Reusable first stages using hydrogen-oxygen, hydrogen-fluorine
and kerosine-oxygen are compared with non-reusable stages using a solid
in addition to the liquid combinations. The criterion used for comparison
is the minimum specific cost of the "loaded and ready for launch"
stage cost per unit of stage payload mass. A closed form relationship
is used in which the empty stage mass without payload is taken to scale
in part proportional to propellant mass, and in part to mass flow rate.
The stage specific cost is proportional to specific cost of engine (or
nozzle) tank and propellant. In the second part the hydrogen-oxygen
combination is consiaered,in more detail. The sensitivity of the
results to changes in various specific costs including that of refurbishing
are described.
Throughout, the stage velocity increments are compared in the
3000-6000 metres/second range with losses
