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RE: [nanotech] Re: Wind it Up

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  • Jean ROCH
    Wow, you actually said something smart ! Congratulations, there might still be hope with you. I m sincere. Jean
    Message 1 of 20 , Jul 6, 2004
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      Wow, you actually said something smart !

      Congratulations, there might still be hope with you. I'm sincere.

      Jean

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    • Mark Gubrud
      ... There s a bunch of unconventional launch concepts out there, including towers, mass launchers of various kinds - ever hear of a slingatron? The
      Message 2 of 20 , Jul 6, 2004
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        Eugen Leitl wrote:

        > Cryogenic hydrogen scramjets/rocket hybrid shuttles seem like an easier way
        > to get into LEO.

        There's a bunch of unconventional launch concepts out there, including
        towers, mass launchers of various kinds - ever hear of a slingatron?
        The scramjet/rocket space plane concept has been around since the 1970s
        at least, and hasn't got off the ground; it must cost more than a big
        dumb rocket with lots of fuel and oxygen to burn. Fuel can't be a big
        fraction of the cost per gram to LEO, but let's say advanced nanotech
        gives us cheap scramjets - that saves something but not such a lot
        compared with say, cheap big rockets.

        The slingatron concept is cute: it would accelerate, say, one ton
        capsules to orbital speed like ball bearings in a giant hula hoop
        wriggled by computer-controlled actuators, with high energy efficiency
        (although you have to heat a lot of air tossing up through the
        atmosphere, compared with the space elevator's gentle ride). Sound
        crazy? Well, it's real physics, so this is the kind of crazy idea we're
        allowed to talk about on nanotech.
      • Eugen Leitl
        ... Nope, that s a new one to me. ... I understand hypersonic combustion processes are a real bitch. Same thing as early jet engines: the first ones had lousy
        Message 3 of 20 , Jul 6, 2004
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          On Tue, Jul 06, 2004 at 10:22:48PM -0400, Mark Gubrud wrote:

          > There's a bunch of unconventional launch concepts out there, including
          > towers, mass launchers of various kinds - ever hear of a slingatron?

          Nope, that's a new one to me.

          > The scramjet/rocket space plane concept has been around since the 1970s
          > at least, and hasn't got off the ground; it must cost more than a big
          > dumb rocket with lots of fuel and oxygen to burn. Fuel can't be a big

          I understand hypersonic combustion processes are a real bitch. Same thing as
          early jet engines: the first ones had lousy lift/weight ratio. Even the
          military doesn't seem to have one, yet, or they've never fielded it in
          sufficient quantities so far (the plasma trail probably looks not at all like
          a micrometeorite ionisation pattern on radar, stealth *this*, nevermind the
          pretty mother-of-pearl clouds from the contrail).

          > fraction of the cost per gram to LEO, but let's say advanced nanotech

          The chief advantage of a scramjet LEO shuttle (or at least the carrier which
          brings you a long way to orbit in terms of horizontal velocity component) is
          that it is reusable -- can take off and land from an airfield (preferrably,
          automatically, so no need for pilots).

          > gives us cheap scramjets - that saves something but not such a lot
          > compared with say, cheap big rockets.
          >
          > The slingatron concept is cute: it would accelerate, say, one ton
          > capsules to orbital speed like ball bearings in a giant hula hoop
          > wriggled by computer-controlled actuators, with high energy efficiency
          > (although you have to heat a lot of air tossing up through the
          > atmosphere, compared with the space elevator's gentle ride). Sound
          > crazy? Well, it's real physics, so this is the kind of crazy idea we're
          > allowed to talk about on nanotech.

          A maglev ramp made out of those not-quite-unobtainium composites looks quite
          nice, though. Lots of nice conic volcanoes near equator as well, so maybe
          even not that much need for a ramp (building a truss ramp some km high at
          several km elevation at a location far removed from large-scale industry is
          no picnic).

          SpaceShipOne is not much different from a stratospheric baloon: at about zero
          horizontal velocity component at 100 km height it is a publicity stunt,
          nothing else.

          --
          Eugen* Leitl <a href="http://leitl.org">leitl</a>
          ______________________________________________________________
          ICBM: 48.07078, 11.61144 http://www.leitl.org
          8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE
          http://moleculardevices.org http://nanomachines.net


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        • Jean ROCH
          The slingatron sounds interesting, Mark : I ll have to look into it ASAP. I don t think we necessarily need scramjets to make cheap space shuttles. Look at
          Message 4 of 20 , Jul 6, 2004
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            The slingatron sounds interesting, Mark : I'll have to look into it ASAP.

            I don't think we necessarily need scramjets to make cheap space shuttles.
            Look at Burt Rutan's Space Ship One : it uses plain old turboreactors and
            rocket engines.

            Cryo-engine are only advantageous because of their fuel (hydrogen) which is
            plentiful, cheap, environment-friendly and very well known. Assuming it was
            produced from water electrolysis using eletricity produced by solar panels,
            it would be free fuel (barring the facilities upkeep costs)

            A clean, plentiful fuel is essential if we're going to make "space planes"
            commonplace. Today's aircrafts are already contributing enough pollution.

            The design of Ariane 5's first stage is very interesting : it is clearly
            inexpensive and the type of fuel tanks use would be reuseable if the whole
            rocket wasn't discarded during launch.

            Rocket-planes aren't a big technical challenge either : need I remind you
            that the world's first plane to break Mach 1 was a rocket plane ? (Bell X-1,
            piloted by Chuck Yeager, if I recall correctly).

            Rutan's craft is pretty much an updated version of the concept, down to the
            carrier aircraft. In fact, the whole thing brings back memories of very old
            projects... Like the X-15 rocket plane, which could reach Mach 5 or 6 and
            almost exit Earth's atmosphere.

            I think such rocket planes are the obvious way to go. The orbital elevator
            is a nice nanotech-related concept, but it's nowhere near as practical as a
            craft you can just load and send up whenever you need it.

            Jean

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          • Jean ROCH
            Speaking of autopilots, I would like to remind you of yet another forgotten project : the russian space-shuttle Buran. Buran was like a copy of the american
            Message 5 of 20 , Jul 6, 2004
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              Speaking of autopilots, I would like to remind you of yet another forgotten
              project : the russian space-shuttle Buran.

              Buran was like a copy of the american shuttles (of course) but it had some
              very nifty technology for its time. One such was its autopilot.

              The Buran project went under at about the same time USSR died. Only one
              machine was ever completed, and another was partially completed.

              The completed craft - Buran - did only one flight, unmanned, to check if
              everything was OK before risking the lives of a crew. This was your typical
              shuttle flight : lift-off, orbital insertion, orbiting the Earth,
              de-orbitation, re-entry, gliding towards a landing track, and landing like a
              plane.

              Buran did all this on autopilot. Even better : despite a strong lateral wind
              on the landing site, she managed to land within 2 meters of its projected
              path.

              If we could do this back in (I think) 1989, then there's no reason we can't
              do it now, and for very cheap. That means it wouldn't even be necessary to
              train shuttle pilots. Or you could just go without a pilot as you suggest,
              Eugen.

              Removing a flight crew from the equation leads to a much simpler spacecraft
              (no life support). That means a big cost reduction. And remember that Burt
              Rutan's X-Prize entry only cost him $20 million, including development
              costs.

              As for maglev launchers... I haven't done any calculations but it seems
              horribly tough to overcome the friction against the atmosphere (do you call
              this "drag", in english ?).

              Typically, to overcome drag you'll need higher muzzle velocity. For a fixed
              barrel length that means higher acceleration. There's only so much
              acceleration a payload (human or hardware) can take before it is
              irreversibly crushed and ruined. So you'll need a very long maglev. And I
              mean VERY.

              Still, in terms of static means of access to space, I'd rather have a maglev
              than an elevator.

              Another long-forgotten project I'll bring back from the grave : at some
              point, a french engineer was recruited by Saddam Hussein to create a gun so
              powerful it could throw its shells in orbit. Orbital shells could then be
              set to perform reentry and impact anywhere in the world. It would have been
              the ultimate unstoppable weapon.

              It looked a lot like a maglev, being set up against a slope (which helped
              camouflage it).

              All small scale prototypes were destroyed and the engineer was murdered
              before the weapon was anywhere near complete. I'm not into conspiracy
              theories but at least I'll say thanks to whoever did that. The world doesn't
              need yet another doomsday weapon.

              Still, it goes to show that the concept is viable : the engineer was certain
              that the shells' guidance systems would have withstood the initial
              acceleration. For your information : this gun used chemical explosives for
              propulsion, detonated at several points along the barrel to avoid creating a
              single huge impulsion.

              Jean

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            • Eugen Leitl
              ... I ve seen a small EU shuttle prototype land autonomously in Sweden on one of those rare occasions I see TV. Of course there was no atmospheric reentry, but
              Message 6 of 20 , Jul 7, 2004
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                On Wed, Jul 07, 2004 at 06:52:54AM +0000, Jean ROCH wrote:

                > Buran did all this on autopilot. Even better : despite a strong lateral wind
                > on the landing site, she managed to land within 2 meters of its projected
                > path.

                I've seen a small EU shuttle prototype land autonomously in Sweden on one of
                those rare occasions I see TV. Of course there was no atmospheric reentry,
                but the technology is there.

                > If we could do this back in (I think) 1989, then there's no reason we can't
                > do it now, and for very cheap. That means it wouldn't even be necessary to
                > train shuttle pilots. Or you could just go without a pilot as you suggest,
                > Eugen.

                Pilots can be killed, don't take accelerations very well, and need plenty of
                empty space and life support hardware and mass. Mass-produced automatic craft
                doing lots of launches from airfields or maglev tracks is the way to go.

                > Removing a flight crew from the equation leads to a much simpler spacecraft
                > (no life support). That means a big cost reduction. And remember that Burt

                Yes, and there's absolutely no problem with occasional loss of craft.

                > Rutan's X-Prize entry only cost him $20 million, including development
                > costs.

                It's not a spacecraft. 100 km orbit is very different from 100 km vertical
                hop.

                > As for maglev launchers... I haven't done any calculations but it seems
                > horribly tough to overcome the friction against the atmosphere (do you call
                > this "drag", in english ?).

                Maglev tracks can be long, and only take juice. They would already pay if
                they bring you into scramjet ignition country. With a long enough ramp and a
                booster you can directly throw stuff into LEO, even on Earth.

                > Typically, to overcome drag you'll need higher muzzle velocity. For a fixed
                > barrel length that means higher acceleration. There's only so much
                > acceleration a payload (human or hardware) can take before it is

                Tac nukes are fired from shells. There are designs for guns to launch into
                LEO but I too think it's too harsh to do useful work.

                > irreversibly crushed and ruined. So you'll need a very long maglev. And I
                > mean VERY.

                The nice things about maglev tracks that the technology to build long ones is
                being prototyped for civilian purposes. Drag is not a problem at low
                velocitieties at high places like Chimborazo.

                > Still, in terms of static means of access to space, I'd rather have a maglev
                > than an elevator.

                Yeah, lots cheaper and not a single point of failure all the way.

                > Another long-forgotten project I'll bring back from the grave : at some
                > point, a french engineer was recruited by Saddam Hussein to create a gun so
                > powerful it could throw its shells in orbit. Orbital shells could then be
                > set to perform reentry and impact anywhere in the world. It would have been
                > the ultimate unstoppable weapon.

                Even sans nuke, a ballistic tungsten rod with the right guidance is a nice
                thing to have.

                > It looked a lot like a maglev, being set up against a slope (which helped
                > camouflage it).
                >
                > All small scale prototypes were destroyed and the engineer was murdered
                > before the weapon was anywhere near complete. I'm not into conspiracy
                > theories but at least I'll say thanks to whoever did that. The world doesn't
                > need yet another doomsday weapon.
                >
                > Still, it goes to show that the concept is viable : the engineer was certain
                > that the shells' guidance systems would have withstood the initial
                > acceleration. For your information : this gun used chemical explosives for
                > propulsion, detonated at several points along the barrel to avoid creating a
                > single huge impulsion.

                There are more advanced designs available now.

                --
                Eugen* Leitl <a href="http://leitl.org">leitl</a>
                ______________________________________________________________
                ICBM: 48.07078, 11.61144 http://www.leitl.org
                8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE
                http://moleculardevices.org http://nanomachines.net


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