Ismail, A. M. (2013) Oxygen/aluminium metal powder space propulsion system : a literature review & trade-off analysis. (MSc(R) thesis), Kingston University, .

Abstract

Metal powder propulsion systems employ metal powder, rather than a fluid, as a fuel which is transported and injected into a combustion chamber where it mixes with an oxidiser, ignites and combusts to provide high thrust. This concept has been addressed intermittently since the Second World War, initially in the field of underwater propulsion where research in the application of propelling torpedoes continues until this day. During the post war era, researchers attempted to apply metal powder as a fuel for ram jet applications in missiles. The 1960's and 1970's saw additional interest in the use of 'pure powder' propellants, i.e. fluidised metal fuel and fluidised oxidiser, both in solid particulate form. Again the application was for employment in space-constrained missiles where the idea was to maximise the performance of high energy density powder propellant in order to enhance the missile flight duration by omitting the use of binders, curing agents and high energy plasticisers. Volumetric propellant density for both underwater and ramjet propulsion would decrease since the oxidiser component, sea water and ram-air, respectively, would not have to be stored within the system. These ordnance delivery systems did not however see the light of day and attention thereafter, i.e. 1980's onwards, expanded to include the use of metal powder as a possible in-situ resource utilisation (ISRU) fuel for space propusion systems where the focus was on the use of gaseous oxygen (GOX) or liquid oxygen (LOX) combined with aluminium metal powder as a "lunar soil propellant" or carbon dioxide (CO[sub]2) and magnesium powder as a "Martian soil propellant". The emphasis of this study is the use of oxygen (O[sub]2)/aluminium metal powder propellant for space propulsion rather than for terrestrial (military) applications. There are two principal objectives of this MSc by Research. Prior to this study, a literature review of metal powder propulsion systems has never been addressed; this being the first objective. The second objective was to employ the knowledge acquired from the literature review and examine all alternative subsystems via a series of detailed weighted decision matrices (WDMs) in order to determine which components would be the most appropriate to utilise in a technology demonstrator. These two tasks are seen as prerequisites to the continuation of researhc and dvelopment of metal powder propulsion systems. The literature review and WDMs comprise tow out of three main sections of the dissertation. The WDMs determined that the bimodal 3/21 [mu]m mix with a 30/70 weight distribution, respectively, was the best option for maximising packing density as well as for powder feed, powder injection and powder combustion. The cylinder connected to a hopper was the most appropriate configuration for powder storage and the mechanically actuated piston and mechanically actuated auger provided the best performance for pwder feed. The dust dispersion system met favourably with all the criteria for powder injection and the pyrotechnic squib supplied the required energy to ignite the O[sub]2/aluminium metal powder propellant. Combustion efficiency is improved by operating the engine initially in fuel-rich mode in a (pre-) combustor and then lean mode in a main combustor. The thrid section presents an ideal schematic for a technology demonstrator based on the aforementioned findings and a final section concludes with recommendations for future work.

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