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Everything posted by RCgothic

  1. So the engines alone for SLS cost as much as five or six band new falcon heavys. Insane.
  2. For the starlink constellation it might be that you don't need a hot spare. Because you have so many sats in the same plane, you just space out the survivors and absorb a slight reduction in signal strength.
  3. My brother and his family just moved from the UK to Australia. There's a good chance I'd be willing to pay to turn days of travel into 20 minutes even at a one in a thousand failure (instant death) rate.
  4. If a flight is only 20 minutes and it involves anything close to a full g or greater, there won't be any bathrooms. In the first instance, the trip isn't long enough for them to be necessary and in the second it won't be safe for people to move about the cabin.
  5. Nearly, I was watching on a minute delay. Actually had more of a heart in throat moment for the side booster entry burn. The centre core was disappointing, but we knew that was a dicey prospect going in.
  6. Could be throttle valve controller. Failure to throttle down might trigger a last moment abort.
  7. Yeah, propellors and wings are both aerofoils. They both create thrust by deflecting quantities of air by Newton's third law. An understanding of Bernoulli just allows you to design shapes that do so efficiently. There's no special distinction for propellors or turbine blades. They just have twist and chord variation to compensate for the varying effective velocity vector of the incident airflow over the aerofoil due to the circumferential speed of the blade varying from the root to the tip.
  8. You learn more from your failures. At least this was a non-mission-critical failure. The side cores did look very much like a RUD. I think it was the infra-red camera getting super-saturated by the exhaust gases, causing the landing burn to look more spectacular than usual!
  9. Or don't turn it off and just hover. If the device uses less energy to run than it would take to accelerate to orbital velocities, you just wouldn't. And if it does use more energy than it takes to get to orbital speed, might not be worth having it at all. The ascent is a relatively small part of the energy requirement for accelerating to orbital speed.
  10. UK radio today reporting that tourist flights to the international space station were to be offered for £28,000. The news was lacking in detail, but that's insane. Even starship with a capacity 100 would struggle to loft a person into LEO for so little.
  11. Plus the fact earth itself moves on its course around the sun due to gravity means than a ship immune to gravity will have trouble tracking with the planet around the sun without applying constant thrust.
  12. 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.
  13. That BE-7 engine looks ridiculously simple. Presume the render is missing out a whole host of control gubbins.
  14. 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.
  15. 0922 BST. Think I'll stick this one on as a short break from work!
  16. Yet another reason SRBs have no business being anywhere near a man rated launcher.
  17. The engine bells shouldn't be too difficult to replace I don't think.
  18. Good call, although CRS-16 wasn't a total loss.
  19. 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?
  20. There's no reason why there couldn't be a reserve for a deorbit burn once payload insertion is complete.
  21. 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.
  22. Stage and a half to not-quite-orbit is such a bizarre architecture.
  23. 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.
  24. 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.