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From: (Henry Spencer)
Subject: Re: Did we land on the moon ????
Date: Mon, 19 Feb 2001 01:58:47 GMT

In article <>,
JF Mezei  <> wrote:
>The one thing that has always bugged me about Apollo 13 is that according to
>the movie, when it takes off, there is a few seconds where the exhaust seems
>to go in reverse and appears to be sucked back towards the base of the rocket.

That's authentic, although it wasn't very obvious in the usual Apollo
launch footage.  The F-1 start sequence was sort of slow and ponderous,
and the engines initially belched out smoke and flame at relatively low
velocity, so it sort of billowed out in all directions.  And then the
pumps came up to speed and the main fuel valves opened, and quite suddenly
there were 15 tons per second of gas going downward into the exhaust duct
at two and a half kilometers per second, and that generates rather a lot
of suction.
When failure is not an option, success  |  Henry Spencer
can get expensive.   -- Peter Stibrany  |      (aka

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