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Everything posted by andrewas

  1. Less time passes for you than for the outside universe, so you arrive at the end of the universe with all your protons intact.
  2. Water is in compressible, so a water layer under a water ice cap can support the weight.
  3. Cyclers are for luxury travel. Build them big, and you can travel to mars with a ship thats only big enough to get to the moon. But the investment needed to create a fleet of Cyclers allowing for regular travel is immense, so this is a far future thing.
  4. On opposite coasts, Iridium is going up from Vandenberg.
  5. I think this is more for attackers - when setting an ambush or positioning snipers you might expect the defenders to be using thermal vision, but they are unlikely to be particularly alert at 2 am after weeks of no action. Unshielded guys stand out like a sore thumb on thermal, this makes you that much less likely to be picked up. Sure, when the shooting starts your gun gives you away, but at that point the enemy has other problems.
  6. It wasn't in restaurant, it was the one where Arthur winds up back on Earth and meets Fenchurch. So Long and Thanks for All the Fish?
  7. We dont know whether metallic hydrogen exists or what its properties are. Its not likely to be a structural metal, and if it is stable enough to be used that way, it cant be used as a rocket fuel. If it is useful, its either going to be as a room temperature superconductor or as a rocket fuel with ISP rivalling nuclear engines and no radiation hazard.
  8. There would have been no more science to do after the landing since Rosetta lacked instruments to sample the surface, so it was programmed to shut down after landing.
  9. Auto repair system. The probe was carrying out a long term observation so it was deployed on a suitable asteroid and equipped to mine the rock and build spare parts. The humans never bothered to turn it off, so by now it's converted the entire asteroid into discarded components which it endlessly recycles, and it still sends it's observations back to where Earth used to be once a week.
  10. A hole less than a nanometer across isn't going to do anything.
  11. The black hole weighs billions of tons and has a cross section smaller than an atom. If it hits regular matter, the interaction is too small to transfer any significant momentum. If the black hole was on an orbital trajectory it would eventually slow down and settle at the core, though it its light enough it will evaporate long before that. But a black hole moving quickly enough to escape won't even notice the planet on its way through.
  12. Consider the ship at periapsis. Its moving above the velocity for circular orbit, so its radial velocity increases. Half way to apoapsis, its velocity drops below the circular orbit velocity so its radial velocity starts to decrease, but its not until apoapsis that it reaches zero radial velocity and starts to fall again.
  13. To survive the heat death, you need to be a perpetual motion machine. The systems you describe have losses, eventually you will exhaust your energy supply and be unable to replenish it because the universe no longer contains energy gradients that can be used to do work. This point can be delayed, but even if proton decay isn't a thing and we always have atoms to work with, we can only eke out so much life, even using extreme measures like manipulating stellar formation so that small, efficient stars form only as we need them.
  14. There weren't any on the drawings I looked at. Maybe BA have a more luxurious layout rather than packing them in like sardines? Or it was just a crap drawing. Point is, seating layouts don't seem to avoid putting passengers in the plane of the turbines.
  15. It would, but if you look at actual aircraft you don't see such protection. The 747 has a gap almost in line with the outboard engines, but not the inboard ones which post a greater risk. The 787 has no gap at all, the A380 has no gap. It might be a thing in older designs, the 727 has its engine mounted just aft of the last row of seats, but that might be coincidence.
  16. You are not remembering correctly. http://www.alcyone.com/max/writing/essays/why-niven-rings-are-unstable.html
  17. If you are far enough away from it, you can orbit it more or less as normal. The gravity will be non-spherical which means that orbits will precess, and since the mass distrbution is much more extreme than Earth's, this precession will be much faster than it is in Earth orbit. I'm not sure how low you can go and still have a stable orbit. Within the ring, gravity will be towards the near side of the ring, and towards the plane of the ring. There are no stable orbits within the ring. At the center point all gravity cancels, but the slightest perturbation will result in you leaving that center point and gravity will accelerate you towards the ring.
  18. Stephen Baxter, Phase Space, the actual story is Sheena 5. The character also appears in Manifold:Time.
  19. Maybe the low thrust was an instrumentation problem, and Falcon corrected for a nonexistent problem and wound up too slow to get to the bargebefore it ran out of oxidizer.
  20. The higher you go, the less it costs to change planes, So you can save fuel by going above GEO, even through it costs more dV to circularize.
  21. https://spaceflightnow.com/launch-schedule/ The next one is Thaicomm 8, currently schedules for may 26th.
  22. The propeller moves a lot of mass backwards relatively slowly. The ion engine moves a tiny mass backwards very quickly. Kinetic energy varies with the square of the velocity, so it takes more energy to generate the same impulse with a faster exhaust.
  23. You can't treat a ringworld as a point mass at the CoM, because the primary is inside the ring and much of the ring's gravity is cancelled out by the other side of the ring. WIth a simple ring perfectly centered, everything cancels. Perturb the ring slightly and the gravity from the low side overpowers the gravity from the high side, and the ring is pulled further out of position until it impacts the primary. No, but as far as I can see you can't do more than stabilize the ring in one horizontal axis. Complete stability appears to be impossible.
  24. The closer to the planet the CoM is, the closer the mass distribution is to a simple ring - and we know those are unstable. I don't know if theres a sweet spot, where the CoM is far enough away from the planet to orbit more or less normally, but close enough to the planet that the ring can't collide. I would guess not, but I can't prove it.
  25. The problem is that the ring won't tidal lock, because the band of the ring will overpower any tidal effects on the mass concentration. Which means the band will eventually hit the planet.
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