wumpus

Hyperfission? Basically we already split the low-hanging fruit of the nuclear reactor: splitting any more isn't clear it will add anymore power. You might also want to look up "plutonium poisoning", I think that is why current reactors pull the fuel rods. Breeder reactors were designed to allow more of the fuel to be used, that is probably what you are looking for (since the amount of nuclear fuel available never turned out to be the limiting factor, breeder reactors simply haven't been used). Earth based or space based? <RANT> Earth-based nuclear [fission] power seems unlikely in the West (especially USA and EU). Most of the reasons are political, although political/economic factors such as the nuclear power plant construction industry grew up with time&materials contracts and now appears completely incapable of developing a power plant remotely on time or schedule. Remember, these things are essentially pre-paid electricity. If you are paying interest on a debt while watching your nuclear power plant slowly being built while running into delay after delay, it is even more painful to look at (also prepaid electricity) solar farms being put up on time and schedule, and also watching the profits on such panels being pumped back into R&D making the next solar panels (which will compete with your electricity, assuming you ever go on line) much more efficient. I doubt any nuclear reactor constructed +/- 10 years will ever be profitable. *** NOTE *** This isn't suggesting Germany's abandonment of nuclear power remotely makes sense. Construction of the nuclear plant is a sunk cost and decommisioning the reactor isn't going to bring anything back. And nuclear power (especially after the sunk cost) is always going to be "more green" than any replacement over the expected life of the reactor. </RANT> Note that after sufficient decades pass it might make sense to have another go at Earth-based nuclear power (especially if using designs made off world), but the whole infrastructure behind nuclear power is hopeless. Nevermind what can be done in the lab, your technology is your infrastructure (see anything by James Burke for a detailed analysis). Spacebased ordinary nuclear power is likely sufficient, although cooling is even more of an issue and big, cheap, heatsinks (like gravity fed watertowers above the reactor) simply aren't an option off planet (maybe some liquid on Mars? Sounds difficult, but possible). Solar power (within Mars orbit or so) is going to be wildly more effective than anything on the ground, so I'd assume that engineers will go for the tried and true (solar) than the difficult and risky (non-RTG nuclear power). And don't forget that there has been one fusion-powered SSTO developed and manufacturable with 1960s tech: the Orion (not the current use of that legendary name, the real Orion.) Unfortunately early calculations ignored the magnetosphere and Van Allen belts, so most of the "fallout" would return to Earth. This could still be avoided by manufacture and launch at Antarctica, but you might still face threat of a nuclear response from India once they realize that they would have the lion's share of deaths due to a planetwide barrage of nuclear pollution (and the Chinese might as well back them on this).

If the engineering solution is a parabolic nozzle, the "ideal nozzle" for vacuum is infinitely long. Thus any real vacuum nozzle is a truncated parabola. What you probably want is something that looks a lot like an additionally truncated parabola for atmospheric use and then clamp down the "only mildly truncated" rest of the nozzle for vacuum use. This would certainly not be optimal for atmospheric use, but then again no nozzle is ideal for the whole range of the atmosphere anyway. I expect my "quick, dirty, and expensive to implement" solution still isn't as efficient as the RS-25 nozzle (across all pressure levels), although maximizing vacuum Isp is absolutely critical for this type of thing. While you Ve equation looks nasty, there aren't a whole lot of parameters that define a 3-d parabola: I think at most 2, not including absolute size (note that the RS-25 doesn't use a true parabola).

GAH. This could be a great physics problem. How many wrong assumptions does this question have? A(n ordinary c-traveling) photon has an energy of hv (that "v" should be a greek "nu" but I'm too lazy to look up how to type it). But that is apparently derived from the Planck constant times c (presumably changed to match the new, improved speed) divided by the wavelength. So the energy would presumably increase for a "superphoton" of the same wavelength. Of course, once it hits your eye (or camera), a curious effect happens. Your eye isn't calibrated for non-c photons. It is calibrated for standard ones, so it assumes that the wavelength (the color) of the light is inversely proportional to the energy of the photon (probably. Or perhaps your retina uses filters. I'd still expect the non-c photons to pass filters based on energy, not "real wavelength"). "Brightness" is based on number of photons, or probably more likely the total energy of all the photons. Each photon of light can only be one "brightness" dependent on the frequency of that photon: this is one of the reasons "quantum" physics is "quantized". Don't bother with "superluminal light": it makes for bad sci-fi. And of course anyone looking at said light would have "second sight" as they are looking into the future.

By definition the voltage across the inductor equals the voltage across the capacitor. Likewise, once the switch is open (and not arcing), the current across the inductor equals that of the capacitor. Of course for sufficiently high frequencies, expect the "parts being equal" to effectively move at the speed of "light" (conduction inside the medium).[Edit] I'd also expect that you need to model the resistances of the wires in the classic case as well. I'd expect it to oscillate, but the conventions of schematic drawings don't always allow for the reality of HF effects. Perhaps some HF engineer can help with how the HF world interprets schematics.[/Edit]. If the inductor remains conducting, the inductance shouldn't change (until it melts) and the circuit will act like a boring old classical circuit, only now with ESR. ESR [Equivalent Series Resistance] is a spec commonly listed in capacitors indicating the amount of resistance you can expect across one. I'd assume that inductors have a similar spec, but don't remember having to bother checking one. I don't think I've used an inductor outside a switching power supply and don't really expect to. So the oscillator simply decays in a boring old fashion (assuming it is sufficiently conductive to not explode). In practice, I've heard that most superconductors are encased in copper (or similar conductive material), especially if the superconductor isn't naturally conductive. In such a case, the inductor would be completely shorted (probably to ground) and the whole think would stop dead. The whole "suddenly act classically" is dependent on being sufficiently conductive and superconductive in the same material (otherwise it would likely explode as I2R not only suddenly becomes high, but heating happens extremely *densely*, being an inductor after all).

While I admit that withstanding 1-2 bar isn't in the realm of sub-mm greenhouse film, I still think that 16mm or 7.8mm is still way too big. And width is mostly irrelevant (except for the greater increase of potential weak spots, something presumably examined on the ground), just how deep the fluid is (pressurized air or water in our thought experiment). The reason you need tensile strength is gravity, simply holding the material doesn't require that at all (think more of the sides [but not edges] of a container, they still have to be strong, but not that strong. I'd suspect that a plastic trash bag could handle a lot of water as long as it was sitting on the ground). Still, I'd really hate to have to design something that takes fuel from an inflated bag and then turns it back into cryogenicly cooled fuel inside a fuel tank. Expect that process to be slow and tedious, mostly thanks to using a blackbody as a heatsink (maybe use semi-conductive mylar, and use the fuel as a blackbody? Or at least as the "coolant", although this assumes that you will always leave a significant amount of fuel/oxidizer in the tank). Either way, cooling the propellant down to cryogenic temperature will be slow.

One of the first Falcon 9 flights had an engine failure. It was shut off and the rocket continued on the rest of the rockets. The "SCE to AUX" of legend is a similar thing with electric power. No idea how long a burn would have to be before replacing something in a running rocket would be viable. But replacing something in an ion engine would unlikely to be as exciting as the thread implies (and the only thing I could imagine "burning" long enough to bother replacing hot).

I was guessing that the SLS would be a great candidate for this type of thing (not many rockets are going to have hydrolox engines, much less something like SSMEs designed for going from pad to orbit). Unfortunately, the SLS "first stage" can't lift itself off the pad without the SRBs. So I assumed that you would remove enough fuel to give a T/W ratio of 1.11 (weight 90% of thrust) and started running the numbers. Assuming an Isp of 450s (total flight) you get a delta-v (no payload at all) of 9200m/s. If you assume an Isp of 366s for the first minute (no altitude compensation will give you vacuum thrust, just maximum efficiency vs. backpressure) you get a delta-v of 8700m/s. Don't forget that as a fully hydrolox rocket, it will have significantly higher aero losses than typical, and with the relatively low T/W ratio gravity losses will be higher. I doubt 9200m/s will be enough (and you can't get that). But I'd assume that with even puny single segment SRBs (such as what rings many delta rockets), the thing could lift off with a nearly full fuel tank and take at least some cargo to orbit. Unfortunately, the whole thing is still going to come back down as the SSMEs can't reignite for orbital insertion. You'd need a *tiny* second stage for insertion (see shuttle maneuvering engines), so your SSTO becomes three stages pretty quickly. Then there is always the temptation to make all the stages roughly equal in delta-v... If Falcon9's booster can basically get into orbit, I'd assume that Starship booster could too although I don't think that thing is ever intended for expendable use. It should be designed for delivering more delta-v to the upper stage (than Falcon9 on a reusable flight), and could presumably burn the return fuel to get into orbit. Why you would want to do this is beyond me, as you could easily get more cargo to orbit by using a much cheaper (even expendable) second stage and still reuse the booster. With the SLS there is no worries about reusing the "reusable" RS-25 engines, but it is still a wildly inefficient means of getting to orbit.

How about miniature giant space hamsters?

I suspect that both the Saturn and N-1 could remain on the pad while being topped off for months. Considering the Apollo budget, I'm sure the fuel bill could have come out of petty cash. Worrying about working next to a fully fueled rocket would be significantly worse near a UR-700, as even if you survived the blast from an explosion you would have to deal with the cleanup (the size of the area in danger would be significantly larger).

It also had a "lip" designed to avoid separation at low pressure. It could mostly ignore high atmospheric pressure inefficiency (but not any danger to the engine/nozzle due to separation) thanks to being carried by the SRBs for the first two minutes of flight (once they staged it was at nearly zero air pressure). I have to doubt the premise of the thread. Can you show that SSTO is viable with a constant Isp of 452s (SSME vacuum pressure)? You don't get to use the RL-10's 510s unless you manage to get enough thrust out of an expander cycle to liftoff (perhaps a stratolaunch lift?). You can expand that "zeroth order approximation" by assuming a T/W of 1.25 and an Isp that approximates 366s (SSME sea level) for the first minute (bv that time you hit 15,000 ft and your air pressure halves), 400s (roughly in between) for the next 30 seconds (at 35,000 ft pressure is halved again), and 450s for the rest.

Is this still true for the temperatures that SpaceX currently use? It makes a lot of sense at the point LOX turns liquid, but they are using just over the freezing points of LOX and kerosene (and presumably nearly solid methane as well). I'd expect oxygen dew on an oxygen tank that nearly has oxygen ice cubes inside (much like water dew on a glass that is 2-3C).

What's so ironic about that? Any DRM that could possibly have been added years ago would be trivially bypassed today (if not days after installation) and would only exist to frustrate paying customers and cause bugs in legit copies. DRM-free remains the best anti-piracy method of all. - Note that KSP-edu *does* have DRM, and I'd admit that situation there might justify it. But KSP-edu doesn't seem to be doing that well in any event.

When it staged, or when it became clear when somebody left off the parachutes?

Were all the people skycraned with solids sitting on top of exploding rockets? I'd accept a much lower degree of safety from a rocket that would get me off an exploding rocket. I can't think of another use case, unless you are talking about the rockets that reduce the landing impact in a Soyuz (presumably the cosmonauts survive even if the solids fail).

What do you mean "fuel from fuel"? If you mean "more heat/energy from current fuels" then you wind up much higher Isp on your rockets and spaceplanes and SSTO become viable. It also doesn't count as "hard science fiction" as the hard limits were known since Carnot's work in 1824 (modern electric plans often are "close enough" to that number that increasing it wouldn't cause many changes: maybe somebody gets a bigger bonus. That's it). "The renewable energy sector takes a huge hit because they can’t compete with free and unlimited fossil fuel. Environmentalism no longer comports with economic reality. " Note: most of the environmental issues are due to fuel binding with oxygen, using less fuel means less CO2. Of course if you had the same heat engine (and atmosphere), you would likely generate more NOx compounds (and more smog and likely more global warming). Designing engines for reduced NOx might get VW-style hacks to cash in the the "cheap gas gold rush". Note that "manned solar exploration is harder than it sounds. If you have the "infinite fuel mod", then yes, burn at 1g and get to Pluto in a week or so. If you only have superior fuel and need full oxidizer, you don't have the "infinite fuel mod", but instead something more like LV-N. This will get you just about anywhere in space, but not quite in a week. Interstellar issues might still be painfully slow (outside of places like Alpha Centauri and Proxima Centauri), but at least you won't be fighting the rocket equation every step of the way (even the mighty Orion needs a high portion of nuclear explosions before getting to relativistic speed). One thing that shouldn't be ignore if fuel became suddenly cheap (not just light) is that aluminum would be dirt cheap. Cheaper than iron, and would not only replace steel, but claw back much of the gains carbon fiber is making. Aluminum is sometime called "frozen electricity". There would be a certain performance gain in all the datacenters of the world as electricity dropped in price and they would be clocked for max performance ignoring efficiency. Probably nothing major, but it would require a certain shift in design (but not that much, modern chips are so tiny that efficiency is required simply to allow them to survive at all (although peltier heat sinks would suddenly make sense)). Note that it is important to decide if this "magic fairy dust" only decreases fuel mass (perhaps it is metalic hydrogen: this might even be a real thing and could be considered [assuming you wrote fast enough that it isn't "proven impossible"] significantly hard scifi), then you only get the rocket bonuses (including spaceplanes, but spaceplane flights aren't much cheaper than previous jet flights). Not environmentalism issues and the cheap aluminum.

This happens to the ISS as well. You only get one hole, as anything making the first hole is vaporized on impact. The solution is to make a somewhat larger if thinner polyethylene bag around your gas tank, fill it with .01bar whatever (presumably He to reduce launch costs) and let it take any hits coming its way (so your 'real gas bag' gets hit with dispersed vapor), and patch as necessary (you'd think a patching robot would be possible, but I suspect that it would require astronaut visits a couple of times a year).

I have to wonder if this wasn't a better idea than I typically thought when I first learned of deep issues in the Shuttle. Designing rockets is expensive. Designing rockets while being micromanaged by Congress is vastly more expensive. The Shuttle's launch cadence never allowed the costs to drop to the marketing used to justify the shuttle, why would anyone assume that building an additional heavy lift craft would make sense? Obviously, grounding all non-Shuttle rockets between the original Columbia launch and the Challenger disaster was a mistake, but that doesn't mean that designing a Shuttle-C could possibly make economic sense.

[1,300] is a list. It is not a number. if a[0]==1: print("True\n") if a[1]==300: print("True\n") will print: True True If you really want it to work on either case, try something like: For i in a: if i==300: print("hello from 300\n") if i==1: print("hello from 1\n") and you should get (but don't cut and paste due my issues trying to type into the fora's silly single space typing difficulties): hello from 300 hello from 1 #note that I'm still using Python 2.x, I don't really know if you still need the \n linefeeds in Python 3. I did fix the print functions for Python 3 (you didn't need the parentheses for python 1/2).

Er, why? Military craft might need sudden unplanned acceleration (either intentionally or momentum transfer from enemy fire), but ordinary spacecraft will likely have the seats normal to the engine thrust (obviously anything that normally faces the other way has to be able to rotate in the "right" direction). Exceptions might include aligning the spacecraft away from the local star for radiation shielding while burning in a different direction. PS: I really think the answer is "as many characters as the story requires". Multi-generational ships would have genetic reasons to have a fairly high number of passengers, but most of them could well be frozen embryos. For long term voyages, you might have to have astronauts that can "cover all the bases", but then they look a lot like astronaut/cosmonauts with "the right stuff" (i.e. pretty much all of current astronauts where NASA can be unbelievably selective as to who can go to space), and you don't need quite so many [it also means that your characters are "really" experts in any one field, which means that not knowing something that can't be easily googled isn't a real error. The character just didn't know that.]

My understanding is that the sudden drop is steep enough that lift often drops well below the weight of the plane, and it is easy to get in a [bad] spin. Mikegarrison's answer was better, but lift isn't just due to low pressure above the wing, it is due to the differential in pressure above and below the wing. If you somehow managed to compress the air beneath the wing to higher than 14.7 lbs/in *more* than the pressure above the wing then you could pull it off. I am unaware of any wing geometry that might pull this off (or why you would want to, the drag would be far worse than just lighter wing loading), but there shouldn't be a hard limit right there. EDIT: If a helicopter doesn't already do this, just reduce the size of the rotors and spin faster (and cover your ears once they break the speed of sound*). Helicopters and/or propellers seem the best bet to break the "limit". * breaking the speed of sound with a helicopter is a good way to break the blades. Then there's the Tu-95, which has supersonic propeller blades. Stay far away to maintain hearing.

There are ways to store multiple numbers, but they all involve grouping multiple variables. Python loves lists, but you could just as easily use a class for multiple variables. Variable names can't be numbers. I'm guessing you tried to type 1=300 and it failed (the compiler wouldn't let you do it). 1==300 means something completely different. Even is unlikely to do what you are trying to do (and they are variables).

This sentence really confused me. I think Shpaget is saying that the cross section of the propeller changes from the center to edge. This can be confusing because the optimal angle of attack of a propeller changes in flight and many planes alter that angle (and it is called "variable geometry"). This is of course rather expensive and complicated, and is only seen on planes somewhat more expensive than a typical Cessna. Misapplying Bernoulli's theory is as old as aviation, even Einstein famously got it wrong: http://wrightstories.com/einsteins-wing-flops/ If you think you understand the source of lift: ponder stalling (lift suddenly dropping to zero once angle of attack is too high for the given speed). If your understanding of lift doesn't account for stalling, it is wrong (I don't understand stalling, so I'll limit my posting in this thread). PS: "Why planes fly" would make a great science fair exhibit (use wings/model airplanes spinning around a spindle as a "wind tunnel"). First disprove the "textbook with arrows pointing up" misunderstanding by showing a airplane flying upside down and proceed to evaluate what is really going on (hopefully including stalling. The technical issues with the Boeing 737-MAX are mostly in the anti-stall software).

You don't need to bring the whole fort, just the name (and possibly a 15 star/15 stripe flag). And just like flags can't wave on the Moon, the vacuum is also completely silent (perhaps you can get the surface to conduct his music...).

If you want a name for waving a flag, it is hard to beat Fort McHenry.

I was thinking more suborbital hops where you can't jettison the capsule (such as the first launch in career). I'm not sure that a booster will get a "quick aggressive deceleration" without firing the engine.