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About wumpus

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    Spacecraft Engineer
  1. Alternative - and fun trajectories!

    Powered swingby burn (H2/O2). That looks like hydrolox and not peroxide to me. I don't think storing hydrogen for 8 months was possible in 1960s/early 70s tech. Maybe with "space race funding" still in place they could have managed it, but the one project that requires similar tech (James Webb telescope) seems infinitely delayed. I wonder how big the 6-9 month habitat is. Skylab was the size of the TLI fuel tank (I think it *was* a retrofitted tank and definitely fit in its place on a Saturn V) which would be my go-to habitat (presumably most of the engineering was already done for Skylab). That doesn't leave much room on the other 2.
  2. Note that on planets with an atmosphere, you wind up optimizing for a lot of variables. An ideal path should only burn along prograde, any used to turn the rocket are considered "cosine losses" (your loss is proportional to the cosine of the angle between your thrust vector and prograde). I'd call what you are asking for "hypotenuse losses". An ideal burn would calculate the vertical delta-v and horizontal delta-v, add them up in right angles and then burn along the hypotenuse. Of course in worlds with an atmosphere, you want to minimize aero losses so you start by heading straight up. Presumably NASA computers work out the amount of aero loss and "hypotenuse" loss and work out a trajectory that minimizes both (actually I'm sure they do a single burn to minimize the thrust needed from the second stage).
  3. Questions

    Gravity falls off faster on Kerbin (73% at 100km) than Earth (89% at 400km), but I suspect that Kerbal spacecrafts' lousy mass ratios (compared to real life) makes that a pretty moot point (assuming that nearly all the gravity losses occur in the first stage).
  4. Is the argument against 0.1c in an [H-bomb based] Orion that you would need 100,000+ tons of dueterium (assembled into H-bombs, natch)? Because that's one means of harnessing fusion that is ready to go (assuming are either willing to build and take off from Antarctica or build something carrier-sized in space). If the rocket equation starts to creep up on you, that will be a problem with Orions, as I expect the fuel gets pretty expensive. It will certainly do the "Mars in 39 days" without issue. Just don't try to fight the rocket equation.
  5. Docking

    I would have to point out that I found the rendezvous part more difficult that pure docking (at least once you get the hang of RCS). In career mode kerbal rescue missions give great practice in rendezvous (you can't really dock, but getting as close as possible helps to find the rescue ship once you've taken control of the "lost" kerbal. - check for an empty seat before takeoff. Jeb loves to grab the seat whether or not he was placed there. If you even touch the capsule after taking him out he might sneak back in (especially after loading a save). There is at least one mod out there to prevent this.
  6. lunar lander inspired cabin

    And astronauts had to be under 6' (~180cm?) to even apply for the astronaut program.
  7. "Several passes" works on Duna/Eve, but going much further afield pretty much means you need as much delta-v going beyond Kerbin's SOI as you need to get to the edge. Still, breaking it into 2 cuts the thrust needed in half (or your lack of Obereth gains in half). I'd also look into Juno slingshots (to anywhere past Duna/Eve). Of course, typically what you really need is an alignment change, so in that case it might be better to kick off Duna, Eve, or any you can reach while it intersects with the plane you need.
  8. KSP EDU version--teaching teens--advice

    Getting rid of the math will be a bit of a problem, but if they don't have the background to understand ln(massfull/massdry) you won't have the time to build up to that. Obviously you need to explain orbits, although centripital forces should be easy for anyone (all they need to understand that gravity goes on forever, and is still strong out by the ISS). Obviously conic sections are relatively easy if you have a cone available for slicing (don't most schools have pre-sliced cones?), although the why pretty much requires multi-variable calculus. Since KSP works on Kepler's system (not really Newton's), that makes it easier to go with Kepler's non-calculus orbital mechanics (he has a nifty speed/area law which should be understandable with little math). Getting the rocket equation without math will be a bit of a problem, but it should be clear that to get "more dakka" (delta-v) you need to add more fuel, and more fuel to push the fuel you added, and so on. Who knows, maybe after having the tyranny of the rocket equation shoved into them by KSP, they will get logarithms. I'm not sure KSP EDU sells well enough for people to know specific mission issues. Since this showed up on a non-EDU forum, you might get at least answers from "regular" KSP (like this one).
  9. NASA SLS/Orion/Payloads - RIP DSG

    POTUS: only motivation of POTUS would be to attack the Senate. Might be possible, especially if Roy loses. VP: VP's power is traditionally limited to making speeches unless deliberately handed power by POTUS (i.e. any VP action is a POTUS action). Should Pence have executive powers (for whatever reason), killing SLS could be useful to be seen as "getting something done" (sure, the current POTUS could do that, but it sounds more like a "first 100 days" thing. So maybe POTUS 2020 as well). Bridenstine: SLS is something like 1/3 of NASA's budget and it isn't remotely clear that they can simply move the money (it is essentially is earmarked for SLS). While some Presidential nominations are specifically hired to kill the agency they were hired to "lead", I don't think (and certainly hope not) that Bridenstine was one. You simply don't gut that much of your agencies' funding. Obviously the Senate can kill the Senate Launch System (presumably so could the House, but I can't remember the two houses fighting each other and that might "not be done"). Sorry about the politics (I try to keep any mention of politics neutral as far as "what should be done" and more to stick to "who can do x" and "who certainly won't do y". Since launching rockets into space is primarily done by large governments, completely avoiding politics is impossible for all but Blue Origin launches (Even Bezos builds in Alabama for political reasons)).
  10. Elliptical Orbital Mechanics

    That's not too bad. I can't really translate UK educational levels, but I remember writing down the derivation for *circular* orbits during a second year university physics exam (had to be done in less than 5-10 minutes just for that question). This can be done with polar coordinates and doesn't require calculus (and thus doesn't explain ellipses nor the area law, but handles the degenerate case of ellipse==circle well). [this may have been deriving gravitation from circular motion, it has been a long time]. Unfortunately polar coordinates are unlikely to remain your friends with ellipses, although it appears that again solving for the degenerate case of ellipse==line works well here, and then showing that orbiting in two orthogonal "lines" forms an ellipse is the method used above (maybe not explicitly, but certainly that is what x and y are doing). The spherical coordinates might be a bit of an issue. Working from Keplar we can show that everything stays on a plane, and I can see how you can show that Kepler's orbits are stable, but I'd hate to show that every [large/small] body will follow conic sections (and remain on a single plane).
  11. What's the most science you've ever gotten from one mission?

    4865 for grinding Minmus (not sure that is a record [I've done similar in other career modes], but I did it Monday and took a screenshot so I have the exact value). Of course, I also stored the data in triplicate so Minmus science bases can process the data well past the tech tree... I'm pretty annoyed with the science grind ("for science" only helped so much in storing multiple data).
  12. Uranium powered RTGs?

    A thermocouple is a pair (or more) of twisted wires of two different metals. Of all the bits of a 100year+ spacecraft, that would have to be the easiest to design (of course, I'd look into peltier devices for better efficiency, but don't expect them to last all that long). The computer electronics I don't have much hope surviving more than a century. I'd assume that any such device (Uranium powered thermal generator) would involve some type of criticality. The obvious choice is for a capture burn decades or centuries after the initial burn, and to send messages back to Earth when you got there. Thus it wouldn't be a RTG but some sort of ultra-simplified reactor (the original "Chicago Pile" had no cooling and produced nearly no heating/power). The reason for going with the reactor is to not require an isotope that lasts the entire journey. A better solution would be to use Americanium241 this is a possible replacement to Pu238 for those (EU and others who simply can't get the stuff, also Pu tends to alarm the general public). It only puts out 1/4 the power per gram, but a 432 year half life makes it almost certain to outlast any other component on the spacecraft (I think we will lose contact with Voyager due to running out of propellant to keep the antenna aligned, it should be a bit over 3/4 power in the RTG).
  13. So instead of being "20 years from now" fusion will be require a steadily increasing size until it exceeds Earth?
  14. SpaceX Discussion Thread

    Presumably a low power beacon is all that is needed (I'd have more than three around the pad for better accuracy) as it will first head back to just offshore in case of failure and they can make contact for the final correction (I'm guessing there is too much plasma during the burn to offshore).
  15. Is there a heat issue? The only thing I can think of is something using up too much CPU time (mining virus, try running "top" in a terminal) or a clogged fan. A clogged fan is a more likely bet as it wouldn't show up until the CPU is working hard enough to get hot, then the CPU throttles itself down to less powerful than your old CPU. You could try blasting the fan ports with compressed air to clear out the dust. And of course, try checking your other processes while running KSP to make sure nothing is using significant amounts of CPU time. An i7 should be able to handle things (I don't think it is a GPU issue, but that is possible. But even an intel i7 GPU shouldn't be that bad).