Re: Delta IV plume question

From: John Schilling (schillin_at_spock.usc.edu)
Date: 12/29/04 

Date: Tue, 28 Dec 2004 20:23:49 -0800
To: sci-space-tech@moderators.isc.org

Reed Snellenberger <rsnellenberger@houston.rr.com> writes:

>Malcolm Street wrote:

>> John Schilling wrote:

>>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.

>It looks to me more like shock-wave interactions between the outboard
>plumes and the central plume. The "streak" brightens and dims in a
>regular pattern, much like the shock diamonds in the exhaust from a
>single nozzle.

Except that A: shock diamonds are usually clearly visible when shocks
interact in such fashion, but aren't visible here, and more importantly
B: the same effect was observed in a test of a *single* RS-68 which
could not possibly have been participating in any multi-plume interaction. 

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