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Everything posted by sevenperforce

  1. Looks like Elon had been playing stock KSP and was surprised by the switch to RO. Thinking about throttle settings. With two engines that’s definitely a suicide burn. But not all suicide burns are created equal. I am guessing that the flip will be timed such that the suicide burn will be achieved at or near minimum throttle for both engines, so if one has a thrust shortfall the other can throttle up to compensate. This is really the inherent problem with these landings...all this stuff is literally rocket science. Having three engines for redundancy is great because it allows these o
  2. It's a surprisingly compact solution. Like I said, I was able to do it in actual KSP without any clipping. But trying to move them inside the skirt is actually really tough. There are enough internal parts to make it a challenging fit. And you lose more of the wide stance than you would think.
  3. So I actually went back to the drawing board and rebuilt this in KSP with the proper dimensions (using 3.5 meter parts instead of 5 meter parts) and.... ......I cannot believe how well it works. Like, it works REALLY well. Amazing shock absorption. I put a single Vector underneath and was able to do a 150 meter hop perfectly the first time with no problem whatsoever.
  4. There might be enough space for six. One thing is that with this wide stance, though, you'd have to have a complete failure to not have SOME kind of support on that end.
  5. Oh, it is clearly way, way too large. No question about that. I was just trying to design it in KSP which is inherently difficult since I don't have Tweakscale installed. Using active hydraulic control for auto-leveling allows shock absorbers to also be the auto-levelers. The best part is no part.
  6. The current landing legs fold out onto the same points that are used to hold onto Starship while it is sitting on the pad. Presumably if you split the heat shield like this you would make the stowed-position feet themselves the hold-down points. I don't know if they could manage six or not. Four seems like plenty.
  7. Okay, so this is definitely my favorite Starship leg concept yet. More:
  8. I know that, and you know that, and @tater knows that, but apparently neither Elon nor Gwynne know that, so we have to assume they will make decisions based on that.
  9. Yeah, if all these insane plans work and "propellant costs only" is really a thing, then you can totally have an abort-capable Starship separate from your BLEO Starship. But it won't work for P2P.
  10. It was the kaboom that launched it in the air, not the 3 bar of ullage pressure. The kaboom was probably 100 bar or more. Beautiful, but for Starship definitely a non-starter. Over at NSF people are discussing launch abort systems for Starship, which has always been an issue because despite the vehicle's excellent payload, the nose section is SO large that a functioning abort system would really cut into your mass budget. And then someone came up with what has to be the best solution I have heard yet. That's.......tremendous. Rubber or plasticized petrol for the
  11. I think the spreading of the aft flaps helped with stability actually. Here's how a three-piston ITS-style solution might work.
  12. I think this is the leeward view. The heat shield would cover the leg completely. In three dimensions, there might be room to do something interesting. Two pistons that descend vertically and one that protrudes through the skirt (perhaps from the thrust puck) to the furthest extent of the foot.
  13. Some good notional renders from Twitter: The fold-out legs a la Falcon 9 would be the simplest, sure, but they're also simply not possible because that would involve (a) a seam in the heat shield, and (b) the entire vehicle resting on the freaking heat shield tiles. His pop-out legs a la New Shepard are also a nonstarter because of the heat shield seam issue and because of load paths. So the straight-down solution seems straightforward. It's also the most capable of auto-leveling and shock absorption. ITS-style legs that descend straight down and then fold outward are
  14. They're the same shape on the lee side and the windward side, so presumably they have a common design. The only way for the windward version to get out of the shielded fairing would be to extend downward first. So clearly they cannot be hinged at the skirt as with the F9 legs. So they may extend down and then out like the ITS legs. Or, they may extend down and then out, similar to the legs on New Shepard.
  15. Here's a gif of the ITS landing leg deployment if you wanna compare.
  16. The RL10C-1-1 is 2/3 of the dry weight of the RL10B-2. It's also substantially smaller: 59% the length and 73% the width. The nozzle is fixed rather than extensible, which makes it simpler and reduces failure modes. The Centaur family of upper stages has always had very good dry mass ratios, which means reducing weight is super important.
  17. ITS was going to be 12 meters, carbon-fiber, with no wings, and primarily intended for Martian colonization. Of course they had no budget for this and so they scaled back and built Starship. Originally designed to be carbon-fiber with PICA-X heat shielding as well, they switched to stainless steel and ceramic tiles because it works better and is a lot cheaper and easier to build. They added the flaperons to control attitude. Unlike ITS, Starship has valid use cases for LEO and cislunar activities. Here's the image from the 2016 IAC showing those giant landing legs:
  18. More evidence that the engines did not contact the ground at touchdown: If they had, there would be vertical crumple damage around the mouth of the engine bell.
  19. I'm not saying it was properly choked or anything. But yes, if you look at slow-motion captures it definitely appears the bulk of the explosion happened in the LOX tank.
  20. I have said this a thousand times but I will never understand why they didn't just build Jupiter DIRECT. Keep building virtually identical SRBs and SLWTs, design a thrust puck adapter and a payload adapter, and mount the early Orion CEV on top using the exact same Shuttle OMS engines to power Orion's service module and complete orbital insertion. Exactly the same launch profile as the Shuttle. Exactly the same contractors as the Shuttle. We would have been flying crew from US soil to the ISS this whole time and building experience toward something like the SLS but far more capable. And we
  21. I guess we could compare the descent rate between SN10 and SN5/6 to get a feel for it. I don't think they have any "change your thrust rate by X if the landing legs don't fully deploy" programming. So if it shut down the engine as if the landing legs had deployed, that alone would have dropped it a meter or so (however long the legs are). Yes, I believe they are very close -- probably only 20 cm or so. I remember looking at the closeup on the SpaceX feed and thinking it was odd how close the flaperons seemed to the ground: For any fans of Doctor Who we have this l
  22. Well it basically was another rocket engine. The ruptured thrust puck probably acted like a nozzle throat. Do we have word of Elon that there was landing engine underperformance? It looked like a landing leg issue to me.
  23. What are we thinking in terms of actual mechanism? My best guess is that when the legs failed to lock out properly, it came down hard on the engine bells and damaged the thrust puck. The impact probably ruptured the methane downcomer, allowing the remaining liquid methane from the methane header tank to mix with residuals in the main oxygen tank. The oxygen tank was basically a fuel-air bomb. Of course, no big deal...until the fire outside the skirt made its way underneath and up to the thrust puck. And then, kablooey.
  24. All three raptors successfully relit for the flip, so I really don’t think they were having any serious problems. Differences in color on ascent were likely related to mixture ratios and deep throttling. The only “testing” they are doing during flight is figuring out how Raptor performs with the force and pressure transients of actual flight. I understood Elon’s tweet a little differently: there was something a little wrong with the amount of thrust being produced, but it wasn’t wrong enough to be a reason not to fly.
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