K^2

Yes. This has to do with how multiple channels are handled. But a single stick in the correct slot won't run faster than a pair of matching sticks in both slots. The slowdown (or total failure to work properly) is only for single stick in the wrong slot.

Within reason, probably. But it would require a medium. You can't really do much about it in vacuum by definition. By the way, to have a better mental picture of how such things work, a classical example of such, "stacking the odds," is Brewster's Angle.

Virtual particle vanishes when it interacts with something else, potentially, another virtual particle*. That energy will be transferred to that particle. If it's virtual, it will then be transferred to another particle, and so on, until it ends up being transferred to a real particle. The probability of that entire chain of events taking place decreases with the length of the chain and the distance. * There are other conservation laws at play here as well. A virtual electron will need a virtual positron at that vertex, because just like energy and momentum, virtual particles conserve things like charge and lepton number.

Nothing. But a virtual particle can't propagate freely, so if you don't give it that energy, it can only go from point A to point B, and not very far at that.

N_las is absolutely right. You need O and t to get coordinates/velocity, which are much easier to update. You can go directly from O to O', but the math for it is insane.

You need to put in enough energy to produce a particle-antiparticle pair. That is a Lot of energy. Otherwise, particle stays virtual, and must interact with something else.

There is still some EEPROM for BIOS. Also, yes, too much ROM will slow your computer down. Enough ROM can make it heavier. But consider offsetting this with more boosters.

That is a gross over-simplification. You do not care about "expansion" and "contraction". That is not really how or why it works. Just another illustrative analogy that leads to bad intuition on the topic. The key to the warp drive is the metric. It needs to have a "tilted" metric in the interior and flat in the exterior. What goes in the middle and constitutes a warp bubble is actually irrelevant for what it does. But it does fully determine your energy need. Further, non linear nature of EFEs means that structure in one location can affect energy needs of another. So it is hard to point to a specific feature and say that it will force negative energy requirement. To demonstrate this a bit better, look at where energy is concentrated in Alcubierre Drive. Almost all of it is in the narrow band along the "equator" of the bubble, if we look at direction of motion as axis. And it goes to zero directly ahead and behind, where most of "expansion" and "contraction" takes place. Also, it is all negative. Both front and back of the "equator".

Yay! You just invented pushing stuff with magnets! Have yourself a cookie. Also, realize that this limits interaction range for the same reason why you can't have two magnets interact from many kilometers apart, unless they are really large magnets. Oh, and there isn't a "photon's point of view," even for real photons. A virtual photon isn't even following a null path. It can jump from A to B instantly, or take a year to travel one centimeter. All of these paths contribute to virtual particle exchanges. The entirety of your knowledge seems to be picked up from popularized science shows and articles, and maybe a bit of Wikipedia. If you want to actually be able to talk about virtual particles, you need a course in Classical Mechanics, Electridynamics, Quantum Mechanics, Special Relativity, Introductory Particle Theory, and Introductory Quantum Field Theory. Typically takes about 3-4 years in college into the first year of Master's program. If you actually want to undertake this, I can point you at some books to start with. But nothing's to stop you from turning ordinary atoms into muonic ones. That's kind of the point. There are loop-holes in just about everything that you might practically want to do. It's kind of what applied sciences are all about. The key is to distinguish understanding all of the rules, and knowing how to exploit them to achieve seemingly impossible goals, from charlatans or honestly misguided individuals who simply press on under a naive delusion that any rule can be broken. Any rule can be circumvented, and that's far from being the same. Conservation of energy and momentum are the most fundamental principles we know. I'm prepared to discuss that with anyone who actually understands where these come from. If one doesn't understand Noether's Theorem, and one wishes to keep insisting that we can't possibly know for sure that these are fixed, one would be much wiser to just shut up. Trying to bet on any tech that violates these is beyond dumb. If we are deciding between funding that and alchemical search for philosopher's stone, it would be stupid not to invest in the stone. But it's not the same thing as saying, "Here's your delta-V, good luck." There's a connection between 4-velocity and 4-momentum, but it can be nudged. In fact, that condition is always violated for virtual particles. They don't have to even be moving in the same direction as their momentum points. More usefully, it is violated by warp drives. FTL travel results in causality violations, and there's a pretty well-argumented conjecture in GR that suggests that it will always require exotic matter, which may or may not be possible to attain in any significant quantities. But on the other hand, no such restrictions exists for sub-light warp. I'm not aware of a viable configuration that allows sub-light warp without exotic matter, but at least that's on the table. There is nothing says that it doesn't exist. In fact, a lot of things suggest that it probably does. A good ion drive, a power supply, and a sub-light warp, and you can go anywhere in the Solar System within hours. This is far beyond anything the EMDrive is promising, and it's very plausible. And here we are, instead of funding theoretical research into things we could actually do, we throw money away on sending leaky microwave ovens into space. Worse, we get a bunch of people with no expertise in the area saying, effectively, "Hur, dur, you can't know it wont' work." Oh, and every time one of these mentions virtual particles, it reminds of a line from Idiocracy. "Duh. It has electrolytes." First you learn what a virtual particle is. No, not read about them in Wikipedia, but actually study some basic Field Theory to actually understand what it means. Then you can talk about them as if they explain something. So you see, I hope, why I'm a bit uncomfortable comparing this to cold fusion. Cold fusion isn't impossible. Some very specific ideas about it are, but someone could, foreseeably, build a cold fusion reactor. Yeah, it will be some sort of "cheating" or other. Whether with a catalyst or some other trick. But there is nothing fundamentally wrong with fusion at room temperature, and so there could exist workarounds of the obstacles within the rules. This is not at all the same as someone suggesting that momentum could be not conserved, or get absorbed into something other than radiation, outflow, or environment. That's not working around the rules. It's pretending they don't exist for lack of knowing better. Erm... Pardon the rant.

There are legitimate ways to lower the barrier, though. Muon catalysis, for example, brings it down enough for reaction to take place at cryogenic temperatures. And in fact, if we had a much more efficient way to produce muons, it would even produce net power output. I wouldn't take any cold fusion claims without a truckload of salt, but there are no fundamental contradictions. Just piles upon piles of engineering ones.

Yeah... You know how quantum physics and gravity don't always mix well? This is one of these cases. You can do Quantum Field Theory in almost arbitrary fixed curvature. It comes with all sorts of problems, but they can be worked around in principle. That's how we can discuss what happens to virtual particles near black hole. We can go a step further and do a mean field approximation to a Quantum Gravity problem to discuss stability of a warp bubble, so long as bubble thickness is greater than Plank length. But when you're suggesting having enough interactions taking place so that virtual particles start to dramatically warp space-time? This is full on, no restrictions, no training wheels, cannot even be quantized, so nobody knows where to even start solving it sort of Field Theory. The most infuriating part, we have all of the equations for it. It'd be sufficient, for a start, to simply consider the basic electroweak theory with gravity. We can state that problem exactly. Without the needless bells and whistles, the gauge symmetry is given by U(1) X SU(2) X R(1, 3) X SO(1, 3). Lagrangian is just a most general form with these symmetries on a basic lepton field. The interactions are given by Yang-Mills theory on this symmetry. That's it. Simple as pie. But that's stating the problem. Solving it has brought to halt the likes of Feynman and Hawking. So to try and answer your question more or less directly, nobody has a stinking clue what will happen if you manage to force that sort of virtual particle density in one spot. Not to mention any ideas on how to accomplish it. Note, however, that it's not a failure of theory, so much as failure of our ability to apply it. Math gets impossibly hard in this case, and normal shortcuts we use to simplify it, like quantization, don't work there.

There is never a deficit of energy or momentum when virtual particles are involved. Simplest case. Electromagnetic interaction between two electrons. To first order, electron emits a virtual photon, which is absorbed by second electron. The energy and momentum of the virtual photon are taken out of the first electron and deposited into the second electron. The part where people get confused is that kinetic energy of a virtual particle can be negative. There can be other weirdness as well, due to the particle not being on the shell. But the total energy and total momentum are always conserved.

This thread wouldn't exist if everyone involved actually understood relativity and field theory in curved space time. That is obviously not the case. I repeat, you have no idea what relativity is actually about, as you keep demonstrating with your posts. Don't project that onto everyone else.

You need something to pick up the recoil within range of the force. In vacuum, that means you need a force with an infinite range. Or if you want an alternative way of thinking about it, the "propellant" is a stream of photons or gravitons. With strong nuclear force, you'd need to be producing a stream of free gluons, which isn't a thing*. With weak force, you'd be producing Z bosons, and these have to decay into photons and neutrinos eventually. So again, you can't beat efficiency of a photon drive. * There is a theoretical edge case involving glue balls, but they'll have mass, so you'll be even worse off.

ISP of a mixture of two fuels will always be worse than ISP of the better of the two fuels. There can be other advantages to mixing fuels, such as getting higher net density, or changing some other physical properties. But ISP will always be worse.

Relativity precisely deals with abstraction of coordinate systems. To the point where time displacement in one coordinate system is a space displacement in another. The example you give is no stranger in relativity than discussing what happens if the pebble is thrown from different locations. Moreover, General Relativity does not require the coordinate system to be universal. It is a local concept. The only restriction General Relativity places is that locally, your chosen coordinate system has Minkowski Signature. So that while the choice of time coordinate is arbitrary, you can chose precisely one direction as time and precisely three others as spacial coordinates. The rest is almost completely arbitrary. Once you introduce the restriction of traveling along time-like trajectories, which arises from field theory, time travel in General Relativity is reduced to a problem of finding Closed Time-like Curves (CTCs). So not only is Relativity adequate for describing time travel, it gives us precise tools for analyzing requirements and consequences of time travel.

Regardless of what can be happening bellow Plank's Scale, the Poincare Symmetry absolutely holds above Plank's Scale. That means that on the scale of the ship moving through space, stress-energy is a conserved current. And so momentum cannot be generated or lost. Any recoil picked up by Quantum Vacuum must become excitations in a field with infinite range. That means, electromagnetic radiation or gravitational waves. Either one would require an energy input equivalent to a photon drive. We are back to 300MW per 1N of thrust. It's a very fundamental limitation, which is rooted into all of Quantum Field Theory and all of General Relativity. Both of these theories have to be completely wrong and work as well as they do by total chance to allow for this sort of violation.

No. While it generates a lot of extra heat, thanks to its high enthalpy, which makes it great for burners, it only has the two hydrogens, and water vapor is going to give you the bulk of your ISP. CO2 is just too heavy in comparison, meaning ecetylene exhaust is going to be much slower.

Yeah, but it's usually much easier to translate from English to other languages without losing subtleties than the other way around. There are exceptions, of course, but in general English is just about the simplest natural language there is, so almost any structure in English is going to carry over to another language. Articles is a notable exception. Anything that accents the article will be hard to translate into a language without articles. But almost everything else works the other way around. None of this takes culture in consideration, naturally, which can make even translation from English to English difficult.

Even TARDIS, as fictional as it is, moves through the time streams, rather than just pop out of one place and into another. Timey-wimey stuff, etc. Antiparticles have nothing to do with time travel. Their backwards propagation is purely a matter of reversed wave vector. The time evolution of anti-matter is exactly the same as of ordinary matter. In order to travel backwards in time, you need to have time flow actually reversed. It's very similar to difference between phase velocity and group velocity. If you wrap your head around that, you'll have the basic idea. As for actual ways to send something backwards in time, there are a bunch of ways from General Relativity. There could be purely Stat Mech methods of doing so as well, and you will need QM to dump the extra entropy. Either way, though, what you're looking for is backwards evolution of the system. To an observer, it will appear as if the rest of the universe is running in reverse. Many Worlds does account for any paradoxes that can arise. But so does Copenhagen Interpretation. Just in very different ways. The branching itself isn't strictly necessary. It's all about the fact that you're dealing with fields, rather than what you normally think of as particles. You have a very poor understanding of relativity, if you think that. You really shouldn't be making claims based on your own misunderstanding of physics and try to present it as fact.

You're taking branching too literally. It's not discrete. And you traveling back doesn't cause anything in the many worlds. Nothing causes anything in many worlds. It is event-free until you introduce a perspective of the observer, at which point you only have a single time-line. That of the observer. Also, all time-traveling schemes require you to be present in every point in between, whether you're going back or forward. So if you don't count that as time travel, then there is no time travel.

I'd go with, "Twist onto the Sun." But it is just one of many phrases that makes you realize that English is a very bad language for translating things into.

In that case, so does cpast's answer. A photon of energy E carries momentum p = E/c. Doesn't matter if it came from a matter-antimatter rocket, a laser, or a radiator. You can get 1N of thrust for every 300MW of power you dump into it.

Total angular momentum is a conserved charge for a rotationally-invariant Hamiltonian. Noether's Theorem. In other words, you cannot change total angular momentum without applying external torque. You can store that angular momentum as rotation of the craft, rotation of parts (such as gyros or wheels), or even elementary particles. There's an h-bar of angular momentum in just flipping spin of each electron. But you cannot dump angular momentum without dumping matter/particles that carry it away or without applying external torque. (Earth's magnetic field would count for "external" in this case.) Angular momentum, as well as linear momentum, are perfectly conserved in all collisions. If you think you've read otherwise, you've misread.

There are plenty of things modeled by KSP which can also saturate reaction wheels. Thrust not being perfectly colinear with center of mass, aerodynamic forces, RCS (mis)use. All of these things can change angular momentum of the craft, and so all of these things can saturate reaction wheels and/or gyros.