I suspect the challenges associated with digging and maintaining the 1km deep holes at each end of the runway might get in the way of an otherwise excellent idea! You could of course make them shallower with some pulley's but I think that would interfere with the aesthetic simplicity of the idea.

Mark.

On Monday, September 3, 2018 at 6:45:05 AM UTC+10, Chris Rowland wrote:

I've wondered if the best way to launch is by gravity, a weight falling
into a mine shaft and attached to the glider by a cable. If you have a
supply of water then the weight is by filling a tank. At the end of the
launch you dump the water, pull the much lighter tank back up, then refill
it. Given enough room you could have a circular airfield round the mine
shaft. The only energy that you need to supply is to retrieve the tank and
cable.

A few things to sort out but it's a start.

Chris