Confused by Mixture ratios

From: David Findlay (david_at_davsoft.com.au)
Date: 07/25/04 

Date: Sun, 25 Jul 2004 20:55:49 +0000

According to the astronautix site, the SSME's use an oxidiser to fuel ratio
of 6. I read that to mean that by mass, it uses 6 times as much oxidiser as
fuel. Is this correct? I'm using the density values 71 kg/m^3 for liquid
hydrogen and 189 kg/m^3 for liquid oxygen. This would mean there would be a
greater volume of liquid oxygen than liquid hydrogen in the space shuttle
ET. Why then is the Fuel tank larger than the oxygen tank?

I don't think i'm wrong in my interpretation of the O/F ratio value, because
a book I have use O/F ratio as a mixture value, and it shows that an O/F
ratio of 2.5 means 2.5 times more oxidiser by mass than fuel. So where am I
going wrong here, or is there something I'm not thinking of? Thanks,

David

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