NASA is a major player in space science, so when a team from the agency this week presents evidence that "impossible" microwave thrusters seem to work, something strange is definitely going on. Either the results are completely wrong, or NASA has confirmed a major breakthrough in space propulsion.
Roger Shawyer (left), receiving a DTI SMART Award for his EmDrive concept in August 2001. (Click Image To Enlarge)
British scientist Roger Shawyer has been trying to interest people in his EmDrive for some years through his company Satellite Propulsion Research Ltd (SPR Ltd). Shawyer claims the EmDrive converts electric power into thrust, without the need for any propellant by bouncing microwaves around in a closed container. He has built a number of demonstration systems, but critics reject his relativity-based theory and insist that, according to the law of conservation of momentum, it cannot work.
The EmDrive itself is simply a microwave resonating cavity in the form of a closed, truncated cone (See below). You fire up a big electrically-powered microwave generator and start beaming microwaves inside this thing, and the microwaves bounce around all over the place, exerting radiation pressure on the inside of the cavity.
According to Shawyer, the EmDrive is able to extert a small amount of thrust that propels it towards the large side of the cone. Shawyer says this happens because inside the resonating cavity, the velocity of the microwaves changes significantly as the cavity diameter varies. The velocity changes enough, in fact, to exert a larger force on the larger end of the cavity, and a smaller force on the smaller end of the cavity, resulting in net thrust.
Prototype of the EmDrive microwave thruster engine developed by scientists at NASA. (Click Image To Enlarge)
SPR's EmDrive Demonstrator Engine (Side View)
SPR's EmDrive Demonstrator Engine (Front View) mounted on a test rig
A video clip of the initial part of an acceleration test run by SPR can be seen on YouTube:
You can also download the folowing .AVI files from the SPR website:
DMtest188.avi (13.7MB)
DMtest188.wmv (5.33MB)
Notes on Test video:
- The field strengths within the thruster equate to a power level of 17MW. Signal leakage causes EMC effects within the fixed video camera. This leads to the apparent vertical movements.
- The engine only starts to accelerate when the magnetron frequency locks to the resonant frequency of the thruster, following an initial warm up period. This test operation eliminates possible spurious forces.
- The rotary air bearing supports a total load of 100kg, with a friction torque resulting in a calibrated resistance force of 8.2 gm at the engine centre of thrust.
- For this test a thrust of 96 mN was recorded for an input power of 334 W.
Research to confirm the results of the EmDrive microwave thruster engine developed by Roger Shawyer came from a team of Chinese researchers headed by Yang Juan, Professor of Propulsion Theory and Engineering of Aeronautics and Astronautics at the Northwestern Polytechnic University in Xi'an and the findings published in a research paper titled "Net thrust measurement of propellantless microwave thruster." The research paper was originally written on June 9, 2011 and finally published in 2012 in the academic journal Acta Physica Sinica, now translated into English.
Yang Juan, Professor of Propulsion Theory and Engineering of Aeronautics and Astronautics at the Northwestern Polytechnic University in Xi'an. (Click Image To Enlarge)
The Chinese team led by Professor Yang Juan built its own EmDrive and confirmed that it produced 720 mN (about 72 grams) of thrust, enough for a practical satellite thruster. Such a thruster could be powered by solar electricity, eliminating the need for the supply of propellant that occupies up to half the launch mass of many satellites. The Chinese work attracted little attention; it seems that nobody in the West believed in it.
Chinese EmDrive Microwave Engine Thruster developed by Professor Yang Juan. (Click Image To Enlarge)
Schematic of the Chinese EmDrive Microwave Engine Thruster developed by Professor Yang Juan. (Click Image To Enlarge)
However, a US scientist, Guido Fetta, has built his own propellant-less microwave thruster, and managed to persuade NASA to test it out. The test results were presented on July 30 at the 50th Joint Propulsion Conference in Cleveland, Ohio. Astonishingly enough, they are positive.
NASA tested a different version of the EmDrive called the Cannae Drive designed by Guido Fetta. (Click Image To Enlarge)
According to Guido Fetta, the "Cannae Drive," was named after the Battle of Cannae in which Hannibal decisively defeated a much stronger Roman army: you're at your best when you are in a tight corner. However, it's hard not to suspect that Star Trek's Engineer Scott -- "I cannae change the laws of physics" -- might also be an influence. (It was formerly known as the Q-Drive.)
The NASA team based at the Johnson Space Centre gave its paper the title "Anomalous Thrust Production from an RF [radio frequency] Test Device Measured on a Low-Thrust Torsion Pendulum".
The five NASA research team spent six days setting up test equipment followed by two days of experiments with various configurations. These tests included using a "null drive" similar to the live version but modified so it would not work, and using a device which would produce the same load on the apparatus to establish whether the effect might be produced by some effect unrelated to the actual drive. They also turned the drive around the other way to check whether that had any effect.
In January 2014, the NASA research team also tested Shawyer's EmDrive design. The test results for this were also positive, and in fact their tapered-cavity drive, derived from the Chinese drive which is in turn based on Shawyer's EmDrive, produced 91 micronewtons of thrust for 17 watts of power, compared to the 40 micronewtons of thrust from 28 watts for the Cannae drive.
In her research paper, professor Yang Juan describes China's iteration of Shawyer's EmDrive that's able to generate 72 grams of thrust with 2,500 watts of electricity. It doesn't sound like a huge amount, but if you compare it to the hands-down most efficient spacecraft engine we've got right now (where efficiency is at an absolute premium), an ion thruster, the Chinese EmDrive gets you four times as much thrust from half as much power without sucking down any fuel at all. Yeah, you need electricity, but electricity is cheap in space and cheaper on the ground. Anyway, you can read the paper here, and if you can make conclusive heads or tails of it, please do us all a favor and explain it in the comments. Below is an infographic comparing the Chinese EmDrive with the European Space Agency's SMART-1 ion engine:
Click Image To Enlarge
Back in the 90s, NASA tested what was claimed to be an antigravity device based on spinning superconducting discs. That was reported to give good test results, until researchers realised that interference from the device was affecting their measuring instruments. They have probably learned a lot since then.
The torsion balance they used to test the thrust was sensitive enough to detect a thrust of less than ten micronewtons, but the drive actually produced 30 to 50 micronewtons -- less than a thousandth of the Chinese results, but emphatically a positive result, in spite of the law of conservation of momentum:
"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."
This last line implies that the drive may work by pushing against the ghostly cloud of particles and anti-particles that are constantly popping into being and disappearing again in empty space. But the NASA team has avoided trying to explain its results in favour of simply reporting what it found:
"This paper will not address the physics of the quantum vacuum plasma thruster, but instead will describe the test integration, test operations, and the results obtained from the test campaign."
Fetta also presented a paper at AIAA on his drive, "Numerical and Experimental Results for a Novel Propulsion Technology Requiring no On-Board Propellant". His underlying theory is very different to that of the Shawyer's EmDrive, but like Shawyer he has spent years trying to persuade sceptics simply to look at it. He seems to have succeeded at last.
Shawyer himself, who sent test examples of the EmDrive to the US in 2009, sees the similarity between the two.
He believes the design accounts for the Cannae Drive's comparatively low thrust. He says.
"From what I understand of the NASA and Cannae work -- their RF thruster actually operates along similar lines to EmDrive, except that the asymmetric force derives from a reduced reflection coefficient at one end plate. Of course this degrades the Q and hence the specific thrust that can be obtained."
Fetta is working on a number of projects which he is not able to discuss at present, and NASA's PR team was not able to get any comments from the research team. However, it's fair to assume that the results will be picked over very closely indeed, like CERN's anomalous faster-than-light neutrinos. The neutrino issue was cleared up fairly quickly, but given that this appears to be at least the third independent propellant-less thruster to work in tests, the anomalous thrust may prove much harder to explain away.
The NASA paper projects a 'conservative' manned mission to Mars from Earth orbit, with a 90-ton spacecraft driven by the new technology. Using a 2-megawatt nuclear power source, it can develop 800 newtons (180 pounds) of thrust. The entire mission would take eight months, including a 70-day stay on Mars.
This compares with NASA's plans using conventional technology which takes six months just to get there, and requires several hundred tons to be put into Earth's orbit to start with. You also have to stay there for at least 18 months while you wait for the planets to align again for the journey back. The new drive provides enough thrust to overcome the gravitational attraction of the Sun at these distances, which makes manoeuvring much easier.
A less conservative projection has an advanced drive developing ten times as much thrust for the same power -- this cuts the transit time to Mars to 28 days, and can generally fly around the solar system at will, a true NASA dream machine.
COMMENTARY: The validation of the Roger Shawyer's electromagnetic drive or EmDrive appears to be a potential gamebreaker for the nation that can develop a fully-functional and scalable microwave-powered EmDrive that can prove its efficiency and reliability in outerspace.
A propellantless rocket thruster that will meet or exceed the requirements needed for future manned space missions to Mars or even neighboring star systems, will depend on fully exploiting this EmDrive technology to its fullest. In fact, the future of mankind could rest on just such a propellantless rocket thruster.
The World is rapidly running out of natural resources used in developing rocket propellants, and since anti-magnetic propulsion systems do not appear to be in our immediate future, ion-powered engine thrusters and EmDrive powered systems are two options that are open to exploitation.
I believe that our country to do everything possible to develop such a propellantless microwave-powered engine thruster for future space travel.
Courtesy of an article dated July 31, 2014 appearing in U.K. Wired, an article dated August 1, 2014 appearing in Sploid Gizmodo, an article dated February 6, 2013 appearing in U.K. Wired, an article dated August 6, 2014 appearing in Guardian Liberty Voice, an article dated February 6, 2013 appearing in U.K. Wired, and Roger Shawyer's website SPR, Ltd
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