The aim of this paper is to investigate LOx/HC engines (focusing in particular on methane and kerosene as propellant), in order to evaluate their capability to support space activities in the frame of RLV scenario. Analysis at system and technological levels are made referring to engines of 200 -300 tons of thrust to be used in cluster configuration on future RLV. The considered architectures are cluster of 2 engines for booster configurations, and cluster of 3 engines for first reusable stages of future TSTO with cryogenic second stage. A trade off analysis of different LOx/HC propellant pairs is performed, whose main result is that LOx/CH 4 is one of the best possible choice for RLVs first stages, due to high methane cooling capability and performance. A comparison between kerosene and methane fundamental physical-chemical and termodynamical properties is reported too. The paper is divided in 3 sections: system analysis, propulsion technologies, thrust chamber. The first section is devoted to system level analysis about launch vehicles coupled with reusable engines, in order to define capability and operational flexibility. The second section is dedicated to key technologies for new reusable 200 -300 tons class engines, particularly focusing on materials, cooling and injector plate issues.In the third section injection of liquid oxygen and gaseous methane in supercritical conditions is analysed.Finally a roadmap on the development of a reusable engine related technologies is proposed.

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The paper presents the design of the pressurization system of the European Service Module (ESM) of the Orion MultiPurpose Crew Vehicle (MPCV). Being part of the propulsion subsystem, an electrical pressurization concept is implemented to condition propellants according to the engine needs via a bang-bang regulation system. Separate pressurization for the oxidizer and the fuel tank permits mixture ratio adjustments and prevents vapor mixing of the two hypergolic propellants during nominal operation. In case of loss of pressurization capability of a single side, the system can be converted into a common pressurization system. The regulation concept is based on evaluation of a set of tank pressure sensors and according activation of regulation valves, based on a single-failure tolerant weighting of three pressure signals. While regulation is performed on ESM level, commanding of regulation parameters as well as failure detection, isolation and recovery is performed from within the Crew Module, developed by Lockheed Martin Space System Company. The overall design and development maturity presented is post Preliminary Design Review (PDR) and reflects the current status of the MPCV ESM pressurization system.

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