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About Rakaydos

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    Senior Rocket Scientist

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  1. 40+%, not 80+%. Half the energy goes the opposite direction and doesn't interact with the plate. That's just how Conservation of Momentum works. A combustion chamber catches that extra 50%, and squeezes it through a nozzle to reach maximum efficiency. But Orion is too powerful for any combustion chamber we can build.
  2. This is SpaceX. They actively target the single 25yo.
  3. Your 1st and 3rd points cancel each other out. While your second point remains true, a parabola remains the optimum shape for a bell to turn pressure into thrust. Other considerations, like the SSME avoiding flow separation despite it's expansion ratio, call for a non-optimum bell structure, reducing the theoretical vacuum thrust.
  4. In a vacuume, an infinite length parabolic nozzle is the most efficient. In variable pressures, ignoring thermal management and combustion efficiencies, an aerospike is theoretically the best possible nozzle type. (practical concerns mean we use staged optimized parabolic nozzles instead.) An orion pusher plate is very inefficient as a nozzle, but allows the use of a "combustion efficiency" orders on magnitude beyond any chemical engine while keeping the "thermal management" survivable. In effect, the combustion is so powerful it reduces the need for efficiency. An Orion-Medusa Sailcraft combines Orion and a parabolic nozzle- a magsail that catches the detonation at a safe distance and directs the products backward, with the actual spacecraft suspended by tethers.
  5. And not actually nessesary for lunar launch. The core stage should have plenty of TWR on the lunar surface, it doesn't need boosters.
  6. Static loads are easy, the trick is to manage the shock loads of the docking itself, without using RCS near the other. Lots of careful trajectory management to softdock at relative speeds below what the docking collar can handle. Starship refueling is going to say "But what if we COULD use RCS, both of us, as long as we don't actually spray each other." This gives them a lot more ability to manage their momentum and orientation.
  7. The missing step is, reusable rockets are cheaper to fly. So it's really, you make cheaper rockets, you get less money for them.
  8. Cathrine Asaro had a science fiction setting with that as her plot-tech. Because technically, the lighspeed barrier is only a point in complex vectorspace, and so a rocket that can generate an imaginary component to their thrust can accelerate past lightspeed if they do it with a partially imaginary (complex is the mathematical term) velocity. Also they stored fuel in complex-space pockets they called Klein bottles.
  9. By launching 3 times a day to distribute those fixed costs among 90 flights a month.
  10. There was a talk about "linier partical accelerator around the circumference of the moon", that offhandedly mentioned that, if we REALLY wanted to, a particle accelerator around the track of Neptune's orbit would be able to reach Plank Energy.
  11. "Arnt real starship only 1/5 that price?" "They're really good decoys."
  12. Depends on the platoons. Seal team 6 was a lot fewer than two platoons. As for it being a one way trip... sometimes, that's acceptable. Usually base to base, but sometimes you need to land it in a field.
  13. Anexceptio to that would be expander cycle aerospikes. Aerospikes have the opposite problem, where it has more throat that needs cooling per unit thrust, which is normally a problem, but solved the expander cycle problem.
  14. Note that packing efficiency (the proportion of engine thrust to area to rocket thrust to area) improves with larger engine clusters. A wider rocket can also be slightly taller, just from reducing inefficiency.
  15. Metamaterials, "flat atom" artificial atomic properties, "island of stability" elements, multi- shell bond chemistry... There's still room for exotic materials.