RCgothic

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Everything posted by RCgothic

  1. If a ship can avoid experiencing gravity it can maintain an orbital altitude without an orbital velocity. In fact, it *needs* to experience gravity in order to orbit, because without gravity any velocity is escape velocity unless you apply constant radial thrust. A gravity manipulating ship doesn't have to orbit unless it wants to. It levitates. So there's no reason its entry to the atmosphere needs to be great other than reducing transit time. If you can sustain re-entry heating, come in hot. If not, walking pace or slower will do. Without gravity all urgency goes away.
  2. That BE-7 engine looks ridiculously simple. Presume the render is missing out a whole host of control gubbins.
  3. RCgothic

    SpaceX Discussion Thread

    Well first off they were usually designed with redundant steam relief valves to stop that happening. Of the fifteen boiler explosions in the UK in the 20th century, only two were failures of the boiler barrel due to incorrectly assembled relief valves (overpressure). Thirteen were due to weakening of the firebox caused by low water level, which is not quite so spectacular. Low water level is caused by either operator error or faulty water level gauges.
  4. RCgothic

    SpaceX Discussion Thread

    0922 BST. Think I'll stick this one on as a short break from work!
  5. RCgothic

    NASA SLS/Orion/Payloads

    Yet another reason SRBs have no business being anywhere near a man rated launcher.
  6. RCgothic

    SpaceX Discussion Thread

    The engine bells shouldn't be too difficult to replace I don't think.
  7. RCgothic

    SpaceX Discussion Thread

    Good call, although CRS-16 wasn't a total loss.
  8. RCgothic

    SpaceX Discussion Thread

    I remember the sea looked pretty rough after the landing. Not surprised nobody could board to make safe if octagrabber wasn't compatible. Still sad though. This the first loss of a block 5?
  9. RCgothic

    NASA SLS/Orion/Payloads

    There's no reason why there couldn't be a reserve for a deorbit burn once payload insertion is complete.
  10. RCgothic

    NASA SLS/Orion/Payloads

    So both second stages are undersized. The core stage is oversized but too anaemic in terms of thrust. And the boosters don't burn long enough. If core and boosters were able to put a sizeable payload in orbit without a second stage the problem wouldn't be half as bad. That would make it mission agnostic, just change what you stick on top of it. If I were designing a SHLV today it would probably look a lot like SA-513 that launched Skylab with flyback side boosters. Two and a half stages to orbit and whatever you like on top.
  11. RCgothic

    NASA SLS/Orion/Payloads

    Stage and a half to not-quite-orbit is such a bizarre architecture.
  12. RCgothic

    SpaceX Discussion Thread

    This is not quite the while story, as you only get robbed of the full 9.81m/s per second if you're burning purely vertical. Once you start burning sideways gravity drag has less and less effect. This is a trigonometric effect. Your thrust makes up the hypotenuse. Gravity drag is vertical. Your desired velocity vector is the difference.
  13. RCgothic

    NASA SLS/Orion/Payloads

    SLS won't be building LOP-G though. It can't co-manifest substantial enough payloads prior to block 2. So we're talking about 3rd party boosters anyway. Falcon can send both the payloads and the crew, separately, within a short enough space of time to be useful. Dragon2 will be able to go to the moon.
  14. RCgothic

    NASA SLS/Orion/Payloads

    Extended deep space operations are pretty pointless if the booster is incapable of taking crew anywhere that requires them. The only difference between extended deep space operations and extended LEO operations is risk to crew.
  15. RCgothic

    NASA SLS/Orion/Payloads

    We do need to launch on the timescales Apollo did because that enables rendezvous mission architectures. Without those we are never going beyond the earth moon system and we are never establishing a significant lunar presence.
  16. RCgothic

    NASA SLS/Orion/Payloads

    We never *will* be ready for the moon or mars or even just significant orbital presence unless and until we have a booster capable of doing the job. Of lifting substantial payloads and performing the required rendezvous mission architectures. Want to forget the competition? Fine. They're forgotten. SLS is *still* not the booster that advances manned spaceflight. Its most advanced form can barely recreate Apollo at 1/4 of the flight cadence.
  17. RCgothic

    SpaceX Discussion Thread

    Yes, payload integration happens after static fire so that if the booster explodes it doesn't take the payload with it, as happened with AMOS 6.
  18. RCgothic

    NASA SLS/Orion/Payloads

    SLS fails on its own terms, nevermind any competitors. It was supposed to take humans to Mars and it never can, not even in its most ambitious block 2 format. It can barely manage the moon. It simply costs too much and can't fly often enough. It fails as a stopgap because it doesn't stop the gap. Better to cancel it now and focus on designing and building a clean slate big dumb booster with a decent launch cadence and have another 10 year gap, than drag this charade on for another 5 years before realising that cancelling it and starting again is what should have happened in the first place.
  19. RCgothic

    NASA SLS/Orion/Payloads

    SLS is a dead end and any money spent on it is a waste. It's a dead program walking. The only thing keeping it going is sunk cost fallacy. There's nothing SLS block 1b or 1b can do that a handful of launches from an alternative extant booster couldn't do for a fraction of the price. Even Block 2 will never have Mars capability, and that is the purpose for which this booster has been touted. If Block 2 ever flies I'll be truly astounded. And the gap in human spaceflight capabilities is not ok. It will have been nine years since the shuttle least flew, and everyone knew that retirement date was coming. "Only 50% longer than the Apollo-Shuttle gap" does not make it ok. 6 years then wasn't ok either, although at least that produced a groundbreaking vehicle. Where shuttle went wrong was keeping it in service for 25 years after it became clear it wasn't going to acheive its required cadence. They should have done something else. The opportunity cost of the last 20 years had been crippling.
  20. RCgothic

    SpaceX Discussion Thread

    Also Orion has full mobility. All Dragon needs to do is hold orientation, which is easy, even connected to a FUS.
  21. RCgothic

    SpaceX Discussion Thread

    There's a difference between a custom fairing to cover Orion and its LES at about 5m diameter at around Falcon's normal fairing size, and flaring out an interstage to cover EUS at 8.4m. The EUS is the same diameter as the SLS core. The Orion service module (built by ESA) is narrower than Orion.
  22. RCgothic

    SpaceX Discussion Thread

    EUS is never going on a FH. FH's maximum fairing size is 5.2m. EUS is 8.4m. ICPS would at least fit within the fairing.
  23. RCgothic

    SpaceX Discussion Thread

    FUS, Plus EUS, Plus ICPS? That sounds even less plausible.
  24. RCgothic

    NASA SLS/Orion/Payloads

    Maybe it's true we weren't ready to build bases on the moon immediately post Apollo. But the only reason we're still not ready is because for 40 years we haven't been making any serious effort in that direction. We've flown the same crafts conservatively long past the time we should have been doing something new and boundary breaking, and SLS/Orion is more of the same.
  25. RCgothic

    SpaceX Discussion Thread

    ICPS on top of the falcon second stage looks wrong. And mass to LEO includes fuel residuals, it's not literally how much weight you can have in the payload section. How do ICPS and FUS stack up DV wise? In terms of thrust? Could ICPS be a straight replacement for FUS? That seems a bit more feasible as all the weight is going on top of FS1, which is used to having the weight of stages above it.