[AR] Re: FW: [NASA HQ News] NASA’s Wallops Flight Facility Completes Initial ...
- From: Peter Fairbrother <zenadsl6186@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Thu, 30 Oct 2014 23:34:56 +0000
On 30/10/14 18:49, (Redacted sender JMKrell@xxxxxxx for DMARC) wrote:
It just missed falling back on the pad. I did a frame by frame analysis
of the NASA video. It shows one engine going fuel rich starting with
yellow exhaust changing to a yellow/red exhaust flame color followed by
a fire in the aft section. At 1 second into the event there is a bright
flash from the aft section coupled with a horizontal radial
flame ejecting multiple parts at high velocity.
To me, it appeared like a burn through in the duct between the turbine
and main combustion chamber changing the O/F mixture and chamber
pressure. The change in pressure across the turbine resulting in an over
rev failure of the turbine/pump assembly.
Regen cooling failure would also change the O/F mixture, but I
would place the duct failure at the top for elimination from the visual
data I have.
Sounds likely - that large-diameter duct vibrates a lot, with one end on
the turbine shaft assembly and the other on the chamber, it contains hot
dirty high-pressure oxygen, and after the turbine it is probably the
second most demanding part of the engine in material terms.
The duct, the turbine and it's NGV are the parts which US rocket
engineers did not believe when the Russians announced an oxygen-rich
staged cycle engines.
I have heard the duct has also been problematic on the RD-170 and -180.
-- Peter F
Krell
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