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K^2

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Everything posted by K^2

  1. K^2
    The only connection between wormholes and entanglement are the names of Einstein and Rosen and some half-baked mathematical constructs that aren't even fully fledged hypotheses yet. For starters, no-communication theorem does not apply to wormholes.
  2. K^2
    I'm assuming mirrors are made from metal foil. That's the only way to pack enough of them. In which case, I propose an upgrade to mirror drive's efficiency. Instead of converting electric energy into light, which tends to be pretty inefficient at required power levels, lets install a rail gun inside, and fire the mirrors using electromagnetic forces.
  3. K^2
    With exception of some murky corners of certain String Theory interpretations, none of the field theories, including General Relativity, predict a mechanism for topology of space-time to vary. Which means, as far as we know, and this is one of the few things that are definitely subject to change, the total number of wormholes in all of the universe is a conserved quantity. That quantity can be very low. It can even be zero. So us not observing any wormholes has a very simple explanation. There aren't enough of them in the universe to make proximity to one to observe sufficiently likely. This is very different from things like Supersymmetry and String Theory predicting buckets of new particles, with none to be found. To put this in more precise and general terms, what scientific theory needs is to withstand a test of critical experiments. Looking for wormholes does not satisfy criteria of a critical test, because we aren't necessarily expecting to find any. String Theory fails critical experiments designed specifically to test it. It leaves loopholes, sure. But with each experiment, validity of that theory becomes less and less likely.
  4. K^2
    At energies where things are going to start getting dangerous, the flow won't really "reflect" from the surface anymore. At the energy levels of typical chemical rocket exhaust, the exhaust particles still interact with the lattice as if it's a solid. But you are already at the boundaries of it with something like a NERVA. As you get into even higher energies, the binding energy in solids becomes lower than kinetic energy of incoming exhaust. At that point, exhaust doesn't interact with a solid, but rather with collection of particles that make up a solid. In other words, fluid dynamics takes over. You'll probably be getting some splash-back, but at much lower energies. You might be getting equivalent of a sand-blasting, but that's true with pretty much any engine, and hopefully, you'll cut duration to a minimum. I wouldn't worry about landing into puddle of molten rock, though. You'll cut a hole in it, but nothing too drastic. As you increase the exhaust velocity, you also reduce the amount of reaction mass by the same fraction. So by the time you're doing serious damage to the surface you're landing on, you also have a pretty low mass flow, so damage will be highly localized.
  5. K^2
    I don't know of a lot of general aviation aircraft that are fly-by-wire. Naturally, the atutopilot can completely take over, but it can only do so much to "fight" the pilot. (Stick shakers, etc.) Personally, I see two good options here. Either have pilot mostly responsible for control, and with flight computer, at most, filtering out "unsafe input" as some commercial aircraft already do. (I think Airbus does this on their fly-by-wire aircraft. Perhaps, someone will correct me.) In this case, the pilot is well-trained both in navigation and actual aircraft control, and there is no reason to do too much on the control correction. Or we go the self-driving car route and have the operator responsible merely for entering destinations. The flight computer would then be responsible for contacting ATC, filing flight plan, and following it safely to destination. There is very little reason not to go all the way here. There are no pedestrians in the air, nor terrain hazards. Most aircraft fly with transponders already. The few that don't are small, slow general aviation aircraft that tend to stay low and aren't too hard to avoid. Everything else is already being looked after by a number of computer systems responsible for air traffic. There is zero reason to let an unqualified person to even touch the stick.
  6. K^2
    We can build one of these, no problems. The pilot's skill is primarily in foreseeing how situation is going to develop, so he can correct for things in advance, as well as react properly in emergency situations. This is why you want a well-trained person in the seat, and why nobody bothered to enable a layman to fly with corrections from the flight computer.
  7. K^2
    It's a theory in a mathematical sense, not a scientific one. As in, "Set Theory," "Group Theory," etc. The mathematical portion of String Theory is solid, so it's fair. The hypothesis part was, "All this math has something to do with reality." And that's the bit that didn't seem to have panned out.
  8. K^2
    String theory got over-hyped early on, leading to it turning into a buzz word, which is why so much pop-sci has been devoted to it. The reality is that interest in string theory among actual particle physicists has been winding down since the late 90s. By now, it is largely considered a mathematical curiosity. While useful dualities can be constructed, they are rarely more convenient than standard model. And the reason for this change has been lack of experimental support. String Theory makes few predictions that can be tested, and these that potentially could be, have not been verified. So while I can see how excitement over string theory can look alarming to an outsider, it's been a very minor setback in the actual field.
  9. K^2
    In the beginning, there was a Word. Just as reliable a hypothesis.
  10. K^2
    If it weren't for the smoke plume, I'd be tempted to make a joke about them playing a launch video in reverse. That's some optimal control landing there.
  11. K^2
    Russians aren't as red as they used to be. By this logic, it will be Chinese. That's also a somewhat more plausible possibility.
  12. K^2
    It's important to distinguish between "shouldn't" and "doesn't" in this case. A well-built and well-shielded closed-cycle nuclear thermal rocket running on pure hydrogen as reaction mass, will not produce any radioactive contamination. Any impurities in your hydrogen supply, and this claim is void. Any cracks, leaks, flakes, etc on your reactor or plumbing, and this claim is void. Any dust that managed to accumulate on pretty much any internal part of the rocket, including just under the shielding, and this claim is void. There are a lot of little things that can go wrong to result in radioactive isotopes in the plume. And this can vary from insignificant to catastrophic.
  13. K^2
    These are pair coincidence counts. They tell us that particle that decayed produced no massive product in the same decay and that its total angular momentum was zero. This is consistent with lepton-antilepton bound state, a bunch of mesons, and yes, the Higgs boson. There is no "directional" or "polarity" information gained from such events. And sure, it'd take billions of collision events. Which is basically what LHC is designed to produce.
  14. K^2
    Two photons is an expected and observed mode of decay for Higgs. The branching fraction just happens to be somewhat low. Keep in mind that pairs of photons just happens to be the thing they are detecting in this experiment. pp collisions create huge showers of all kinds of junk. We might not be able to detect WW pairs. They are short-lived and interact with stuff in the shower, making coincidences harder to detect. Photon-photon, on the other hand, is very easy to pick up on coincidence counters. Here is a picture from Wikipedia. As you can see, at 750GeV we see something like 10-7 of decay events going to photon-photon.
  15. K^2
    No, the claim is that there is a heavier Higgs Boson which has a decay mode into two photons. It's entirely plausible given general Higgs mechanism. Whether there is a single Higgs Boson or several different ones, potentially with different masses, depends on the exact symmetry responsible for Higgs Mechanism, and there are several that are compatible with current observations. Could always be a completely new field with its own symmetries, of course. P.S. I'm tempted to say that it's the supersymmetry pair, but I doubt a lot of people would appreciate that humor.
  16. K^2
    Given the oil prices, it came down to either annexing Crimea and fighting a war in Syria or having social and exploration programs. Russian government went with the former.
  17. K^2
    HTSC has pretty low critical field at LN temperatures. I'd wager, it will transition to normal as soon as you turn on the magnetron, making the whole thing work even worse than a good conductor like copper. If you want a superconducting cavity here, you need the sort of superconductors that are used in particle accelerator coils and medical MRI equipment. That means liquid helium cooling, keeping the superconductor at 2-4K. Another thing to note is that you don't have flowing LN. That's not how you cool things with LN. It cools by evaporating, which means, all you have to do is submerge something in it, then make sure you keep the container topped off. Same with LHe. However, if you want to go down to 2K or so, you'll have to also reduce pressure in the chamber to drop boiling point to 2K. This requires very expensive hardware, which is why it's only used on particle accelerators, where they really need cavities to be superconductive. Backing HTSC into whatever shape you need is fairly straight forward. I mean, in the way that it's not harder than just making HTSC. And that's an interesting project all on its own. There are a LOT of safety factors there, however. If you want to try it, make sure you understand all of the relevant precautions for both working with the oven you'd need to bake HTSC and for working with LN.
  18. K^2
    Straight up epoxy should hold. Its ultimate strength is over 100MPa, and your bind area is comparable to cross section, where you will need about 3MPa. Just make sure it is a close fit and coat inner walls of the mouth with epoxy. The only reason you need fiberglass on the rest of it is that walls are going to be relatively thin, compared to relevant cross sections. Oh, and one could absolutely build something like that in their backyard in US. None of the materials are flagged, it is not meant to explode, so it is not a destructive device. And only limitation on hobby rockets is total impulse, which is quite generous. There are additional limitation if you plan to actually fly a high power rocket, but ground tests are fine.
  19. K^2
    That's just prejudice. ISP is defined by fuel mixture, chamber temperature/pressure, and nozzle shape. All of these things are easily matched in a garage. What you aren't going to match is low weight and reliability you want for space launches. But OP isn't going for either of these. Still, actually getting the full ISP does require a bit of math. OP isn't going to get that with nozzle design he has. But he can get well above hundred, and still be 3x - 5x better than a black powder rocket you'd get in a hobby store. It's a pretty cool project. Just so long as safety is kept in mind.
  20. K^2
    Suspiciously accurate for "guessin".
  21. K^2
    Are you just trying to see how many times I can say "double planet" in one thread?
  22. K^2
    For "many centuries", it will last even on our Moon. It will constantly be cooling, of course, thanks to atmo evaporating away, so it won't be nearly as warm as on Earth. In fact, it will be downright cold. But hey, if you plan to dump enough atmo on the Moon-like object to make a breathable atmosphere, realism went out the window long ago. You probably will insist that it's being heated as well. At these kind of energy expenditures, I don't know why you're even asking about realism of that system. Just maintain orbits with large rockets.
  23. K^2
    Got nothing to do with magnetosphere. Moon's escape velocity is 2.4km/s. Given the mean temperature this distance from the Sun, a sizable fraction of Moon's atmosphere will have escape velocity at any given time. You need at least 5km/s, which is the size of Mars, to have a chance to keep atmosphere this close to the Sun. So your Luna would have to be size of Mars at least, putting barycenter FAR above Earth. The Luna and Earth would orbit a common center, rather than Luna orbiting Earth. You'd have a Dual Planet situation. There is no way to avoid it if you want it to have breathable air.
  24. K^2
    I wouldn't mess with the bottle. Use it purely for storage. Filled and purged through the throat. Now, bellow the throat, you can set up a manifold that lets you do whatever you need. I'd make manifold from a solid piece of metal and drill into it as necessary.
  25. K^2
    Earth's Moon is already pushing definitions of a Moon in a lot of ways. For Luna to have breathable air, it would have to be a planet, making Earth-Luna system a double planet system without any doubt. (I still insist that we should be classifying Earth-Moon system as a double planet.)
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