e of pi

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About e of pi

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  1. On the "sifting through the entire thread" front, I recently got done going back through to threadmark all the actual posts, in case anyone is having that issue, but if anyone want to print a copy for their own use, then they can be my guest.
  2. @Workable Goblin and I are okay with it as long as it's not for monetary gain. We're glad people enjoy it after so long, even if some of it is fairly rough-hewn.
  3. That is a magnificently large stack of propellant. If I may toss a performance question back at you, how's it perform compared to M02 and H03 to the same orbit, or to escape?
  4. Answering the SRB thrust for Carrack requires a bit of definitions. Solids can't really be throttled in-flight, but they can be throttled in the grain design, the pattern cut into the center. Since the wall tends to burn in a constant rate away from the center where the flame is, the wall's circumference at a point in the burn tends to approximate thrust. See here for a bit more. The idea was that the upper stage uses a regressive burn grain design, meaning it tapers as the burn proceeds instead of increasing, thus controlling runaway acceleration. The idea was that the grain geometry selected for the center cores and strapons for the "heavy" Carracks was intended to leave the center first stage solid burning after the strapons had burnt out and separated, at least for a little. Don't ask about the particular grain, I didn't have any really great sources at the time so that's just hidden under the "I know this is possible with enough engineering" hood. Star for the strapons or the first stage on the lighter Carracks, a moon burner or something for the second stage, and a simple circle or a moon burner for the center on Heavies, something like that?
  5. Where'd you get the MOK module model?
  6. No, that was pretty much the mission plan as we envisioned it. It's why Gerry Mitchell is so nervous during that mission. I'm pretty sure we mentioned the use of using thruster packages tied into the AARDV avionics for fine manuevering someplace. You can certainly see the truss ones hiding on the outboardmost of the two "X" sections just beside the center truss module in this @nixonshead render. (Note similar thruster modules leftover on most of the lab modules, too.)
  7. Well, you successfully nerd-sniped me. I see two major drawbacks, and possibly a third depending on a question. First, as Abrecan points out, you have no abort options during the crew launch on the second lander, nor do you have any options for early return if you have to abort during the landing--you'd have to wait in lunar orbit or at L-2 until the Apollo is sent to bring you home. That's a pretty serious problem, since it means that the a far larger number of loss-of-mission incidents have risks of becoming loss-of-crew. For instance, if the Apollo fails to launch on time, the crew could run out of supplies while waiting for it even if everything else goes off as planned--the crew's life is bound to not one launch, but two--the Saturn-without-LES they ride, and the other that separately carries up their capsule. Second, I think the total payload to the surface is a bit lower. I suppose that since it looks like you're using 2xH03 and some medium-with-solids variant there's not a major surprise there, but given the mass tied up in the surface shelter, rovers, surface instruments, ascent stage, and other hardware, the added benefit of 5-10% in payload to the surface has a far larger increase in available surface stay capabilities. Third, and this may be limited more by the Kerbal parts available to you than the mission concept itself, do you only have two crew landing in this mission? You show two figures next to the lander launch and two next to the Apollo launch, with all returning on the capsule, but the ones on the APollo would never have a chance to land. If that's correct, that's a major drawback since it instantly halves your surface science crew-hours.
  8. That array deploy was awesome! Really fun video, and I'm pleased to see that looks as bonkers in execution as it looked in my head. Doable, sure, but still I'd be nervous. Did you have forward thrusters near the radiator end of the truss, or were you flying wholly on the AARDV thrusters?
  9. No, I just lurk this thread because content like Drakenex's really awesome recreation of Challenger and Freedom's first assembly mission blows my mind, but I know very little about mods (I played almost pure stock back when I played a lot) and thus have this tendency to lurk unless spoken about. As mentioned, this video is super awesome!
  10. Not quite. Twin main engines staged combustion kerolox engines of roughly RS-84 design (~4.5 to 4.75 MN sea level each), and two gas gen kerolox engines in the class of the FASTRAC but designed for easy reuse instead of low-cost expendability (~200 kN each, throttle to 70%). Same basic concept, just kerolox.
  11. I'd say we were pretty good about trying to keep to what might be possible in a practical budget. Several times we were inclined to put a finger on the scale and steer the TL in a direction we preferred rather than perhaps the most plausible path. For instance, the Saturn IC and Multibody based on it are fun rockets and feasible, but probably not great approaches at the times they're approved, and the entire period 1970-1973 or so is one giant handwave over the politics. There's alternate options that'd be more sensible, either equally capable and cost-effective per flight as Saturn IC while having lower upfront cost of development (even options that aren't Titan, something like cost-reduced volume production of Saturn IB, perhaps with boosters), or more capable for similar development cost (something like introducing a multicore 6.6m kerolox rocket right from the start, perhaps even in a version with 2xF-1A based on some of the Boeing Saturn V LRB concepts). Of course, either would involve such rewrites and butterflies it'd be a totally different timeline. The launch vehicles in the early timeline are probably the biggest issue, but there's a few other subtle ones: Space Station Freedom moves pretty freaking quick in development, as does the lunar landing program in the 90s, but on the whole I'm still proud of it.
  12. There actually were a few! Late model Titans used a 5m fairing on a 3m core. Scaling that to Saturn's 6.6m diameter would actually be an 11m fairing, which makes the 10m fairing we went with actually a bit smaller than ratios demonstrated in real flights.
  13. It's not that they have the ability to have the same ISp in both vacuum and sea level pressure, but rather that they compensate to be close to ideal expansion in both, offering close to the best possible performance from their chamber pressure possible in the given atmosphere. Because of the soup, that ideal performance is lower at sea level than in vacuum, but normally an engine must choose between a large bell for vacuum operations and sea level performance, unless firing at staged-combustion levels of chamber pressure. For instance, balancing a 30-bar, 5.5 O/F ratio hydrolox engine to be ideally expanded at sea level (exhaust pressure=1 atm) would give 353s at sea level, but top out at about 394s in vacuum because the ideal expansion ratio there is about 4:1. At a more normal vacuum expansion for an engine like that, say 40:1, you can get 453s in vacuum, but you see only 257s at sea level due to serious flow separation. The difference is less serious for staged combustion: 270 bar chamber pressure at the same mixture ratio buys 418/455 with the 40:1 nozzle (no flow separation), and a ~20:1 ideal sea level nozzle that gets 439s in vacuum. Long story short, you will always get lower performance in sea level atmosphere than vacuum, though bonkers chamber pressures reduce the magnitude of the change. Normally you have to pick a case to optimize for since changing from a 6:1 bell to a 40:1 bell is a challenge, but aerospike nozzles are a system that "automagically" does so.
  14. It'd look like the S-II: spray on foam was used on Apollo 13 on due to issues with the honeycomb originally used.
  15. I'm not sure I ever specifically said one engine on the S-IVC in text, and we didn't show the aft end of an S-IVC in any artwork Nixonshead did to my ability to check. I can't say we didn't screw up though--we screwed up a lot. So...I dunno. If you have a cite for something we overlooked on the S-IVC engine count, please feel free to point it out. Now that they edit window on AH has been upped to "forever," I can at least ensure any retcon is comprehensive. Be aware, in keeping with the spirit of Dawn of the Dragon, any such modules should be extremely silly. Dawn was an exercise in what kind of silly stuff I could get up to with only mid-60s-class launchers: Gemini, and Titan. No Saturns, no LH2, nothing. I then had to do something silly enough to fit that silly premise, and a Chinese program built of Rule of Cool and explicitly pointed out to be hamstrung by political demands to the same degree they were boosted beyond all reason by them, which was why they never built up their foundations was enough to just barely justify all that. Those stations are just interesting in the sense of "well, I guess it would work but why...?"