Stephen,
OK. After thinking a bit more about it, Ron may have supplied a good reason why this won't work, unless you can drive a turbo-compressor efficiently with an electric motor?
...and the idea may have been a bit hastily concocted anyway, but...
If you just use the tether as a guide line and a long extension cord, you might as well dispense with it entirely for all that it's buying you.
In the event that some of these problems have solutions, don't forget the tether is carrying megawatts of power "up" so it is far more than just a guide line. If you can engineer an elevator-type lifter, which will fit around the tether, so that it can induce its own power parasitically, then a fraction of the electrical current will drive the lifter's separate propuslsion system (maybe something like an Moller aerocar turned 90 degrees)... get the picture?
The lifter then can shuttle small loads back and forth, continually from the ground-up - to the limit of load-carrying ability of the drone, which may be small. I guess the wingspan of the drone would have to enormous with the air being that thin, but imagine a U2 airplane, scaled up and with electrically driven fan compressors, but perhaps much larger fuselage.
If loads of only 100 kg are shuttled upwards, and each takes an hour, round trip, then in a few days you have a pretty large third stage payload with rocket engine, in effect an assembled composite, ready to launch above most of the atmosphere - one which has dispensed with the first two stages and maybe 90% of the weight and cost of a normal launch? who knows? this is very green, admittedly.
....and I am going to leave it that way for now and get back to something which is cutting edge, but more likely to be possible soon - the Gaia subcritical reactor.
Anybody who want to improve on this tether idea is free to do so, and if you pass Ron's flight test criteria, then you can name it after yourself... hey, the Lawrence Expressway sounds fitting (which is a local joke in the SV, as it is many lanes but far from "express")...
Jones
