Re: Lufthansa Chair sees no superjumbos

From:         Don Stokes <Don.Stokes@vuw.ac.nz>
Organization: Victoria University of Wellington
Date:         10 Jul 95 03:18:20 
References:   1 2 3 4
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mezei_jf@eisner.decus.org writes:
>With today's technology which can produce the stealth bomber, is it reasonable
>to expect that a second generation SST plane would generate a much "quieter"
>sonic boom ? Can they not create a plane whose shape and materials and engines
>attenuate the sonic boom ?

A radar invisible SST would not give ATC a happy feeling.  8-)

Seriously, Stealth is achieved by going subsonic and using an airfoil
composed of flat plates which reflect radar in directions other than
back to the source, rendering the aircraft invisible, as opposed to
curved surfaces that reflect radar in many directions incluing back to
the source and hence to the enemy's screens.

>I know that part of the reluctance to allow the Concorde to land was the high
>noise during the take-off and landing. Was that the major stumbling block for
>the Concorde, or was it really the sonic boom while it was at cruising altitude

Take-off noise is the big issue.  Supersonic aircraft cannot use a high-
bypass engine.  Concorde's intakes use a system of "ramps" to bring the
(relative) speed of the air coming into the compressor down to 0.5 Mach
so that the compressor fan can deal with it.  This only works because all
air entering the engine goes into the compressor.  Bypass would actually
slow the aircraft down.

Some noise reduction is achieved in subsonic flight by use of the nozzles,
which in subsonic configuration channel "unburnt" air around the exhaust,
but there weill never be the 5:1 or more bypass ratio found on large
subsonic transports.

--
Don Stokes, Network Manager, Victoria University of Wellington, New Zealand.
don@vuw.ac.nz(work) don@zl2tnm.gen.nz(home) +64 4 495-5052 Fax+64 4 471-5386