The current paper provides an outline and first results of the ESA-EMAP project. This project pursues activities regarding the experimental modeling of alumina particulates in solid boosters (EMAP). The issue regards the particles residing in the atmosphere after the passage of a launch vehicle with solid rocket propulsion, which might contribute to local and overall ozone depletion. The question is to what extent since the particle size distribution left behind is essentially unclear. For this reason, the ESA-EMAP investigations focus on the characterization of the solid exhaust plume properties for well-defined combustion chamber conditions. Thus, details of the rocket motor assembly, of the developed solid propellant grains, and of first measurement results are provided. The paper presents technical findings concerning the rocket motors and reveals aspects to the feasibility of the applied measurement techniques.
Aluminum combustion in solid propellants generates condensed products leaving the burning surface. The population of this particles is quite wide, spanning from smoke-oxide to molten metal drops. Their properties depend upon both intrinsic propellant features and combustion conditions (e.g. composition, microstructure, combustion pressure, and propellant burning rate). In propellants, aluminum is typically used in the shape of a micrometric powder. This class of energetic materials produces spherical agglomerates having the size between some tens to few hundreds of micrometers. When the metal fuel turns to nanometric, flake-kind aggregates emerge from the burning surface. Some macroscopic properties, such as the burning rate, are affected. This paper presents some results obtained from a set of aluminized propellants based on inert binder (hydroxylterminated polybutadiene) and ammonium perchlorate. The effect of both powder size and pressure is explored in terms of ballistics and condensed combustion residues. A nonstraightforward trend with pressure emerges when the condensed combustion products of propellants containing micro-aluminum and nano-aluminum are compared.
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