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sevenperforce

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Everything posted by sevenperforce

  1. This is a super simple and cheap render but a cool comparison now that we officially have Starship, Superheavy, and the full GSE in the same frame: And here's a closeup of the tip of Starship: You can see the red adhesive they're using. Above picture normalized to pad height:
  2. The only suborbital test platform capable of handling a six-engine static fire is currently occupied by BN3. My money is on a stack for fit check and photo op. If they weren't going to stack for a fit, they would have left it in the high bay and completed the heat shield there, where it's easier to do. Also it appears they are preparing to pull off the load spreader on BN4:
  3. I think you forgot about Chang'e 3 and Chang'e 4.
  4. I believe the crane that they used to stack the launch tower is big enough, but I'm not sure. Here's what I'm going off of: IIRC there was discussion on NSF that while the cranes they currently have can absolutely do hoists at well over 140 meters, the crane lift capacity at that height is less than the dry mass of Starship. But perhaps that was before they built Frankencrane.
  5. It was my understanding that their cranes couldn't go high enough to lift Starship onto Superheavy on the orbital pad...how are they going to stack without the lifting arms?
  6. Of course Elon has the best shots. Here's a closeup showing how the clamps will be oriented with respect to the booster skirt. Presumably the engines that are white inside have never been fired. Or at least the nozzle. It's possible that the engines have been fired but the bell was replaced.
  7. I wonder what the odds of ice impingement on exposed Raptor plumbing is..... The inner engines -- in Falcon 9 configuration -- are all gimbaled inward.
  8. Now imagine the booster hovering right here, waiting to be caught by the tower arms.
  9. It looks like they have a buckeyball configuration for the very tip. I'm really curious what the black COPVs on the outside of BN4 are. Especially since we know they are doing attitude control via propulsive vent. EDIT: According to SNF, the eight COPVs contain high-press GOX and methane for startup and tank press.
  10. Oh man!! That infographic looks really, really butthurt. Come on, guys.
  11. I take back every rude thing I ever said about Tim. https://everydayastronaut.com/starbase-tour-and-interview-with-elon-musk/ THE SEPARATION SYSTEM! THE ATTITUDE CONTROL! GREAT SCOTT!
  12. My understanding of the 1:1 L/D ratio is that Falcon 9 is able to “glide” at approximately 45 degrees from an otherwise ballistic trajectory. That is much lower than most aircraft, even the Space Shuttle, but it is much higher than a ballistic object. Even the Apollo Command Module, which was designed to get as much lift as possible, only had an L/D ratio of 0.37:1.
  13. Yes. Everything @RCgothic said. Additionally, both Falcon 9 and Superheavy are designed to use body lift to add range during descent. Performing a boost back burn requires a lot of propellant. Anything that reduces that propellant consumption means more propellant can be used to push the upper stage higher and faster before stage separation. If the fins were fixed, like the ring fin on New Shepard, then the booster would fall back to the ground on a ballistic trajectory like a lawn dart. However, if the booster is able to lean its “head” forward into the wind as it falls, then the entire booster body generates body lift, converting some of its vertical speed into horizontal motion. It’s not much, but it is enough for the booster to be able to boostback only 90% of the way and then glide the remaining 10% (or something like that). The grid fans don’t need to provide very much roll authority or yaw authority, because the booster is more or less passively stable. However, it takes a lot of pitch authority to lean into the wind like that. So it makes sense to move the grid fins closer together so that they can work together to provide pitch authority.
  14. Wow, that makes a LOT of sense. The more pitch authority they can get, the more aggressive body lift they can get, which means less propellant consumption on the boostback burn. And having them out to the sides keeps them out of the booster’s wake. Super smart.
  15. Yep! Those icicles on the outside of the RL-10 are just incredible. Of course, the RL-10 uses an expander cycle so it has to suck every last Kelvin it can out of that engine bell in order to function. And while the RS-25 doesn’t need the heat to operate since it uses a staged-combustion preburner, it is also using liquid hydrogen, which has a much greater heat capacity than liquid methane. Even so, the heat capacity of subcooled liquid methane should be plenty to keep the Raptors chilled.
  16. That would actually be illegal, believe it or not. You cannot use work product gained from the interview process without paying for it. It’s unlikely that someone would do an “on the spot” challenge like this using actual work, but it does come up, more often in the context of more significant projects. You might be asked to prepare a brief or a report or code block as part of the selection process for the job. If that ever happens, do it, but if you DON’T get the job then you should absolutely send them an invoice for your time. Billed at your contractor rate (which should be 70-80% higher than your hourly rate). The only time this happened to me was when I was interviewing for an engineer position and I had not done any engineering work since graduating. The team lead handed me a dry erase marker and asked me if I could draw the diagrams and write out the equations for a simple electromagnet. I thought that was an acceptable ask because they were just making sure I had retained enough technical knowledge to be useful. Which I had.
  17. I stated it very poorly, so I fully understand why @mikegarrison was taken aback. When the engines are firing, they are regeneratively cooled, so they aren’t hot. If kerosene-regenerative cooling can handle nine Merlin engines, methane-regenerative cooling can definitely handle the full array under Superheavy. My point with respect to the outer ring was separate (and, again, poorly-phrased). The only time the engines are not regeneratively cooled is during the retropropulsive burn, when the outer engines are just sitting there and the inner engine(s) are roaring. There is more physical distance between Superheavy’s outer ring and its core cluster than there is between Falcon 9’s outer ring and its core engine, so the heat flux from the core exhaust plume to the outer ring of Raptors will be lower than from the core Merlin to the outer ring of Merlins. Thus the larger the outer ring of engines, the less heat those outer engines receive from the overall thermal environment. But, again, very poorly phrased. Mea culpa.
  18. The nozzles are cooled by the liquid methane which has a MUCH better heat capacity than kerosene AND comes in at a much lower temperature. So if Falcon 9 can handle nine Merlin engines in close proximity, Superheavy can DEFINITELY handle 20 engines in close proximity. The more engines you have in the ring, the less radiative heating there is from one engine to the next.
  19. SN20 aft flap install. This is happening SO fast. Do we think this is the flap root cover? EDIT: For those watching the livestream, BN4 is starting to inch her way out of the High Bay.
  20. I think the straight seams that run circumferentially are fine. It would be longitudinal seams that would cause trouble. During the worst of re-entry, Starship will be flying in with a high angle of attack in order to achieve a lifting-body entry, and thus the plasma flow path will be at a sharp angle to any circumferential seams.
  21. That's my thought. @RealKerbal3x Interesting that they already freely have circumferential straight seams. Also, I think we have a candidate for those catching arms: Look how absolutely massive those hinges are.
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