A very enlightening letter written by Mr. Clarke saved by Letters of Note (an excellent online resource for all sorts of obscure letters, memorandums, etc.).
He may also have been the first person to propose satellite communications, in a 1945 article in the ‘Wireless World’ magazine, though I do not have acces to the original source to confirm.
A bit of imaginative thinking married with practical technical knowledge goes a long way it seems.
M. Y. Z. 