Re: [NTLK] up in the sky

From: Eric L. Strobel (
Date: Mon Jun 24 2002 - 09:48:52 EDT

on 6/23/02 6:15 PM, Karel Jansens at wrote:

> Um, IANAE but... I don't think the SR-71's jets ever operate as ramjets.
> The huge cones (which are adjustable) serve to keep the air intake speed
> below mach 1. It is true that the compressors don't do much compressiong
> anymore at cruise speed, but they keep churning...

Yes and no... As Mark Bock pointed out, at operating speed a substantial
amount of the compression is coming from the ram pressure of the air.
Depending on the speed, one might term it a ram-assisted turbojet or a
turbo-assisted ramjet. But I don't recall anyone ever terming it as simply
a ramjet.

> Technically I'd say the V1's engine is a ramjet because it gets all its
> compression from the air itself but, because it operates at low speed (way
> below mach 1), it needed mechanical aids to achieve that compression, i.c.
> the valves in the combustion chamber.

No, think of it more as a linear internal combustion engine. The
distinction is that in a true ramjet, the inlet compresses and slows the
incoming supersonic air flow to subsonic speeds. The thermal energy
released in this process is so great that it heats the fuel-air mixture to
the ignition point. In the buzz bomb-type pulse jet, as in an internal
combustion engine, IIRC, the ignition source is separate. (That is, it I
don't think it was 'dieseling'.)

> Isn't a supersonic ramjet called a 'scramjet'?

That's a ramjet where the fuel and air mix and combust while the incoming
air is still moving supersonically, in sharp contrast to the ramjet
operation (as outlined above). The reason it's taking so long to build a
scramjet is that mixing and supersonic flow are damn near mutually

- Eric.


Eric Strobel (fyzycyst_at_NOSPAM^

===================================================================== The odds are greatly against you being immensely smarter than everyone else in the field. If your analysis says your terminal velocity is twice the speed of light, you may have invented warp drive, but the chances are a lot better that you've screwed up. =====================================================================

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