Abstract
A series of the firing rest was conducted to obtain the history of the instantaneous value of the fuel thickness during the firing test. An ultrasonic pulse-echo method was used to the firing test for that purpose. Gaseous oxygen and polyethylene were used to the firing test about the combustion of the solid fuel in the oxygen jet collision area. A preliminary experiment revealed that the variation of the propagation time caused by the change of fuel temperature is negligible small because the thermal boundary layer in the solid fuel is thin. The fuel regression rate at the stagnation point of oxidizer jet depends on Reynolds number.
