Ever since NASA announced the prototype of the controversial EM Drive (resonant cavity radio frequency motor), criticism has not dwindled, and any reported experimental results have sparked heated debate. And since most of the announcements take the form of "leaks" and rumors, it's no surprise that the degree of skepticism hasn't subsided.
And yet reports keep coming in. The latest results were obtained from Eagleworks Laboratories at the Space Center. Johnson. The leaked report shows that the controversial engine is capable of generating thrust in a vacuum. And like the peer review process, the ability of an engine to operate in space has been a bothersome issue for quite some time.
Given the pros of EM Drive, it's not hard to see why people want it to work. In theory, it could generate enough thrust to reach the Moon in four hours, Mars in 70 days, Pluto in 18 months, all without a drop of fuel. Unfortunately, this propulsion system is based on principles that violate the conservation of momentum.
This law states that the momentum of the system remains constant, is not created or destroyed, but only changes under the influence of forces. Since the EM Drive includes electromagnetic microwave cavities that convert electrical energy directly into thrust, it has no reaction mass. And therefore it is "impossible" according to the laws of traditional physics.
A report titled "Measurement of the impulsive thrust of a closed radio-frequency cavity in a vacuum" was made public in early November. Its lead author is, of course, Harold White of Eagleworks, who designs advanced propulsion systems at NASA.
In the paper, he and his colleagues reported that they had completed an impulsive thrust test on a "conical radio frequency test specimen." It consisted of forward and reverse thrust phases, a low thrust pendulum, and three thrust tests at power levels of 40, 60 and 80 W. As follows from the report:
"It is shown here that a dialectically loaded conical RF sample, fired in TM212 mode at 1937 MHz, is capable of consistently generating a thrust of 1.2 ± 0.1 mN / kW with a force directed towards the narrow end under vacuum."
To be clear, this level of thrust to power - 1.2 mN per kilowatt - is quite negligible. Indeed, the paper puts these results in context for comparison with ion thrusters and laser sails:
Promotional video:
“The best thrust to power in the Hall engine to date is about 60 mN / kW. This is an order of magnitude higher than the test sample produced during operation in a vacuum. The performance of 1.2 mN / kW is two orders of magnitude higher than other forms of "no fuel" propulsion such as laser sails, laser propulsion and photonic rockets, which develop a thrust of 3.33-6.67 mN / kW."
Ion engines are currently considered the most fuel efficient form of propulsion. However, they are quite slow compared to conventional solid fuel engines. For example, ESA's Dawn mission relied on a xenon-ion engine that produced 90 millinewtons per kilowatt of thrust. Using this technology, it took the probe nearly four years to get from Earth to the asteroid West.
Conversely, the concept of directed energy (like laser sails) requires very little thrust because it uses a small apparatus - a tiny probe weighing a few grams and chip-like instruments. Currently, this concept is being investigated as promising for travel to the nearest planets and star systems.
Two good examples are NASA's DEEP-IN interstellar concept, which is currently being developed by the University of California, Santa Barbara, and will try to use lasers to accelerate spacecraft to 0.25 the speed of light. Meanwhile, the Starshot project (as part of the Breakthrough initiatives) is developing a device that can reach up to 20% the speed of light and reach Alpha Centauri in 20 years.
Compared to these offerings, EM Drive boasts that it does not require any fuel or external power source. But based on his test results, the amount of energy required to generate significant thrust makes it impractical. However, let's not forget that the original purpose of these tests was whether the thrust generated by the engine could be attributed to any unnoticed anomalies.
The report also acknowledges the need for further testing to rule out other possible causes, such as center of gravity and thermal expansion. And if external causes can be ruled out as well, future tests will challenge the performance of the EM Drive. And all this on condition that the "leak" is genuine. Until NASA can confirm the reality of these results, EM Drive will be suspended in a state of uncertainty.
ILYA KHEL