Propellant

Carbon-based caged and heterocyclic compounds tend to have strained molecular structures leading to high heats of formation and energetic behavior. In the current paper, molecular modelling calculations for 10 caged compounds of this type along with 2 strained aliphatic compounds and 4 simple cyclic chains are presented in view of their possible use as oxidizers in propulsion applications. Density functional theory (B3LYP) was employed for the geometry optimization of the proposed molecular structure using the 6-311++G(d,p) basis set. Heats of formation of the compounds were calculated using the molecular modeling results and their specific impulses were computed using the NASA CEA [1] software package to evaluate their potentials as propellant oxidizers.

This paper presents the procedure of uniaxial mechanical characterization of composite solid rocket propellant based on hydroxy-terminated polybutadiene (HTPB), whose mechanical properties strongly depend on temperature, strain rate, natural aging and accumulated damage. A method of processing data is presented in order to determine time-temperature shift factor and master curves for tensile strength, ultimate strain and relaxation modulus, depending on reduced time. Functional dependences of these features represent an input for structural analysis of a rocket motor propellant grain. The effects of natural aging on the mechanical properties are also considered.

Composite propellant mainly contains hydroxyl-terminated poly (butadiene) (HTPB) based binder and oxidizer like ammonium perchlorate (AP). The mechanical properties requirement of composite propellant is very stringent. The mechanical properties of the final product is mainly depends on the microstructure of HTPB prepolymer binder. In HTPB, three different types of microstructures are possible like cis, trans and vinyl. In this article, three different grades of HTPB are subjected for experimentation. Quantification of cis, tans and vinyl microstructure were carried out by peak area calculation in characteristic Nuclear Magnetic Resonance (NMR) peak. Gel permeation chromatography (GPC), rheology and simultaneous thermal analysis (STA) were also carried out with different grades of prepolymer. The correlation of microstructures concentration with various properties like molecular weight, polydispersity, rhelogy and thermal properties were also established. The composite propellants processed from these various HTPB prepolymers, were also evaluated by means of physicochemical and internal ballistic properties. Composite propellant produced from prepolymer containing higher cis and trans concentration i.e. HTPB Grade II showed better tensile mechanical properties. Marginal variations were observed in internal ballistic properties.

Over the past 70 years, solid rocket motors (SRMs) proved to be a reliable and cost-effective propulsion system for a wide range of rocket-based applications starting from small tactical weapons up to current large space boosters. Many designers and manufacturers from different organizations prefer the SRM option when compared to other types of rocket propulsion systems. Although SRMs are relatively simple in principle, their modern types are complex systems that must incorporate several technical disciplines and teams to meet stringent mission requirements and design criteria. To accomplish their objective within given overall system requirements and constraints, SRM subsystems and components must be carefully designed and optimized. In this survey, the authors have attempted to highlight the most used algorithms, the most common design objectives, the recent trends, and the main challenges in SRM design optimization in a simplified and organized manner. The current effort was intended to serve as an initial guide for SRM designers and researchers in selecting the optimization method that well suits their problem, and to help them know where to go next.

ABSTRACT Recent studies of solid-propellant combustion models are briefly analyzed. The models are divided into purely one-dimensional (classical and phenomenological models with various generalizations of the Zel’dovich approach) and non-one-dimensional. The latter include models with local non-one-dimensionality, which is always accompanied by local unsteadiness. This all can be eliminated by averaging. The main disadvantage of unsteady solid-propellant combustion models, which is no fault of their authors, is the same as in the case of steady-state models: the lack of detailed information on chemical and physical processes in the condensed phase. Impropriety of extending the purely one-dimensional approach to the instability region is noted. Possible directions for further development of unsteady (and quasi-steady-state) solid-propellant combustion models for homogeneous compositions may involve accounting for local non-one-dimensionality and the unsteadiness due to instability of the subsurface reactions zone and verification of the possibility of the existence of chemical instability capable of causing similar non-one-dimensionality and unsteadiness.