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Everything posted by wumpus

  1. You might want extra nozzles on an expansion-cycle hydrolox engine, but even then I'd expect additional combustion chambers would be better. Expansion-cycle hydrolox engines are more or less limited to combustion chamber+nozzle sizes similar to RL-10 or higher, but you could get greater performance from more combustion chambers and nozzles. For some reason I remember hearing the nozzle was the limiting factor, but I suspect that the chamber might be as well. No idea if they attempt to cool the chamber. No idea if a mini-mag has scaling issues. And as mentioned, the reasons for multiple combustion chambers are combustion-specific issues. And if you went multiple nozzles for a hydrolox expander-cycle it would be for thrust *inefficiency* (you want to scavenge the heat from the thrust to power your turbopumps).
  2. Currently that's the CPU "drivers". Microsoft only includes the thread optimizations to balance Intel CPU "P-cores" and "E-cores" on Windows 11. They must have been bored with GPU drivers and start playing with CPU issues to force new editions of Windows.
  3. No idea. Falcon Heavy was the only rocket I ever heard of that was planned to use asparagus staging, although only NASA and Spacex typically publish their iterative design process so there may be plenty others. Ask them why it didn't work.
  4. "Asparagus would be a great tech for spacecraft" is one of the many lies KSP teaches you. To speed up the gameplay, Kerbin is tiny. But to keep the difficulty with an orbital velocity 1/3rd Earth's, kerbal fuel tanks are miserably heavy when empty. For example: the "Rockomax X200-32 Fuel Tank" (which I *think* is the classic "orange tank" or yore, I haven't play in some time) has a dry weight 11% of its wet weight. A remotely modern space fuel tank is much closer to a can of coke (.1%?). In other words, the fuel tanks aren't quite as critical as they seem. On the other hand, they need enough fuel for 3 times the delta-v, and need to reduce dry weight as much as possible (no, SSTO still isn't useful). Also don't forget that during the heyday of asparagus design in KSP, they aerodynamic model was much more primitive: so "pancake" rockets were the rule and aero drag ignored. I'd be curious to see the difference you'd have with an asparagus (the original idea) Falcon Heavy vs. what flies. The biggest problem is that I doubt asparagus would buy you anything unless you expended the center booster (like they did last flight). Giving more delta-v to the center stage means it is going to hit the atmosphere with even more delta-v coming down, and make recovery that much harder. In any event, it showed just how difficult changing fuel tanks mid-flight would be even on an engine famous for its ability to start and restart on command. At its heart, asparagus simply allows you to fire all engines simultaneously, thus ignoring the mass of engines yet to be staged. And this was yet another issue old-KSP left out, you could use vacuum optimized nozzles without worry. In practice, and even moreso for a rocket designed for re-use, I'd suggest simply adding additional stages. Have the lowest stage return to launch site (preferably with air-augmentation). Have the next stage get to at least 1/2 orbital velocity (a lot depends on the amount of thrust needed after stage 1 is staged, and also on surviving atmospheric re-entry). Using side booster with significant thrust (not the little guys that ring some main boosters) is apparently a significantly hard problem.
  5. I worked for a US defense contractor in the 1990s specializing in Navy contracts. They had at least one project doing this, at least close to US shores (and it was a small company, I'd suspect the Navy had lots of such projects). Also told that active "pinging" SONAR was pretty important onboard destroyers (small surface ships) to find submarines. In general, the more microphones you can string along (especially if you have a microphone or two per wavelength) the better a map you can get. I'm sure someone has tried modulating messages into synthetic whalesong. That stuff travels nearly around the world.
  6. It can't compete with methane. And old coal fired plants (the last economically viable ones anyway) were for "base power" (i.e. can't start/stop quickly at all but gets good efficiency). So not only is the cost of coal power higher per Watt than methane, it has to produce it over longer spans. And those spans can easily include bursts of cheap green power that even methane can't compete with. Arstechnica mentioned that there was a relatively new "base power" methane station shut down. Of course it was in Southern California: between near constant solar bombardment and ideal wind locations (I remember seeing a wind farm near Palm Springs in the 1980s, it was much larger in the 1990s) sometimes methane must get completely squeezed out. I doubt this is true most places, at least so far.
  7. I'd assume that if the Gemini crews could tolerate each other, future spacecraft will have enough separation to prevent such things. Those capsules were *tiny*. Apollo capsules may look big in movies, but they are tiny in person at a museum. There was a famous science fiction story* with a backstory involving a double-murder-suicide. The author had been a career (US) naval officer. And part of the backstory was careful psychological compatibility of the crew. So at least one guy with similar experience assume such things were possible. And while I've never heard of a "intra-crew fight" in space, there has been a rebellion against ground control: https://www.latimes.com/business/hiltzik/la-fi-mh-that-day-three-nasa-astronauts-20151228-column.html * Stranger in a Strange Land, of course.
  8. The Senate has gone out of their way to make this as least reusable as possible. Expend "reusable" RS-25s first and then start on specifically designed non-reusable RS-25s. Also, rocket reuse has so far required many experiments that can only be done with actual boosters. I'm pretty sure Spacex lost more boosters (check the blooper video) than the most optimistic SLS launch schedule has launches. The only other comparison is Rocket Labs, which is 0-2 in recovery (their method is unlikely to work on something the size of SLS). They are already "reusing" bits of existing shuttle hardware, at a cost that exceeds simply designing a new rocket. I'd expect SLS project managers (at Boeing/NASA/Senate) to find a way to "reuse" a SLS in a way that costs more than a new build if at all possible (which more or less happened with the Shuttle. But at least the Shuttle was driving the technology that we need today).
  9. Isn't this a Boeing project? Or do you mean "NASA stop micromanaging the real rocket scientists and stick to things like probes". From Atkin's Laws of Spacecraft design: 38. Capabilities drive requirements, regardless of what the systems engineering textbooks say. 39. Any exploration program which "just happens" to include a new launch vehicle is, de facto, a launch vehicle program. 39. (alternate formulation) The three keys to keeping a new human space program affordable and on schedule: 1) No new launch vehicles. 2) No new launch vehicles. 3) Whatever you do, don't develop any new launch vehicles. Or in other words: howabout stop demanding new launch vehicles for the sake of new launch vehicles. It may help that Sen Shelby finally retired this year (well, technically next January). Edit: the really embarrassing thing about all this is that the whole idea of "keeping shuttle jobs" is that it was too late to save the old shuttle jobs (a lot of new guys got to be trained on cutting edge 1970's technology) and reused parts of an old vehicle at prices that vastly exceeded new (commercial) launch vehicles (and expect NASA/Senate to be the source for most of the excessive costs. Boeing just shut up and saw dollar signs in their heads as the crazy requirements/modifications rolled in). Source: I've dealt with DoD projects and the DoD's cavalier attitude to costs. Nothing specific to NASA, but they tend to hire the same types and answer to the same Congresscritters.
  10. Don't expect the 4% "random stuff" to be contain enough equipment to survive re-entry and landing on Earth. For existing fuels, just use the rocket equation. It will tell you that SSTO ain't gonna happen (at least re-usable SSTO). But now with anti-matter (sufficiently "magic Isp" to allow SSTO). Why worry about heat issues? Assuming you are throwing the anti-matter into something more or less like a "combustion chamber" of a 21st century rocket, you should have exactly the same issues of lifting a similar massed rocket to orbit. The important bit is to use open-loop cooling where the hot stuff is simply thrown out the end of the rocket (which is what you want for rocket efficiency anyway). PS: once you are in vacuum, the theoretical maximum for cooling in space should be ~60MW per radiators the size used on the ISS. I computed this for a space combat thread and was shocked that it was a physical limit (going beyond this isn't just engineering, it would require a bunch of physical laws we know nothing about).
  11. Chemically, there's typically some matrix holding the whole thing together which you can now lose. Mechanically, do you really want to pump molten aluminum through a turbopump? I guess you could use pressure fed engines, but only as a lower stage (I'd assume that they are going to have some significant dry mass in leftover fuel). So the answer is NO when the inevitable "will this work with SSTO" followup comment comes up.
  12. And once again we are back at the rocket equation. But oddly enough, the rocket equation that KSP teaches you won't help. Often the critical variable used is ve (exhaust velocity) instead of Isp (specific impulse) as used in KSP. The key issue of exhaust velocity is you want the lightest metals possible. So Al works (standard SRB fuel), you might even get Na to work as well (nasty rocket fuel). But something like iron or even mercury is right out.
  13. Works until an unknown man wearing glasses hurries the hostages away and uses his super-strength (even though he doesn't match any known super-hero thanks to his glasses) to remove the collar. I thought the D&D manual stated 1d4 damage (through the eye might count as a critical hit, so maybe (1d4)*2). D&D was never very good at simulating damage. I never followed it, but I though most of the X-men stories centered around how "the status quo" treated mutants.
  14. First: if we burn *all* the fossil fuels, the Earth will probably be too hot for humans to survive. Terraforming planets is presumably easier tech than "warp drives", so this might not be an issue. Fertilyzers, plastics, and other chemical production (don't ask how many chemicals require methane feedstocks) will all be willing to pay more for hydrocarbons than its use as an energy source, so presumably fuel usage will be disproportionately small when they are "all used up". Finally, it doesn't take "natural magic" to generate hydrocarbons. Photosynthesis is just means of solar production of hydrocarbons, and certain decay processes produce traditional fuel sources out of these hydrocarbons. With enough power sources (presumably nuclear, but perhaps we'd have enough solar/wind/hydro) it isn't that hard to produce similar hydrocarbons from H2O and CO2.
  15. So all you need to do is find some noise control engineers and convince them to do a custom job. Curious if you could look up some speaker design information and simply design the worst speaker possible. There might be more resources for that.
  16. What is missing from the Shuttle engines from that description? I was pretty sure the were. Something about it being relatively easier than kerolox.
  17. The straightforward answer is likely larger fans moving slower (same amount of air/time). If they don't fit in the case, then you have to move to more complicated answers (like careful notches applied in the fans to reduce noise). Pretty sure I'm not hearing any bearing noise in the fans, but they aren't spinning all that fast. But I'd look for more quiet fans by starting with the largest that fit the case. Not sure about sound dampening, but you should be able to get similar rubber sheets to add to side panels. Granted, the only time I've ever seen them was in postal sorting machinery. We ripped them out (they tended to collapse and interfere with the machinery) and cursed german engineering for making things to complicated and fragile. Mufflers sound like an idea, but all air would have to go in and out of separate mufflers, and they would obstruct the air so you'd need bigger fans. I doubt they'd really work.
  18. Does it matter? Learn the rocket equation first, then you can understand how rocket fuel works. Then find a workable ISRU. And as long as you are committed to "just magic", there's not point caring about which chemicals are used.
  19. Depends on what you call "orbit". In KSP you aren't in "orbit" unless both your Ap and Pe are above the atmosphere. An optimal launch would follow a trajectory similar to an orbital trajectory but never stop burning until it got to the final escape trajectory. It could conceivably do the burn entirely "not in space", but it would take remarkably high thrust to do this under the Kármán line (maybe some of those multistage solid rocket orbital spaceships could pull it off with a small cargo). Even harder to do so under Virgin Galactic's "definition". Apollo did a few orbits in a very low parking orbit, but I'm sure that was significantly higher than the Kármán line.
  20. I think a better question is what happens when the supply chains don't just get a little sand thrown in them like the last few years, but are utterly destroyed? Can you farm without gasoline (I guess any farmer can make e100, just don't count on running the tractor much)? How about fertilizer? And do you have enough seeds (thanks Monsanto)? How good is the local farmland, and can you bust the sod if necessary (and live until harvest)? And while the "defend your foxhole/fallout shelter against all comers" future may have been shown to be bunk, I'd be curious how helpful people were to those outside their villages. Can't say for certain how reliable those 'looters will be shot' pictures the media loves to show. I doubt it will be all that easy to rebuild large economic zones. You'd go from 21st century to medieval pretty quickly, with a good question on what tech could be rebuilt (every chemistry student learns the Haber process, but how many can build a neighborhood fertilizer plant)?
  21. Has anyone run any reasonable "nuclear winter" scenarios through any reasonably modern climate model? I'm not sure how advanced climate modeling was in 1989 (really a few years later) when nuclear winter fears were hard to publish. Lots of work done on climate models since. I guess the easiest way would be to compare the Krakatoa eruption (200M) with that of an all out global thermonuclear war. Of course nearly all of those would be air blasts, and I have no idea how much dirt would be kicked up by a high-energy air blast. Presumably pre-1960s data would have to suffice. Even then, Krakatoa lead to the "year without a summer", but the effects were gone in roughly a year.
  22. Those boosters weren't light. And sending more mass for little reason just means you have to send even more mass. I'd strongly suggest mining asteroids or even recycling existing space junk than adding more to it (although it you *could* recycle space junk then it would make sense to eat the tiny delta-v needed to carry the Shuttle fuel tank into orbit). I'm on the polar opposite camp. Not only did the Falcon 9 show the way to go: put 90% of your engines on the booster, only send it up a short ways (so the re-entry damage will be minimal) and recover it. I'd even recommend using a third stage (like the Falcon heavy, only easier to design) that would return to launch site and preferably be air-augmented. Granted, that assumes recovering a somewhat smaller booster from somewhat over 5,000m/s (lots of re-entry issues, but only 25% of orbital re-entry) makes sense. Adding delta-v to mass for no reason takes exponentially more fuel and more rocket. Don't make any bit of mass go any further than it has to. Once you can recover boosters, a lot of the old assumptions (three stages only make sense for escaping Earth orbit) need to be questioned. Since playing KSP and the falcon landings I've wondered if the DC-3 design (two "spaceplanes", fully reusable) would have made a lot better shuttle. But it couldn't launch Hubble (maybe another telescope half the mass) and it would have to send the ISS up in much smaller pieces (DC-3 could only deliver 1/4 the mass of the final shuttle design). More pieces - more problems. And of course there is that pesky crossrange requirement.
  23. The original STS program was supposed to include the shuttle, a space station, and two tugs (chemical and nuclear). The advantages of a chemical tug escape me. I am not aware of the space station being canceled in time to allow the size of the shuttle to drastically change size. In any event, the Shuttle had to be large enough to fit the latest keyhole satellite (i.e. the envelope of Hubble) in the cargo bay. Also it needed the massive wingspan to meet the crossrange requirement. This appears to be the reason it had to be large enough to act as a "space station" even if it was supposed to go to a much larger one. The real question is how much mass the wings add and how such mass increase scales vs. parachutes. Propulsive landing appears superior for large uncrewed boosters, but it isn't clear how effective it is for human cargo (except as a means to lessen an already survivable shock).
  24. Pretty sure that relativistic mass was a mistake in special relativity that needed to be corrected in general relativity. My understanding is that Newton's second law should really be F=dp/dt (derivative of momentum) and that momentum increases to infinity. Velocity is then scaled by the Lorentz equations to asymptotically approach c. If you assume "relativistic mass" under general relativity you then have issues of high-speed massive objects becoming black holes and then leaving said hole. This confused me for awhile as some physics professors at my college refused to teach F=ma (although my first semester prof did) so at least half the class refused to accept such an equation. When I realized the black hole bit I looked up the rest it became more clear.
  25. The real reason the Shuttle required astronauts was political. NASA wanted to launch 7 astronauts as many times as they could, and using crewed flights to launch satellites was a way to get Congress to fund more and more crewed missions. As far as I know (and this might only be with the latest revision of electronics), the only thing really required for an uncrewed shuttle launch/landing was an extra long cable (and presumably quite a bit of software, I doubt NASA was willing to let anyone write it without an act of Congress). This made every satellite/probe proposal have to think whether or not such a mission was worth risking 7 lives just to get it in space. Don't forget that the computers NASA had on the ground were unlikely to be all that spectacular. The birth of supercomputing can be traced to CDC shipping the CDC6600 in 1964, but early models typically went to intelligence services (who paid a hefty premium for serial #0001 or whatever special model CDC was selling). They may have been able to check the Apollo trajectories on one of these, but recent history implies that they'd prefer hand/sliderule calculations (it didn't help that Seymour Cray didn't like parity memory either). 64 bit floating point calculations were an afterthought in computing before the CDC6600, and tend to be rather important in computing for spaceflight (KSP uses 32 bit floats, and this leads to all sorts of issues most notably the "Kraken" of yore that simply deleted ships going too fast or too far from Kerbin. Havester was so impressed by his work-around to prevent this that he named his next company after the trick).
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