[LINK] SR-71 / Valkyrie was: Finally up to date on the Shuttle

hartr@interweft.com.au hartr@interweft.com.au
Thu, 20 Feb 2003 09:37:44 +1000 (EST)

On 17 Feb, Robin Whittle wrote:
> Curiously, ordinary, non-ram-jet, jet engines have to have their intake
> air slowed down to subsonic speeds.

This is hardly curious...think of the what would happen as supersonic
air hit the stationary and rotating compressor blades. The compressor
(of necessity) must handle subsonic flows after all (as of course must
the turbine).

There have been a number of concepts on the 'turbo/ram/rocket'
principle, which involve feathering the compressor/turbine blades to
allow the engine to become a ram jet and (by sealing the front end of
the combustion chamber) a rocket. None of these has proceeded beyond the
lab (AFAIK).

The Concord handles this problem by careful design of the engine
intakes. At supersonic speeds, the intakes induce a pair of inclined
shock waves to reduce the airspeed to below Mach 1 (and incedentally
preheat and compress the engine air).

Robert Hart					 hartr@interweft.com.au
Strategic IT & open source consulting                +61 (0)438 385 533
Brisbane, Australia			    http://www.interweft.com.au