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Science Forum

  1. Standard member sonhouse
    Fast and Curious
    25 Jun '10 06:43
    I wonder which of these nascent technologies will come first? If a Manhattan like project were to happen on carbon nanotubes for instance, could we see the cable that has to be 100X stronger than steel to make an elevator to space or will we see the development of nuclear rocketry first? Lots of pros and cons on both. Any thoughts?
  2. 25 Jun '10 14:19
    Originally posted by sonhouse
    I wonder which of these nascent technologies will come first? If a Manhattan like project were to happen on carbon nanotubes for instance, could we see the cable that has to be 100X stronger than steel to make an elevator to space or will we see the development of nuclear rocketry first? Lots of pros and cons on both. Any thoughts?
    It is quite likely that neither will be used for quite some time. They are not the only alternatives.
  3. Standard member sonhouse
    Fast and Curious
    25 Jun '10 14:31
    Originally posted by twhitehead
    It is quite likely that neither will be used for quite some time. They are not the only alternatives.
    Besides brute force chemical rockets, what other alternatives are you talking about? Laser beam force launchers? I saw something about that where a very high powered laser beam aimed at the rocket gives the heat needed to blast out propellant with enough energy to give usable thrust. That's about the only other device I know of.
  4. 25 Jun '10 15:47
    Originally posted by sonhouse
    Besides brute force chemical rockets, what other alternatives are you talking about? Laser beam force launchers? I saw something about that where a very high powered laser beam aimed at the rocket gives the heat needed to blast out propellant with enough energy to give usable thrust. That's about the only other device I know of.
    I think brute force chemical rockets will probably remain the best option for some time to come.
    I can however think of alternatives:
    1. Delivering power by laser beam, seems like a good idea.
    2. A land based track that provides the initial propulsion seems like a good idea to me.
    3. Space planes.

    Any technique that doesn't require the spacecraft to carry its own fuel is so much more efficient, but is fuel the main cost?

    As always, Wikipedia does a far better job than I:
    http://en.wikipedia.org/wiki/Non-rocket_spacelaunch
  5. Standard member sonhouse
    Fast and Curious
    25 Jun '10 16:08
    Originally posted by twhitehead
    I think brute force chemical rockets will probably remain the best option for some time to come.
    I can however think of alternatives:
    1. Delivering power by laser beam, seems like a good idea.
    2. A land based track that provides the initial propulsion seems like a good idea to me.
    3. Space planes.

    Any technique that doesn't require the spacecraft t ...[text shortened]... s, Wikipedia does a far better job than I:
    http://en.wikipedia.org/wiki/Non-rocket_spacelaunch
    As far as I know the liquid hydrogen fuel for the shuttle, a noticeably large container there costs only about a half mil to load so you are right, the actual fuel cost is a very minor part of the launch.

    Space planes, I presume you mean hyper jets, ramjets and such could get a craft to the top of the atmosphere but above 100,000 feet there is not enough O2 to sustain a reaction so they would poop out there. Better than nothing though if you can develop such a launch beast. You would presumably have a space shuttle sized plane with several kinds of engines on board, regular jets to get off the ground, ramjets to get to mach 10 or so and then launch the rest of the assembly off the plane which would have regular rockets but needing a lot less in the way of delta V to go into orbit. I suppose it could be done but I don't see any megabuck layouts for such a project yet.

    I guess some kind of hybrid could be made where the final kick to LEO could happen with ground based super high powered lasers providing the energy to a propellant to make a rocket into LEO but I don't think that technology is past the demo stage yet with vehicles about the weight of a canary so far
  6. 25 Jun '10 16:28
    Originally posted by sonhouse
    I suppose it could be done but I don't see any megabuck layouts for such a project yet.
    You just haven't looked. It is the number two technology to the standard staged rocket.
    http://en.wikipedia.org/wiki/Spaceplane
    http://en.wikipedia.org/wiki/X-33
    http://en.wikipedia.org/wiki/X-43
    http://en.wikipedia.org/wiki/WhiteKnightTwo
    http://en.wikipedia.org/wiki/SpaceShipTwo

    Admittedly, many of the above are sub-orbital, but the potential for full orbit is there, and these suborbital precursors are the being invested in heavily (megabuck layouts).

    I don't see any layouts for space elevators or nuclear rockets in the near future, do you?
  7. 25 Jun '10 16:35
    Originally posted by sonhouse
    Space planes, I presume you mean ....
    On Wikipedia the term includes the shuttle which only really uses its wings on the way down. I was referring to the idea of using wings on the way up, which significantly reduces the amount of fuel needed to reach a given altitude.
    There are two factors:
    1. The wing is more efficient at gaining altitude than a plane rocket (which is one reason why modern jets don't simply do vertical takeoffs).
    2. For a large part of the trip, half the fuel (the oxygen) does not need to be carried with you.
  8. Standard member sonhouse
    Fast and Curious
    25 Jun '10 22:24
    Originally posted by twhitehead
    On Wikipedia the term includes the shuttle which only really uses its wings on the way down. I was referring to the idea of using wings on the way up, which significantly reduces the amount of fuel needed to reach a given altitude.
    There are two factors:
    1. The wing is more efficient at gaining altitude than a plane rocket (which is one reason why moder ...[text shortened]... For a large part of the trip, half the fuel (the oxygen) does not need to be carried with you.
    Well sure the shuttle doesn't use its wings on takeoff, the actually just cause drag on the whole rocket at takeoff, but those wings still give lift, if it could take off from an airport, clearly you need a lighter maybe bigger version of the shuttle but a winged ground takeoff space transport is possible in theory, the only problem is at what cost?

    If each takeoff cost a half billion, it isn't doing anybody any good. I still think a huge investment in carbon nanotubes would pay off in many ways even if in the end it proves to be too weak for an elevator, just the effort going into making it as strong as possible and as conductive as possible opens up all kinds of applications short of an elevator. For instance, as a tie down to a conductive line for a kite flown wind generator, that would be a big improvement over the copper lines in use now, which is very heavy, to carry the load and carry the electric power generated. That is just one app that comes to mind.
  9. 26 Jun '10 05:13
    don't think you will see any nuclear rockets. unless the big powers are hiding the capability for emergency use.
  10. 26 Jun '10 05:15
    Originally posted by twhitehead
    You just haven't looked. It is the number two technology to the standard staged rocket.
    http://en.wikipedia.org/wiki/Spaceplane
    http://en.wikipedia.org/wiki/X-33
    http://en.wikipedia.org/wiki/X-43
    http://en.wikipedia.org/wiki/WhiteKnightTwo
    http://en.wikipedia.org/wiki/SpaceShipTwo

    Admittedly, many of the above are sub-orbital, but the potential fo ...[text shortened]...

    I don't see any layouts for space elevators or nuclear rockets in the near future, do you?
    National Aerospace Plane (Rockwell X-30). the poster is one of the most beautiful space posters ever published, i think. kind of 50's/60's, though.

    http://en.wikipedia.org/wiki/National_Aerospace_Plane

    http://upload.wikimedia.org/wikipedia/commons/5/5a/X-30_NASP_3.jpg
  11. 26 Jun '10 14:51
    Originally posted by sonhouse
    Well sure the shuttle doesn't use its wings on takeoff, the actually just cause drag on the whole rocket at takeoff, but those wings still give lift, if it could take off from an airport, clearly you need a lighter maybe bigger version of the shuttle but a winged ground takeoff space transport is possible in theory, the only problem is at what cost?
    If each takeoff cost a half billion, it isn't doing anybody any good.
    A space plane.

    I still think a huge investment in carbon nanotubes would pay off in many ways even if in the end it proves to be too weak for an elevator,
    I fully agree. Except I don't see a space elevator as being a viable reason for developing it. Start with developing the nano-tubes for other reasons then later on use them for a space elevator.
  12. 26 Jun '10 20:30 / 1 edit
    Originally posted by sonhouse
    If each takeoff cost a half billion, it isn't doing anybody any good.
    I just realize part of my last post got lost somewhere.
    I mean to say that a space plane is far more efficient in terms of fuel and overall cost per launch than a multistage rocket. The main reason they haven't been used is the technical difficulties in the two stage system (normal jet to high altitude then rocket to space).
    I think that even at half a billion per launch there would be lots of takers - but I expect it would be much lower than that.
  13. 26 Jun '10 23:13
    i thought the space shuttle costs a half-billion per launch, not including development costs. no serious competitors except the russians' multi-stage rockets.
  14. Standard member sonhouse
    Fast and Curious
    26 Jun '10 23:25
    Originally posted by zeeblebot
    i thought the space shuttle costs a half-billion per launch, not including development costs. no serious competitors except the russians' multi-stage rockets.
    Yeah, its funny, you can buy a whole shuttle for about a bil but just getting it off the ground, a half bil. The fuel only costs a half mil so its not that.
  15. 27 Jun '10 04:21
    http://en.wikipedia.org/wiki/Space_shuttle

    ...

    Building Space Shuttle Endeavour cost about US$1.7 billion. One Space Shuttle launch costs around $450 million.[6]

    ...

    Roger A. Pielke, Jr. has estimated that the Space Shuttle program has cost about US$170 billion (2008 dollars) through early 2008. This works out to an average cost per flight of about US$1.5 billion.[8] However, two missions were paid for by Germany, Spacelab D-1 and D-2 (for Deutschland) with a mission control in Oberpfaffenhofen, Germany.[9][10]

    ...