• Content Count

  • Joined

  • Last visited

Everything posted by RCgothic

  1. The reason that accelerated flow exhibits a lower pressure is that a greater proportion of the air molecules are moving in the same direction. In highly simplified form, if all the air molecules are moving parallel to a surface, they are not colliding with that surface so zero pressure. Bernoulli is just Newton for air. Obviously it's more complicated than that because fluid flows do not behave simply.
  2. Consider flat disc moving at some arbitrarily stupidly large velocity, presenting its flat side to the airflow. On the reverse side, every air molecule will be removed from its path. Effectively a vacuum. The limiting low pressure is -1atm gauge at standard temperature and pressure, or 0atm absolute. You can't get an air pressure lower than zero. On the other side the plate is colliding with vast quantities of air molecules. The faster the plate goes, the more collisions, pretty much without limit. The high pressure upstream can therefore be arbitrarily high. So there is no limit to the potential pressure differential across the plate, as determined by velocity. Now angle the plate into the airflow. Now the pressure difference is at an angle to the airflow. Congratulations, you've now got an arbitrarily high lift component. Everything else about aerofoil design is about chasing efficiency or operating window.
  3. Newton's laws always apply. In equilibrium, the force of gravity is balanced by lift pushing on the wings. The wings push equally on the air. (3rd law). A mass (in this case of air) experiencing a force is accelerated (2nd law). The air is pushed down.
  4. A tug doesn't necessarily have to be a pusher.
  5. Launch Escape System. Usually a solid rocket attached above the capsule.
  6. Docking's a solved problem. Being bigger doesn't make it harder. Potentially it makes it easier as more minute corrections are possible.
  7. There is zero requirement for a man-rated superheavy launcher. You don't need a superheavy to put a crew in orbit, and you don't need to man-rate a cargo superheavy and make everything five times more expensive than it needs to be. RS-25 only had to be uprated because of the poor launcher architecture. Does Raptor need to withstand the heat and vibration of solid boosters? No, it doesn't. Because raptor will only fly on competently designed vehicles.
  8. So the engines alone for SLS cost as much as five or six band new falcon heavys. Insane.
  9. 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.
  10. 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.
  11. 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.
  12. 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.
  13. Could be throttle valve controller. Failure to throttle down might trigger a last moment abort.
  14. 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.
  15. 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!
  16. 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.
  17. 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.
  18. 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.
  19. 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.
  20. That BE-7 engine looks ridiculously simple. Presume the render is missing out a whole host of control gubbins.
  21. 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.
  22. 0922 BST. Think I'll stick this one on as a short break from work!
  23. Yet another reason SRBs have no business being anywhere near a man rated launcher.
  24. The engine bells shouldn't be too difficult to replace I don't think.