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I just wanted to point out that thrust without expending mass is already possible without an emdrive. Anything that asymmetrically radiates photons will gener
by trelliscoded 10y ago
I just wanted to point out that thrust without expending mass is already possible without an emdrive.
Anything that asymmetrically radiates photons will generate a net acceleration. This very mechanism has been experimentally verified as the pioneer acceleration anomaly.
If the emdrive is some kind of special case of this mechanism, it's entirely compatible with existing physics. The proposals so far are based on mechanisms which are different, and incompatible with the existing understanding of the universe.
It's also worth noting that in 2016 the Chinese research team was unable to replicate their findings after accounting for a power cable that was magnetically inducing a force on the experimental apparatus.
- beevai142 10y agoPhoton rockets are not actually reactionless, because the emitted photons carry momentum and energy out of the system. This makes conservation laws to hold for such systems, cf. https://arxiv.org/abs/1506.00494 https://arxiv.org/abs/1506.00494 Now, the emdrive people are apparently claiming that it is truly reactionless. If so, you can build a perpetual motion machine of the first kind (produces energy from nothing) out of it --- which should demonstrate the degree of plausibility of such claims. For photon rockets, there's apparently a hard upper bound on the efficiency, which limits the practical usability.
- trelliscoded 10y agoYou're right, what I really meant was radiation pressure doesn't require reaction mass.