“…In order to become an acceptable technology for in-flight LOX separation, it is necessary to achieve in vortex tubes a minimum oxygen purity of 90% for the oxygen enriched stream. Otherwise impurities in the combustion can significantly reduce the specific impulse and therefore the thrust of the liquid propellant rocket [5]. Also, the yield or separation efficiency of LOX, which is the ratio of oxygen mass in the enriched stream to the oxygen mass in the inlet stream, has to be greater than ~60% to make the LOX separation process viable for launch vehicles.…”