K^2

Alright, yeah, 15M is a bit much. 5M would be only a touch more fuel than a clean de-orbit, though. And that's still almost clear of any other sats. And while it'd be nice to mothball the station in a way that allows it to be quickly brought up to habitable state, just to keep it for emergencies, it's not strictly necessary. Yeah, there's a chance that it will expire or get knocked out of alignment by something. Might even have a leak that will cause it to spin up until it falls apart. But if it doesn't, you'd get to keep using the station for whatever observation and comm caps it would still have unmanned, and it might make a nice museum piece some day. I'd like to think we'll get capability to retrieve some old space ships in the future the same way we do with sunken ships today. Why throw out something that's such a big part of space exploration history? That's really the main point here. Save it if it can be saved for "free".

That seems unreasonably grim. Atmo is absolutely unnecessary. Dump it. Station keeping isn't necessary. Higher orbits have considerably less traffic. Especially, at that inclanation. Get it into a 15M x 15M, and all it could possibly ever collide with are a handful or Molniya sats. The odds of it happening any time in foreseeable future are not worth mentioning. Attitude stability is almost trivial. Get it aligned with gravity gradient, and it will stay that way. It's a sub-optimal orientation for solar power use, but who cares? So attitude control isn't needed either. We're down to power and heating/cooling. Equilibrium temperatures, while far from habitable, should stay within electronics tolerance range. And power, well, it'll last as long as it will last. I wouldn't expect the station to last past a decade. It could last longer, but it's likely to last less. And then, it will be a pile of debris. But I wouldn't classify it as a hazard because, again, this wouldn't be exactly a useful orbit. So it literally costs us nothing to keep it there. Even if it's going to serve absolutely zero purpose and just floats about as a pile of junk, there's just no reason not to keep it. And if we happen to make good use of it for however many years it manages to keep functioning, that's just gravy.

I think, his idea is to boost it to higher orbit, so that it can keep serving as an unmanned, autonomous station. Maybe as an emergency supply store. Not a proper manned station. Could be a nice museum piece some day. I see no reason not to do this, since it would cost the same as deorbit.

It can, depending on orientation of the torque. Gyro is literally an angular momentum storage. If applied torque changes magnitude of angular momentum, the speed of the gyro will change to compensate.

I wonder why, though. Was it only a problem with older CPUs? I can see timing problems arising from TSC desync between cores, but modern CPUs use invariant TSC.

That said, if the reason you are accumulating momentum is due to asymmetry of the craft, flipping it around every once in a while might do the trick. Having some RCS is still a good idea, though.

You guys overclock, and we are then left staring at game crash reports that look impossible. Keep in mind that just because the system looks stable, does not mean it will not totally flip out every once in a while.

This is one of these cases where distinction between "Science Article," and "Article about Science," matters.

Where'd you hear that nonsense? It's completely wrong.

That's called gravitational waves. They require 300MW per 1N of thrust. Same as photon drive.

They can. The excitations in these fields are called particles. For example, if you try to push off electromagnetic field, as you would from water, you produce photons which take the recoil. You just built a photon drive. You can do the same with gravitational waves. Which sounds all sorts of awesome, but gives you the same 1N / 300MW of power input. You can even push from fermion fields, producing particle-antiparticle pairs in your wake. That requires even more energy. The reason things are so easy with water is because water already has mass. Vacuum is at zero point, and there is no way to bring it bellow zero point, so anything you do to push from it requires extra mass. And that is tons and tons of wasted energy. Efficiency that EMDrive demonstrates absolutely proves that what it pushes off from is a bunch of real, massive particles. Whether it's something from the environment, say, ionized upper atmosphere, or if it's something ejected from the craft, say a leak, there is a reaction mass. Which means that all they've really built is an ion drive. It might end up the most efficient ion drive we know with some work. So it's worth looking into. But it's going to have all the limitations of a conventional ion drive. If the thrust is due to environment, it will be fundamentally limited to tiny fractions of N, because atmo is so rare so high up. If it's due to a leak, it will be limited to stored propellant. Either way, this keeps us within current limitations of ion drives.

Energy isn't a conserved quantity. Stress-energy is. And the only way to not violate it at that power-to-thrust is with a reaction mass. I have actually outlined that above. As I was saying, you don't even have a first clue what the problem is. You refuse to listen about it. You only keep repeating that there is a possibility that it's not a problem. Your entire statement is, "I have no idea what you're talking about, but I'm sure there is a chance you could be wrong." Not only that, but you keep trying to invent scenarios wher it would be. Without having a first clue of what the problem is. And you still don't think you're doing anything wrong.

The original QT idea was never about getting more thrust than a photon drive. It was always supposed to be a photon drive. Just with fewer losses than you'd get out of a laser. So it's actually a neat idea, and it can be explained with virtual particles. It's just not some miracle reactionless drive that people seem to make out of it. No. It's a symmetry violation. It'd have "ears" all over. In far more conspicuous places. We wouldn't be able to get the math right on a whole lot of things that we actually can predict with incredible precision. And it's not just particle accelerators. Anomalous magnetic moment would be wrong. A whole lot of math on neutron stars would be completely wrong.

It's worse. Lets do everything in c = 1 units, because I'm lazy. And lets say that you want to get momentum p. Your options are: 1) Just turn on a flashlight: E = p. 2) Create mass m and give it momentum. E = Sqrt(m² + p²) 3) Take mass m that already exists and expell it. E = Sqrt(m² + p²) - m For m >> p, that last one is approximately p²/(2m), which is your standard mechanics Kinetic energy. But in absolutely any scenario, that's the smallest number, and 2) is always worse than 1). Edit: I think I might be mis-reading you. You don't want to use matter-antimatter as reaction mass, but just burn it in antimatter drive? Then it's the same as just using a direct photon drive. I mean, it is a photon drive. (All of these assume 100% efficiency, by the way.)

They are. Again, energy and momentum aren't two independent things. If you want to carry away a certain amount of momentum without pulling in and ejecting mass, you have to expend a certain amount of energy. The circumstances that have been excluded with hundreds of years of experiments. You are seriously on the level of, "They're going to find unicorns, because they are looking where nobody else did." Yet you keep insisting that you are right based on what, exactly? I understand if you're having this conversation with a random person off the street. What makes you think that you know better than somebody who spent over a decades studying the subject, with all of the history, math, and experimental background? Or are you so naive that you really think that we waste our time with the education, and it's anything goes in science? I don't get it. Is it the, "You're all winners," sort of education that everyone's brought up with these days? You can't "all be right". There are subjects on which you cannot have a right opinion unless you've spent many years studying said subject. You lack every qualification required to make a good call on the subject. You WILL NOT be able to come up with "what if" in a few minutes that you've been exposed to the subject that thousands of far better educated people who spent decades on the subject have not considered. It is a fact. You need to learn to deal with such a fact.

747 on approach with flaps fully extended has a glide ratio of about 5. So the deflection angle is going to be much smaller, which suggests that it grabs a lot more air. Which is, most certainly, true.

Yes. It could be useful to know why it works. While no variation on QT can beat photon drive in absolute vacuum, this stuff might be interacting with atmosphere in interesting and very indirect ways. And even if it's simply a leak of some sort, we're still learning a lot about making fine measurements. Caveat, I see absolutely no reason to test it as an orbital unit. There is nothing we can't test better and cheaper in the lab. No. It is not the long shot. It is the longest shot. Ever. By many orders of magnitude. Conservation of energy and momentum were the most fundamental principles of Newtonian Mechanics. They went into foundations of more advanced Mechanics as it developed, with Noether's Theorem connecting it to symmetries. In Thermodynamics, which was originally developed as fluid dynamics, these were founding principles. And later, as it became Statistical Mechanics, it held. Quantum Mechanics was built on these principles as well. But it wasn't until Gauge Theory that we understood why it is so fundamental. When Gauge Theory came along, we suddenly had one, clear explanation that worked on every scale, from Quantum to Cosmological. We've done measurements at both ends of this scale to 12 decimal places. Twelve. One part in a trillion. Absolutely no theory has ever stood up to such a test. The statistical significance is incomparable. The odds of these principles failing, by smallest amounts, are effectively zero. As close to it as anything ever was. Anything else you consider a certainty is nowhere close to that certain. It could be wrong. But then we are talking about absolutely all of science being absolutely wrong. Error here would mean that we cannot trust measurements as a point of principle. That predictive power of any model is null. And here you go, trying to convince yourself and others that it could be wrong, just to satisfy your desire for a cheap thruster, without even clearly understanding just what it is that you're suggesting.

Would you like to venture a guess how much extra energy that will take? ANY generation of mass will result in efficiency of a photon drive at best. The reaction mass must already exist for better-than-photon-drive efficiency. Then the Poincare local symmetry is broken, and then you can extract any amount of energy from free space. Best part? You can actually use this to make free energy with magnets. All you need is a tiny symmetry break, and you can pump as much energy out of it as you need. Except absolutely nothing in the universe works that way. Not just here, but anywhere. That symmetry holds from subatomic particles, to distances spanning galaxies. We've been testing and probing this stuff with far, far, far greater precision than this device is capable of exploiting. I completely understand that you guys don't know better. That as far as you know, this is entirely plausible. It is not. Unicorns and leprichauns literally have better odds of existing. I'm not even talking about lottery, because that's practically a certainty in contrast. That's something you can go, and actually win. EMDrive working without reaction mass would require the entirety of field theory to be a fluke. Black holes, neutron stars, superconductors, superfluids, semiconductors, metals, nuclear energy, lasers, and countless other discoveries and models - totally by chance. Versus EMDrive being a flop. People who invest money in EMDrive are the same people who spend all their savings on lotery tickets. Except, as I've pointed out, that would be an improvement.

You are aware of the fact that I've done graduate work in particle theory, right? As in, this is my actual field of study? This simply isn't how virtual particles work. Particle-antiparticle ocean is a very bad analogy for vacuum. While certain parallels between quasi particle-antiparticle systems in solid states do exist, the particles, virtual or otherwise, that we are talking about here are not quasi particles. There is no lattice to absrob the momentum. These particles are excitations in fields, and carrying momentum means having an excitation in the field. But more importantly, if vacuum simply picks up that amount of momentum, it must gain mass. Whatever else happens, anything that carries away the momentum must be on the shell. So it either has mass, and we have regular reaction drive, or it is a null current, and what you have is a photon drive, which drains ridiculous amounts of energy. Anything else violates conservation laws in very fundamental ways.

It does, actually, because there are conserved currents involved. Would you trust this idea if it was promising free energy to power a city? No, you'd call its inventor a crackpot, and any "working" prototype a mistake, at best. Well, for EMDrive to have efficiency it promises without pushing from real, massive particles, it has to violate the same symmetry that protects conservation of energy. If EMDrive works, free energy is possible. In fact, it should be way easier to build a free energy generator than an actual propulsion unit based on this principle. I understand that it's difficult for a lay person to recognize, but EMDrive can't work for exactly the same reasons that you would use to explain to someone why magnets can't be arranged to power a perpetual motion device. There is just a bit more tensor math involved. Again. Magnets pushing magnets. But let me try explaining it from this perspective. Virtual particles can't vanish if you have acted on them. Because they now carry excess momentum that has to go somewhere. If you draw all possible diagrams of action on virtual particles, the only ones that will not cancel are ones where force is applied right back at the source. Because there is a momentum-conserving delta function in the integral. Because momentum is conserved. And net thrust is still going to be zero. This is pulling yourself up by bootstraps with a fresh coat of paint.

Convey to what? If net is still less than 300MW per N, then whatever it is, it has mass. In fact, mass flow is exactly sqrt(F^2*c^2 - P^2)/c^2 Anything with better efficiency than photon drive is a reaction drive. That is just basic physics. How the reaction force is conveyed can be very creative. We could be seeing a very odd sort of an ion drive, but it is not reactionless one.

Totally irrelevant. Even if EMDrive uses virtual particles for recoil, virtual particles must vanish. The total "exhaust" mass must therefore be zero. Massless "exhaust" is equivalent to photon drive, which has maximum efficiency of 1N/300MW. Efficiency higher than that guarantees presence of reaction mass. It's that simple. Virtual particles are ones that propagate off the shelf. They violate E² = p²c² + (mc²)², which is true for "real" particles. Virtual particles show up in various interactions, as exchange particles, for example. Virtual photons carry electromagnetic forces, etc. Finally, because virtual particles "temporarily" violate conservation laws, they must promptly vanish. That's a hand-wavey explanation of it, but it should do for purposes of discussion at hand.

Could easily be a "dirty snowball" of water and amonia ice with some rocks in it. It'd have sufficient structural strength and have that sort of density. You are assuming a perfect sphere with uniform density, which it almost certainly isn't. But it's going to be good enough for a ball park estimate. Since asteroid is going to turn around its maximum moment of inertia, or close to it, expect the figure to be a bit higher.

This is still several orders of magnitude more thrust than they should be measuring. There is going to be a reaction mass involved.

Ah, yes, I looked at the wrong number and used 450m/s for exhaust velocity. 230kg sounds right.