Question: why did someone build this drive if theory predicts it won't work? Were they just tinkering or did they have an alternative theory from which they could deduce it might work?
The 'impossible' EmDrive could reach Pluto in 18 months?
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Re: The 'impossible' EmDrive could reach Pluto in 18 months?
#102I've been following this story pretty closing for several months now. So here's the opinion of an actual research scientist. Q. Does the Em drive produce thrust? A. Undetermined. Several tests from multiple independent labs have reported thrust, including in a vacuum. However several of the labs that reported positive thrust come from a sketchy background. Q. Does it violate conservation of momentum? A. Undetermined.…
> I think the last thing anyone wants to see here is "new physics". The article's responds with the nonsensical "Some damage to our theories of physics is an acceptable payoff if we get a working space drive." EDIT: Let me clarify why it's a nonsensical statement: First, I think it meant to say "cost", not "payoff". Second, there would be no cost. None of the things we were able to do with our existing theories would…
Not sure what is to fear from new physics. Sounds like something new and exciting to work on. Aren't physicists tired of perpetually iterating over string theory and making no new discoveries?
Re: The 'impossible' EmDrive could reach Pluto in 18 months?
#103Earlier quoted context omitted.
Oh! This is one of my favorite questions about scientific progress. People seem to regard scientific progress as this kind of wave function, where some theory comes along and then some other theory or discovery disproves the previous one and so on and so forth. But if you want to think of scientific progress that way, then you have to think of it as a dampened sine wave ( https://en.wikipedia.org/wiki/Damped_sine_wav…
http://amasci.com/weird/end.html
Yeah, that specific article was on my mind when I wrote my comment. But I didn't say there were no more discoveries left to be made; I said they weren't happening in people's garages anymore, which is true in the majority.
Re: The 'impossible' EmDrive could reach Pluto in 18 months?
#104Earlier quoted context omitted.
Why the assumption that if it works it must violate a conservation law? That's the last thing I would suggest after exhausting every other possibility, even weird ones like space time distortion thst would still operate within known conservation laws.
The whole reason the EmDrive is supposedly so revolutionary is that it's claimed to produce thrust without requiring any propellant. If conservation of momentum isn't going to be violated, something with mass-energy has to be carrying that momentum away from the spacecraft, and if it's not matter, it has to be radiation. But the claimed efficiency is about 5 orders of magnitude higher than radiation pressure could po…
I'm not suggesting it's explained by current physics. What I'm saying is that if it works, I'd consider new physical explanations that maximally preserve conservation laws first -- sort of for Ockham's Razor reasons.
Re: The 'impossible' EmDrive could reach Pluto in 18 months?
#105Earlier quoted context omitted.
The whole reason the EmDrive is supposedly so revolutionary is that it's claimed to produce thrust without requiring any propellant. If conservation of momentum isn't going to be violated, something with mass-energy has to be carrying that momentum away from the spacecraft, and if it's not matter, it has to be radiation. But the claimed efficiency is about 5 orders of magnitude higher than radiation pressure could po…
Explanations aside, if in the slight chance it's workably better than ion thrusters for certain applications, that's great. If it turns out to be snake oil or a hoax, that would not be a huge surprise either.
There are independent replications, which IMO mostly rule out hoaxes -- or at least greatly reduce the likelihood to below other explanations. It's tough to create an independently reproducible hoax.
Right now my guess is either measurement artifact or some form of obscure but conventional effect like EM interaction with the surround environment. That's most likely.
If those can be ruled out, then we're in new physics territory.
Re: The 'impossible' EmDrive could reach Pluto in 18 months?
#106Earlier quoted context omitted.
What would it take to get one of these into space?
from the looks of how testing is going, a good old fashioned rocket.
Well yes, I don't expect a tiny fraction of a Newton of force to get them into orbit, but I meant more as a way to test whether the anomalous force is usable for spaceflight.
After all, it will either sit there and do nothing or it will move.
Re: The 'impossible' EmDrive could reach Pluto in 18 months?
#107I've been following this story pretty closing for several months now. So here's the opinion of an actual research scientist. Q. Does the Em drive produce thrust? A. Undetermined. Several tests from multiple independent labs have reported thrust, including in a vacuum. However several of the labs that reported positive thrust come from a sketchy background. Q. Does it violate conservation of momentum? A. Undetermined.…
Thanks, nice summary. > I think the last thing anyone wants to see here is "new physics". I really want to see new physics, because I want to see us get off this rock and far away. I think most people want to see new physics. I think that's why this topic is so popular. That said, I can understand physicists not wanting to see new physics. Wait. In a way, that sentence is crazy . In a way, physicists should want to s…
99.99% of the time when "new physics" is invoked, it amounts to crookery or kookery. Nobody wants to see that, because it takes energy to disprove even the obviously flawed claims, and the energy is taken away from more promising endeavors, that are usually less appealing to the public.
"Free Energy" is very appealing, so is "10x better batteries", "10x more flash storage", "momentum-defying space thruster", and so on. These modern-day fairy tales are gaining press simply because people want them to be true, not because they actually show a path for progress.
Similarly, a promise of a "miracle cure" is very appealing to the public, and so it may seem cynical to downplay any such claim right away, but it has absolutely nothing to do with actual advances in medicine.
Re: The 'impossible' EmDrive could reach Pluto in 18 months?
#108It's good to see that someone finally got around to testing this in a vacuum. Here's the paper mentioned in this story: http://arc.aiaa.org/doi/abs/10.2514/6.2015-4083 High levels of skepticism are still warranted, as much as I would love for this to pan out. Every time this gets tested—presumably more and more carefully—the measured force gets smaller. The original test at Chinese Northwestern Polytechnical Universi…
What would it take to get one of these into space?
At least $4000 per kilogram, based a quick google.
I'm sure someone will put the cash together eventually if the dirtside experiments look promising, but there's no sense in risking the money until we're pretty sure.
Re: The 'impossible' EmDrive could reach Pluto in 18 months?
#109Earlier quoted context omitted.
The Chinese test used kilowatts rather than watts of power: http://www.you-tech.it/index.php/content/download/12369/1124...
All the more possible for small extra forces to slip through the cracks from magnetic fields or whatever.
Maybe so, but it makes it meaningless to compare the measured forces and claim that they've decreased in later tests.
Re: The 'impossible' EmDrive could reach Pluto in 18 months?
#110Earlier quoted context omitted.
What would it take to get one of these into space?
from the looks of how testing is going, a good old fashioned rocket.
No one's ever claimed that the EmDrive could launch payloads to orbit, to my knowledge. That's not what it's for. Once you're already in space, a drive that can produce 0.001G indefinitely will get you going way faster than a rocket that can produce 10G for a few minutes before its fuel runs out.
Solar sails and (to an extent) ion thrusters work on the same principle.