Novel aspects for thermal stability studies and shelf life assessment of modified double-base propellants

Modified DB propellants, based on energetic nitramine(RDX) were manufactured by solventless extrusion process. Thermal stability and shelf life assessment of modified DB propellant were investigated. Shelf life assessment was evaluated using Van’t Hoff’s formula and artificial aging at 70℃ up to120 days. Quantification of total heat released and heat flow with aging time was conducted using differential scanning calorimetry(DSC) and thermal activity monitoring(TAMIII) respectively. Modified DB formulation based on 20 wt % RDX demonstrated enhanced thermal stability in terms of controlled heat flow, and slow decomposition reactions at elevated temperature. This formulation demonstrated extended service life up to 56 years compared with reference formulation. These novel finding was ascribed to the high thermal stability of RDX and its compatibility with DB constituents. This manuscript shaded the light on novel and effective approach for thermal stability via monitoring thermal activity with aging.

Chemical stability, thermal behavior, and shelf life assessment of extruded modified double-base propellants

Double base propellant suffers from lack of chemical stability; this could result in self ignition during storing. Modified double base(MDB) propellant based on stoichiometric binary mixture of oxidizermetal fuel(Ammonium perchlorate/Aluminum), and energetic nitramines(HMX) offered enhanced thrust as well as combustion characteristics. This study is devoted to evaluate the impact of such energetic additives on thermal behavior, chemical stability, and shelf life. Extruded MDB formulations were manufactured by extrusion process. Artificial aging at 80℃ for 28 days was conducted. Shelf life assessment was performed using Van't Hoff's equation. Quantification of evolved NOxgases with aging time was performed using quantitative stability tests. MDB formulation based on HMX demonstrated extended service life of 16 years compared with(AP/Al)-MDB which demonstrated 9 years. This finding was ascribed to the reactivity of AP with nitroglycerin with the formation of perchloric acid. Thermal behavior of aged MDB, exhibited an increase in heat released with time; this was ascribed to the autocatalytic thermal degradation during artificial aging. The increase in released heat by 31% was found to be equivalent to evolved NOx gases of 6.2 cm^3/5 g and 2.5 cm^3/1 g for Bergmann-Junk test, and Vacuum stability test respectively. This manuscript shaded the light on a novel approach to quantify evolved NOx gases to heat released with aging time. MDB based on HMX offered balanced ballistic performance,chemical stability, and service life.

Novel approach to quantify the chemical stability and shelf life of modified double-base propellants

Double-base(DB) propellant is vulnerable to auto-catalytic decomposition reactions during storing with the evolution of nitrogen oxides. Modified DB propellant based on energetic nitramines(RDX) can offer enhanced thrust and action time. This study is devoted to evaluate the impact of RDX on chemical stability and shelf life of DB propellant. Extruded modified DB propellant based on RDX was manufactured by solventless extrusion process. Shelf life assessment was performed using an artificial aging at70 ℃ up to 120 days and employing Van't Hoffs formula. Quantification of evolved NOx gases and stabilizer depletion with aging time was conducted using Bergmann-Junk test and HPLC respectively.Modified DB formulation based on RDX 20 wt % demonstrated enhanced chemical stability and extended service life up to 46 years compared with reference formulation. This finding was ascribed to the high chemical and thermal stability of RDX as well as its compatibility with DB constituents; no side chemical reactions could take place during storing. This manuscript shaded the light on RDX as effective energetic constituent that offered DB propellants with enhanced performance, good chemical stability, and extended service life.

A Study of Estimating the Safe Storage Life, Self-accelerating Decomposition Temperature and Critical Temperature of Thermal Explosion of Double-base Propellant Using Isothermal and Non-isothermal Decomposition Behaviours

A method of estimating the safe storage life （τ）, self-accelerating decomposition temperature （TsADT） and critical temperature of thermal explosion （Tb） of double-base propellant using isothermal and non-isothermal decomposition behaviours is presented. For double-base propellant composed of 56±1wt% of nitrocellulose （NC）, 27±0.5wt% of nitroglycerine （NG）, 8.15±0.15wt% of dinitrotoluene （DNT）, 2.5±0.1wt% of methyl centralite, 5.0±0.15wt% of catalyst and 1.0±0.1wt% of other, the values of r of 49.4 years at 40℃, of TSAOT of 151.35℃ and of Tb of 163.01℃ were obtained.

Combustion Properties of Metal Particles as Components of Modified Double-Base Propellants

Metal particles such as aluminum（ Al）,magnesium（ Mg）,boron（ B） and nickel（ Ni）,as well as Mg/Al alloy（ Mg/Al = 3/4） are currently the most widely used ingredients in modified doublebase propellants. In this contribution,the combustion properties of the metal species are studied by means of the high-speed photography technique and the non-contact wavelet-based measurement of flame temperature distribution. The combustion process of the Al,Mg and Mg/Al samples shows both gas phase reaction and surface oxidation,which yield volatile and nonvolatile products,corresponding to the oxide and suboxide respectively. However,the combustion of B and Ni shows only gas phase reaction,due to their high melting point as well as high enthalpy of vaporization. In addition to the experiments,a hypothetical combustion model has been proposed to clarify the combustion characteristics of metal species in modified double-base propellants.

不同铋化合物对双基系推进剂燃烧性能的影响

为研究环境友好型非铅类绿色燃烧催化剂的燃烧催化效果,对比5种不同铋化合物对双基系推进剂燃烧性能的影响。结果表明,芳香族的铋化物对双基推进剂有良好的催化作用,S-Gal-Bi对双基推进剂的燃烧催化效率最好,β-Bi可有效降低双基推进剂的压强指数。当含铋化合物双基推进剂中加入少量炭黑(CB)后,各催化剂的燃烧催化效率明显增强。β-Bi和CB复合,既能显著提高低压下的燃烧催化效率,又能降低高压下的压强指数。β-Bi/β-Cu/CB的复合不仅能提高双基推进剂低压下的燃速,而且也能使推进剂在高压区出现平台燃烧效应。S-Gal-Bi/CB的加入大大提高了RDX-CMDB推进剂的燃速,并显著降低了推进剂的压强指数,与少量的铜盐复合后推进剂燃速提高更多。

Efficient Tate pairing computation using double-base chains

Pairing-based cryptosystems have developed very fast in the last few years. The efficiencies of these cryptosystems depend on the computation of the bilinear pairings, In this paper, a new efficient algorithm based on double-base chains for computing the Tate pairing is proposed for odd characteristic p 〉 3. The inherent sparseness of double-base number system reduces the computational cost for computing the Tate pairing evidently. The new algorithm is 9% faster than the previous fastest method for the embedding degree k = 6.

Thermal kinetic and thermal safety of Shuangfang-3 gun propellant based on thermal decomposition characteristics

Differential scanning calorimetry(DSC)was used to investigate the thermal decomposition and thermal safety characteristics of Shuangfang-3(SF-3)gun propellant.The kinetic calculation of the DSC curve was carried out by Kissinger and Friedman models,and the time to the maximum rate under adiabatic conditions and the self-accelerating decomposition temperature were calculated by using the AKTS thermal analysis software in combination with the heat balance equation.The thermal history experiment was carried out to further analyze the autocatalytic properties of SF-3.The results show that the initial decomposition temperature,decomposition peak temperature,and decomposition completion temperature of SF-3 all move to the high temperature direction with the increase of heating rate,and the average decomposition heat is 1521.4 J/g.The kinetic model showcased that SF-3 has different reactions in different reaction stages,and its apparent activation energy is 168.2 kJ/mol.When the times to maximum rate under adiabatic conditions are 2.0 h,4.0 h,8.0 h,24.0 h,respectively,the corresponding temperatures are 130.7℃,124.8℃,119.2℃and 110.5℃,respectively.When the masses are 5.0 kg,15.0 kg,25.0 kg,50.0 kg,100.0 kg,respectively,the corresponding self-accelerating decomposition temperatures are 110.0℃,105.0℃,102.0℃,99.0℃and 96.0℃,respectively.As the packaging mass increases,it is more difficult to exchange the liberated heat into the surrounding environment and its safety would be further reduced.The thermal history experiment demonstrates that the thermal decomposition of SF-3 is an n-stage reaction and does not have autocatalytic properties.Therefore,the size and ventilation conditions of the sample have a certain impact on the storage stability of SF-3.In the actual production,usage,storage and transportation,sample size and ventilation conditions should be controlled,and practical and effective measures should be taken according to the actual situation.

ESKD-A New Structure of Expert System Based on Knowledge Discovery

A new structure of ESKD (expert system based on knowledge discovery system KD (D&K)) is first presented on the basis of KD (D&K)-a synthesized knowledge discovery system based on double-base (database and knowledge base) cooperating mechanism. With all new features, ESKD may form a new research direction and provide a great probability for solving the wealth of knowledge in the knowledge base. The general structural frame of ESKD and some sub-systems among ESKD have been described, and the dynamic knowledge base based on double-base cooperating mechanism has been emphased on. According to the result of demonstrative experi- ment, the structure of ESKD is effective and feasible.

Three Median Relations of Target Azimuth in one Dimensional Equidistant Double Array

On the basis of the linear positioning solution of one-dimensional equidistant double-base linear array,by proper approximate treatment of the strict solution,and by using the direction finding solution of single base path difference,the sinusoidal median relation of azimuth angle at three stations of the linear array is obtained.By using the sinusoidal median relation,the arithmetic mean solution of azimuth angle at three stations is obtained.All these results reveal the intrinsic correlation between the azimuth angles of one-dimensional linear array.

Efficient Scalar Multiplication for Elliptic Curves over Binary Fields

Scalar multiplication [n]P is the kernel and the most time-consuming operation in elliptic curve cryptosystems. In order to improve scalar multiplication, in this paper, we propose a tripling algorithm using Lopez and Dahab projective coordinates, in which there are 3 field multiplications and 3 field squarings less than that in the Jacobian projective tripling algorithm. Furthermore, we map P to（φε^-1（P）, and compute [n]（φε^-1（P） on elliptic curve Eε, which is faster than computing [n]P on E, where φε is an isomorphism. Finally we calculate （φε（[n]φε^-1（P）） = [n]P. Combined with our efficient point tripling formula, this method leads scalar multiplication using double bases to achieve about 23% improvement, compared with Jacobian projective coordinates.