wumpus

I remember a "history of technology" describing the birth of complex systems (the printing press is presumably a great early example. It took something like 20-30 modifications of *everything* (things like use paper not velum and a need to change the ink a bit) to start printing books. The claim was that simple machines *broke* (you could see why a shovel wouldn't work before you used it) but a complex machine would have *bugs* that were less obvious. Machine learning has "hives", or bugs on the next level. Things we know as "broken in spec" today, but at least since human programmers try to meet the specs, they hopefully know when the specs are wrong (even if the organisation they work for doesn't want to hear it). With machine learning, there is no way to communicate "what I mean" to the system developing the answer.

The last design I saw had nearly all napalm outside the combustion chamber. I'm not sure why it was drawn and posted. I was googling side boosters to learn a few things about Falcon Heavy, when I ran into this: http://www.aircommandrockets.com/howitworks_1.htm It describes how to build a water powered rocket (toy) with side boosters. I'm wondering if anyone has any experience with model rocketry to be sure that side boosters are beyond amature rocketry. I'd want to start with a TWR of ~3 and enough delta-v to get to just passed the transonic region (yes, this means nearly max thrust at maxQ. This might not be ideal). http://www.rrs.org/a-hydrogen-peroxide-rocket/ this seems to have failed entirely due to such rockets. A backup means of removal might be needed (or simply fire them off in a korelev cross before they burn out).

I gave up while using windows 98. I had toyed around with Linux from nearly day 1 (it took nearly a week to download about 8 floppies for the SLS distro over 2400bps dialup...), but eventually once I had an external DSL modem I could switch to Linux (my "DSL card" remains the only piece of hardware I never had drivers for. Note that I also have a tape drive that never had windows drivers (but worked under Linux). Turns out the best way to connect a windows machine to the internet in those days was to connect a Linux machine to DSL, and then connect the Windows machine (presumably using a swapped ethernet patch cable) to the Linux machine. Windows DSL drivers were pathetically unstable. It didn't take very long to switch my desktop machine to Linux as well, and suddenly the internet felt like it was in "native mode" (possibly because I learned to use Unix before DOS. A weird situation). This made watching windows XP security debacles amusing (Lockheed Martin's response to the Melisa virus was to finally shut down mail once the virus overwhelmed their system. Presumably they didn't care *what* programs hackers ran on their windows boxes until it interfered with actual operation). Eventually, Microsoft managed to make somewhat functional computers (and hackers learned about holes that even effect the mighty Linux: check badUSB if you laugh at the idea of worrying about sticking an known USB stick in your machine). But then microsoft came up with Windows 10 (and made it wildly difficult to avoid having your machine hacked into surrendering to this malware). Now your machine exists to spy on you to get any information that Microsoft wants (and expect any security updates from XP on up to include this spyware). Linux (or OSX) is the only way to avoid such things (and you probably want to avoid Ubuntu. Like win8's "give a desktop a tablet's interface", Ubuntu was there first.

I was busy plugging KSP on another site (it had suggestions about learning rocket science for sci-fi. I pointed out KSP cranked up "rocket science" smarts faster than anything else. I wanted to include a demo (for cheapskates or simply the chance to try before you buy), but it looks like the demo no longer exists on the Squad site nor Steam (I *think* Squad's demo was the ancient, pre-cost KSP with mods disabled, while Steam's was 1.0.0 based. No idea why they were different). I hope this isn't a 2k change, it was one of the last great demos out there (and KSP and demo should easily be great enough to sell the game, if other 2k demos can't sell the game that's their problem). [I did search for "demo", but I don't think the responses were all that current. I remember seeing a question about the demo in the hints discussion a few months ago.]

The cat pack would presumably be *before* the combustion chamber (unless all your catalysts can survive combustion temperature. Silver certainly won't). It needs to somehow maintain pressurization going in>going out>combustion chamber. Which is certainly interesting as each subsequent stage is designed to increase pressure (presumably Bernoulli's principle is critical).

I'm not kidding about "recondensed plasma". A 4g spacecraft at .2c needs 7.2*1012 J of energy to get that fast (not including relativistic changes in mass). Even spreading the energy fired at it over a month (by which I think it should be outside Pluto, a distance which you simply *can't* focus lasers. Look at the Hubble pictures for obvious proof) gives you power requirements in the MW/g range. And here's the thing: adding more heatsinks or radiators add the mass but don't change the MW/g needed from the lasers. The radiators will have to somehow radiate all the inefficiency converting MW of laser power into speed. This might be a great method for building a spacecraft that can outrun Voyager, but will never get near relativistic speed.

The question seems pretty moot. We've never discovered an inhabited part of Mars so we would presumably simply settle the surface and not be a problem. The only time this question would come up is if we wanted to terraform Mars. This would likely finish off any life holding on to Mars and I believe should be avoided. Thus leaving the question as to whether we should settle a planet with the idea that we can never terraform it. Personally, my visions of terraforming inevitably include dumping a packet of specifically designed life forms and waiting centuries or millenia for the necessary changes (presumably with timed/and adjusted packet dumps for new "invasive" species for each step).

Two stage to orbit is fine for the big boys (and presumably even down to Falcon 1), but expect to need even more efficiency gains as you get smaller. Pegasus launches at altitude (which helps nozzle Isp as well as drag losses. But it still uses two stages), and I think a recent Japanese* attempt at using a tiny rocket for satellite launch had 5 stages. * not to be confused with a fairly current private sounding rocket that is in the news.

Any idea how quickly a laser range finder can spit out range? You need some sort of range finder pointed at the ground. I'd also wimpout and use a fake "0 altitude" measurement fairly high off the ground (and let my rocket fall from that distance). I'm guessing that trying to figure out exactly what time the range finders finding was accurate is going to be the big killer (you can calculate your position easily based on that, but getting those two numbers to agree with each other is probably the reason robotics is hard (I've never been in field*). * In the dawn of time I had a small job doing the telemetry of a drone designed by Burt Rutan. But I was so green it might as well been considered a student project.

This is my big issue with AI. For some things (such as chess playing), debugging/testing an AI isn't all that hard. If it plays better chess/wins more often it is "doing it right" if not it is "buggy". For more complicated things, debugging/testing/grading such an AI becomes much harder. Presumably "using a non-English language" is on the "buggy" side.

I'm not quite sure what this means, but it is very likely that Roman viaducts and sewers were the only reason Rome grew to its size. Prior to the 19th century (and probably the later half of it), cities simply couldn't maintain their own populations, the death rate was faster than the growth rate. It wasn't until sanitation took off (presumably due to cholera, but I suspect people liked cities with the sewage removed) that urban population could grow. And it also wasn't until about the same time or slightly later (at least the 1920s in smaller US cities) that commuter railroads were built and suburbs were possible (until then living far outside the city meant cheap land and a long walk to work). A lot of things we take for granted are remarkably new.

Energy losses (beyond the atmosphere, and make sure you use expensive adaptive optics) should be minimal, although even the thinnest mylar sail will weigh a few grams (to cover expansion of a beam across 100km). But 100km is completely irrelevant: that's LEO, and once you start hitting the thing it is leaving LEO fast (i.e. once it gets up to Earth escape velocity). At that point you will need a bigger sail (to remain remotely efficient). "Without destroying it", well that's the joke. Radiating MW/g is a technology so far beyond magic to go well into heavy duty miracles. You are sending a recondensed plasma to the stars. https://what-if.xkcd.com/13/ I might be vastly underestimating the difficulty in keeping the beam tight. Although I remember the Apollo program leaving a small reflector on the Moon that was hit by Earth lasers. Note that the Moon has a rather low albedo and you don't need a very tight beam for such an experiment, but it certainly needs a diameter closer to the m range than the 10-100km range shown in the what-if.

Earth or space mounted? They need (ignoring relativistic mass increase) 7.2*1012 J of kinetic energy going into that thing. If they only have a month to bombard the sprites (before it slips out of range at .2c), they will need 3MW of power delivered by laser. That doesn't mean "3MW lasers" firing continously for a month, that means "3MW of laser converted into kinetic energy", which means gods only know what type of power delivered from the lasers. Not that this isn't outside the realm of possibility (although I suspect that anything going .2c will be gone before a month's time). The completely impossible bit is keeping the radio transmitter (and any implied sensors) alive after superheating the thing into a plasma. It also leads into question how an organisation floating such a proposal will obtain multiple (hundreds of?) megawatt lasers spaced around the globe for continuous firing.

Presumably if they had enough warning from investors they could drastically raise prices and still have a "mostly full" manifest. I'd assume that they aren't charging "enough" money in order to get the volumes they want (while building a rocket has to be at least a $30M proposition, *designing* a rocket is in the billions. Additional volume isn't terribly expensive). Presumably this follows from Musk's strategic perspective. I'm still shocked that they keep prices so low if they are still losing money. I'd expect ULA to be all over them (or not. They probably don't want to admit just how much they are charging the federal government).

Reality check: escape velocity of the solar system: 42km/s (from Earth Orbit) .2c: 60,000 km/s These "Sun Sprites" can take as long as they want to get to 42km/s, but then only have to suddenly accelerate to relativistic speed before leaving the solar system. Solar power simply is *not* a way to gain relativistic speed (and triple-digit km/s seems really unlikely). The rocket equation retains its tyranny, and requires extreme effort to get to relativistic speed. Not to say that a solar sail is necessarily bad for speeds up to (and slightly beyond, presumably with a push from Jupiter) solar escape velocity. They just can't go much beyond it. The simple requirement is their efficiency falls terribly past Mars, and once they get some speed they start going well past Mars (and only get a tiny bits of acceleration thanks to Kepler's laws governing rate of time in orbital positions, and can't get another orbit after they hit 42km/s).

To someone with no fusion background, what NIF (national ignition facility, a laser confinement program) looks a lot like a small scale thermonuclear bomb. I'll admit confining the thing with a laser vs. heating with a nuclear explosion is significantly different. But it certainly is a series of thermonuclear explosions. The railgun sounds feasible, but you realize that the explosion is going to be going right back at the railgun? With laser confinement you might get away with mirrors downstream of the blast.

Do *you* want to jump off a cliff and hope your jetpack starts? Most jetpacks are low speed barely >1g. The "ram" bit is going to require pretty close to supersonic (pulse jets might work better, but still require a lot of speed and probably painful jerks). I don't think the "build a jet engine out of a car turbo's turbine" on youtube get remotely close to a TWR>1, not even including pilot.

Does KSP (or RSS/RO) model the differences in temperature in the atmosphere? I understand that on Earth 50km is roughly "peak temperature" (near sea level temps, but obviously less heat due to less pressure) and 10km-20km is minimum. You might want to avoid the lower end of that, but since heating comes from compressing the atmosphere aerobraking works best with the least amount of heat to compress.

I use windows [8] for gaming and Linux (Mint debian edition) for everything else (which means my KSP saves aren't available when I comment, and if I haven't updated Steam/KSP for awhile it isn't even feasible to fire KSP to test before commenting). My main gripes with win 8 are that it keeps popping up its demand that I "upgrade" (I don't want my OS to be spyware) and the usual inability of windows to shut down (I *hate* hearing a machine I commanded to shut down whirring away 10 minutes later. Linux tends to believe humans know what they are doing). I don't interact with windows internals enough to have issues with every little control panel absolutely having to use up my (28" desktop) display. Note that it *needed* the 8.0 -> 8.1 upgrade, and I suspect much of the grief it gets is from the idiotic interface (everything must act like a tablet. But I think 10 came out before Surface took off). 8.0 managed to crash a lot when a game went full screen (which is crazy considering that win8's big thing was "full screen apps").

You really don't want to look to deeply inside your computer. Assuming you are using a standard Intel compatible system, it is carefully designed to be backward compatible to the 1977 8086 microprocessor and to be assembly-language compatible with the Apollo-era 8080 (and yes, the amount of Rube Goldberg compatibility plumbing this requires is unthinkable). This is the nature of engineering. If it works, just carefully adjust and evolve, don't break it. Once a design matures it is hard to find the original simplicity underneath all the evolution. Just try fixing your modern car sometime (you might want to find a classic beetle afterwards). Forget Splinter: Either Musk or Bezos (or anyone else building a SLS competitor) should name equipment after Pre-Raphaelites.

I can't take jetpacks seriously (and there is hardly room for significant fuel. It could very well use homemade HTP). Copenhagen Suborbitals used homemade HTP (small amounts, because this appears to be a test that wasn't followed up on. Current engines BPM2 and BPM5 appear to use LOX and alcohol.) Small monoprop engine used homemade HTP. Larger monoprop engine doesn't appear to list a source, and used a few gallons in test and presumably a bit more in the launch attempt. Judging by the fact that no attempt was made to further distill the HTP for the final launch (between source and launch attempt it had decayed from 90% to 85%) I suspect that the HTP was sourced at 90%. The comment "Note that 90% Peroxide will auto-decompose at 140 degrees Fahrenheit; this procedure is not recommended to those not fully familiar with Peroxide" implies that the author may work with HTP and sourced it from/alongside his commercial or academic employer. This certainly shows that at least some people have used homemade HTP and lived (note survivor bias). Presumably this would be more than enough to run a test HTP+napalm hybrid static fire. How do you source the catalyst? My first instinct would be a catalytic converter, preferably from a junk yard (and obviously those things are removed before crushing), but I have to wonder if you can separate the right catalyst from unneeded ones. If you know the industrial name, you can probably obtain a "real" (chemical production) used catalyst for pennies on the dollar on ebay if you have sufficient patience (of course, you still have to outbid the raw material cost going to a recycler).

I'd expect you can send a message *to* a black hole. The big question is if any of the entropy is returned when/if the black hole decays. Looks like the nearest black hole is 1,600 light years. So a 3000 light year range should be enough. But as I noted, you aren't going to be transmitting much to your black hole (probably the classic prime number sequence). The text refers to a 1Hz signal. So if your target understood all your modulation techniques (maximum transmission is indistinguishable from pure noise unless you know the exact decoding sequence) you might get a 1bs signal. That's 1 bit per second, about 1/56,000 less than dialup. Don't expect to be downloading any starship plans. http://curious.astro.cornell.edu/about-us/88-the-universe/black-holes-and-quasars/observation-of-black-holes/452-where-is-the-nearest-black-hole-intermediate

Polar orbit? It can't be much of an advantage over Vandenburg. You would essentially be adding right angle vectors and getting the hypotenuse. For equitorial orbits it isn't much, but it should add up. For GTO orbits (which typically want eventually to be exactly equatorial and not "as equatorial as you can launch") this may be justified. Polar orbits you might as well launch anywhere.

One of the weird things about fusion rockets is that being power negative isn't a terrible thing. The real issue is the exhaust temperature (all "fire breathing" rockets rely on exhaust temperature for Isp, although fission rockets "cheat" by heating H2). If you confine your exhaust product in a magnetic bottle and then allow them to expand against a magnetic (instead of a physical nozzle) you suddenly can use exhaust temperatures higher than the melting point of any known material. This lets you get away with some rather high ISPs. The exhaust is also a mix of various monotomic hydrogen isotopes and helium, which should compare well to fission using H2 exhaust. But it should be a lot easier just to build an Orion. And all the fusion issues are solved (if not how to build the rest of the spacecraft).

Note: I've been lead to believe that there are limits to just how much power you can focus to such an extreme degree (I've never seen such claims derived from equations I'm familiar with, but I've never been familiar with much past Maxwell's equations). I *know* there are mathematical limitations on how much bandwidth you can transmit depending on how much power you can deliver (if only to overcome cosmic background noise). Assuming the black hole was sufficiently noisy across the entire spectrum (or sufficiently far away), and the goal was to send the information across the Schwarzschild radius it might take a lot longer than you would expect to transmit each bit. Doing this across the universe is of course even worse. We've seen *a star* at something like 13 light years. Now imagine how much energy a bright star has, and that gives you just one bit. Obviously we aren't sending messages to 10 digit light years, regardless of whether they are being bombarded with noise or not. - see Shannon's laws of channel capacity for the mathematical limits on sending data - can't comment on the physics side - you might manage to block out the noise from other directions (although of course all bets are off inside a black hole), but there will still be all the background radiation in the direction between transmitter and receiver. That is absolute. Expect some really weird issues from "lock on" issues and being able to focus both spatially and temporally. A lot of signal analysis hits almost the same issues of Heisenberg's uncertainty principle. The whole point of this is that "merely very difficult" might require physical and mathematical limits to require some vast amount of energy and power (you don't necessarily need the power, just expect to need more energy over time than if you used a lot of power) to simply send one bit. Hitting the limits of anything gets complicated, and sending messages to black holes sounds like it could easily hit some limits.