In article ,
"Keith Willshaw" wrote:

wrote in message
...
On Thu, 08 Apr 2004 12:10:00 GMT, (John
Bailey) wrote:


It is interesting how far back the design elements of these aircraft
can be dated. High altitude jet aircraft technology was achieved by
the Germans in WW2. A Horton aircraft design which was apparantly
first conceived in 1931 was capable of flying at 52,000 feet.


AFAIK it never flew an inch from the ground as no aircraft
capable of flight was produced.

The Ju-86R on the other hand managed to get up to altitudes
in excess of 47,000 ft IRC

Keith



The problem with thos WW-II designs at high altitude was critical Mach
number. Designers in those days did not have a handle on Mach, or "high
speed" stall. Most airfoils in those days had a critical Mach number
around 0.75-0.80. If you exceeded this speed, the plane would "tuck
under," and you would be along for the ride until you reached higher
temperature air to raise the speed of sound and higher density air to
provide enough drag to slow you down.


The range between Mach stall and normal stall for a U-2 at altitude was
something like 3 knots.