If you could find a euctectic mix of oxidizers that melted at around 100'
C, and asphalt or euctectic sugar or peg with similar melt temp, you could
have a fully steam heated rig with proportional pumps and use a static
mixer to mix the fuel and ox as they were pumped into the heated casing.
No solid loading issues, no significant amount of mixed propellant outside
the motor, no voids issues.
Would maybe have to control crystalization and flexibility.
Burn catalysts etc could be premixed in the fuel component.
jim fackert