Electric propulsion does produce low levels of thrust. To make them useful for manned missions you need a lot of electrical power. Generally in the multi MW range. For comparison the ISS with nearly and acre of solar arrays has an instant ours maximum power of less than 250KW, (actual usable is around 100KW, less as the arrays age). So we are talking nukes for power.
Let me clear somethings up about the EM drive. It's either:
- Groundbreaking Nobel Prize winning new physics OR
- Subtle experimental error
(Here's the OT thread BTW Link)
It's effectively a microwave resonance chamber where microwaves at a certain frequency bounce around inside an enclosed tapered cavity. While the measured thrust is very small, (10-100s of millinewtons) it's orders of magnitude higher than a radiation pressure drive. (Anything that radiates photons asymmetrically actually produces tiny amounts of thrust. A flash light for example)
The amazing thing is the drive requires NO propellant. While other plasma and ion drives produce similar low levels of thrust they all require a propellant to accelerate per Newtons laws of motion, (every action has an equal and opposite reaction - conservation of momentum).
If it actually works it's basically Star Trek impulse power. The controversy comes from the fact it has no verified theory for operation and it appears to be violating conservation of momentum. These two facts means we should be skeptical about it actually functioning or not.
If it was only the two independent inventors who were promoting this it could likely be ignored as a hoax. However three independent teams have tested these devices and recorded anomalous thrust.
- A Chinese university research team
- Eagleworks - a small advanced propulsion research group at NASA Johnsons Space Center
- A research team at the University of Dresden
The NASA folks have tested it in and out of vacuum, reversed direction of the thruster and it has produced a measurable thrust. When they tried an RF sources without the tapered cavity as a control they did not see thrust. Currently they are upgrading their test rig to reduce experimental error from magnetic fields and thermal interactions while increasing input power to get a larger thrust signal. These were things recommended to them by a panel of physicists after their first round of tests. If they can reach a bit higher thrust levels other NASA centers will try and replicate their results.
What was recently reported is they now have a paper undergoing peer review. This should hopefully shed some light on what's actually going on.
The benefit of an EM drive to space exploration is enormous. As long as your vehicle has electrical power it can thrust. Most vehicles must have propellant as a major portion of the vehicles mass. Not with EM drive. Eagleworks did a rough estimate of what some crewed missions would look like at various thruster efficiencies. Mars in 28 days could be feasible:
Hell probes to Alpha Centauri would be possible in a human lifetime.
At any rate it's exciting technology but one we should approach with skepticism. Because of that skepticism NASA is not betting the farm on it. They have however put a nickel in the slot machine. With that low level of funding it will still take awhile to chase down every possible source of experimental error to definitively show it works or it doesn't.
Stay tuned.
Wow, I had no idea. That is insane.
Out of curiosity, if this EM drive turns out to be the real deal are they saying that it could produce thrust at a rate of 4N/KW?
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