"Charles Talleyrand" wrote in message
...
It seems that for rockets of multiple stages with only one fuel
combination,
there is an interesting engineering decision.

Consider a two stage rocket where both stages burn the same fuel
combination.

You could use 1 engine for the upper stage, and 4-ish engines of the same
design for the lower stage. The advantage is that you need only design
one
engine type. The disadvantage is that with 4-ish engines on the lower
stage
you probably cannot tolerate an engine failure, and clearly not a
catastrophic
failure.

Use five, one in the center, and design so that 3.5 or 4 at rated thrust
would be sufficient. Then, run 5 at 80-90%; if the center engine dies, the
others can be revved up. If an outer one dies, the opposite one can be cut
back for balance while the others rev up.
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