SI-C inboard engine shutdown

Did the inboard engine on the SI-C shut down on all flights? This PDF
http://www.klabs.org/history/reports...1970023342.pdf
figure 2 doesn't show a drop in acceleration for the SI-C (as it does
for the S-II).
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On Tue, 04 Aug 2009 15:02:37 -0400, Jud McCranie
wrote:

Did the inboard engine on the SI-C shut down on all flights? This PDF
http://www.klabs.org/history/reports...1970023342.pdf
figure 2 doesn't show a drop in acceleration for the SI-C (as it does
for the S-II).

And it shows a max of about 4.5 Gs whereas the manned missions had
about 3.9.
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In article ,
Jud McCranie wrote:

On Tue, 04 Aug 2009 15:02:37 -0400, Jud McCranie
wrote:

Did the inboard engine on the SI-C shut down on all flights? This PDF
http://www.klabs.org/history/reports...1970023342.pdf
figure 2 doesn't show a drop in acceleration for the SI-C (as it does
for the S-II).

And it shows a max of about 4.5 Gs whereas the manned missions had
about 3.9.

The center engine was shut down to prevent "pogo" effect, where the
acceleration and vibration created extra pressure head in the
propellant, resulting in extra thrust and structural resonance at
approximately 1 Hz, which is harmful to humans aboard.

This phenomenon was discovered in the first (unmanned) flight; shutdown
times were varied so as to reduce pogo.

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On Tue, 04 Aug 2009 23:50:34 -0400, Orval Fairbairn
wrote:

This phenomenon was discovered in the first (unmanned) flight; shutdown
times were varied so as to reduce pogo.

Actually it was the second Sat V (Apollo 6) that had the pogo, so that
chart must have been from A4 or A6.
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Orval Fairbairn wrote:

The center engine was shut down to prevent "pogo" effect, where the
acceleration and vibration created extra pressure head in the
propellant, resulting in extra thrust and structural resonance at
approximately 1 Hz, which is harmful to humans aboard.

It's not just that it's harmful to humans at that particular
frequency, it's that pogo (whose frequency varies with vehicle) is
high amplitude and thus potentially damaging to structure and systems.

D.
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Oct 5th, 2004 JDL

"Derek Lyons" wrote:

The center engine was shut down to prevent "pogo" effect, where the
acceleration and vibration created extra pressure head in the
propellant, resulting in extra thrust and structural resonance at
approximately 1 Hz, which is harmful to humans aboard.

It's not just that it's harmful to humans at that particular
frequency, it's that pogo (whose frequency varies with vehicle) is
high amplitude and thus potentially damaging to structure and systems.

On Apollo 6, it actually caused some of the outer laminated material
covering the conical Lunar Module adapter between the third stage and the
command/service module to sheer away from the launch vehicle. They were
very close to a total structural failure on the SLA during that launch due
to pogo.

T.B.