- Experimental and theoretical work in progress on supersonic COILs at Ben-Gurion University is reported. Following the achievement of a record value (40%) for the chemical efficiency of a supersonic 5-cm gain length COIL in our lab, a 10-cm gain length device was experimentally studied. Maximum output power exceeding 0.6 kW with chemical efficiency of 35% was obtained for 1% total mirror transmission in preliminary studies. Comparing the results of three-dimensional computational fluid dynamics model calculations to available experimental results [Nikolaev et al., IEEE J. Quantum Electron. 38, 421 (2002)], we show that the model is applicable to high pressure, ejector type chemical oxygen-iodine laser (COIL), reasonably reproducing the measured gain and temperature.