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sevenperforce

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Everything posted by sevenperforce

  1. I think it is a fundamentally different question. Willingness to fail is great when you are working with dev articles. You design a test that will push a disposable test article to its limits in order to figure out the unknown failure modes. Repeated unforced errors in a system that’s supposed to be in its final configuration, ready to fly human beings? Particularly when the company claimed more flight tests weren’t needed because they had validated everything on paper? That’s...disconcerting.
  2. Looking closely at the tile inspection process on SN20. Many of the tiles with red-orange tape are visibly cracked or damaged. None of the tiles with green tape are visibly damaged but many look misaligned. If you blow up the image you can see “OK” scrawled on many of the other tiles. My guess is that red means broken and green means loose. It does seem like a lot of inspection work. But when you consider that it took sixteen hours to replace a single Shuttle tile.... Agreed. Unwillingness to fail is unwillingness to succeed.
  3. It is true that for a blunt body experiencing re-entry with 0° angle of attack, the body cross-section is the only thing that has any effect on drag and heat distribution. A sphere functions the same way as a cylinder (assuming the cylinder’s axis is perpendicular to the airflow). A delta-wing aircraft with a flat bottom and rounded fuselage functions the same way as a capsule with a flat bottom and a rounded top. But this is only if there is no angle of attack (or, depending on your frame of reference, a 90° AoA). With a nonzero angle of attack, lots of things start changing. And that is what someone seems intent on ignoring.
  4. Peroxide is, incidentally, hyperbolic. It is also what the Mercury capsule used. And of course Dragon 2 vents its residuals while descending under chute as well. All capsules do. Less than 1 tonne or more than 1 tonne, it doesn’t matter how much. Any hypergolic propellant tank breach in a capsule’s RCS or propulsion system, even a modest one, is a catastrophic LOCV. Always. Besides, while we are talking about hypergolic fuel tanks on a crew vehicle, what about the Shuttle? Well, this is still just hypothetical in terms of configuration. We don’t know anything for sure yet. One advantage of the design I’ve put together above is that the lift block interfaces directly with the hinge points on the arms, so the cantilever moment is provided by interface with the carriage in tention.
  5. You are correct that a primitive cylinder moving with its axis at 90° to the direction of flight will have the same L/D ratio as a sphere—zero—and will descend ballistically. You are incorrect in supposing that Starship will perform re-entry with its long axis at 90° to the direction of flight. Starship will fly with a significant angle of attack and have an L/D ratio significantly greater than a capsule like Apollo.
  6. Heaven forbid that a crew capsule would have hypergolic fuel tanks inside of it!! That has only ever been done with Mercury, Gemini, Apollo, Orion, and Soyuz! Indeed. In fact, the Shuttle specifically had too much lift for reentry and had to do lengthy and complex S-curve maneuvers to survive.
  7. Ignoring this ongoing war and back to the main topic... I’ve been discussing the catching arm structure with the folks at NSF and this looks fairly promising. Also, here’s a solution for precise positioning.
  8. You realize SN8-SN15 were all gliding tests, right? You understand how body lift works, correct?
  9. A glider that could neither have functioned in space nor survived re-entry from space. Because Shuttle docked to Skylab so many times, right? Oh, wait, it didn’t, and so they had to change the entire docking structure for Mir and ISS.
  10. It didn’t even have engines. And I assume you also agree that the Shuttle didn’t even know how to dock until 1995, because that was when the docking adapter was installed in Atlantis to enable it to dock to Mir in STS-71? Oh, wait, that was a different docking adapter than the one Atlantis ultimately used for the ISS, so.......
  11. The Shuttle concept was announced in 1968 and the Shuttle design was finalized in 1972. The first landing tests took place in 1977 and the first orbital test took place in 1981. The original ITS concept was announced in 2016 and the design was finalized in 2019. The first landing tests took place in 2020 and the first orbital test will most likely take place in 2021, with operational flights in 2022. The Shuttle took 4 years for a finalized design; Starship took 3. The Shuttle took 5 years to go from a finalized design to landing tests; Starship took 1-2 (depending on whether you count unsuccessful tests). The Shuttle took 4 years to go from the first landing test to an orbital launch test; Starship will have taken less than 2. It took 39 years from the date that the Shuttle design was finalized for the Shuttle to reach 135 orbital launches. How many times do you think Starship will have launched by 2058?
  12. I suppose you could accurately say that SLS is closer to its operational launch configuration than Starship+Superheavy. The vehicle currently stacked in the VAB is much more similar to the Artemis II launch vehicle than SN20/BN4 is to a fully-operational Starship launch system. However, the only reason for that is that Starship has many more capabilities. Once BN4 test-fires, then the Starship+Superheavy combo will be every bit as close to being an operational super-heavy-lift launch vehicle as SLS is. Even in its unfinished state, Starship+Superheavy is SLS’s equal. It’s like comparing a prototype Corvette to a four-wheeler....just because the ‘Vette doesn’t have it’s AC system installed yet doesn’t make it less driveable than the ATV.
  13. **sobs in Jupiter DIRECT** Could they have used three-segment boosters with two SSMEs and an ET for Orion Lite to the ISS?
  14. SpaceX: “We’re going to refuel in configuration A, but we’re not entirely sure how it will work.” Kerbi and Friends: “Preposterous! It will never work!” SpaceX: “If we refuel in configuration B, we can use thrusters for propellant settling.” Kerbi and Friends: “You don’t know what you’re doing! Paper rocket!” SpaceX: “It turns out we can use thrusters for propellant settling even in configuration A, which simplifies GSE operations.” Kerbi and Friends: “You’re contradicting yourself! Just admit defeat! Shuttle!”
  15. We know Mechazilla will not only be catching Superheavy, but also lifting Superheavy and Starship onto the pad for mating. We know where Mechazilla’s crane lift point is, about 20-30 degrees off from the launch table. For that lift to be efficient, the fulcrum for the lifting/catching mechanism needs to be under the crane lift point, or as close to it as possible. So we can conclude that the lift mechanism will have a fixed-axis fulcrum but have a “skew” capability allowing it to turn within a ~60 degree arc. If the OLT can handle the fire and fury of 30+ Raptor 2 engines firing simultaneously, it should be fairly impervious to an empty Superheavy exploding on the landing pad twenty or thirty meters away. SpaceX just has to make sure the OLT doesn’t take a direct hit. In summary, you don’t need a rotation all the way around the tower; you just need the arms to be mounted on a rotating frame with ~60 degrees of arc.
  16. Since we do not yet presumably have any actual catch arms at the site, it is hard to know what they will look like. Here is an alternate configuration.
  17. Here's what it looks like when you add the rest of the structure. I'm assuming that the components for the arms themselves are not yet on site. The GSE and stabilization arm can rotate around from the back. This is what I was talking about with the stabilization arm:
  18. If the crane lift point was between two of the rails then I would agree, but it is clearly over a single rail and you need more than one rail slide for proper stabilization, so it will have to connect to three rails. The GSE and stabilization arm can rotate around from the back.
  19. I've been looking more closely at the catching arm structures, and here's what I'm thinking currently. The big black pipe structures are carriages which sit on either side of the tower and slide on the outer rails. They are stabilized by the smaller truss structure, which probably provides braking on the central rail as well. The pointy bits protruding out of the black carriage structures come together right under the lift point; that's where the main lift frame is mounted, which can rotate around that lift point axis and provides the main lifting force for the arms. The sides of the arms are coupled to and actuated through the carriages.
  20. The actuators are inside. I am with @RCgothic on this one. IIRC they seriously considered the wet lab proposal but found that they would essentially be taking the tank to LEO as a payload. They would need an adapter to convert the tank into a workshop, which would take up the additional payload capacity and be located in a fairing on the nose of the external tank.
  21. I just had a horrible, terrible, no-good thought that definitely should not be explored or discussed in any way. What payload would Starship be able to get into low earth orbit if it had twin New Glenn side boosters? EDIT: To be clear, I am talking about using Starship as a sustainer stage. No Superheavy booster at all. Your choice whether to cross feed from the New Glenns into Starship.
  22. Stripped down and expendable, it would be vastly more capable to TLI than Saturn V.
  23. Yesterday: Tallest rocket in history: Saturn V Most powerful rocket in history: N1 Highest operational LEO payload: Energia Largest reusable lower stage: Shuttle Boosters Largest reusable upper stage: Shuttle Orbiter Today: Starship (all of the above)
  24. And of course I ran out of likes. Also this: I wonder if they will use hard points under the forward flaps for the tower chopstick lift.
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