K^2

That article is fairly useless if you don't know some basic General Relativity already. It does deliver one important point, however. That while Alcubierre Metric is fairly straight forward for computations, it's not practical, as it requires impossible amounts of energy to work with. There are other metrics, though, which reduce the energy requirements to quite plausible levels, and there is no reason why there can't be metrics bringing it down even further. Discussion on negative energy in that article is very limited, and that's been a big part of discussion here. The other part is trajectory taken by the ship under warp drive under influence of gravitational field, and that requires far more serious math than what's presented in the article. (I've discussed some of that in other threads on the topic.)

Batteries have higher capacity per weight and better conversion factor. I don't know what other measure of "efficiency" you have in mind, but these are the only things that matter to spacecraft applications, so you're wrong either way. You still haven't demonstrated any knowledge, even as far as basic mechanics goes. 300m/s is a structural limitation. You can't go much faster. Very funny. I have degrees in mathematics and physics. Why don't you try and impress me with your difficult mathematical proofs.

If you are going to use a polywell with direct conversion as your energy source, you don't want to use it to run an electric motor. It'd be like using nukes to do urban demolition. You probably could, but why would you want to? You have a source with considerable current and a huge voltage output. You should be building an arcjet. Dry air is what, about 30kV/cm? That makes a 1MV+ source absolutely perfect for an airliner jet engine. And you can use the arcjet principle to build anything from a high bypass turbofan, to a scram jet, to a pure rocket engine. None of these are going to be super efficient, but you're running on nuclear energy. And it can still be cleaner than a combustion jet engine, despite the efficiency drop. You don't need to worry about throttling, either. Just change reaction rate. With direct conversion, current flow is going to change almost instantly. You'll have just as good of response as with conventional jet turbines, if not better.

Hm. What are your credentials? Edit: It just occurred to me that this might come off as a bit condescending. It's just that questions can be very broad in a lot of ways. When one person answers them, it has to be either someone with huge amount of experience across the board, or better yet, a group of people with variety of experience. For example, I would not doubt for a moment that this forum, as a community, could construct a very good answer on just about any space-related subject. Probably more general science questions as well. There would still have to be an "editor", if you will, somebody who compiles the bits and pieces of the answers into something that flows well. But having just one person answer the questions is an extremely difficult task. I have a vast background in physics, with a lot of interest in space, and I'm good at doing research on the fly across both popular resources and academic papers, but I still make quite significant errors frequently enough, as many members of this forum will attest to. And I'm always glad to have this community correct me. So that's why I'm asking what sort of background you are planning to rely on, if you are going to answer questions yourself.

Who's going to be answering the questions, and what sort of arbitration is there going to be on answers? That's sort of important to establish, if there's going to be any point to this.

Any idea where I can get some of these for my super villain lair? Anyways, the only reason why AC motor can have advantages is because of the limitations of the solid state controller for the brushless. And these are about the same as limitations for the solid state inverter. So you might as well go with brushless.

Forward air speed isn't necessary for auto-rotation in general. It's necessary for helicopters, because of the fairly high loading and the vortex state. It's the same reason why you should never increase collective sharply while in hover. If you are designing something specifically for descent, however, you can build a rotor that will auto-rotate just fine without any horizontal speed. And yeah, with a rotor, you can flare before hitting the ground, so you can have a gentle landing even if your descent speed is pretty high. But to be honest, parachutes with retro-rockets seem more reliable.

Same theory that predicts Warp Drives. And I really can't wait to see how you'll try to argue your way out of this one.

A flywheel of mass m spinning with surface velocity v has total energy mv²/4. Maximum surface velocity for a steel flywheel is a little over 300m/s regardless of diameter. So a flywheel can only store about 25kJ/kg. Modern Li-poly battery holds more than 500kJ/kg. In other words, a modern battery is more than 20x better than a flywheel at storing energy. That's why you see a lot of remote controlled airplanes with batteries and none with flywheels. Oh, and there are commercial busses that run on batteries. Please, stop arguing by posting various nonsense, when you don't know the physics or math to back it up. You really don't have any idea what you're talking about.

There are no matter states with negative energy, so you can't. You can only get negative energy densities in a very specific environment, which means you have to haul all the equipment with you.

You really have no idea what these words mean. And more than a decade of research into solar arrays had nothing to do with it? I know for a fact that ISS arrays are much better at continuing to work after a micro-asteroid impact. Flywheels are only slightly better than best batteries. And as I've said above, photon drive doesn't make sense even with nuclear reactors. Again, unless your batteries are matter-antimatter storage, this isn't going to help.

Eh. Sort of. It'd be enough to lower energy bellow zero point. That would still repel from masses, albeit, more like bubble surfacing in a liquid. But you wouldn't be able to use it to lift something out of gravitational field, because everything you need to produce such negative energy density will be much heavier. So net mass will always be positive. That's not a problem for warp ship. We can work with this, and that's the main reason people are hopeful about the idea overall. But you can't use it to escape the star system. You'll still need reaction drives to do that. So to escape a star system, or a planet, you'll still have to use ion drives or conventional rockets to accelerate to escape trajectory. But then you can use warp to speed up the process, so that instead of months, you could reach outer Solar system in hours. I don't share your enthusiasm for wormholes, however, Mazon Del. Yes. Same principles that can be used to build a warp ship can be used to make an untraversable wormhole traversable. In fact, FTL ship can traverse some untraversable wormholes already, because it can follow time-like trajectories. Problem, however, is in making a wormhole of any kind in the first place. The kind of wormhole you are thinking of requires a change to topology of space-time, and there is no mechanism for that. We can alter geometry, but only within existing topology. Which means, if we were to find a natural wormhole, we could move its openings to where we need them and make it traversable. But we can't make one completely from scratch.

Except, no such sources exist. Top of the line modern solar panels will produce up to 300W/m² in direct sun light and have mass of about 1kg/m². They'll last two decades at the most. So we have 1μN/kg for 20 years on a photon drive. That's 630m/s of delta-V maximum. That's it. 630m/s. In the entire life of the craft. And to achieve that, you'll need to carry 1,000T for every 1N of thrust. I could do better with model rocket engines out of the store. Again, the only way that a photon drive makes sense is with matter-antimatter reactor. If your reactor has less than 100% mass-to-energy conversion, you are better off with ion drive of some sort. Always. And the best mass-to-energy ratio we have is nuclear reactors. These can do less than 0.1%, and it's still way, way better than chemical sources or even "renewable" energy, such as solar. And a larger array will get hit that much more frequently, causing failure of that many more cells. You aren't winning anything with larger arrays. If you double the thrust, but more than double the mass of the ship with batteries, it doesn't give you extra delta-v.

No, it doesn't. Because we are talking about total delta-V you can get. And you can get smaller, cheaper ship with higher delta-V using electrostatic thrusters already than you could ever with Quantum Thrusters. Again, it's physically impossible to build Quantum Thrusters that are more efficient than ion drives, unless you master matter-antimatter energy production. It's not an engineering issue. It's a simple mathematical fact. You do understand that odds of impact scale with size, right? Oh, really? Why don't you look up energy density of modern batteries. You'll get more delta-V with chemical fuel than batteries. Don't even need to get fancy here.

So do solar panels. And yeah. A solar sail is going to be 5-10 times more efficient for the same area. They are a bit more difficult to position for maneuvering, though. At any rate, I only used solar panels as an example. A 300kW power source of any kind is going to be huge and heavy. And it's going to be way more efficient to bring a much smaller power source and propellant for absolutely any mission.

Ion thruster will require about 100x less power. To generate 300kW of power, your ship will need about 3,000 square meters of solar panels. That's about the size of a football field. For 1N of thrust. With an arcjet, you can get the same 1N of thrust from 5kW. Just 50 square meters. Now, which do you prefer to carry with you on your ship? Propellant, or a football field worth of solar panels?

You can reduce the size of your power supply, add the propellant for an arcjet or similar electric thruster, and still have a lighter system with more delta-V than you could ever get out of Quantum Thruster. The idea of using Q-Thruster as RCS is stupid. It can only occur to people who don't understand enough field theory to know that it can't outperform a photon drive, and that believe in the absurd 3kW/N figure.

A flashlight can work as a photon drive. Just not a terribly efficient one. Basically, any drive where recoil is carried away by electromagnetic radiation is a type of a photon drive.

You are forgetting mass of the reactor fuel you have to power the drive. If you have matter-antimatter reactor, yes, nothing is more efficient than a photon drive. But if you are using a nuclear reactor, you are stuck with a lot of dead weight. There is the used up uranium mass, the mass of moderators, and the mass of the reactor itself. You don't use it as propellant mass, but it adds to mass of the rocket. As a result, if you consider effective exhaust velocity, instead of c of the photon drive, you end up with a tiny fraction. In fact, a photon drive with a modern nuclear reactor yields something in the 3km/s - 30km/s range. I'd have to do some math to pin-point it better. This makes arcjets competitive at the worst, but I'm pretty sure they'll turn out to be better once I put in all of the numbers. It pushes against the fields. Predominantly, electromagnetic field. Naturally, whatever carries away momentum is the excitation in the relevant fields, carrying the momentum. Which brings us right back to it being a photon drive. So yeah, performance numbers are bogus.

That is a high school derivation used only for being very intuitive. While Tsiolkovsky did, as it turns out, use something similar, it ignores a number of problems. The foremost being variations in velocity, direction, and composition of the exhaust gas flow. Indeed, these things are going to vary even with respect to position relative to the nozzle of the rocket. Not to mention interactions with atmosphere during ascent. Worse, this derivation takes a rather primitive look at what the effects of acceleration and loss of momentum to gas flow actually are. They do end up canceling each other out in case of momentum, but using same analysis on energy leads to errors. Correct derivation is frame-independent, and is written in the following manner. I'm going to use primed terms, such as p', to denote time derivatives: p' = dp/dt. First, velocity depends only on mass flow. Velocity cannot be "carried away" by any part of the rocket leaving, so the equation for v' is simple. v' = ∂v/∂m m' In contrast, momentum is carried away by the mass flow. So we have to use an expression familiar from fluid dynamics. p' = ∂p/∂t + ∂p/∂m m' It's easy to see that momentum lost to the flow is equal to the fraction of mass being lost. ∂p/∂t = p m'/m Finally, we know that velocity and momentum are always related. v = p/m So we differentiate with respect to time using the chain rule. v' = (d/dt)(p/m) = p'/m - p m'/m² Substituting result for p' and v' we get the following. ∂v/∂m m' = (∂p/∂t + ∂p/∂m m')/m - p m'/m² = (p m'/m + ∂p/∂m m')/m - p m'/m² The p m'/m² terms cancel on the right side, and we can cancel the common m' factor on both sides to leave us with what we expect. ∂v/∂m = ∂p/∂m (1/m) If we assume that ∂p/∂m = ISP is a constant, we can integrate the above to yield Tsiolkovsky equation. v1 = v0 + ∂p/∂m ln(m0/m1) Note that specific impulse, defined as the impulse gained per unit mass, shows up explicitly. Exhaust velocity has not yet been considered. It is, however, easy to see that the effective velocity has to be defined as Ve = ∂p/∂m = ISP. This is a consequence of the rocket formula, and not one of its assumptions.

Real world orbits do depend on inclination and ellipticity of the orbit, but only because Earth is not perfectly spherical. In KSP, all planets are assumed to be perfect spheres, and therefore, period of any orbit depends on semi-major axis only. The game does, also, take an approximation that mass of the ship is negligible, yielding a formula T = 2À Sqrt(a³/μ). The gravitational parameter μ is equal to GM, where M is mass of the planet, but in KSP, the value for μ is stored directly in the game's data.

Contrary to that page's claims, it takes 300kW of power to generate that 1N of thrust. In other words, with modern reactors, even an arcjet is going to make for a more efficient RCS.

That would just be silly.

I'm not going to speak for moral, theological, or legal issues. But in terms of underlying physics, no, they are not a problem. Field theory only requires causality locally, which there is no known way of violating, and global causality violations are not actually a problem. The fact that there are paradoxes in classical limit is just a reflection of the fact that we've built assumption of global causality into classical limit. In other words, our "every day physics" isn't built to deal with time travel, but that's the problem with our description, and not with the concept itself.