A recently leaked, unpublished paper from NASA reveals that NASA has made a functioning Radio Frequency Resonant Cavity Thruster, otherwise known as electromagnetic propulsion drive or EM Drive or Warp Drive – a space engine with fuel-free propulsion system. The EM Drive uses magnetic waves to create thrust by bouncing microwave photons within a closed cone-shaped metal vessel shown below. The motion causes the pointed end of the drive to generate thrust and propel it in the opposite direction. The microwaves gather electricity via solar power and it does not require a propellant.
Critics remain skeptical about the idea saying that the engine violates basic Newton's Third Law of Motion, which states that for every action there is an equal and opposite reaction.
According to state-of-the art theory, a warp drive could cut the travel time between stars from tens of thousands of years to weeks or months, of transporting humans to Mars in 10 weeks, fly to the Moon in four hours, and travel to Pluto in only 18 months - all without the need for a propellant.
As detailed in the paper, NASA physicists led by Harold “Sonny” White and Paul March were able to generate thrust in a “tapered RF test article” (EmDrive prototype) during a series of tests at NASA’s Eagleworks Labs at Johnson Space Center in the fall of 2015.
In short, the NASA engineers are trying to determine whether faster-than-light travel — warp drive — might someday be possible. The team is attempting to slightly warp the trajectory of a photon, changing the distance it travels in a certain area, and then observing the change with a device called an interferometer.
“Space has been expanding since the Big Bang 13.7 billion years ago,” White told the New York Times in 2013. “And we know that when you look at some of the cosmology models, there were early periods of the universe where there was explosive inflation, where two points would’ve went receding away from each other at very rapid speeds. Nature can do it,” he added. “So the question is, can we do it?”
As detailed in the leaked paper, the NASA EmDrive test consists of a closed copper cone, that is bombarded with microwaves. The researchers powered it with 40, 60, and 80 watts and found that it generated up to 58, 128, and 119 micronewtons of thrust, respectively. Given that this “anomaly” was still observed by White and his colleagues after accounting for error, this suggests that the results of the experiment show an EmDrive is possible.
Based on the released paper, the researchers estimated that their contraption would be capable of generating approximately 1.2 millinewtons of thrust per kilowatt in a vacuum were they to scale up the power input. To put this in perspective, the Hall thruster—one of the most powerful in development and powered by ejecting plasma—generates about 60 millinewtons of thrust per kilowatt. While the level of thrust to power is significantly smaller than ion thrusters, the researchers said it is twice as powerful as the thrust of light sails - currently the most popular form of zero-propellant propulsion, which uses beams of sunlight to propel it forward.
“The issue involved here is whether the experiment is seeing something real or not,” Jim Woodward, a physicist at California State-Fullerton, told Motherboard. “I know Paul does clean work and to be honest, I suspect there may really be something there. But the result they're seeing can't actually be explained in terms of the theory they're proposing. So the question is: what is causing it?”
As Newton showed in the 18th Century, if you want to propel a rocket through space, you’re going to have to eject some material in the opposite direction of the rocket’s travel. But an EmDrive appears to generate a reaction without any action.
“Absent a convincing physical explanation that doesn't fly in the face of well-known principles of physics, you should hold in abeyance any judgment as to whether or not the NASA results are real,” said Woodward. “This stuff is much harder to do and get right than almost anybody who has not actually been in the trenches doing it really appreciates. The odds against anything being real in this business are very high.”
A number of theories have been floated attempting to explain this ostensible violation of the bedrock of physics. White has been a proponent of the quantum vacuum explanation, which posits that the EmDrive is able to generate thrust by acting on virtual particle pairs that are generated by fluctuations in the quantum vacuum (in this theory, these vacuum fluctuations are created by the electromagnetic field generated by the EmDrive). In essence, the microwaves would be ‘pushing off’ of these virtual particles within the EmDrive cavity to generate the thrust that has been observed by White and his colleagues in EmDrive experiments.
Another leading explanation is that the EmDrive’s thrust is generated by radiation pressure, a position held by its inventor Roger Shawyer. On this view, when the microwave radiation enters the copper cavity, the radiation pushes against the walls of the EmDrive and generates thrust.
Yet, according to Woodward, both of these theories are unlikely to be correct for the simple reason that physics doesn’t allow them. But since the EM Drive involves electromagnetic microwave cavities, it does not have a reaction mass.
In 1994, a Mexican physicist, Miguel Alcubierre, theorized that faster-than-light speeds were possible in a way that did not contradict Einstein by harnessing the expansion and contraction of space itself. Under Dr. Alcubierre’s hypothesis, a ship still couldn’t exceed light speed in a local region of space. But a theoretical propulsion system he sketched out manipulated space-time by generating a so-called “warp bubble” that would expand space on one side of a spacecraft and contract it on another.
An Alcubierre Warp Drive stretches spacetime in a wave causing the fabric of space ahead of a spacecraft to contract and the space behind it to expand. The ship can ride the wave to accelerate to high speeds and time travel. The Alcubierre drive, also known as the Alcubierre metric or Warp Drive, is a mathematical model of a spacetime exhibiting features reminiscent of the fictional "warp drive" from Star Trek, which can travel "faster than light/"
“In this way, the spaceship will be pushed away from the Earth and pulled towards a distant star by space-time itself,” Dr. Alcubierre wrote. Dr. White, the NYT reports, has likened it to stepping onto a moving walkway at an airport.
Alcubierre’s theory, however, depended on large amounts of a little understood or observed type of “exotic matter” that violates typical physical laws.
In general relativity, one often first specifies a plausible distribution of matter and energy, and then finds the geometry of the spacetime associated with it; but it is also possible to run the Einstein field equations in the other direction, first specifying a metric and then finding the energy-momentum tensor associated with it, and this is what Alcubierre did in building his metric. This practice means that the solution can violate various energy conditions and require exotic matter. The need for exotic matter leads to questions about whether it is actually possible to find a way to distribute the matter in an initial spacetime which lacks a "warp bubble" in such a way that the bubble will be created at a later time.
Yet another problem according to Serguei Krasnikov is that it would be impossible to generate the bubble without being able to force the exotic matter to move at locally FTL speeds, which would require the existence of tachyons. Some methods have been suggested which would avoid the problem of tachyonic motion, but would probably generate a naked singularity at the front of the bubble.
White believes that advances he and others have made render warp speed less implausible. Among other things, he has redesigned the theoretical warp-traveling spacecraft — and in particular a ring around it that is key to its propulsion system — in a way that he believes will greatly reduce the energy requirements. But ”We’re not bolting this to a spacecraft,” he said of the technology.
Richard Obousy, a physicist who is president of Icarus Interstellar, a nonprofit group composed of volunteers collaborating on starship design, said “it is not airy-fairy, pie in the sky. We tend to overestimate what we can do on short time scales, but I think we massively underestimate what we can do on longer time scales.”
White likened his experiments to the early stages of the WW11 Manhattan Project, which were aimed at creating a very small nuclear reaction merely as proof that it could be done.
“Routine travel among the stars is impossible without new discoveries regarding the fabric of space and time, or capability to manipulate it for our needs,” says Neil deGrasse Tyson, astrophysicist at the American Museum of Natural History, said “By my read, the idea of a functioning warp drive remains far-fetched, but the real take-away is that people are thinking about it — reminding us all that the urge to explore continues to run deep in our species.”
Still, one of the most dubious is Dr. Alcubierre himself. He listed a number of concerns, starting with the vast amounts of exotic matter that would be needed. “The warp drive on this ground alone is impossible,” he said. “At speeds larger than the speed of light, the front of the warp bubble cannot be reached by any signal from within the ship,” he said. “This does not just mean we can’t turn it off; it is much worse. It means we can’t even turn it on in the first place.”