Re: Delta IV plume question

From: Malcolm Street (mstreet_at_internode.on.net)
Date: 12/26/04 

To: sci-space-tech@moderators.isc.org
Date: Sun, 26 Dec 2004 14:20:30 +1100

John Schilling wrote:

Hmm... The core engine IIRC is only going at c. 58% thrust at liftoff, so
its operating conditions are different from the two strap-ons which are
going flat-out.

Wonder if this lower power makes it more liable to combustion instability
during liftoff?

> Except, the core engine *only*, is showing a streak of bright
> yellow down the center of the plume. In this picture, but not
> it others that I have seen.
>
> I saw the same thing, firsthand eyewitness, during I believe
> the penultimate RS-68 test at the AFRL/Edwards site. About
> three-quarters of the way through the test, the abrupt onset
> of a yellow-streak flame in the plume, vanishing equally
> abruptly a few seconds later. So, a transient event, but not
> a start or stop transient. Consistent with it showing up in
> the BBC photo but not all the rest, and now that we have a
> photo I'm confident that it's real. 

-- 
Malcolm Street
Canberra, Australia
The nation's capital