[AR] Re: B-58 \ was Ozone etc.
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Fri, 23 Sep 2016 14:15:03 -0400 (EDT)
On Wed, 21 Sep 2016, William Claybaugh wrote:
I'm in agreement with your broad point... But....
... As the J58 showed, the path to a supersonic engine is not all that
obscure; one _just_ needs to replace the compressor section with blades
that will take the high temperatures coming out of the inlet...
Here I will agree with Bill, with minor reservations. Yes, until you get
into lunacy like scramjets, the engine proper is always working with
subsonic air; all the real excitement is in the intake, and to some extent
the exhaust nozzle. So the only big difference the engine sees in
supersonic flight is that the arriving air is hotter, which will affect
materials choices.
The "minor reservations" part is that there might be small subtleties that
also have to be handled, things that were dealt with half a century ago by
rule of thumb and didn't rate mention in the historical accounts. With
the old designers all gone (people who were then junior engineers working
on small details don't count for this), nothing short of actually building
and running an engine can positively eliminate this concern; simulations
are not enough. So a bit of caution is in order.
(A historical example of the sort of difficulty that can crop up: nobody
expected big difficulties in integrating the first afterburning turbofans
into a fighter prototype -- they were just like turbojets, right? Well,
no, it turned out that they weren't: they were rather more sensitive to
irregularities in the incoming airflow, and the original F-111 intake
didn't try hard enough to give the engine smooth air. The result was
terrible problems with compressor stalls -- cascading flow separation in
the compressor -- that contributed heavily to the F-111's massive cost and
schedule overruns.)
It's not an impossible problem and the market for supersonic b-jets
(north of 200 units) does appear to justify that investment.
Agreed. We should have some real data on this soon.
Henry
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