Tag Archives: emDrive

The Fact and Fiction of the NASA EmDrive Paper Leak

A NASA paper outlining work that appears to substantiate the EmDrive concept that involves the production of a thrust in a way that violates the laws of physics was leaked last week, and this story tries to figure out what has been learned.

To me, the key is this paragraph:

In essence, the NASA EmDrive in the paper consists of a closed copper cone, the inside of which is being bombarded with microwaves. To test the EmDrive, 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 indeed possible.

Based on these results, the researchers estimated that their contraption would be capable of generating approximately 1.2 millinewtons of thrust per kilowatt 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. [emphasis mine]

Interestingly , the article did not comment on how little thrust this EmDrive test produced. This tiny amount, however, to me suggests strongly that what they are measuring is some outside force acting on the drive that they have missed that would invalidate all the theories listed in the article. And even if the thrust drive does prove a new component of fundamental physics, as suggested in the article, the system simply doesn’t appear to produce enough thrust to make it practical.

NASA confirms “impossible” drive

Life imitates science fiction: NASA engineers have confirmed the functionality of an “impossible” space thruster drive.

British scientist Roger Shawyer has been trying to interest people in his EmDrive for some years through his company 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.

According to good scientific practice, an independent third party needed to replicate Shawyer’s results. As Wired.co.uk reported, this happened last year when a Chinese team 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.

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.

Since no one understands the physics that are producing the thrust, it is wise at this point to be very skeptical of these results. A lot more testing and experimentation will be necessary before this can be made practical.

However, if it is what they think it is, it will make it possible to turn sunlight into thrust, meaning that spacecraft will no longer need fuel, and will be able to go places much faster using the constant thrust this drive will provide.