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International Business Times writes:
A new peer-reviewed paper (open, DOI: 10.1063/1.4953807) on the EmDrive from Finland states that the controversial electromagnetic space propulsion technology does work due to microwaves fed into the device converting into photons that leak out of the closed cavity, producing an exhaust.
So how could something come out that you can't detect? Well, the photons bounce back and forth inside the metal cavity, and some of them end up going together in the same direction with the same speed, but they are 180 degrees out of phase. Invariably, when travelling together in this out-of-phase configuration, they cancel each other's electromagnetic field out completely.
That's the same as water waves travelling together so that the crest of one wave is exactly at the trough of the other and cancelling each other out. The water does not go away, it's still there, in the same way the pairs of photons are still there and carrying momentum even though you can't see them as light.
If you don't have electromagnetic properties on the waves as they have cancelled each other out, then they don't reflect from the cavity walls anymore. Instead they leak out of the cavity. So we have an exhaust – the photons are leaking out pair-wise.
(Score: 2) by takyon on Friday June 17 2016, @01:22AM
If it has a strong enough thrust to be measured reliably, it doesn't need to be tested in space.
The creator of the Emdrive has hinted at domestic applications of emdrive and thrust good enough to counteract Earth gravity (yup, Back to the Future 2 style flying cars, and probably bullshit). But there is no need to send an emdrive in space in order to determine if it can compete with ion drives. If it works, it will be very obvious. The Chinese teams testing emdrive have reported higher thrusts than NASA, the creator of emdrive is hiding behind trade secrets, so perhaps the problem is not the concept but the specific design and small budget that NASA scientists have to work with.
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(Score: 2) by jmorris on Friday June 17 2016, @02:25AM
Those high thrust figures are for a proposed version built with superconductors. To date the trusts have been small enough for reasonable people to suspect it is measurement error or side effects like the heat generating drafts of air, magnetic fields attractingt the test stand, etc. If the thing were levitating in mid air I doubt there would be any debate about whether it worked.