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| | | |-+  During Apollo 11 Quickstart, is the center SII engine supposed to cut off early?
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Author Topic: During Apollo 11 Quickstart, is the center SII engine supposed to cut off early?  (Read 1257 times)
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« on: May 10, 2009, 03:55:14 PM »

Is that normal procedure? Or did something go wrong?
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Tschachim
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« Reply #1 on: May 10, 2009, 04:13:50 PM »

normal procedure
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Shadow Addict
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« Reply #2 on: May 10, 2009, 05:11:42 PM »

Thanks!
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bluespace88
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« Reply #3 on: May 11, 2009, 08:56:29 PM »

Some background on that:

Apollo 8 and 9 both had all 5 engines on the SII stage burn until fuel was exhausted, but there were pogo oscillations reported by the crews during the latter stages of the burn, and this was (I believe, correct me if I'm wrong) due to the center engine causing the oscillations, so beginning with Apollo 10, the center engine was shutdown early to prevent it from occuring.  While it did not solve the problem totally, as seen with Apollo 13, it did help reduce them during launches.

And on another note, the S1C center engine was shutdown for another reason, that being to reduce the acceleration on the booster as it ascended and got lighter.
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