I remember seeing this a few years ago on UK freeview (so I guess that must help narrow it down), although I can't remember whether Beeb, ITV, Ch4 or 5...
An interesting documentary covering flight and the space race. It does feature Nazi's Bell and the Fly trap and talks about nuclear-powered space craft, and also talks about UFO citings and whether a convenient cover up for US black projects, defection of Nazi German scientists to the States...
I seem to remember it's narrated by a British chap, was probably about an hour long.
I've searched everywhere on youtube but can only find American docs that hover around the subject but not the actual one I'm looking for.
Does that ring any bells with anyone (multiple puns not intended!)?