An Analysis of the Initiation Process of Electroexplosive Devices

Electroexplosive devices, EEDs or squibs (an electric resistance encapsulated by a primary explosive), fundamentally convert electrical energy into heat, solely to start off an explosive chemical reaction. Obviously, the EED activation shall not happen by accident or, even worse, by intentional exogenous influence. From an ordinary differential equation (ODE), which describes this device thermal behaviour for both continuous and pulsed electrical excitation, a remarkable, but certainly not intuitive, dependence of the temperature response on the heat transfer process time-constant is verified: the EED temperature profile dramatically changes as the time-constant spans a wide range of values, from much lesser than the pulse width to much greater than the pulse period. On the basis of this dependence, important recommendations, concerning the EED safety (and efficient) operation, are presented.

Pre-Test and Analysis of a Reinforced Concrete Slab Subjected to Blast From a Non-Confined Explosive

A large scale experimental program consisting of testing 10 RC slabs with different variations of concrete compressive strength, reinforcement ratio and retrofit was conducted in Brazil. As part of that test program, a small-scale blast pre-test setup and associated dynamic analysis were conducted in order to confirm the proper functioning of the blast test sensors (pressure gages, displacement meter and accelerometers). The results of the pre-test were compared with theoretical blast wave parameter predictions using established equations and maximum displacement predictions using simplified dynamic analysis. The pre-test experiment provided useful insights and was shown to be critical for the success of the subsequent large scale blast tests.

Design and Testing of a Lab-Scale Hybrid Rocket Motor to Evaluate Swirl Injection Characteristics

This research aims to provide a methodology for the project of labscale hybrid motors. This development began with the thermal analysis of the fuel grain using the Flynn, Wall and Ozawa method, generating simulation entry data to maximize the motor performance. The simulation was performed with the Chemical Equilibrium Specific Impulse Code. Based on the optimum oxidizer to fuel ratio, the literature was used to supply the mathematical background to calculate the motor geometrical parameters whose operating conditions were determined throughout the simulation. Finally, firing tests were conducted to verify the reliability of the project methodology. The firing tests were performed with three injectors: two swirling and one axial. The tests showed that the higher the operating pressure the more suitable is the project, meaning the methodology developed works best in hybrid rocket motors with high operating pressures. Additionally, it was shown that the swirling flow injectors produce higher efficiency.

Solid Rocket Motor Internal Ballistics Simulation Considering Complex 3D Propellant Grain Geometries

Solid rocket motors (SRM) are extensively employed in satellite launchers, missiles and gas generators. Design considers propulsive parameters with dimensional, manufacture, thermal and structural constraints. Solid propellant geometry and computation of its burning rate are essential for the calculation of pressure and thrust vs time curves. The propellant grain geometry changes during SRM burning are also important for structural integrity and analysis. A computational tool for tracking the propagation of tridimensional interfaces and shapes is then necessary. In this sense, the objective of this work is to present the developed computational tool (named RSIM) to simulate the burning surface regression during the combustion process of a solid propellant. The SRM internal ballistics simulation is based on 3D propagation, using the level set method approach. Geometrical and thermodynamic data are used as input for the computation, while simulation results of geometry and chamber pressure versus time are presented in test cases.

Dynamics of the Internal Flow in Swirl Atomizers by CFD Simulations

This work presents the simulation of the internal flow in a swirl atomizer. The geometry of the atomizer is calculated by analytical equations used in engineering. The numerical simulation of the two-phase flow is performed by using two equations k-ε turbulence model. The fluids are presented as two-fluid homogeneous model. The interface between two phases is calculated by free surface model. The distribution fields of the axial and tangential velocities, pressures and air core are obtained. The aim of this work is to compare the results obtained by numerical simulation with ones obtained analytically. Also, to study the internal fluids flow inside the atomizer.

Accelerated Aging Tests of HTPB-Based Propellants

In the late twentieth century, liquid and solid propulsion technologies have been integrated into hybrid engines currently apllied in propulsion launch vehicles and missiles. The reaction of polyol (HTPB) and diisocyanate (IPDI) provides the most versatile of the binders in the production of solid propellants due to its ability to withstand high loads combined with low cost and ease of processing. A propellant based on HTPB obtained in this study was submitted to natural and accelerated aging tests, seeking to evaluate the modifications of mechanical properties as tensile strength, elongation and hardness up to 360 days. The mechanism considered in the aging process is the increase of crosslink density by breaking the double bond contained in the HTPB molecule, which causes the instability of the propellant, increasing its handling risk. Samples of these propellants subjected to aging presented variations in their properties that match the values available in the literature.

Green Propellants

Friendly or green compositions are being sought in many kinds of applications, such as fertilization, building materials, energy generation, and so on. Thus, this classification (green) can be established after the subjection of the compound to a thorough toxicity study. The research for low toxicity and no damage to the environment has stimulated the development of specific investigation lines in many areas. Inevitably, the criteria for safe handling, sensitivity and, mainly, specific impulse (efficiencies) of propellant compositions is still superior compared to ecological appeals. Nowadays, however, the solid or liquid propulsion, as aerospace as military, has already compounds to efficiency and eco-friendly characteristics. Thus, the chapter proposed will show a review in the energetic materials area, aiming at the most promising materials to be used as oxidizers and combustibles in a green propulsion system.

Study of Factors Influencing the Life Predictions of Solid Rocket Motor

Storage of rocket motors loaded with composite solid propellant for long periods may change the propellant properties, thus causing failure and affecting the safety during launch. In this study, an accelerated aging assay was carried out, in order to predict the useful lifetime and to evaluate variations on the propellant properties with time by means of thermal analysis (TG/DSC). The aging temperatures used were 65°C, and samples were withdrawn after 3 months. Aging was also carried out at room temperature. There was significant variation in the activation energy of the solid propellant samples thermal decomposition in the two kinetic methods used – Ozawa or model-free isoconversional method and Kissinger method – during the aging period. There was significant decrease of enthalpy of aged propellant enthalpy causing changes in ballistics parameters of the solid propellant grain affecting the rocket's performance.

Thermal Decomposition Kinetics Studies of HTPB/Al/AP Solid Propellants Formulated With Iron Oxide Burning Rate Catalyst in Nano and Micro Scale

The thermal decomposition kinetics of ammonium perchlorate (AP)/hydroxyl-terminated-polybutadiene (HTPB) samples, with Iron Oxide catalyst at nano and micro scale were studied by thermal analysis techniques at different heating rates in dynamic nitrogen atmosphere. The exothermic reaction kinetics was studied by differential scanning calorimetry (DSC) in isothermal conditions. The Arrhenius kinetic parameters were obtained by Flynn-Wall and Ozawa Kissinger and Starink methods. The propellant samples thermal decomposition was studied simultaneously by TG-DTA. For this purpose, solid propellant grains containing nano and micro scale iron oxide were formulated. The effect of catalysts on the propellant burning rate and the propellant initiation sensitivity were also evaluated by friction and impact. The effect of the catalyst in the propellant binder reaction was evaluated by viscosity and mechanical properties. SEM/EDS technique was used to evaluate the iron oxide morphology. Three bench firing tests were performed with rockets motor in order to know the ballistics parameters.

Innovative Solid Rocket Propellant Formulations for Space Propulsion

Solid rocket propulsion enjoys unique properties favoring its use in space exploration and military missions still for decades to come. Yet, it also suffers a limited performance especially in terms of gravimetric specific impulse. Although new high-energy materials have been identified, most of them are far from being practically usable in the short range. Presently, no integrated vehicle designs make use of these new ingredients. A broad overview is discussed in this paper and attention is paid to Ammonium Dinitramide, ADN to overcome the current limitations of Ammonium Perchlorate, AP. The latter imply not only a limited gravimetric specific impulse but also a negative impact on the environment and personal health. ADN-based dual-oxidizer formulations, with Al-based dual-metal fuels and inert or energetic binders, are promising solutions for a variety of solid rocket propulsion missions aiming respectively at minimizing environmental impact (ADN + AN) or maximizing performance (ADN + AP).