"The conventional TJ cycle can function up to approximately Mach 3. This upper limit results from the high air stagnation temperature in front of the compressor and the associated compressor performance deterioration. At high freestream Mach numbers, air compression is no longer important for cycle thermal efficiency, and compressor survivability is threatened by the high stagnation temperature of the captured air. The current technology limit of 650 K is soon reached even with 4:1 pressure ratio systems. Existing TJ technology therefore requires very
advanced materials and cooling technologies to make a realistic Mach 4 system. Any higher flight velocity than this is currently technically impractical."

"The SteamJet Cycle is based upon conventional TJ technology using hydrocarbon fuel that will allow vehicle acceleration with a single engine up to Mach 6+ without significant design modifications."

"The proposed solution ...snip... involves an inlet flow conditioning device consisting of a water injection system in front of the conventional TJ compressor that will reduce the high incoming air stagnation temperature and keep the compressor at its efficient operating point, thereby allowing for higher operational Mach numbers."

"Patent US 6,202,404 covers the injection of any "consumable cooling fluid into the air at a variable rate, reducing the temperature of air entering a compressor of the engine." If a major goal is to keep air temperature within the appropriate temperature range (from a compressor materials and aerodynamics prospective), water is probably the best candidate for the cooling fluid due to its possessing the highest latent heat of evaporation value among known
fluids. Thus, water-specific enthalpy change from the liquid state to the temperature of 600 K, which seems to be an upper limit of the air entering the compressor, is 4 to 5 times higher than that of LOX. However, the use of an oxidizer for precooling has the advantage of allowing the TJ combustor to remain in operation to a higher altitude."

source

The study shows that MIPPC works best with turbojet engines rather than turbofan engines. The RASCAL microsat launcher is supposed to accelerate vertically and achieve an altitude of 100,000 ft (30 kilometers) before launching its microsat rocket.

Coincidentally, this would be a great technology for an ARMXER Orbital Skyhook rendezvous scenario. But private companies worldwide ought to have this technology to make the 17000+ launches annually possible (glad that patent is only valid in USA! heh heh).