Micro and nano-aluminized solid propellants behavior under transient burning conditions

Paper number

IAC-06-C4.2.07

Author

Dr. Luigi T. DeLuca, Politecnico di Milano, Italy

Coauthor

Dr. Roberto Dondé, CNR, Italy

Coauthor

Dr. Luciano Galfetti, Politecnico di Milano, Italy

Coauthor

Mr. Giovanni Colombo, Politecnico di Milano, Italy

Coauthor

Mr. Filippo Maggi, Politecnico di Milano, Italy

Coauthor

Dr. Laura Meda, Italy

Coauthor

Dr. Gianluigi Marra, Italy

Coauthor

Mr. Alessio Bandera, Politecnico di Milano, Italy

Coauthor

Ms Daniela Orsini, Politecnico di Milano, Italy

Year

2006

Abstract

Nanometric size aluminum can be used in a variety of propulsive or power generation devices.  A full control of these tools require an adequate knowledge of the transient burning features in addition to the usual steady laws.  It is a well-known fact that steady burning rates are sensibly increased by nano-size aluminum thanks to their large specific surfaces.  Thus, the purpose of this work is to investigate if and to what extent similar effects can be observed under unsteady regimes, in particular those involving the controlled extinction sequences occurring in multiple or repeated application devices.
Ammonium perchlorate (AP) – based, aluminized composite solid rocket propellants having the same composition (0.68 AP + 0.17 HTPB +  0.15 Al) but different aluminum particle size were contrasted in terms of steady state burning rates and extinction boundaries (due to fast depressurization or deflagration limit).  Typically, micrometric size aluminum (spheres or flakes) and nanometric size aluminum (obtained by electric wire explosion, uncoated or coated) were used for this comparative investigation.  A nonmetallized 0.80 AP + 0.20 HTPB propellant served as a reference composition.  Quasi steady-state burning rates, prior and after fast depressurization, were measured from high-speed video-recordings taken during the whole event.  The resulting go/no-go extinction boundaries were represented in terms of maximum depressurization rate vs. initial pressure.  The initial pressure ranged from 20 to 50 bar while depressurization always occurred to atmospheric pressure. 
The experimental results so far obtained show only minor differences for the nonaluminized reference propellant and the micro-Al propellant in terms of both steady-state burning rate and extinction boundaries.  On the contrary, outstanding effects were shown by the tested nano-Al compositions.

Abstract document

IAC-06-C4.2.07.pdf

Manuscript document

IAC-06-C4.2.07.pdf (🔒 authorized access only).

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