Passion for the "impossible": the EmDrive engine

Passion for the "impossible": the EmDrive engine
Passion for the "impossible": the EmDrive engine
Anonim

At the end of 2016, a surprising message spread around the world news agencies: China is testing the "impossible" EmDrive engine in space. The one that seems to violate the law of conservation of momentum.

EmDrive engine

At a press conference in Beijing, Dr. Chen Yue of the China Academy of Space Technology (CAST) announced that his country has been successfully testing this technology in a laboratory for a long time. Moreover, China has now tested the engine on board the Tiangong 2 space station. The announcement only fueled a controversy that has been going on for almost 10 years. After all, the question of whether EmDrive works is actually equivalent to a dispute with Baron Munchausen about the possibility of pulling oneself out of the swamp by the hair, and even along with the horse. Let's try to figure it out.

The story began in 2001 when British engineer Roger Shawyer founded a small company, Satellite Propulsion Research Ltd. In this he was helped by a grant from the British Department of Trade and Industry and some private investors. The good reputation of the engineer with extensive experience in the space industry affected. In particular, Scheuer worked for 20 years with EADS Astrium, one of the world's largest manufacturers of spacecraft. As a result of the work in December 2002, the first working prototype of the "impossible" engine, named EmDrive, was presented to the public. In fact, the device was a hollow copper conical resonator, sealed at both ends. A magnetron, a device that generates microwave radiation, was attached to the resonator. Such magnetrons are widely used, for example, in microwave ovens.

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The operating principle of EmDrive immediately raised a lot of questions from specialists. The inventor himself claims that the operation of the engine is described by long-known physical laws and no "new physics" is needed to explain it. It is known that electromagnetic waves can carry energy and momentum. The effect of light pressure is well studied and even used for the orientation of some spacecraft. In EmDrive, the waves generated by the magnetron experience multiple reflections in the internal cavity of the resonator and press against its walls. And then the most controversial place in the theory begins. According to Scheuer, you can choose the size and shape of the resonator and the length of the electromagnetic waves emitted by the magnetron so that the pressure on the side walls of the cone will be zero. Then it turns out that the pressure on the large and small bases of the cone will be unequal, and thrust will arise in the engine in the direction of the plane of the base of a larger area. However, this fact contradicts the laws of physics, namely Newton's third law.

The fact is that the only way to travel in outer space that mankind has mastered so far is jet propulsion. It is based on the law of conservation of momentum. The thrust in a jet engine occurs due to the fact that the launch vehicle or spacecraft throws matter in the direction opposite to the motion. One of the main characteristics of such an engine is called specific impulse - it is the ratio of the impulse generated by the engine to the fuel consumption. Thus, the higher the specific impulse value, the less fuel the spacecraft spends to change the speed. The greater the speed with which the substance is expelled from the jet engine, the higher the specific impulse. Such an engine can accelerate the spacecraft to a higher speed, while spending less fuel.That is why ion engines have recently become increasingly popular in the space industry. They have low thrust, but high velocity of material flow, which makes them very effective for long-term space missions. However, they also face the main problem of all jet engines - a limited supply of fuel.

Another well-known way to travel in space is the space sail. Such a device will use to move the pressure of sunlight or solar wind - a stream of charged particles flying in the direction from our star at high speeds. Also recently, several projects have been presented, proposing to accelerate an apparatus with a sail using powerful laser radiation. But, despite the abundance of such projects, all of them are still far from effective practical application.

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Both a jet engine and a space sail need to interact with matter (fuel or solar wind) or electromagnetic waves to move. However, if the inventor of the EmDrive is to be believed, his motor does not interact with anything. In fact, Scheuer created a device to help Baron Munchausen pull himself out of the swamp by his hair. Needless to say, almost no one believed in the performance of EmDrive.

Over the next few years, Roger Scheuer worked on improving the "impossible" engine. In 2006, he introduced an improved water-cooled version of the EmDrive. According to the inventor, this should have increased traction. New Scientist magazine even featured a photo of the engine on the cover of September 8, 2006. The article concluded that the scheme of the device looks plausible, and in every possible way emphasized the arguments of its supporters. This caused a negative reaction from the readers of the magazine. The famous Australian science fiction writer Greg Egan published an open letter in which he accused the authors of the article of scientific illiteracy. Subsequently, New Scientist published a letter from the former technical director of EADS Astrium, Alvin Wilby, in which he in every possible way denies the company's participation in the Scheuer project.

Interestingly, the EmDrive isn't the only one of its kind. In 2006, inventor Guido Fetta developed a similar project called the Cannae Drive, or Q-drive, which works on a similar principle. The main difference between the two projects is the shape of the resonator. In Cannae Drive, it is not a cone, but a flattened pill-like container.

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The independent verification began only in 2008 and, surprisingly, in China. Under the guidance of Professor Yang Juan, a working prototype of the "impossible" was created at China's Northwestern Polytechnic University. According to preliminary data, the engine developed a thrust of 720 mN at a power of 1 kW. A weight weighing 72 grams will put pressure on the scales in approximately the same way. Subsequently, the results obtained in the article were refuted by the authors themselves, since a large error in the measurements was discovered. After taking it into account, the resulting engine thrust did not exceed 1 mN with an expended power of 230 W, which turned out to be less than the instrumental error.

However, since 2013, the Advanced Propulsion Physics Laboratory, or simply Eagleworks, has joined the testing of the "impossible" engine. It exists at the Lyndon Johnson Space Center - NASA's center for manned spacecraft development, astronaut training and manned space flight training. Eagleworks is a small research group tasked with testing new ways to move spacecraft. At one time, this laboratory was already well known in connection with the work on proof-of-concept of a semi-fantastic Warp engine. It is a hypothetical engine capable of propelling a spacecraft across interstellar distances at a speed greater than the speed of light. Typically, the Warp engine is a frequent visitor to science fiction books and films, not scientific publications.But in 1994, a work by Mexican physicist Miguel Alcubierre was published in the journal Classical and Quantum Gravity, in which he proposed the theoretical concept of a space-bending engine. Eagleworks hoped to demonstrate the very ability to bend space using a strong electric field. But the experiment carried out in the laboratory did not show convincing evidence of the curvature of space, although the authors themselves explain this by the insufficient sensitivity of the installation.

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To test the "impossible" engine, a sealed chamber and a special torsion balance, capable of detecting tens of micronewtons thrust, were used. Two versions of Cannae Drive were studied on the balance, which differed in the presence of grooves inside the resonator of one of the samples. According to Guido Fett's assumption, they were supposed to influence traction. It was measured several times, each time the engine was turned on and once after changing its orientation by 180 degrees. Also, in order to eliminate possible hardware errors, in addition to the motors on the scales, load tests were carried out, which does not create thrust when voltage is applied. According to the authors of the experiment, the installation turned out to be so sensitive that it can “feel” the sea in the Gulf of Mexico in windy weather. And this is about 40 kilometers southeast of downtown Johnson. And a thrust of the order of 30-50 micronewtons has indeed been discovered.

However, Harold White, head of research at Eagleworks, explains how the engine works in a very different way from its creators Scheuer and Fetta. According to him, "the additional thrust in the engine is obtained due to the magneto-hydrodynamic force acting in the quantum fluctuations of the vacuum, that is, due to interaction with the" quantum vacuum virtual plasma "by creating a virtual plasma toroid." The fact is that, according to modern concepts, a vacuum is not an empty space. It is filled with constantly emerging and annihilating elementary particles, called "virtual", since we cannot observe them directly. Simply put, according to the laboratory staff, EmDrive and others like it interact and, as it were, are repelled by these virtual particles of vacuum. Needless to say, this explanation was met with hostility by the scientific community. One of the main arguments against Eagleworks' experiments was the fact that the engine was not tested in a vacuum. The thrust could well have arisen as a result of air convection around the sample. It has also been suggested that microwave radiation "trapped" inside the resonator heats up the balance, which leads to a bias in the readings. NASA itself does not share Harold White's optimism about the impossible engine. The agency notes that Eagleworks is a small laboratory, which employs 5 people. And the other 18,000 space agency employees may not share their point of view.

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Some of the flaws in the experiment at the Johnson Center were addressed in a study carried out by physicists at the Technical University of Dresden. This time the tests were carried out in a vacuum chamber. The authors also tried to take into account the effects created by the induced electrical wiring of the installation. The result was the detection of a thrust of 20 micronewtons with a magnetron power of 700 watts and a frequency of 2.44 GHz. The main goal of the experiment of the researchers from Dresden was to try to detect the hardware effect that causes cravings. But what causes it, the authors of the work failed to understand.

The next time they started talking about the "impossible" was in November 2016. Information has leaked to the Web that Eagleworks is preparing its first publication in a peer-reviewed journal. And so it happened. A new study of the engine has been published in the Journal of Propulsion and Power, published by the American Institute of Aeronautics and Astronautics. It was done more accurately.As a test model, it was the Scheuer version that was used - the one that looked like a copper bucket. Researchers again used a torsion balance and this time with a vacuum chamber (8 × 10-6 Torr), due to which it was possible to further improve the accuracy of the experiment. The thrust measurements were carried out for three values ​​of the magnetron power - 40, 60, and 80 W. The experiment showed that the engine gives a thrust in a vacuum of 1.2 millinewtons per kilowatt. Interestingly, this value is 42 times greater than what was observed in the German experiment. The work now honestly considered possible sources of measurement errors. There were 9 of them, including a possible leakage of photons from a magnetron (the so-called photonic rocket), electromagnetic interactions with currents in the electrical circuit of the installation, thermal expansion of some elements of the torsion balance, and possible evaporation of molecules from the surface of the sample under study. However, according to Eagleworks, all of these effects cannot produce the observed thrust effect. For example, if there was a leakage of photons from the resonator, the thrust would be orders of magnitude less, the study says. According to current estimates, a photon engine needs a minimum of 300 MW (the power of a small power plant) to generate 1 Newton thrust.

The explanation of the principles of engine operation in the article again raised more questions than answers in the scientific community. According to the authors of the work, thrust can be explained by the so-called Pilot wave theory. This one of the possible interpretations of quantum mechanics was proposed by the French theoretical physicist Louis de Broglie in 1927. It is believed that the quantum-mechanical description of the properties of elementary particles is used only because we cannot yet notice their real dynamics. In fact, they move like macroscopic bodies along certain trajectories, described by the parameters hidden so far. As explained in the article, EmDrive can interact with virtual vacuum particles in the same way that a ship's propeller interacts with water, pushing a ship forward. However, 90 years have passed since the inception of the pilot wave theory, and today it is completely unpopular with specialists in quantum mechanics. So, the hypothesis of the emergence of thrust set forth in the work did not exactly arouse special enthusiasm in the scientific community.

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The scientific community for the most part did not believe in the test results of the controversial engine. Mark Mills, who headed the now defunct Breakthrough Propulsion Physics lab, believes that the abnormal thrust could have been caused by the interaction of the engine with the test chamber. Mills' laboratory was once engaged in tasks similar to the Eagleworks, that is, testing various semi-fantastic space engine projects. So he has enough experience to make such assumptions. Rochester Institute of Technology astrophysicist and Forbes science columnist Brian Coberlein noted that publishing an article in a peer-reviewed journal does not mean that the result will be correct. And examples of this happen more than once, for example, the recent story with the BICEP2 collaboration, in which they announced the detection of gravitational waves based on the polarization of the relic radiation. The work received a wide response and was published in the highly trusted journal Physical Review Letters. However, subsequent analysis and new data from the Planck space telescope showed that the authors of the study, instead of gravitational waves, saw the thermal contribution of interstellar dust to the relict background. Some experts pay attention to the large error in the measurement of engine thrust. The errors are so great that, if desired, it was possible to draw a line of dependence of the thrust on the power of the magnetron not increasing, but, for example, constant or even decreasing.

By the way, the Journal of Propulsion and Power does not have such trust.Its impact factor - the ratio of the number of articles cited in other journals to the total number of publications in the journal - is about 1.19 (for the period 2015/2016). This is pretty small, as many critics of the publication point out. For example, the Impact Factor for Physical Review Letters was 7.6 and Nature was 42.3.

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Russian scientists also criticized the EmDrive idea. Astrophysicist, editor-in-chief of the Troitsky Variant newspaper and member of the RAS Commission for Combating Pseudoscience Boris Stern called the very possibility of creating an impossible engine nonsense. “There is no need to understand the device. The law of conservation of momentum has exactly the same status in the foundation of the structure of the world as the law of conservation of energy (in the theory of relativity this is one law - the conservation of energy-momentum). But for centuries, new and new semi-literate inventors have proposed new and new versions of a perpetual motion machine, some instances even quietly work on parasitic effects and confuse eyewitnesses who are not too firm in a rational view of the world. Craftsmen with new perpetual motion machines have been sent from the doorstep for a long time,”the scientist wrote on the newspaper's website.

Internet users interested in astronautics also actively joined the discussion. At the end of last year, an interesting comment from a user with the nickname thatonefirst appeared on Reddit.com in a related topic, who believes that he discovered a bug in the Eagleworks experiment. After examining the graphs of the deviation of the torsion balance on which the motor was tested, he found that when the EmDrive was turned on and when a test pulse was applied, the behavior of the installation was slightly different. When a calibration pulse is applied, the balancer deflects almost instantly and just as quickly returns to its original position when turned off. But when deflected due to the EmDrive thrust, the torsion scales behave more inertly and even seem to continue to increase the deflection angle for some time, when the engine power is already turned off. The commentator suggests that this clearly indicates heating and thermal expansion of some element of the installation, which ultimately affects the readings of the scales. The experimenters themselves in the article explained such an unusual deflection of the balance bar by the design features of the torsion balance. Which of them turns out to be right, can only be shown by further tests.

However, if the impossible engine actually worked, it would radically change space flight. Of course, a spacecraft would not be able to rise from the Earth's surface using only the EmDrive thrust, here we still would not be able to do without chemical rockets. Indeed, even a small thrust can become effective in space, the main thing is that it can be maintained for a long time. Today, the promising Hall effect ion thruster can provide 60 millinewtons per kilowatt of thrust, which is far beyond the capabilities of EmDrive. But his fuel supply is not unlimited. And the Scheuer and Fett engine, running constantly, will prove to be more efficient. According to the inventors, an automatic station with such an engine could reach Mars in 70 days or deliver a load of 2000 kg to 0.1 sv. years in 15 years. Sounds fantastic? But even aside from such optimistic claims, the use of an "impossible" engine to correct the orbits of geostationary satellites would significantly reduce their weight, and hence the cost of launching.

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But does EmDrive actually work? Most of the scientific community is sure that most likely not. The very history of the creation of EmDrive looks very unscientific. The inventor who created the engine and NASA, who tested it, offer completely different theories to explain how it works. Moreover, the scientific nature of these theories raises big questions. Such a story could well have happened in the 19th century, but our time has long left no chance for accidental discoveries in the field of physics.Now the experiment almost always follows the theory, either confirming it or refuting it. And this is not the first time that the inventor of the miracle technology “Baron Munchausen” is trying to convince the whole world that his method will definitely not fail. So it was in the second half of the 50s, when Dean's car appeared. Its creator, Norman Dean, assured that with the help of springs and eccentrics, he could defeat the force of gravity. Or the recent story about the famous "Gravitsapa" - also an engine without jet mass emission. This device, despite numerous protests from the RAS Commission for Combating Pseudoscience, was sent into space aboard the small scientific satellite Yubileiny. But, as expected, no one canceled the laws of physics, and the "Gravitzap" in space was just ballast. Nevertheless, tests of the "impossible" continue. And even if this does not give humanity an easy way to conquer space, it will teach us how to conduct tests more accurately and more carefully look for measurement errors. Perhaps EmDrive will still benefit the scientific community, albeit a little differently than its creators expect.

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