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Re: Zeppelin Spaceship

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  • ptgalt@hotmail.com
    ... Also, to my surprise, I learned recently that while some of the Hindenburg passengers were killed by a diesel-oil fire aboard, and others as a result of
    Message 1 of 7 , Nov 30, 2001
      Matt Kramer wrote (11/25):

      > [Responding to PT Galt 11/25]
      >
      > P.T.,
      >
      > I like the idea. There are a few things that could be
      > improved, though.
      >
      > > A heavy-lift, high-altitude zeppelin lifts off,
      > > carrying a 100-ton cargo-bearing spacecraft.
      > > The zeppelin is filled mostly with helium,
      > > but contains a bladder of hydrogen running down the
      > > center of its gas envelope. Being surrounded by
      > > nonflammable helium, the hydrogen is
      > > not a threat of a Hindenburg-type disaster.
      >
      > Actually, that's not necessary. Contrary to popular
      > belief, hydrogen was not actually responsible for the
      > Hindenburg's demise (see
      > http://www.ttcorp.com/nha/advocate/ad22zepp.htm ).

      Also, to my surprise, I learned recently that while some of the
      Hindenburg passengers were killed by a diesel-oil fire aboard, and
      others as a result of jumping from the ship, all those that rode the
      flaming craft to the ground survived. Since hydrogen at atmpspheric
      pressure is so diffuse, gaseous hydrogen does not generate much heat
      per unit volume (or surface area, of a person or object near the
      fire), and the gas disperses fairly rapidly.

      > So the helium could be omitted. However, the hydrogen
      > wouldn't be very useful as a fuel in its gaseous state
      > anyway--so maybe helium would be better, if it's
      > cheaper, even though it's heavier.

      Yes, now that you mention it, it would probably take considerably
      more energy to compress or cool the hydrogen into a useful fuel (and
      therefore, mass for the fuel to provide that energy) than it would
      take to just carry the ship fully-fueled in the first place,
      regardless of whether the zeppelin uses hydrogen or helium.

      The helium, though heavier atomically, provides about 90% as much
      lift as a comparable volume of hydrogen. The main problem I see with
      helium is that it's a non-renewable resource derived primarily from
      natural gas fields in the US. The Hindenburg used hydrogen largely
      because the U.S. government didn't want to supply the Nazis with
      helium, especially in the light of the military role zeppelins played
      in World War I. Since the United States government would likely be
      less than enthusiastic about providing a necessary resource for a
      libertarian-oriented space project, I think a hydrogen zeppelin might
      be a better way to go.

      > > As the ship rises, the hydrogen is used to power its
      > > engines and/or compressed as fuel for the spacecraft.
      > > This allows the helium to expand as the ship reaches
      > > higher altitudes without stressing the zeppelin's
      > > airframe while saving the weight that would otherwise
      > > have been required for the fuel the hydrogen is
      > > replacing.
      >
      > So you have liquid oxygen and hydrogen stored then?

      When I was writing this, I was aiming for an ideal use of resources
      and energy in which little to nothing is wasted. However, as you
      correctly point out, the gaseous hydrogen in the zeppelin's envelope
      wouldn't be of much use as a fuel (which is why it's also safe to use
      to lift the zeppelin). It would therefore be more energy-efficient
      to simply vent the helium or hydrogen to climb to higher altitudes.

      For powering the motors, I'd aim for a combination of solar power and
      hydrogen fuel cells. For this purpose, hydrogen can be stored in
      metal-hydride cells which release the hydrogen when warmed above a
      certain temperature (the exact number escapes me at the moment, I
      think it was something like 67 degrees) or in hydrocarbon form such
      as natural gas.

      The engines could also be powered by biodiesel (diesel fuel generated
      from biomass) or some other non-fossil fuel. If all fuels for the
      project (both the zeppelins and the rockets) can be produced locally
      by renewable means, we would not be dependant on access to fossil
      fuels produced in potentially hostile nations.

      > I like this idea. A lot. It makes me wonder why it
      > hasn't been tried before?

      Thanks. Here's why, IMO: Up to the present, space programs have all
      been government projects. Since WWII, zeppelins have had little
      military utility (though they are now being considered as heavy-lift
      military cargo vessels, high-altitude communications platforms, and
      for reconnaisance). Ballistic missiles, OTOH, were/are the ultimate
      symbol of military supremacy and national prestige. To my knowledge,
      the Saturn V was the first rocket designed and built specifically for
      civilian space travel. All previous spaceflights and satellite
      launches were accomplished using modified ballistic missiles.

      When Kennedy called for the Apollo program, resources were shifted
      from other (IMO) viable approaches to manned spaceflight such as the
      X-15 program to the area most relevant to Cold-War military needs and
      national prestige: rocketry. There was, and is, no
      institutionalized "zeppelin lobby" in the U.S. comparable to
      ballistic-missile contractors like Morton Thiokol (sp?) and
      Lockheed.

      Since ICBM's were already in manufacture in the '60's, it made a kind
      of sense to use those technologies rather than try something
      radically different like a zeppelin/lifting-body spaceship combo or
      SSTO. In a race to put a flag and footprints on the Moon, disposable
      ballistic missile-type rockets were the best option. They're a lousy
      option if the goal is to create cheap, widespread access to space and
      permanent settlement there. But then that has never been the goal of
      the US or any other nation.

      P.T. Galt
    • P.T. Galt
      ... Does this apply at high altitude, such as in the stratosphere? I can imagine this would be a problem launching vertically and/or at close to sea-level
      Message 2 of 7 , Dec 1, 2001
        Matt Kramer wrote (11/26):

        > I realized today that I said something massively
        > stupid [in my last post]. You can't use hydrogen
        > at all, never mind the Hindenburg, unless you blast
        > off the rocket far, far away from the zeppelin.
        > The blast-off reaction is extremely exothermic...
        > And you'd have to make the zeppelin out of extremely
        > durable material, even if you used helium. It'd
        > just melt otherwise.

        Does this apply at high altitude, such as in the stratosphere? I can
        imagine this would be a problem launching vertically and/or at close
        to sea-level atmospheric pressure (e.g. the titanic controlled
        explosion it takes to get a space shuttle off the ground). At
        stratospheric level, the air is much thinner, thus much less
        conductive of heat and shock waves (unless my limited understanding
        of atmospheric physics is very wrong. >grin<).

        If the spacecraft is being dropped horizontally from the zeppelin, it
        could fire its engines at a more modest thrust, enough to give it
        forward motion and aerodynamic lift, gradually accelerating as it
        moves away from the zeppelin and arcs into a climb. Unlike a ground-
        launch, it does not need to ignite its engines with enough thrust to
        lift its mass straight up initially. As someone else has pointed
        out, there have been launches of small rockets from high-altitude
        balloons. I'd expect that by the time the rocket goes to full
        throttle, it would be at least as far away from the zeppelin as a
        space shuttle is from the crowds watching it.

        In short, I don't think a zeppelin-launched rocket would need
        to "blast" off.

        P.T. Galt
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