Space 21: On Payloads and Magic Mirrors

(…a curious observation about relativistic light-sails, … followed by a teentsy bit of obligatory, if undeserved, "Stargate: Universe" bashing.)

A couple of questions that come up in trying to imagine how the interstellar transit economy/infrastructure is all going to work:

1. Is there some ideal size for a solar power satellite?
   This to some extent lies at the heart of my questions of what the solar power extraction regime is going to look like, what orbits we're going to prefer, how many satellites we'll be needing to build, how close to the sun they need to fly, etc.
   
   
2. How big a mirror/solar-sail are we going to need to propel our interstellar payloads?
   This will be a central issue in transit tube design since it affects everything else, e.g., how far apart the laser ships need to be, how much antimatter they will need to be supplied with, etc.

Reviewing what I said earlier on the subject of mirrors/sails:

[We'll need them to be] extremely lightweight, totally reflective, micrometeoroid-tolerant, blah-blah-blah. There will be some engineering tradeoff to determine the size (i.e., the smaller we make it, the more accurate the rocket/laser thing has to be, and the more energy density it has to withstand, but the less vulnerable it'll be), which I'll leave the engineers to figure out.

My original thought was that our two applications for mirror-building don't really have much to do with each other beyond their reflecting (pardon the pun) the supply and demand sides of our energy economy, that once we got into the details, the differing goals (energy collection vs. propulsion) would assert themselves and ultimately there'd be very different requirements/designs.

For one thing, for solar satellites, why care about making them lightweight? We're just putting them in orbit, and, beyond occasional questions of servicing and refurbishment, they're not going anywhere. And, if anything, we want them sturdy enough to stand up to the stress of being in however close to the sun we need them to be.

Lightweight only matters in that the less material we use, the more we can make, and we will ultimately have to be making millions of them.

It's not that any of this is wrong; we're just missing an important detail is all.

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