In article ,
Andrew Nowicki wrote:

Joe Strout wrote:

But airships (whether filled with hydrogen or helium) are.
Big ones can have a quite impressive lift capacity, too.

The problem is how to bring the balloon or the airship
back to the earth -- you would have to release lots of
expensive hydrogen.

Why? Normal airships don't release lifting gas; they compress it, by
inflating internal bladders with air. I don't see why it should be any
different for this application.

Did you consider a power source on the ground beaming power
to the helicopters in the form of lasers or microwaves?

Leik N. Myrabo experimented with this idea some 20 years ago.
It works, and it is not very expensive. The microwave
electronics would cost about $100 per 1kg of the rocket weight.
(Batteries cost about $200 per 1kg of the rocket weight.)
I did not mention microwaves because the safety concerns would
drive up the cost.

But they reduce the logistical issues. I wonder whether the safety
issues can be mitigated by careful selection of the wavelength used.

Best,
- Joe