A closed-type strand bomb was used to trap all species participating in solid propellant combustion to measure combustion efficiencies of aluminum (Al) and boron (B) using titration techniques. Variations of combustion efficiencies (17) of Al and B with pressure and oxidizers of propellants were investigated. In order to improve B combustion, effects of the addition of Al, granulated propellants, and oxidizers were also investigated. It was found that burning of B particles could be enhanced by using fine powders. Boron particles granulated with potassium nitrate had the highest r/B (40%) in the strand burner. Burning of Al was found to be hindered by B burning when Al and B particles coexisted. These observations could be interpreted by considering the agglomeration and ignition processes of metal particles.

Combustion Efficiencies of Aluminum and Boron in Solid Propellants

Complexes of nitrocellulose (NC – low and high nitrogen content) with copper oxide (CuO) have been synthesized and studied for morphological behaviour on heating from room temperature to 500°C with the help of hot stage microscopy (HSM).

Combustion Behaviour of Nitrocellulose and its Complexes with Copper Oxide. Hot stage microscopic studies

The aging of propellants in PMDs is considered to be one of the primary factors affecting the performance of PMDs. Thus, studies on the aging mechanism of propellants, which have not yet been addressed extensively, pose a solution to securing the sustainable operation of PMDs. We characterized one of the most commonly used commercial propellants (boron potassium nitrate (BKNO3)) and investigated its aging mechanism rigorously. Based on thermal analyses, we demonstrate that the decomposition of laminac, a polymer binder, is the fastest spontaneous reaction. However, it will not self-initiate at a storage temperature as high as 120 °C. The effect of the humidity level was examined by characterizing BKNO3 samples prepared. The heat of reaction and the reaction rate decreased by 18% and 67% over 16 weeks of aging, respectively. This is attributed to the oxide shells on the surface of boron particles. The formation of oxide shells could be confirmed using X-ray photoelectron spectroscopy and transmission electron microscopy–energy dispersive spectroscopy. In conclusion, surface oxide formation with the aging of BKNO3 will decrease its propulsive efficiency; oxidation reduces the potential energy of the system and the resulting oxide decreases the reaction rate.

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Study on the Aging Mechanism of Boron Potassium Nitrate (BKNO 3 ) for Sustainable Efficiency in Pyrotechnic Mechanical Devices

Probing boron thermite energy release at rapid heating rates

A laser ignition microthruster was developed for microspacecraft propulsion. Small solid-propellant pellets were ignited by a diode laser beam to produce a high impulse from a very small power source. Basic experiments showed that the microthruster produced an impulse of 60 mNs, using 60 mg B/KNO3 pellets ignited by a 1 W laser beam. A space-based demonstration of the microthruster system is planned onboard a microspacecraft named KKS-1, which has been chosen by the Japan Aerospace Exploration Agency as one of the six small satellites to be launched with the Greenhouse Gases Observing SATellite, which is scheduled to be launched on a H2A rocket in early 2009.

Yutaka Yano

Papers

Condensed phase reaction of boron with potassium nitrate