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About mikegarrison

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    Junior Rocket Scientist
  1. Useful metric for high-relativistic velocities

    That's the thing about metrics -- they are tools. Which one you use (or even invent) depends on what you are trying to do with it. A hammer is one of the most useful tools ever invented, but it works terribly for driving screws. The OP made the (common) mistake of asking for a metric without specifying what it will be used for. That's roughly the same as walking up to a carpenter and asking, "Hey, can I borrow a tool?"
  2. Useful metric for high-relativistic velocities

    There is already a recognized metric for working with speeds near the speed of light. https://en.wikipedia.org/wiki/Lorentz_factor Since many of the physical effects (time dilation, length contraction, relativistic mass, etc.) are linear w.r.t. the Lorentz factor, it's probably what you really want to use.
  3. Recovering upper stages - in orbit?

    And what do you think is different about what you said from what I said?
  4. Recovering upper stages - in orbit?

    There were many, many proposals to do exactly this with the Space Shuttle external tank. Not so much to return them to the ground, but to use them for orbital habitats or storage tanks or some kind of orbital infrastructure. It never made it past the science fiction stage. First of all, as noted, these stages would all be in different orbits, so it wouldn't be completely free to gather them in one place. But a large number of shuttle flights did go to the same place (the ISS), and we could have gathered a bunch of shuttle tanks there. But what would we do with them? They aren't designed to do anything except hold hydrogen and oxygen. The tanks would have had to be redesigned from the start in order to be easily converted to something else. Not cheap or easy. There was a proposal back in the Apollo days to make a space station out of a Saturn IIb stage. https://en.wikipedia.org/wiki/Wet_workshop But in the end, the US decided to make Skylab a "dry workshop", in other words a space station purpose-built on the ground rather than assembled out of the hulk of a lifting stage.
  5. Aldrin Cycler Ships

    Actually ... the "inconvenient gravity" is one of the attractions. Obviously people can live for months in microgravity, because they do on the ISS. But there are still a lot of suspicions that living years without gravity will cause health issues. Nobody knows for sure, of course.
  6. Aldrin Cycler Ships

    These "cycler" ships are not terribly useful when talking about 10 or 100 people at a time. If they make sense at all, they need to be big, self-contained, space habitats that just happen to go between planets and can carry along people and supplies. They have to be amortized over a LOT of trips before they start making sense.
  7. Caterpillar track as landing gear

    Electric taxi has been discussed a lot, but it has issues. There is no general rule for ground idle. It's set high enough to keep the fire going in the engine, but that can be different for different engines. Some airplanes will start rolling with the engines on ground idle unless the brakes are applied. Others need the throttle to be pushed up in order to start rolling. And taxiways are not all level. Also, engines need to come up to operating temperature before they get shoved up to full power. So part of what is happening during taxi is that the engines are warming up. It's possible that they would have to be running anyway even if you did have electric taxi.
  8. Caterpillar track as landing gear

    To be fair, all landing gear for large planes are really heavy.
  9. Why do they not fair engines nozzles?

    Yes, the shape of the back of the fuselage is important, if that's what you mean.
  10. Will StratoLaunch Fly?

    Well, I'll just point out that this amateur with a big bank account *did* manage to put together the first privately funded/designed spaceship that carried a live human into space (three times, including twice in a week). Besides, if we're going to be making fun of amateurs with big bank accounts, that kind of describes Elon Musk and Jeff Bezos, too.
  11. Basic Course Aerospace Engineering Lessons

    I would guess this is the same material. https://www.edx.org/course/introduction-aeronautical-engineering-delftx-ae1110x-2
  12. Will StratoLaunch Fly?

    Stratolaunch Systems is owned by Paul Allen, so he could build 100 Roc planes and not really notice it in his bank account. It would not work as a large cargo freighter.
  13. Why do they not fair engines nozzles?

    Weight. Complexity. Loss of radiative cooling. Constraint on gimbal freedom.
  14. Cassini's last year at Saturn

    Cassini died on 14 Sept 1712 and is going to die again on 15 Sept 2017.
  15. How does Gravity exist?

    Gravity pulls us toward the center of the Earth. What (obviously stronger) force keeps us from falling there? What creates the resistance that keeps one solid object from moving through another? The standard answer seems to be "the Pauli Exclusion Principle", but if everything comes down to four forces, which one is involved in that? Is that electromagnetism?