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View Diary: XCOR: wanna take a ride into space? (187 comments)

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  •  Orbital velocity is almost exactly the same ... (0+ / 0-)

    ... at high altitudes, as it is on the ground, unless you're at a significant distance from the center of our planet, which doesn't seem to be in XCOR's plan.

    All my life I've seen rocket craft flown aloft in vain attempts at orbit. Saving a few tens of miles does not justify hauling a rocket with sufficient thrust above the surface of our planet -- it's been best just to launch it from the ground.

    Are space passengers supposed to share their ride with a second or third stage which will fire at the height of their trajectory? I hope MY vehicle is FAR away from the butt-end of a rocket!

    Equivocating height with orbit makes me very suspicious -- I can see sub-orbital craft as fast transportation systems around Earth, but then I wonder about the true costs.

    The prospect of public spaceflight is cool, but I want to see more than these guys are offering.

    It's ... ridiculous to expect the market to police itself as it would be to expect a baserunner to walk off the field if no one is calling outs.

    by MT Spaces on Sun Nov 06, 2011 at 01:41:16 PM PST

    [ Parent ]

    •  OH, I see, (1+ / 0-)
      Recommended by:
      MT Spaces

      you're commenting on the idea of launching an orbital vehicle from the primary vehicle.

      Well, having the primary vehicle far away from the butt end of the orbital vehicle would be pretty easy to arrange, it could be ejected by spring or other stored energy along the path of the primary vehicle early in the exo-atmoshperic coasting phase of the trip when both items are heading upwards at a pretty steep angle. It could be pretty far away from the primary vehicle when lit off. It would also be on a slightly different trajectory so it wouldn't reach its peak until the primary vehicle was already on the way down, so its exhaust wouldn't be pointed at the primary vehicle. Also, in a vacuum, the exhaust actually spreads out in a "cone" with an included angle of roughly 180 degrees, so it's pretty rarified at even a moderate distance from the primary vehicle.

      As for hauling a rocket aloft vs launching it from the ground, rocket boosters do the hauling for ground launches. Multiple stages are still necessary for orbital or flight because you have to keep the weight down. In essence, it's like throwing the empty part of the fuel tankage away as soon as you can as it is emptying.

      Lockheed almost got a single stage to orbit (SSTO) vehicle working, but it proved very difficult or impossible to get enough weight out of it and still have sufficient structural strength to do the job. If I remember correctly, for SSTO you need a vehicle whose launch weight is less than 10 percent structure to make it work, which is to say its launch weight has to be greater than 90 percent fuel weight. A tough challenge.

      Moderation in most things.

      by billmosby on Sun Nov 06, 2011 at 03:59:24 PM PST

      [ Parent ]

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