Spherical Propellant Research Articles

Preparation of the porous spherical propellant by using the additives of alkali-metal salt

This article presents the research results on using some alkali-metal salts as additives in the technological process of making porous spherical propellants and the effects of some of these additives on the porosity and some characteristics of the propellant. The porous spherical propellants are prepared using the emulsion method with additive concentrations of Na2SO4, K2SO4, and KNO3 from 0% to 3%. The important characteristics of the sample were determined, such as heat of combustion (Qv), bulk density (ω), temperature of ignition (Tig), and chemical stability. The porosity is calculated and converted through bulk density and theoretical density. The results show that the sample with the Na2SO4 salt has the best porosity (51÷53%) at concentrations over 2%. The important characteristics of the porous propellant do not change significantly compared to the no-additive spherical propellant.

Wetting behavior and drying mechanism of a cellulosed-based aqueous coating solution on the spherical propellant

In order to determine the wetting and drying mechanism of Surelease®-Nitrocellulose aqueous coating solution during the coating of small-sized spherical propellant, and thus to provide theoretical guidance for the preparation of the coated spherical propellant. In this paper, combining with the surface wetting theory, the adhesion work, interfacial tension and the spreading coefficient of the coating system on the surface of the spherical propellant were calculated. The infrared spectrometer was used to explore the chemical interaction between the coating layer and the matrix propellant. In addition, based on the emulsion film-forming principle, the drying kinetics of the coating system was investigated in detail, and the influences of nitrocellulose content on the drying process were investigated. Meanwhile, the macro and micro morphology of the aqueous coating solution during the drying process were also investigated with the help of camera and scanning electron microscope.

A brand new green coating technology for realizing the regulation of spherical propellant energy release process

To achieve the controllable release of energy of nitrocellulose-based propellants, this paper combines the cellulose-based nanocomposites aqueous coating (Surelease®-NC) with fluidized bed coating equipment to successfully prepare the coated spherical propellant for the first time. The effects of fluidized bed coating temperature, air velocity, flow speed and atomization pressure on the adhesion rate, coating integrity and coating uniformity of the coated spherical propellant were investigated, and the preparation of coated spherical propellant with homogeneous size and structural integrity was achieved for the first time. The microscopic morphology, chemical structure, water vapor adsorption behavior, combustion performance, and ageing resistance property of the coated spherical propellant were systematically investigated by, Fourier transforms infrared spectroscopy (FTIR), Micro confocal raman spectrometer, field scanning electron microscopy (SEM), dynamic vapor adsorption techniques, and closed bomb test, confirming the surface core-shell structure and the tightly bonded interfacial structure of coated spherical propellant. Meanwhile, the coated spherical propellant has good hygroscopic, excellent progressive burning and long storage stability.

An approach for simultaneous monitoring the content of insensitive agent in the double-base oblate spherical propellant by application of near-infrared spectroscope and partial least squares

The content of insensitive agent is an important parameter that has been shown correlated with the combustion characteristic of double-base oblate spherical propellant (DOSP). This work focused on the feasibility of simultaneous monitoring the content of insensitive agent (dibutyl phthalate (DBP) and N, N′‐dimethyl‐N, N′‐diphenylurea (C2)) in DOSP by using near-infrared (NIR) spectroscope coupled with partial least squares (PLS). The optimal spectral intervals for creating models of DBP and C2 corresponded to 5964 cm−1–4212 cm−1 and 6240 cm−1–4380 cm−1, respectively. It had been demonstrated that derivative tools were more suitable for spectral preprocessing as which had the lowest root mean squares error of cross-validation (RMSECV). The best-performance models of DBP and C2 were built under 4 and 7 PLS factors, respectively. The results showed that the determination coefficients of calibration (Rc2) and the root mean squares error of calibration (RMSEC) were 0.9771 and 0.0173 for DBP; 0.984 and 0.0072 for C2, respectively. Besides, the developed models exhibited excellent ability in prediction with the determination coefficients in prediction (RP2) and the root mean squares error in prediction (RMSEP) of 0.9681 and 0.0275 for DBP, and of 0.9554 and 0.0107 for C2, respectively. The residual predictive deviation (RPD) of prediction set were 5.68 and 5.12 for DBP and C2, respectively. The average relative errors of the proposed and reference methods were 0.652% for DBP, and 0.429% for C2, revealing a good correlation between the reference values and predicted values. Therefore, it concluded that the proposed plan has shown to be an attractive means since its efficient and highly accurate which could provide a better option for quality control in the large-scale production of DOSP.

Fast assay of ethyl acetate content of double-base oblate spherical propellant after balling process by near-infrared spectroscope

Ethyl acetate (EAC) is commonly used as a solvent in the balling process of double-base oblate spherical propellant (DOSP) because of its excellent performance in swelling. However, the residual content of EAC in the DOSP has an adverse effect on combustion performance of DOSP. Therefore, it is necessary to fast assay the EAC content of DOSP in the production process for avoiding economic loss caused by unqualified products. This work is to investigate the feasibility of using a Fourier transform near-infrared (NIR) spectroscope coupled with partial least squares (PLS) algorithm to construct a quantitative model, which can rapidly monitor the EAC content of DOSP after balling process. In the NIR spectra, two characteristic peaks were observed in the range of 6096–5464 cm−1 and 4824–4524 cm−1, which were employed as modeling intervals for analyzing the content of EAC in DOSP intermediate samples. According to the minimum value of the root mean square error of cross-validation (RMSECV), first derivative and standard normal variate (SNV) were chosen as original spectral preprocessing method, and the optimum number of PLS factors for EAC calibration model was 6. The quantitative EAC model was developed based on PLS algorithm. The determination coefficients of the calibration (RC2) and prediction (RP2) for the developed model were equal to 0.9786 and 0.9883, respectively. The root means square error of calibration and prediction (RMSEC and RMSEP) were 0.0536 and 0.0412, respectively. The residual predictive deviation (RPD) values of calibration and prediction were 6.83 and 10.7, respectively. Using independent samples as prediction set to test robustness of the developed model, and the average deviation between traditional measured values and NIR predicted values was 0.017%. Therefore, the experimental results indicated that the NIR spectroscope can give a fast and accurate analysis the EAC content of DOSP after the balling process.

3DOF-rigid-pendulum analogy for nonlinear liquid slosh in spherical propellant tanks

The problems of large-amplitude lateral sloshing, rotary sloshing and liquid rotation-starting in liquid-filled spacecraft remain of great concern to aerospace engineers. A composite 3DOF-rigid-pendulum model is proposed in this paper for nonlinear liquid slosh in spherical propellant tanks. The primary modes of liquid behavior in moving tanks, including the overall rigid motion, the liquid spinning motion, the lateral sloshing and the rotary sloshing, can be approximately described by using this equivalent mechanical model (EMM). First, the liquid sloshing dynamics equations are derived via the Lagrangian approach. Next, by giving three different simulation cases and comparing the forces generated by the EMM with that generated by the actual liquid, the equivalency of the mechanics is validated. Finally, the primary nonlinear effects of liquid in partially-filled tanks, which has been recognized in published experimental researches, are investigated by the proposed EMM. Additionally, the drifting phenomena, which indicate symmetry breaking, are displayed in the non-planar motion of the 3DOF-rigid-pendulum under unidirectional lateral motion of moving tanks.

Effect of components on the curing of glycidyl azide polymer spherical propellant through rheological method.

We have conducted a novel study of the influence of energy components (RDX, AP and CL-20) on curing kinetics of glycidyl azide polymer (GAP) spherical propellant based on rheological method. The autocatalytic model was used to describe curing kinetics and the parameters were determined by the model-fitting method. It was found that the incorporation of components hinders the cross-linking reaction of GAP spherical propellant. Integral isoconversional method was used on rheological kinetics to investigate the changes of the activation energy and we confirmed that the incorporation of components increased the activation energy. It was also found that such components had no effect on the trend of activation energy curves but shrank the peak value at a = 0.2. Dynamic mechanical analysis (DMA) showed the differences between pure curing system and its components. These findings are potentially helpful to control the curing effectively and optimize the processing schedules. The addition of components decreased α translation temperature which means the reduction in cross-links. The differences in the values of loss factor tan δ and β translation showed that pure curing system has lower resistance for side chain to motion.

Large-Amplitude Sloshing Analysis and Equivalent Mechanical Modeling in Spherical Tanks of Spacecraft

Liquid sloshing of a large amplitude is prone to take place under excitation, especially when the gravitational intensity becomes small. A composite equivalent mechanical model is established to efficiently and accurately predict the slosh forces and moments exerted on a spherical propellant tank in a spacecraft. The modeling is based on an assumption of the dynamic equilibrium position of the liquid, which changes with time-dependent tank motion. Equivalent gravity is defined to describe the dynamic equilibrium position and act as a restoring force during sloshing. Sloshing of the liquid is assumed to take place around the dynamic equilibrium position. The validity of the modeling method is verified through numerical examples. Good stability and the ability to accurately predict the dynamic response under the violent sloshing of the composite model are revealed.

Using rheometry to study the curing kinetics of glycidyl azide polymer spherical propellant by non-isothermal method

The curing kinetics of GAP spherical propellant was studied by rheological non-isothermal measurement. The kinetic parameters were determined by rheometry based on conversion degree α described by storage modulus. The non-isothermal method was first used in rheometry as conversion α determined by a novel method, considering that storage modulus variation was a complex process which increased with polymerization and decreased as the temperature increased. The variation of apparent activation energy was obtained by the isoconversional method of Kissinger–Akahira–Sunose. It was found that Ea is little lower in the range of 0.05 < α < 0.50 than it is in the range of 0.50 < α < 0.70. During the complete curing process, apparent activation energy can be considered a constant. A new kinetic equation had been established and showed great agreement with experimental data. Altogether, the rheological non-isothermal method can be used to investigate the mechanism and kinetics of thermosetting reactions, and the obtained knowledge of the curing kinetic will form a contribution to the study of GAP spherical propellant.

The kinetic and viscosity analysis of glycidyl azide polymer spherical propellant

The kinetic and rheology processes of isothermal curing of glycidyl azide polymer (GAP) spherical propellant have been studied using isothermal rheological data. A new equation has been proposed to predict the degree of conversion of heterogeneous reaction. The kinetic and rheological parameters were experimentally determined using rheometry based on the conversion degree α described by storage modulus $$ G^{\prime} $$ . The differential isoconversional method was used to determine the value of the apparent activation energy (E a). It was found that apparent activation energy varied during the curing time, but in the conversion range α = 0.05–0.80, E a is practically a constant (E a = 1.11 × 105 J mol−1). The kinetic model of cyanate/GAP spherical propellant system had been accomplished and showed a good agreement with experimental data. Chemorheological analysis confirmed that curing of GAP spherical propellant has two stages and the second stage has a much higher activation energy than the first one due to the different steric hindrance of two isocyanate groups. Both activation energies of two stages are much higher than that in liquid GAP. An empirical model was used to predict the variation of complex viscosity and showed a good prediction effect.

THE INFLUENCE OF SPHERICAL GRANULAR PROPELLANTS ON THE COMBUSTION PROPERTIES OF HIGH-BURNING-RATE PROPELLANT

Novel spherical grain-binding, high-burning-rate propellant is a kind of compound structure propellant (called a consolidated propellant) that is prepared using a spherical granular propellant (spherical propellant grains) as the dispersed phase and a colloidal binder as the continuous phase. The effects of composition, particle-size, and morphology of spherical propellant grains on the combustion performance of propellants were each investigated. The results show that the burning rate of the propellant decreases with the increase of the burning rate of spherical propellant grains. The greater the difference in burning rate between the spherical propellant grains and the binder, the higher the burning rate of the propellant will be. The burning rate of the consolidated propellant increases with a decrease in particle size. When compared with that of propellants prepared with smooth-faced spherical propellant grains, the burning rate of propellants prepared with shaggy spherical propellant grains is much higher; however, combustion can become less stable.

Combustion Characteristics of a Novel Grain‐Binding High Burning Rate Propellant

AbstractThe novel grain‐binding high burning rate propellant (NGHP) is prepared via a solventless extrusion process of binder and spherical propellant grains. Compared with the traditional grain‐binding porous propellants, NGHP is compact and has no interior micropores. During the combustion of NGHP, there appear honeycomb‐like burning layers, which increase the burning surface and the burning rate of the propellant. The combustion of NGHP is a limited convective combustion process and apt to achieve stable state. The larger the difference between the burning rate of the binder and that of the spherical granular propellants exists, the higher burning rate NGHP has. The smaller the mass ratio of the binder to the spherical granular propellants is, the higher the burning rate of NGHP is. It shows that the addition of 3 wt.‐% composite catalyst (the mixture of lead/copper complex and copper/chrome oxides at a mass ratio of 1 : 1) into NGHP can enhance the burning rate from 48.78 mm⋅s−1 in the absence of catalyst to 56.66 mm⋅s−1 at P=9.81 MPa and decrease the pressure exponent from 0.686 to 0.576 in the pressure range from 9.81 to 19.62 MPa.

Configuration for Propellant Gauging in Satellites

Accurate propellant gauging is of prime importance insatellite industries. This paper explores the possibility of using a new propellant tank configuration, consisting of a truncated cone centrally mounted within a spherical propellant tank, to measure the amount of liquid propellant present within the tank. The liquid propellant present within the propellant tank orients itself in geometry by virtue of its dominant surface tension force in 0 g condition, which minimizes its total surface energy. This study reveals that the amount of liquid propellant present in the tank can thus be estimated by measuring the height of the propellant meniscus within the central cone. It is also observed that, for the proposed configuration, the precision of the estimated propellant fill-fraction increases towards the end of life of the spacecraft.

Thermal Stresses in Spherical Case-Bonded Propellant Grains

Expressions are derived for the bond stresses induced by a radially symmetric temperature distribution in spherical propellant grains bonded to spherical casings. Equations for the evaluation of radial and tangential stresses in the propellant and its casing have also been derived. Both solid and hollow propellant grains have been investigated. Design considerations have been developed to enable the designer to minimize the bond stress. A comparison between the hollow and solid spherical propellant assembly shows that the hollow sphere has a lower bond stress than the solid sphere, assuming all other factors are the same.