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wumpus

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Everything posted by wumpus

  1. wumpus
    This is Star Wars we are talking about. Expect it to mean "over 12 parsecs".
  2. wumpus
    Except that passenger jets have access to arbitrary amounts of -35C (more typically -50C, but you can only count on -35C) air. Don't forget that "warm" levels is cheaply available (by using liquid nitrogen as a coolant), and superconducting equipment shouldn't be generating heat that uses up that coolant. I suspect that regulations on how far a plane needs to coast after losing "x amount" of engines will take some engineering (if this means that the plane will fly lower with less motors) as well as issues as to just what happens when the coolant fails and the electricity is shoved into the copper "insulation". But don't assume that planes need anywhere near "room temperature" (and remember that cars are expected to drive from Phoenix to Palm Springs in the summer, so moving from the industry that is likely driving development to planes should be pretty easy).
  3. wumpus
    I'd expect that "revolution" to be a flow-battery. These can be thought of as "reversible" fuel cells. Unfortunately, I don't think that there are terribly useful in cell phones (so the primary driver of battery technology isn't driving them) but would be extremely useful for cars. While their primary interest is low-cost capacity (the idea is to increase the chemical parts storing the energy and decreasing the parts/catalysts that do the chemical process), it should be extremely likely that you could have multiple/larger "battery heads" recharging the chemicals much faster than the plane's equipment possibly can. This type of thing would essentially make electric cars replace gas engines in most situations (although I wouldn't count on recharging stations that directly charged the chemicals like suggested above). No idea on much more research it takes to get there (there doesn't appear to be a workable set of chemicals), but it is a potential game changer. - Note: as electric car companies work closer to battery manufacturers (like the gigafactory), there is much less willingness to try this type of thing. Don't count on it happening.
  4. wumpus
    Guilty. Can't remember doing it remotely recently, you need a Pe that is very close to the edge of the atmosphere. Also I don't think I've ever pushed to get into orbit (although I've tried the jump free and use that 400m/s to get into orbit and wait for a rescue, but never successfully [other restrictions meant I didn't have enough delta-v for that]).
  5. wumpus
    Controlling such a hot launch is a bit different from a more mild liquid-based launch with a TWR around 1.2. Snark isn't kidding about "immediately" and for small craft once launch clamps are available you should consider launching them at an angle (although not 15-20 degrees as the starting offset changes things a lot, try 5-10 or even 0-5). Once the craft hits the transonic region you tend to lose all control of the rocket (although this is great in stabilizing other wise unstable rockets). * reality check: I've seen at least on high-powered model rocket manufacturer claim that a TWR>5 was needed to stabilizing model rockets using their engines (obviously for rockets with absolutely no guidance or steering controls). Apparently this "lock in" is a real thing (planes designed for subsonic operation become uncontrollable in transonic speeds: this was a problem for US WWII plane designers, especially Kelly Johnson and the Lightning).
  6. wumpus
    Efficiency is mediocre. Isp does not include "dry mass". "The maximum temperature concentrated sunlight can heat a material to is 5800K. How do we approach this limit?" I suspect that to achieve this, the ratio of the size of the lens to the size of the target is similar to the ratio of the sky covered by the Sun. I also suspect that hitting those levels of temperature won't make sense. You want to take advantage of large amounts of stretched thin films which are unlikely to maintain accurate curves. The final product is unlikely to focus well, but should be able to use easily available reaction mass (comets would be a good start). I'm also suspicious of that Earth-Mars escape-capture plan. I'd have to assume the bulk of the journey is matching Mars velocity (unlike standard Hohmann transfers). Judging by the length of the "burn" to escape Earth, I'd expect the thing to sail clean past Mars and not spiral in as shown.
  7. wumpus
    A lot depends on if you are using solid boosters for your first stage. I've noticed that having TWR>2 (at launch, it will climb and you can't reduce it with SRBs) seems to be a bit excessive, but with SRBs you can get plenty more TWR than liquids. I might keep adding SRBs until I hit TWR>2, then pull some off until it is back under. I followed the "cheap and cheerful" challenges (an attempt to get high KEO cargo/fund without recovery), I was under the impression that they were pretty much stuck to ~1.2TWR, but one of Slashy's better attempts appears to be at 1.68 for KSP version 1.0.5. I'd link to the latter (1.1.3) challenge, but the files don't appear to be maintained and I can't tell what the launch TWR were. One thing that I am fairly convinced is that you should [almost] never reduce your thrust during initial launch (burn hard to main engine cutoff). If you have "too much thrust", then you should look into using lighter engines/less SRBs. My favorite rule of thumb for efficient rocket design (which comes up elsewhere, but not often enough in Kerbal circles) is to at least start with equal amounts of delta-v per stage (this might get altered a bit as kickers provide extra cheap delta-v for a first stage and vacuum engines provide efficient delta-v thanks to tremendous Isp, but it is a great place to start.
  8. wumpus
    I'd expect something more like a tardigrade would be your typical "interstellar life form". Note that tardigrades wouldn't be considered "living" between stars, just dried out and dormant [you might need a "super tardigrade" for such journeys], this means absolutely no form of navigation. Somehow I'd expect the universe to end before these tardigrades actually hit anything. My understanding of the origin of life on Earth shows no "band" of time between the possibility of life living on Earth and the oldest fossils (presumably with only indirect evidence, since they would be dealing with single celled organisms). First this shows that Earth wasn't seeded by anything as advanced as a tardigrade (it would have started with complex multicellular life if it had). It may well have been seeded by RNA-like matter, but if so we should expect at least fossil remains on other planets/moons in the Solar system.
  9. wumpus
    You can't have a 6 month thread and not include pictures! Is that even possible with your setup? I'd assume that for "real" astronomy, you need pictures with fairly significant shutter lengths. Ouch. I'd assume that adapting the viewfinder isn't that hard, but tracking costs big bucks. You might go far with a highly optimistic HDR sensor (you will need plenty of bits "in the noise") that simply sits in place and later moves and combines the images. This technique works well many places, but if there is no "negative sensor levels" to average out to zero in pictures, it might not work well here. Certainly any such things are for a much later project.
  10. wumpus
    US political whims tend to have certain timeframes: a president can typically expect to provide a plan for four years and will typically plan for 8 (Kennedy's "within the decade" managed to break this, largely by being nearly done when Nixon took over. Spending was already down and missions were being canceled before Apollo 11 landed). One of the reasons the Moon looks like a more attractive target is that it sounds easier to get a [crewed] mission there than Mars in four years. Florida (and I expect Texas soon enough) is a contested state, so expect either party to lavish it with pork. Alabama might depend on the current situation for high levels of pork, but I suspect that Houston and the Cape will remain funded (of course right now they are funding SLS). US political whims are typically reliable enough for specific missions, just not crewed missions beyond Earth (although the Moon is becoming more a possibility). I have no idea about Chinese politics, and the EU doesn't appear interested in such things. A lot of people make careers out of making such things work out (and since it is so common around Washington DC, NASA Goddard [and contractors] have an easier time hiring such people [they won't require relocation]).
  11. wumpus
    I had always assumed that a crater at the southern pole of the Moon would be ideal for a base, it is literally a place "where the Sun don't shine". I had assumed that this would block most of the radiation (it would, of course, block the deadly burst radiation from a solar flare: probably the most difficult shielding for human exploration), but I've heard elsewhere on this forum that galactic radiation is equally a problem and would likely require something like this cave.
  12. wumpus
    I'm fairly sure that fuel use on a V1 was extremely poor (although as an airbreather, it almost certainly had to be better than a V2). It was probably worse than a true jet, which are pretty much only used for supersonic military jets now (everything else are [high bypass, if recent] turbofans). Back in the 1990s, there were various attempts to build air-breathers that detonated the fuel, rather than combusted it (Ve should be higher that way). This of course led to severe noise issues for any potential crew/passengers, but it never seemed to work well for even uncrewed launches. I don't think I've heard of detonation-based takeoff for at least a decade. As far as I know, a scaled down Orion worked with conventional explosives, but the real thing would deal with much more extreme stresses.
  13. wumpus
    A BFR should manage twice the payload to GTI as the listed SFR can to LEO. It would take a lot of launches to amortize a SFR. Musk also claimed the BFR (or maybe an earlier ITS) achieved that via "1000 launches". There's no reason to believe spacex is anywhere near 99.9% launch probability (hopefully they can get that for the crew via a launch escape system, but the "amortized over lifespan" requires saving the booster as well), let alone 99.9% landing safety. I'd really want to check *all* the numbers on BFR cost. Hondajet is apparently shipping. It may still be losing money, but I doubt Honda is ready to pull the plug. While I'm not sure what part 23 and 25 mean, I'd expect having Honda compete will shake things up.
  14. wumpus
    Any idea if simply loading up the BFR with roughly twice the payload (to LEO) and sending it out as if it were going to GTI? Do any inclination changes out there (at least for groups of customers with weird inclinations) and then aerobrake down to LEO (and finally bring perigee back up to sanity)? Designing a rocket is *expensive*. We saw this with Falcon Heavy (and it still hasn't launched), and scaling down a rocket will be far worse. Of course, if my design had to replace ITS *and* falcon 9, I'd probably at least work in a way to replace half the engines (and fuel tanks and resulting plumbing) with lightweight dummy loads to avoid a full design. Replacing falcon 9 with this giant appears odd. Finally, look at the cost to launch a "proven" rocket. At least half the cost is either simply the cost to put a rocket on the pad and light the candle (at least $50M) [this might be due to an attempt to stop burning investment money, but that just means they need to keep doing it to remain profitable]. They might just decide to forget the whole "small rocket" and simply launch the biggest they have (when was the last time they fired off a Falcon 1?).
  15. wumpus
    I suspect that "vertical drag" is more the issue than lift: getting any sort of glide ratio would be tremendous help. The shuttle had a glide ratio of 4:1 and was considered a falling brick. KSP vertical landing works well after gliding in at 1:1, I wonder if that is close to realistic. I wonder how hard it would be to make an elliptical rocket (probably manufacturing costs would be painful, especially if *anything* gets done on a lathe). One question I have about spacex plans is about landing this (or similar) on Mars (or the Moon if NASA is paying). Elon talks about "vertical launch and land" but NASA tends to avoid such things. The LEM (or correctly "LM") used two separate rocket engines, allowing the landing rockets to be damaged during landing. There was a pitch for a rocket-propelled lunar vehicle (the rover made infinitely more sense), that required a "launch blanket" placed underneath it to avoid damage from moondust. Curiosity was dropped by a "skyhook"that kept the rockets from covering Curiosity with dust. All these show that NASA really doesn't like landing on uncontrolled surfaces (completely different from the platforms that Spacex lands on now) and hasn't changed their opinion with plenty of experience. I've heard there are explanations for why they think they can launch with landing rockets on Mars, but I wonder if any actual landing engineers are convinced.
  16. wumpus
    The only reason the heat shield was ever in danger was that it was exposed during launch. This doesn't happen with capsules. Also the Columbia's heat shield was so large it was built with delicate tiles: something that was never necessary with capsules. The spaceplane design directly doomed Columbia by exposing the heatshield and doomed Challenger's crew by having the crew cabin an integral part of the oversized cargo bay: every other [capsule based] rocket has had a launch abort system, but the Shuttle was too massive for one (the Shuttle had plenty of abort modes, nearly all with zero chance for survival). How could falling debris during launch possibly damage a capsule's heat shield?
  17. wumpus
    The Columbia was destroyed thanks to failed/damaged/knocked off heat protection, and thanks to the spaceplane configuration that protection was vulnerable. I don't see how you can claim it wasn't due to heat.
  18. wumpus
    I wonder just how long it would take to justify building an aluminum plant (or other chemical process where the standard procedure uses a lot of electricity). From a chemical production view, cracking water for hydrogen (and oxygen) is pretty silly and there are certainly plenty of other chemical processes that require electricity. Aluminum is pretty obvious, the stuff is called "frozen electricity" for a reason. Basically look at what chemicals are being produced near Niagara Falls and see what has low startup costs. Also how much of Texas? There are three grids in the US: East, West, and Texas. I'm guessing it is too far to run a DC line (avoiding grid issues) to Louisiana and the chemical plants there. No idea what this has to do with Spacex (Tesla bought Solar City, not Spacex).
  19. wumpus
    Eating high g-forces in the lower temperature parts of the atmosphere will be safer. A lifting spaceplane will be slow and have far higher heating thanks to the bits of the atmosphere you slow down in. So far, Columbia is the only spacecraft lost in re-entry (Soyuez 1 had a failed parachute) and isn't the method I would recommend for kids. Typically you will get g-forces less bad than a roller coaster (bad Soyuez landings excepted). Beats the dangers of spaceplane heating.
  20. wumpus
    So if you colonize Haumea, does it bring wealth (and arbitrarily prolonged life*)? * I'm not sure the 7 had that effect on the dwarves, but they apparently brought wealth with little side effects. Sauron wasn't happy with the results.
  21. wumpus
    Oddly enough, digital signal processing (basically anything computing a fourier* or related transform) will see effects rather similar to Hiesenburg's uncertainty principle. I *think* that they are related primarily due to underlying math behind waves in general, but really don't have the math to tell. Basically it all comes out under "windowing theory". * image, audio, and video compression often use discrete cosine transforms, a related transform. I also took an undergraduate class on DSP in the early 90s which could now be almost completely replaced with the phrase "just take a 1k FFT...".
  22. wumpus
    If it is in the same spot every time, you can assume that variable factors won't effect it. This pretty much leaves out weather patterns. Fluid dynamics, hill geometry are certainly factors. I suppose that if there is a sufficiently prevailing wind, that might matter (after taking into account any local aerodynamics).
  23. wumpus
    While I watched the video, I can't remember the reasoning. I'm guessing that you won't get much deflection angle (and thus little slingshot effect) once you have enough delta-v (less slingshot effect) to get to Duna/Eve (and it only gets worse by going further). This gets compounded as without the deflection angle you are much more limited to when you can leave, which means you lose more from changing your launch window than you gain from the slingshot. While I find it a lot easier to use the Mun to slow down from Minmus, I suspect that the math doesn't work out for Aerocapture from outside of Kerlbalsoi. But it still might be worth trying (assuming you have the delta-v to correct from the Mun).
  24. wumpus
    R7, Redstone, and Atlas were all built with suborbital nuclear warheads in mind. Mercury and Vostok were presumably built with their respective capsules in mind (based on rockets designed as ICBMs). While it would be a wild exaggeration to claim that the Shuttle was "built with keyhole in mind", the Shuttles dimensions, cargo capacity and return capacity were dictated by the spy satellite. Google (and lost bookmarks) have let me down, but from memory one of the "rules of rocketry" is "any mission involving a new launch method becomes a launch project". Rockets built for specific missions are budget breakers and can only be expected for "milestone" missions.
  25. wumpus
    There's also all the Orbital rockets. Considering that Orbital's business has been to refurbish surplus ICBMs into orbital launch vehicles, there is plenty of kerbal "put rockets together like LEGOs" designs. I suppose the Antares rocket might be less Kerbal in that it places a solid stage above a liquid first stage (the liquid first stage isn't surplus ICBM, but was originally surplus N1).
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