A buck a squafoot (was LEO vs GSO; colony-isolation tests)

> Why would such a plant be built in orbit in
> order to produce a few specialized chips for the "superior hardware"
> you imagine would be built? A valid point. In reality, Ithink the progression will be something like this. Right now we're at square zero, where every last single thing we use in space is boosted up from the surface of the Earth. Square one might represent using some lunar soil in a radiation shield for some humans orbiting above the Earth's magnetic field. The next step might be use of lunar-material-derived oxygen as the heavier part of both propellant and water. Then we start manufacturing large glass windows, and large steel and aluminum bulkheads from lunar material, along with I-beams and tension cables. Then we start making solar panels which use lunar material for around 99% of their mass. This is the era when SBSP really starts to take off. Now let's look at a sophisticated, pneumatically-driven industrial system working in some orbital factory. At this stage of the process, perhaps the large steel parts of this system are manufactured locally, with ET materials. But the computer which guides the system is still being bought from Earth. But the computer is only a smallfraction of the weight of the heavy steel parts, so this is still significant leveraging with ET materials. At a later stage, some of the components of the computer system are being made locally, but the computer chips are still being boosted up from Earth. Fortunately, their weight is trifling. Earth-lift costs, which once dominated over everything,are becoming a vanishing fraction of the total expense. Only at a much later stage might even the computer chips be manufactured in orbit from ET materials. But that will be the stage where we see two separate, independentbranches of human civilization: the Earth branch and the space branch. That time is a very long time off. But I think you can see how use of space materials can get us to significant leveraging even at the much earlier stages, by initially attacking the "big dumb stuff" i.e. things of large mass which require lower levels of processing and manufacturing.