Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: That SRB flame
Message-ID: <1988Oct4.170712.16686@utzoo.uucp>
Organization: U of Toronto Zoology
References: <3447@ihuxz.ATT.COM> <141@enuxha.UUCP>
Date: Tue, 4 Oct 88 17:07:12 GMT

>> Since we all have been talking about this backflow theory on the SRBs,
>> I was wondering if the same didn't happen on the Saturn V first stage.
>> I seem to remember all the long camera shots looking like the last 30
>> seconds of stage 1 burn was going up the sides of the bird? Anyone else
>> remember this?

As outside atmospheric pressure drops off, the plume does extend itself
upward.  At very high altitude, a typical launcher will be enveloped
completely in its plume, which is a real nuisance if you're got a payload
that really cares about contamination.  (Or if you're trying to build a
missile-interception system and you want an infrared sensor to find the
missile, not the plume.)

>IF memory serves me correctly, I seem to recall a few rather strange facts
>relating to the development of the Saturn V.  There were a few designs, such
>as the Saturn III and Saturn IV, which were to use 3 and 4 of the F-1 
>engines respectively.  The Saturn IV was to have these engines arranged
>in a square pattern at the base of the stage.  The reason this idea was
>NOT carried through is that a SEVERE backflow...

Well, not quite.  The Saturn 3 and Saturn 4 were indeed paper designs with
three and four F-1s respectively.  However, the main reason for adding the
fifth engine in the center of the Saturn 4 was simply that it was fairly
trivial to do -- the structure was X-shaped so there was already ample
support for the center engine -- and it made for a much larger performance
margin.  It did have the useful side effect of reducing the problem with
hot-gas stagnation in the center, but that wasn't the main motive.  (See
"Stages to Saturn", one of the NASA History books, for the details.)
-- 
The meek can have the Earth;    |    Henry Spencer at U of Toronto Zoology
the rest of us have other plans.|uunet!attcan!utzoo!henry henry@zoo.toronto.edu