andrewas

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About andrewas

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    Sr. Spacecraft Engineer
  1. Non-stop slingshot mothership

    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.
  2. SpaceX Discussion Thread

    On opposite coasts, Iridium is going up from Vandenberg.
  3. Personal Thermal Camouflage

    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.
  4. The history of falling and missing the Earth

    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?
  5. 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.
  6. 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.
  7. 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.
  8. Singularity Bombs?

    A hole less than a nanometer across isn't going to do anything.
  9. Singularity Bombs?

    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.
  10. 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.
  11. The Heat Death - Is it survivable?

    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.
  12. Blue Origin Thread (merged)

    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.
  13. Blue Origin Thread (merged)

    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.
  14. You are not remembering correctly. http://www.alcyone.com/max/writing/essays/why-niven-rings-are-unstable.html
  15. 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.