A prototype engine based on a new compressive combustion principle due to colliding pulsed supermulti-jets for aerospace was designed and developed by ourselves, in order to achieve very high thermal efficiency even for small combustion chambers. Experimental results on combustion reliably suggests high compression, combustion noise level comparable to that of traditional engines, and nearly-complete air-insulation effect on combustion chamber walls. While combustion at a lean burning condition occurs for the upstream fuel tank condition of about 3bar and for only a very small combustion-chamber diameter of 18mm, we also measured the thrust over about 100 N. Then, conversion evaluations based on the experimental data show that the present new engine due to the supermulti-jets colliding with pulse has a potential of thrust comparable to those of recent rocket engines having high thermal efficiency due to recycle of heat from chamber wall. If some geometrical optimizations are added, we get a possibility that thermal efficiency of the present new engine will be over 50%. Maximum thrust may be large because pulse type of combustion induces large pressure difference between upstream and downstream of combustion chamber, i.e., negative pressure in chamber after combustion, which leads to more gas supplied into the chamber.