UPDATE 5/11/15: The story of "NASA's impossible space engine" has roared back to life, prompted by an updated report on NasaSpaceflight.com. But the sad truth is that not much has really changed since my original investigation. The space engine still violates known laws of physics. The evidence that it works is still marginal, based on the limited information that the NASA Eagleworks team has reported. Those findings have not been submitted to peer review, so there is no way to evaluate them independently. And NasaSpaceflight.com is not in any way a NASA outlet. The official NASA statement: "This is a small effort that has not yet shown any tangible results." Being skeptical about a delicious story like this isn't much fun, but it is essential if we are going to make real progress in space exploration. Marc Millis, who for years directed the Breakthrough Propulsion Physics program at NASA's Glenn Research Center, calls things like the EmDrive "idea zombies," because they keep returning even when objective evaluations do not back up their claims. Meanwhile there are other, much more promising experimental spaceflight technologies (such as laser lightsails and electromagnetic rockets) that deserve a lot more support than they are getting. I truly believe that humans will eventually get to the stars--but it will require being smart and, yes, skeptical about where we place our hopes. -------- original story 8/6/14 ---------- Physicist John Baez has another, more colorful word to describe the spate of recent reports about a breakthrough space engine that produces thrust without any propellant. The word starts with "bull--." I won't finish it, this being a family-friendly web site and all. Baez himself has softened his tone and now calls it “baloney,” though his sentiment remains the same: The laws of physics remain intact, and the "impossible" space drive is, as far as anyone can tell, actually impossible.

Yes, that would be awesome, but we still have no idea how to do it. (Credit: Paramount Pictures) The story begins several years back with a British inventor named Roger Shawyer and his EmDrive, a prototype rocket engine which he claimed generated thrust by bouncing microwaves around in an enclosed metal funnel. Since no mass or energy emerged from the engine, Shawyer’s claim was another way of saying that he'd found a way to violate the conservation of momentum. In Baez’s words, “this is about as plausible as powering a spaceship by having the crew push on it from the inside.” Shawyer argued that he was exploiting a loophole within general relativity. Baez calls his explanation "mumbo jumbo." Everything in science is open to questioning, of course, but nobody is going to throw out all the textbooks on the say-so of a single inventor trying to raise money for his company, SPR Ltd. Conservation of momentum is one of the most fundamental and thoroughly confirmed principles in physics. The EmDrive therefore got little notice outside of the “weird science” web sites. Last year, a Chinese group reported success with a similar device, prompting another blip of fringe coverage but little more. Then Guido Fetta (a self-described “sales and marketing executive with more than 20 years of experience in the chemical, pharmaceutical and food ingredient industries”) built a third version of the EmDrive, renamed the Cannae Drive. Fetta convinced a sympathetic group of researchers at the Eagleworks Laboratories, part of NASA’s Johnson Space Center, to give it a test. The results were maybe, tentatively, a little bit encouraging. And that is when the nonexistent propellant really hit the fan. A number of publications that should have known better threw caution to the wind. “Nasa validates 'impossible' space drive” was the headline in an online story by WiredUK. The author, David Hambling, declared that an engine like the EmDrive could “take astronauts to Mars in weeks rather than months,” and even managed to work in nationalistic hand-wringing about “another great British invention that someone else turned into a success.” Soon the madness crossed the pond; “Space Engine Breaks Laws of Physics,” declaredPopular Mechanics. “EmDrive is an Engine That Breaks the Laws of Physics and Could Take Us to Mars,” summarizedMashable. Put It to the Rocket-Science Test Perhaps we should take a long cool drink at this point. Let’s start with the “NASA validates” part. NASA is a huge agency, with more than 18,000 employees. The testing was done by five NASA employees in a lab devoted to exploring unorthodox propulsion ideas. The team leader is a researcher named Harold “Sonny” White, himself a proponent of ideas about faster-than-light warp drives that most of his colleagues have classified as physically impossible. The lead author is one of White's Eagleworks teammates, David A. Brady. Calling this group “NASA”—as almost every popular news story has done—is a gross oversimplification.

The EmDrive produces propulsion without propellant, according to its inventor. (Credit: SPR, Ltd) Still, science is science: What matters are data, not motivations or semantics. Did White et al actually validate Fetta’s version of the EmDrive? The abstract of their paper, which was presented at a propulsion conference in Cleveland, is freely available online. Reading it raises a number of red flags. The methodology description makes it unclear how much of the testing took place in a vacuum—essential for measuring a subtle thrust effect. The total amount of energy consumed seems to have been far more than the amount of measured thrust, meaning there was plenty of extra energy bouncing around that could have been a source of error. Worst of all is this statement from the paper: “Thrust was observed on both test articles, even though one of the test articles was designed with the expectation that it would not produce thrust.” In other words, the Cannae Drive worked when it was set up correctly—but it worked just as well when it was intentionally disabled set up incorrectly. Somehow the NASA researchers report this as a validation, rather than invalidation, of the device. Did I say that was worst of all? I may have take that back. In the paper by White et al, they also write that the Cannae Drive “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.” That last bit stopped me. What’s a quantum vacuum virtual plasma? I’d never heard the term, so I dropped a note to Sean Carroll, a Caltech physicist whose work dives deeply into speculative realms of cosmology and quantum theory. Carroll wrote back immediately, with a pointed message: “There is no such thing as a ‘quantum vacuum virtual plasma,’ so that should be a tip-off right there. There is a quantum vacuum, but it is nothing like a plasma. In particular, it does not have a rest frame, so there is nothing to push against, so you can't use it for propulsion. The whole thing is just nonsense. They claim to measure an incredibly tiny effect that could very easily be just noise.” There is no theory to support the result, and there is no verified result to begin with. The Cost of Spaced-Out Dreams It is possible that there is some way around conservation of momentum. It is possible that there is a way to tap into the quantum vacuum. Heck, it is even possible that there is a way to build a useful warp drive. Nobody claims that our current understanding of physics is complete, and the things we do not know could be vast. At the same time, the important point here is that the things we do know are also vast. Overthrowing centuries of well-established ideas about how the world works is not something to be done lightly—certainly not on the basis of a single paper that has yet to be vetted by any independent researchers (the “NASA validated” headlines notwithstanding). That’s part of why this space-drive story bothers me so much. Abandoning known science when it feels good to do so is a dangerous proposition. As Carroll later tweeted, “The eagerness with which folks embrace sketchy claims about impossible space drives would make astrology fans blush.” I am personally a huge space enthusiast; I would love to see a new type of propulsion that would make it easier to explore the universe. But having your heart in the right place is no excuse to walk away from normal critical thinking. It is not materially different than the approach of people who reject science when they don’t like what it says about climate change, vaccines, or genetically modified organisms. The other danger here is that glorifying dubious shortcuts like Cannae Drive takes away attention--and, potentially, political support and funding--from the real space-exploration advances. You know, the ones that result from the hard work of large teams, not the tinkering of lone inventors. [UPDATE: This is one statement I regret from my original story. I didn't mean to denigrate the role individual creativity, which is incredibly important in developing new ideas. My intention here was to call out the secretive loners who make grand claims but then won't collaborate or present all of their work openly, making it impossible to distinguish hype from a genuine breakthrough.] When the results of the Cannae Drive prove impossible to validate (as will almost surely happen), it may produce an unjustified cynicism about how NASA has failed us once again. I'm not just speculating here. In a whiplash pivot, the same Popular Mechanics story that starts with the breathless headline ends with a sneer. The writer concludes, “But I'm still wondering, how much did it cost to run this test? During this era of tight budgets, is NASA wasting money on fringe science?”

While Rosetta circles, the Philae lander will touch down on comet Churyumov-Gerasimenko this fall--a real-world triumph. (Credit: ESA/ATG) That question is easy to answer, actually. Five researchers at Eagleworks Laboratories spent a total of 8 days testing the Cannae Drive, using mostly existing equipment. Assuming they each spent about half a day on the test, that is the salary equivalent of about $7,000, give or take. In the annals of government waste, $7,000 ranks as a footnote to a footnote to a footnote. I find it telling, then, that the issue of money is coming up at all. It is the crash that comes after inhaling the high of an up-with-people story in which sheer optimism can trump the laws of physics. The reality is that space exploration is expensive, difficult, and time-consuming. Therein lies both its challenge and its glory. The Rosetta mission making a historic rendezvous with comet Churyumov-Gerasimenko this week was in development for two decades. The intrepid New Horizons mission, scheduled to soar past Pluto next July, is fulfilling a cancelled part of NASA’s Grand Tour, originally planed in 1972. It took tremendous determination and engineering prowess to make these missions happen. The people who did the hard work deserve our respect and our admiration, not our delusions that there is an easy way out. Someday space travel may be simple and accessible to all. I certainly hope so. For now, though, we still live in the age of ad astra per aspera: through hardship, to the stars.

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