XPost: sci.space.policy   
   From: larryg@u.washington.edu   
      
   This is partly in answer to the Scientific American article about cosmic   
   rays likely preventing human spaceflight.   
      
   I have long believed that O'Neill colonies are vastly superior to Mars   
   or any other planetary surface as an abode for human life and development:   
      
   (a) They permit nearly total control over sunlight, day-night cycles,   
        temperature, atmosphere, radiation, and gravity, all of which can be   
        set at earth normal levels, or to almost any level you desire   
      
   (b) Initially they will be positioned in near earth-moon space reducing   
        the problems of radiation, transport, communication, and rescue.   
      
   (c) They have access to energy that is superior not only to that   
        which you find on Mars, but better than anything on earth -- solar   
        energy in free space far from the shadow, gravity, or atmosphere   
        of any large planet or moon has no rival   
      
   (d) When they are later built in the asteroid belt they have access   
        to materials enough for hundreds of times the surface area of   
        earth.   
      
   (e) Scaled down, highly modified versions of such colonies propelled   
        by Medusa type fission-fusion nuclear blasts will permit manned   
        interstellar flight   
      
   However, as Henry Spencer once told me, most believe that Mars colonies   
   can start out small whereas O'Neill colonies require huge up-front costs,   
   as the smallest Island I colony of O'Neill can't be made much smaller than   
   3 million tons if it is to provide earth normal gravity.   
      
   But two things have changed:   
      
   (a) Instead of the spheres or cylinders which cannot be made small   
        w/o sacrificing gravity, the Stanford Torus can be scaled down   
        dramatically while retaining full 1 gee   
      
   (b) Asteroids such as Nereus, which require only tiny amounts of   
        energy to move material to L5, drastically reduce the cost   
        of raw materials for L5   
      
   Here are the economic assumptions I make:   
      
   (a) All the costs are for production and transport, not design.   
      
   (b) The launch cost is assumed to be $1M/ton ($500/lb) to LEO, $4M/ton to   
        L5, and $5M/ton to soft landing on the Moon   
      
   (c) The cost of manufactured materials in space is set at $1M/ton (same   
        as current aerospace)   
      
   (d) The mass of material to be launched from the earth into space for   
        construction of a product is 20% larger than the mass of the final   
        product.   
      
      
   So first let us look at the O'Neill/Island One concept:   
      
   (a) The mass driver on the Moon weighs 10,000 tons and launches 600,000   
        tons/year at 2.4 km/sec for 6 years to send 3.6 M tons or 7.2B pounds   
        to L5.  The cost would be:   
            $5M*(10,000 + 2000) + $1M*(10,000) = $70B or ~ $10/lb to L5   
      
   (b) The earth launch to L5 is 42,000 tons, so the cost is:   
            $4M*(42,000) + $1M*(42,000) = $210 Billion   
        So the total cost of Island One is $280 Billion   
      
   Now look at the Nereus/Torus based version:   
      
   (a) To move a 500,000 ton chunk of Nereus through a dV of 60 m/sec using   
        an ISP of 200 (about 2 km/sec) requires the expenditure of 15,000 tons   
        of material.  If done over 5 years that equals 3000 tons/year.  So the   
        size of this mass driver should be:   
           10000*(3000/600000)*(2/2.4)^2  = 35 tons.   
      
        To be conservative we will set it at 50 tons.  It would take about   
        10 tons of Krypton at $10/oz using ion propulsion to send it to   
        Nereus, so the cost would be:   
                 $1M*(50+10)+$1M*(50)+ $3.2M = $113M   
        but we will set it at $200M to be conservative.  So 10 of these   
        would return 5M tons or 10B lbs to L5 at a cost of $2B or 20 cents/lb,   
        50 (!) times cheaper than launching it from the Moon.   
      
   (b) The full Stanford torus was 6000 feet in major diameter and 430 feet   
        in minor diameter, and weighed 250,000 tons (by the way, the Stanford   
        Torus site no longer appears to be available). The 250,000 tons refers   
        only to the raw structural mass w/o atmosphere, soil, water,   
        buildings, people and about 10,000,000 tons of cosmic ray shielding.   
      
        For the 1st colony I select 1500 feet in major diameter and 43 feet in   
        minor diameter, so using strict scaling it should be   
        (1/4)*(1/10)*(1/10) = 1/400 of the mass of the Stanford torus (the   
        last (1/10) occurs because the tube would be 1/10 as thick as well as   
        1/10 as wide).  This yields a structural mass of 625 tons, but we will   
        set it at 1000 tons to be conservative.   
      
        We might need 200 tons of Krypton to move it to L5 ($32M worth).  So   
        the cost would be:   
              $1M*(1000 + 200 + 200) + $1M*(1000) + $32M = 2.7 Billion, which   
        we will round to $3B   
      
        Now once the raw colony has been moved to L5 we will send 200 people   
        (at $1M/person for $200M) to L5 where they will not manufacture   
        anything but simply fill in the 250,000 tons for the cosmic ray   
        shield, soil, water and air (baked out of the asteroidal material),   
        and add seeds, plants, etc and settle down for a few years to learn   
        how to live there.   
      
        The next step is to build a 2nd identical colony.  We will assume that   
        this will need only %10 of the material from earth, so the cost to   
        earth will be $300M.  Once both colonies are in place and functioning   
        they will build the next one which has the same major diameter but a   
        minor diameter of 85 feet and can support 400 people, again for a cost   
        of $300M from earth.   
      
        So we end up with a cost of:   
            $2B      for the 10 mass driver launches   
            $3M      for the 1st small colony   
            $0.6B    for two additional colonies   
            $0.8B    to send 800 people to L5   
            ------   
            $6.4 Billion   
      
        and we still end up with about 4M tons of material to play with,   
        enough for one Island One colony   
      
      
   There is a lot more I can say about this topic, and how it can be   
   expanded and moved to the asteroids, but I will stop for now.   
      
      -- Larry Gales   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)