🚀 go-pugleaf

People keep debating the merits of 2sto vs ssto, and are overlooking what
I think is the main consideration.

In climbing and accelerating to orbit it can be said there are 2 distinct
environments in which the rocket operates.  Near liftoff, there is
substantial atmospheric pressure and aerodynamic loads as the rocket
accelerates through 'max-q' and towards the 2nd environment: near vacuum
conditions at altitudes above about 200,000'.

So, for the 1st environment, the 1st stage should have the durability to
cope with the aerodynamic loads and have engines optimised for use in
atmpsphere.  As the velocity attained by the 1st stage will be less than
the exhaust velocity, the mass ratio and specific impulse will be moderate.

Also, a means of recovery would be built into the 1st stage (but not nec.
the 2nd).  The 1st stage might also have a shroud to contain and protect
the 2nd (for small rockets, at least).

The 2nd stage will have the highest Isp possible, a large nozzle for the
vacuum conditions, and little or no consideration for aerodynamics.

The general idea, it seems, is not to take any component or capability
of the rocket past the point it is needed.  ie, wings, landing gear,
parachutes, rugged construction etc for low altitude conditions not go
beyond staging point.  The Saturn V is a good example--O2/RP1 for 1st
stage and H2/O2 and vacuum operating engines for altitude.
-- 
Charles Pooley                  ckp@netcom.com    GEnie  c.pooley
EE consultant, Los Angeles, CA