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Aerospace plane with atmospheric oxygen collection for oxidizer supplying on rocket part of trajectory is very attractive concept. The key unit of power plant of such plane is an air liquefaction and separation system. It is proposed to accomplish the oxygen extraction on the bank of vortex tubes of special kind. The compressor of low speed turbojet engine would served in oxygen collection phase of flight as pressure generator for air separation system. Poor air after oxygen extraction is supposed to use actively in one of power plant combustion chambers. The configuration of integrated air separation and propulsion system and results of estimation of system using on two stage aerospace plane are discussed.

Using LH2 heat sink capacity for air precooling in turbojets allows to increase specific impulse and in many cases to reduce specific mass (mass-to-sea level thrust ratio). A number of precooled turbojet schemes are considered. Classification of turbojet according to the cooled air amount and depth of cooling is proposed. ATR with extended precooling (Tout=100K) is examined in more detail. For propulsion systems including different types of engines, running simultaneously the concept of LH2 heat sink capacity concentration for turbojet air precooling is proposed.

Hydrogen-air heat exchanger (HEX) and condensor in the engines with air precooling amount to, by various estimations, (in different schemes) 20-40% of total engine mass. The influence of some heat transfer increase methods on cooler mass and size is discussed. Atmospheric air cooling may result in frost formation on cooled surfaces and heat exchanger characteristics deterioration. The location of probable frost formation zones in different conditions may be determined by using two- dimensional mathematical model of heat exchanger. The model experimental study of frost formation was carried out. The quantitative parameters of this process are discussed. It was found that both reduction and increase of heat transfer may be obtained according to flow regime. Significant instability of flow with air condensation accompanied by large pressure pulsations was obtained. Methods to prevent the phenomenon are under study.