reviews are glacially slow.”

Peer review is the process where other experts in a field try to achieve the same results as claimed in a research paper before its official publication.

According to March, NASA doesn’t want its team members to release all the details regarding EMdrive in public domain as the American space agency is not yet in a position to give its approval to a technology which many people believe will not work at all.

In April 2016, Dr Mike McCulloch, a researcher from the Plymouth University in the UK, came up with a new theory which attempted to explain how Roger Shawyer’s seemingly impossible EMdrive could actually work.

The new theory is based on the concept of “Unrah effect”. It states that any accelerating object experiences black body radiation, or in other words, the universe warms up when an object accelerates. According to McCulloch, it is possible to predict and test EMdrive’s thrust by taking into account radiation pressure from Unruh waves. McCulloch says EMdrive’s thrust can be predicted by “assuming that the inertial mass of the photons in the cavity is caused by Unruh radiation, whose wavelengths must fit exactly within the cavity, using a theory already applied successfully to astrophysical anomalies such as galaxy rotation where the Unruh waves have to fit within the Hubble scale.” McCulloch argues that Unruh waves are responsible for increase in the momentum as the thruster moves, and that the same effect causes anomalies to appear when spacecraft accelerate around a planet.

MIT also notes that the wavelengths of Unruh radiation become so large at small accelerations that they can no longer fit in the observable universe. In this case, inertia can take only some specific “whole-wavelength values and so jumps from one value to the next.” Thus, the inertia of photons inside the truncated cone will change as they bounce back and forth, and therefore a thrust must be generated to conserve momentum.

According to McCulloch, the model predicts thrusts of: 3.8, 149, 7.3, 0.23, 0.57, 0.11, 0.64 and 0.02 mN compared with the observed thrusts of: 16, 147, 9, 0.09, 0.05, 0.06, 0.03, and 0.02 mN. It also predicts that “if the axial length is equal to the diameter of the small end of the Cavity, the thrust should be reversed.”

In September 2017, Chinese scientists claimed that they have created a working EM Drive. A video released by the China’s space agency showed Chinese scientists with a  working EMdrive.