Tuesday, November 15, 2016

The NASA EmDrive

From Daniel Oberhaus' 11-14-16 Motherboard article entitled "The Fact and Fiction of the NASA EmDrive Paper Leak":
"If humanity ever wants to truly explore the outer reaches of our solar system or travel to other stars, we’re going to have to build a better engine for our spacecraft. In fact, this engine will have to be so good that it will be capable of generating thrust without consuming propellant. That’s right: If we ever want a four-hour trip to the moon or a two-month trip to Mars, we’re going to need a rocket engine that doesn’t need rocket fuel.
"This is the idea behind the radio frequency resonant cavity thruster—otherwise known as EmDrive—a theoretical reactionless engine powered by turning electricity into microwaves and bouncing them around a closed metal funnel.
"The EmDrive has been dismissed as 'impossible' on more than one occasion because it appears to violate Newton’s Third Law of Motion, which states that for every action there is an equal and opposite reaction. But if a leaked NASA paper posted online last Saturday is to be believed, then not only are NASA scientists pursuing an EmDrive, but they actually made one that works.
"As detailed in the paper, a team of NASA physicists led by Harold 'Sonny' White and Paul March—both leading figures in exotic propulsion systems—was able to generate thrust in a 'tapered RF test article' (read: EmDrive prototype) during a series of tests at NASA’s Eagleworks Labs at Johnson Space Center in the fall of 2015.
"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.
"'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 [March] 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?'
"Per Newton, 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—so what gives?
"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 a simple reason: Physics doesn’t allow them."
To read the read of Oberhaus' article, click HERE.

No comments:

Post a Comment