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liquidosu.jpgMars Space Ltd following a study performed for the University of Southampton by S.B. Gabriel and M. Coletti is currently preparing a proposal for the European Space agency Innovative Triangle Initiative (ESA-ITI) to study build and test advanced injectors for liquid propellant rocket engine in partnership with a big European company operating in the rocket engine market.

In a chemical rocket engine, injection is a key process realizing feedback couplings of the combustion chamber with other engine components. In addition to its main function of injecting propellant and preparing a combustible mixture, a liquid-propellant injector simultaneously acts as a sensitive element that may generate and modify flow oscillations because of its intrinsic unsteadiness and interactions with the combustion-chamber and feed-system dynamics. Injectors always function in non steady flow environments and are therefore considered as a dynamic component of an engine, as they may generate and modify flow oscillations.

Critical to achieving good performance is the atomization process, whereby the propellant and oxidizer are transformed into small droplets; in essence the size of these drops determines the mixing process and evaporation rates, which have a profound influence on the combustion reactions. Optimal mix between the fuel and the oxidizer allows achieving efficient and stable combustion and ultimately the required thrust without endangering hardware durability. 

Several injector design inspired by alternative technologies have bee already studied for their potential to yield a new, more active injection scheme for a rocket engine. Some of these technologies have theorically demonstrated high potential for the high atomization rate, the precise control they offer, and the possibility of full throttling control, varying the mass flow rate (hence the thrust) from zero up to its maximum value, along with active control of combustion instabilities, and increased efficiency.

The requirements needed by these "active" injectors to be actually used inside a rocket engine will be defined together with the performance required to provide a sensible improvement in the rocket engine performances to justify their application.

Basing the judgment on technical, economical and practical consideration a develop candidate will be chosen between these three kind of injectors. A prototype of the chosen injector will then be designed, built and tested to assess its real performances in term of power consumption, droplets size distribution and mass flow rate throttling capabilities.

The control over the mass flow rate gives the possibility of throttling the engine changing the thrust across a wide range of values allowing for a wider range of manoeuvres. Since the mass flow rate can be controlled in every single injector and since in the combustion chamber there is a number of injectors there is also the possibility of controlling the local fuel/oxidizer mixture ratio hence giving the possibility of controlling the heat flux to the chamber walls and of actively controlling combustion instabilities.

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