AP HTPB PROPELLANTS PDF

Special considerations[ edit ] Though increasing the ratio of metal fuel to oxidizer up to the stoichiometric point increases the combustion temperature, the presence of an increasing molar fraction of metal oxides, particularly aluminum oxide Al2O3 precipitating from the gaseous solution creates globules of solids or liquids that slow down the flow velocity as the mean molecular mass of the flow increases. In addition, the chemical composition of the gases change, varying the effective heat capacity of the gas. The combustion time of the aluminum particles in the hot combustion gas varies depending on aluminum particle size and shape. In small APCP motors with high aluminum content, the residence time of the combustion gases does not allow for full combustion of the aluminum and thus a substantial fraction of the aluminum is burned outside the combustion chamber, leading to decreased performance. Particle size[ edit ] The propellant particle size distribution has a profound impact on APCP rocket motor performance. Smaller AP and Al particles lead to higher combustion efficiency but also lead to increased linear burn rate.

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Special considerations[ edit ] Though increasing the ratio of metal fuel to oxidizer up to the stoichiometric point increases the combustion temperature, the presence of an increasing molar fraction of metal oxides, particularly aluminum oxide Al2O3 precipitating from the gaseous solution creates globules of solids or liquids that slow down the flow velocity as the mean molecular mass of the flow increases.

In addition, the chemical composition of the gases change, varying the effective heat capacity of the gas. The combustion time of the aluminum particles in the hot combustion gas varies depending on aluminum particle size and shape.

In small APCP motors with high aluminum content, the residence time of the combustion gases does not allow for full combustion of the aluminum and thus a substantial fraction of the aluminum is burned outside the combustion chamber, leading to decreased performance. Particle size[ edit ] The propellant particle size distribution has a profound impact on APCP rocket motor performance. Smaller AP and Al particles lead to higher combustion efficiency but also lead to increased linear burn rate.

The burn rate is heavily dependent on mean AP particle size as the AP absorbs heat to decompose into a gas before it can oxidize the fuel components. This process may be a rate-limiting step in the overall combustion rate of APCP. The phenomenon can be explained by considering the heat-flux-to-mass ratio: As the particle radius increases the volume and, therefore, mass and heat capacity increase as the cube of the radius. However, the surface area increases as the square of the radius, which is roughly proportional to the heat flux into the particle.

Because of the size discrepancy between the AP and Al, Al will often take an interstitial position in a pseudo-lattice of AP particles. Geometric[ edit ] APCP deflagrates from the surface of exposed propellant in the combustion chamber. In this fashion, the geometry of the propellant inside the rocket motor plays an important role in the overall motor performance.

As the surface of the propellant burns the shape evolves a subject of study in internal ballistics , most often changing the propellant surface area exposed to the combustion gases.

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Ammonium perchlorate composite propellant

Jump to navigation Jump to search Hydroxyl-terminated polybutadiene HTPB is an oligomer of butadiene terminated at each end with a hydroxyl functional group. It reacts with isocyanates to form polyurethane polymers. HTPB is a translucent liquid with a color similar to wax paper and a viscosity similar to corn syrup. This provides side-to-side linkage for a stronger cured product. HTPB is usually cured by an addition reaction with di- or poly- isocyanate compounds. Uses[ edit ] Polyurethanes prepared from HTPB can be engineered for specific physical properties; polyurethanes may be highly elastic or tough and rigid. Some products include: rigid foam insulation panels; durable elastomeric wheels and tires used for roller coasters , escalators , skateboards , etc.

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Laser-recoil response of AP-HTPB propellants (1-5 atm): Selective pyrolysis response

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Hydroxyl-terminated polybutadiene

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