GreeningGalaxy

You trip over that elemental sodium brick you left lying around and spill your water all over it. The reaction sets your chair on fire, and your fire extinguisher turns out to be a hand grenade in disguise. You promptly get some sleep, but it's not very restful sleep, and you miss a lot of stuff you were hoping to get to because your coma lasts for several weeks. I'm about to go turn off that fan in the window. What's the worst that could happen?

Moving a giant mylar concentrating mirror into position over the planet, increasing the solar radiation flux by a factor of a million. You're sure to get tan now! Making maps.

My torchship cleanly skims past the surface of the planet at 300 km/s. A few ball bearings which I 'accidentally' dropped at some point impact the hill and evenly distribute its mass across the landscape, negating its hill status. I start my braking burn, aiming for arrival on a nearby moon where I plan on claiming a different hill.

I've got this too, on Debian 8. Antialiasing doesn't normally work at all in my experience with my card and any distro, unless I install fglrx/Catalyst and force-enable it with amdcccle. Since fglrx/Catalyst tends to thoroughly break the graphics in several of my other games, I prefer not to install it, so I don't know if the fairing z-fighting occurs under Catalyst as well. I hope this can be fixed, because it often gives me a headache, and fairings aren't exactly optional with the new aerodynamic system. :/

I exiled Jeb, Bill and Bob to interstellar space because I was tired of them showing up for every single mission. Val is on Vall, but two malfunctioning ISRU drills mean that she's probably not coming home any time soon.

Regardless of how unlikely it is, I find the idea that the X-37 is some kind of satellite bodysnatcher quite amusing. Maybe the current version is just a test for something much larger that can be used as a sort of "nope" vehicle - somebody you don't like just launched a nuke-armed satellite? No problem. Just launch that planey thing, grab the sat as soon as it finishes its insertion burn, and then return it right to their doorstep, free of charge. No nukes in space for you today! Yes, I know that there are at least fifteen things wrong with that. Still, being able to steal satellites out of orbit and land them intact sounds like a very fun toy.

Evidence to whether that thing actually works or not is dubious at best, and anyone who says otherwise is just being overexcited. The argument "But the chances that someone overturned the law of conservation of momentum with their little steampunk brass can are still technically nonzero!" doesn't hold a lot of water. I could be proven wrong (I'd love to be) but I'm not signing up to invest in it until we see some peer-reviewed papers. Alcubierre drive carries the implication of a causality violation/closed timelike curve (see the 'tachyon pistol duel' thought experiment), so it's also likely to be impossible. We're likely to learn lots about how spacetime works while we explore why it's impossible, but I'm also not getting my hopes up that someone will ever build a working device.

Isn't it hard to say what the term "glitch-powered drive" would mean in real life? A 'consistent glitch' is kind of an oxymoron when you're talking about how the universe works - if it behaves consistently, we usually just call it a physical law. If you like, you could say that the Casimir effect is a glitch in reality, and that exploiting it to make a quantum vacuum plasma thruster is building a Kraken drive, assuming such a device is even possible. Personally, I'd be more inclined to call it a harnessing of physical principles rather than the exploitation of a glitch, but it really just comes down to terminology.

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A few raisins I have with your proposed stealth ship design: 1). Liquid water (even liquid water spiked with antifreeze and cooled below 0 C) is still quite a lot warmer than the cosmic background, and it's going to show up on thermal scans pretty easily. 2). No matter how you cut it, 400 kilowatts of thermal power made into 100 kilowatts of electricity means you're radiating 300 kilowatts of infrared into space. if your radiators are gigantic enough for you to dissipate that without your radiator surface getting hot enough to be seen against the cosmic background, you're going to show up just by eclipsing stars. 3). Even if that magsail ship could remain discreet with its waste heat, it won't be very useful in combat. Once it's detected, its tiny maximum acceleration will leave it a sitting duck to the first missile fired, and its low mass budget will severely limit the amount of armaments it can carry. (more mass will require more power to push it around, which requires miles more radiator mass to keep it cool enough to stay invisible, which in turn requires more power to push around...) I suppose you could always strap an entire fusion torch assembly to the back which you can boot up as soon as you're detected and the jig is up, but those aren't renowned for being very light, either. Other notes: -Attaching spotlights to booms and whatever other smoke and mirrors you care to pull isn't going to fool your enemy. They're still going to see different types of radiation coming from the decoys than from you, and their telescopes will probably be able to resolve pretty good images of the decoys to tell that they're just spotlights on booms and not real fusion torches. In any case, the multiple viewpoints afforded by the sensor beacons the enemy has no doubt been launching are going to see through you pretty fast. The problem is just that the enemy can make too many measurements that you don't have good ways to fool, other than by using the real thing. -Webb telescope-style radiation shielding won't work to hide a heat radiator. The sun would only be providing the telescope with a few kilowatts per square meter at that distance from the sun, and a radiator would be putting out hundreds of kilowatts at the very least, and if it's a true combat-capable ship, probably hundreds of megawatts. It doesn't matter how many layers you use on your mirrors; you'll still either have hot backsides or gigantic unwieldy things that can be spotted from Mars. I'd interject that none of the numbers you just provided make a particularly good case for stealth, and do a rather good job of making one against it - you have atrociously low acceleration, huge amounts of waste heat, and impractically large radiators that still don't spread it out thin enough to be stealthy. Also, no, nobody on this thread has made a case for stealth in space that isn't full of rather serious holes yet. But: Even if you don't do that, I'd recommend reading that page. It does pretty exhaustively cover the arguments for stealth in space, and if you find anything you disagree with in their reasoning, Atomic Rockets makes it sound like you might be able to get them to explain it to you better than anyone here could. If you do have an idea that would actually work, though, please share it over there, because it would be pretty cool if stealth in space were a thing.

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Magsails still have that problem where you require a ton of power. No, solar energy won't be enough (and even if it were, the panels would get very hot and easy to see). You'll need a nuclear reactor, and with a reactor comes glowing hot radiators, and with radiators come huge, brilliant heat signatures that you can detect from three stars away. Also, even if you somehow managed to get ahold of a perfectly-efficient source of electricity, the charged particles being redirected by your magnetic field are probably going to give off synchrotron radiation, which will be pretty easy to pick out by enemy sensors. The short and easy answer to the problem is that there isn't (and never will be) a propulsion system capable of providing any amount of thrust without also lighting up your ship like a Christmas tree; there are just too many steps in the energy conversion process and the efficiencies necessary to avoid transmitting detectable amounts of waste heat just aren't possible with any known or theoretical mechanism. Atomic Rockets discusses in very good detail why decoys won't work - they're too easy to see through (thrust power is easy to measure from long distances, and they'll appear from your ship's position, so your enemy will easily be able to follow their little trails of bread crumbs straight back to you. With the added expense of hauling the things around, you might as well just send more ships. As for directional heat radiation, Atomic Rockets also lays that one pretty much to rest - There just isn't a way to reflect thermal radiation with enough efficiency to prevent the back of the mirror from heating up, and even if there were, the losses in radiator efficiency would be very substantial and liable to make your ship so large that you could see it just by waiting for it to transit a planet or star. Believe me, nobody here wants to believe that stealth in space is impossible, it's just that nobody so far has come up with an idea for it that would work.

Differentiating colors the same way is not the same as seeing them the same. However, I might argue that since which colors are which is learned during development (and all the associations with each color as well), it might be entirely meaningless whether your 450nm registers the same in your brain as my 560nm. In fact, I might hazard to guess that no one sees colors exactly the same way - as far as the interaction between the eyeballs and the brain goes, the red you see might be a totally alien color to everyone else, and someone else's red might not make any sense to you. Ultimately, I think this problem just tries to draw some kind of line between how your brain receives a piece of information and how it processes it, which might not be separable processes at all. Human brains share a good deal of structure in common, but it's foolish to assume they're all exactly the same in the way they handle sensory stimuli - that much, at least, we can see.

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I'd be interested in seeing a tidally-locked hot Jupiter with an asymmetric texture and no atmospheric bands to speak of, sort of like this artist's depiction of HD 189733 b: Also would be interested in: -Small moons with thick atmospheres (You can never have too many Titan analogs IMO) -Small atmosphereless body with lots of high, flat plateaus surrounded by deep fissures -Body like Potatus or Inaccessible that rotates fast, but still slow enough that the equator is moving at slightly sub-orbital speeds -Largeish non-round body, possibly a victim of some cataclysm in the past

Fine. Those aren't really the reasons why fusion is hard to use for aircraft, but that doesn't really matter anyway - it doesn't matter how the engine power is generated, be it gas-core fission, inertial fusion, nuclear pulse propulsion (both fission and fusion), or antimatter; all I'm saying is that a starship-age shuttle is likely to be a "simple" engine-with-wings type of thing, rather than a complex single-use multi-stage vehicle. More likely than not, we're going to have something with the power density to hop up and down between the ground and space with relative ease long before we have any ability to fly between stars.

You're describing an open-cycle magnetic-confinement fusion engine, which would indeed require a vacuum to operate and would have far too little thrust to take off from an earth-like planet. However, things like inertial-confinement laser fusion could potentially be done one a smaller scale and at a very high power density. And yes, I know the drive shown at that link would also need a vacuum to operate - for an atmospheric vehicle, you would make that into an internal reactor assembly which would be a vacuum chamber, and surround that chamber with shielding, through which you would run your working fluid and capture the heat from the thermalized neutrons and alpha particles. For many feasible designs, the power density would be far higher than anything you could get with fission. Yes, there are lots of engineering hurdles - how to shield the lasers, how to make the lasers lighter, the best ways to capture the charged particles to make electricity, and so on. However, my point still stands that these are likely to be overcome on the way to finding methods of interstellar travel, so by the time we do reach other solar systems, there won't be any point in building crazy multi-stage landing craft with chemical and simple fission thermal propulsion.

I'm not making any assumptions that we'll be constrained to current-day designs for fusion reactors in a future that contains starships. My guess is that we'll have a pretty good handle on how to make a small, powerful deuterium/tritium fusion reactor long before we figure out how to generate antimatter in quantities measured in thousands of tons (which you would need for a proper interstellar torchship), much less find a way to bend space and make an Alcubierre bubble, which is pretty likely to be totally impossible anyway. Theoretically speaking, heating stuff (like air or propellant) with fusion isn't that hard. The deuterium-tritium reaction results in lots of fast neutrons (which are easy enough to thermalize into the propellant), and charged alpha particles (which are even easier to thermalize). You'd then pump the propellant through channels in all that nice hot tungsten shielding surrounding the reactor, heating up to extreme temperatures and firing it out the back of the ship at high speed. You do need a lot of heavy stuff like magnets and vacuum bottles to make fusion work, but the theoretical power density (and the power density that might one day be achieved) is certainly high enough to allow a shuttle to scream its way into orbit without burning much propellant at all. In fact, it's likely that you could just skip the thermal jet stage entirely and do the entire ascent on closed-cycle engines only, but that would make your required mass ratio a little bigger than you're probably willing to carry aboard a starship. All this will involve building some kind of fusion reactor, obviously, but it's probably safe to say that that's less than a century away. Starships are almost certainly further off than that.

Gets a different universe, with a speed of light equal to 4,825,021,266 m/s and a sigmas instead of protons as the main stable charged baryon. Puts in a 25mg tablet of diphenhydramine HCl.

I've been considering the things you might do on arrival to a planet in another star system for a hard-SF story I'm writing. My plan so far is something like this: Phase 1: -Begin arrival burn with a nice powerful antimatter engine. (This could either be the velocity-match burn for an Alcubierre starship, or the post-skewflip burn for a sublight torchship like my story uses.) -At some point during arrival burn, start dropping probes, with a little bit of thrust so you can make them encounter as many planets as possible on their fast flyby trajectories. These will provide forward reconnaissance, arriving in-system long before you do and providing some preliminary analysis of various planets before they go shooting off into interstellar space again, Voyager style. -If your crew are in cryogenic stasis, there's no need to wake them up yet. It'll be a while before you get there. That said, wake up the commanding officers right away if any of your probes receive any weird radio signals or see signs of civilization. And if any of them get shot down as they whiz past the planet, you might want to consider turning your ship away from there ASAP. Phase 2: -Complete arrival burn; capture into orbit of desired planet and shut engines down. -Deploy hordes of scanning satellites into various orbits, thus pre-establishing a GPS network and obtaining a detailed surface map of the planet. -Drop hordes of tiny UAVs into the atmosphere. Get even better map of the planet, take atmospheric data (you could probably tell whether or not this planet had an atmosphere before you left home; we can already do that with some planets today, and our tech for that kind of thing is only going to get better), find out how hard it's going to be to keep the crew alive down there. Some of these drones could also be dropships for rovers, if you like. -Inflate some orbital habitats. -Now wake up the crew, if they were frozen. For the moment, they can move into those nice orbital habitats you just inflated while they regroup, read over all that neat map data from the planet, and get ready for their next moves. This step and the previous one are optional if your crew weren't frozen. Phase 3: -Pick a nice spot to land on the surface. You'll probably want it near the ocean for refueling reasons; if you're worried about biological contamination, you might want it to be offshore. In any case, make sure it's a nice day down there. -Get a landing party together and get in your descent/ascent vehicle. This will probably be a big planey thing with giant fusion engines. You'll probably have fusion if you have antimatter (read: at the very least, having antimatter means you'll have antimatter-initiated microfusion at the very least). You'll probably have antimatter because not much else will give you the ÃŽâ€V you need for that arrival burn. -Descend. Ideally, this won't need much in the way of engine burning; you'll be able to just fire a short retrograde pulse to drop into the atmosphere, then glide in, pull the airbrakes, and switch over to your vertical engines once everything stalls. You'll probably want to have vertical engines, since alien planets aren't known for their abundance of runways. Your descent vehicle doesn't have to be a plane; If you like, it can just be a main-engine-down style lander, but then reentry will be more complicated and harder to control. Most of your engines will be fusion thermal jets, which use the local atmosphere as propellant the same as a thermal rocket does. You might be able to get away with large fusion-electric ducted fans for your VTOL engines if the gravity is low enough/your reactors are powerful enough, or you could just have some high-bypass thermal turbojets capable of aiming down somewhere in there. -Touch down. If you're coming down over the sea, inflate some kind of nifty skirt around the bottom of your plane so you don't sink or flip. If this is on land, look for someplace level. As a third alternative, you might skip the landing step entirely and instead inflate a big blimp envelope over you and hang from that for a while. Phase 4: -Get some science done. You're on an alien planet you've never seen before; you know the drill. -Refuel. If you decided to come down near the ocean, pick up some of that water and stuff it in the tank; it'll do nicely as propellant. You can also electrolyze it into hydrogen if you prefer. Whatever you do, be aware of who you scoop up in that sea water. Even if you suck it through a fine mesh, there's going to be microbes in it, probably ones you don't want to haul off the planet with you. Boil the water, give it a dose of hard radiation, do whatever it takes to be sure you kill everything in it, and then test it to be absolutely sure before you leave the surface. Of course, ISRU is optional. You'll use hardly any propellant getting down to the surface, and you won't need much more getting back up. If you don't want to haul an extra-big, extra-flexible landing craft with you, you might not want to bother with all that risky surface-refueling business. If you're trying to use a weak propulsion system like current-day fission (or worse, chemical rockets), you'll certainly need the ISRU, but if you've got a respectable fusion engine or two, you'll probably be looking at an Isp in the thousands and won't have to worry about most of the takeoff due to those nifty thermal turbojets. Phase 5: -Lift off. As mentioned before, the first couple km/s of velocity won't be hard to get ahold of, they'll just cost you a few kilos of deuterium and tritium. You'll need variable-geometry intakes and a number of other fun things to keep your engines from exploding at high speed, but by the time you get to thermal rocket handover, you'll be doing some serious speed. In closed-cycle mode, your engines will probably have an Isp high enough that reaching orbit won't be an issue. -Dock with your mothership. Phase 6: -Do as you please. If you've come on a sublight ship, your ultimate goal might be to establish a permanent colony or research station. If you came on something FTL and can hop home whenever you please, maybe this mission is done.

Gets THE OVERNEWB *dramatic music* *camera shaking* *screaming* Inserts a 5kg iron rod at 0.98c.

Banned for weak sarcasm.

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