报废固体推进剂的降感技术

为了清理火箭发动机内报废的推进剂,采用萃取法对含能组分进行降感处理,研究了萃取剂质量浓度对萃取效果及含能组分溶解度的影响,最后对萃取液中含能组分采用蒸馏方法进行回收。结果表明,从报废复合固体推进剂中萃取出AP后,推进剂的撞击感度、摩擦感度降低60%,推进剂本体发生裂解、失强,有利于发动机内报废推进剂的安全销毁,优选出最优萃取剂为T J-3,AP组分的回收利用使推进剂中大量氧化剂得以回收,有利于环保。     

Disposal of Energetic Materials by Alkaline Pressure Hydrolysis and combined techniques

Due to the reduction of armament and especially due to the German reunification we are met by the objective of the disposal of energetic materials. Environmentally friendly disposal methods available for the different propellants, explosives and pyrotechnics are urgently needed. The main component of gun and rocket propellants is the energetic polymer nitrocellulose. One method to dispose nitrocellulose containing propellants is the combination of rapid chemical destruction by pressure hydrolysis and the biological degradation of the reaction mixture. The study describes the results of pressure hydrolysis of different gun and rocket propellants. Under alkaline conditions (propellant to NaOH ratio 2.3:1; reaction temperature 150 °C; pressure below 30 bar) biological degradable reaction products were formed. The main products in the liquid phase were simple mono- and dicarboxylic acids. Dependent on the reaction conditions 30–50 % of the nitrogen content of the propellants was transformed to nitrite and nitrate. The gaseous nitrogen containing products were N₂ (16–46 %), N₂O (2–23 %), NO_x (0–5 %). Overall 40%–60% of the propellant nitrogen was transformed to gaseous products. In the solid residues a nitrogen content between 2 % and 9 % was found. The residues were mostly due to additives used in propellant manufacturing. In the case of nitrocellulose pressure hydrolysis below 30 bar and reaction temperature about 150 °C are sufficient.     

Thermal structural damage and thermal decomposition characterization of GAP propellants with nitrate ester plasticizers

GAP and nitrate ester compounds are introduced into the solid propellant formulation as energetic binders and energetic plasticizing agents, respectively, to further enhance the energy level of solid propellants. However, under abnormal thermal conditions, various components within GAP propellants, especially nitrate ester plasticizers, can collectively result in the generation of a large number of voids within the propellant due to factors such as thermal stress and slow component decomposition. This phenomenon can impact the safety of solid rocket engines, necessitating research into their thermal decomposition processes and thermal damage structures. In this study, the thermal decomposition characteristics and gas products of GAP propellants with different nitrate ester plasticizer formulations were investigated using DSC-TG and FT-IR. The damage structure of GAP propellants heated under unignited conditions was studied through Micro-CT, examining the influence of heating conditions and nitrate ester plasticizers on the thermal damage structure of GAP propellants. During heating, the thermal damage structure of GAP propellants was found to include voids generated within the GAP binder and cracks at the interface between the GAP binder and particles, with nitroglycerin as a plasticizer exacerbating the thermal damage of GAP propellants (about 2.2–2.9 times).     

Some Aspects on Safety and Environmental Impact of the German Green Gel Propulsion Technology

This article gives a short introduction into the technology of gelled propellant rocket motors and gas generators. A brief introduction outlines the specific features of the German green gelled propellant rocket motor technology and the family of monopropellants that cover a variety of requirements with respect to smoke, combustion temperature, and combustion pressure ranges. The discussion of the hazard potential comprises military insensitive munitions (IM) and civil classifications as well as a comparative assessment of the environmental and health impacts from manufacturing over use and finally to disposal. Summarizing the properties over all categories shows that gelled propellants provide a unique combination of good insensitivity and low environmental and health hazard potential compared to other liquid propellants, fuels, and oxidizers or solid rocket propellants.     

Effect of the physical state of the activators on the combustion of composite rocket propellants. I. The applied catalysts

The effects on the burning and thermal decomposition of composite rocket propellants, based on ammonium perchlorate and butyl rubber, of oxide coated catalysts applied to tge surface of the ammonium perchlorate crystals and introduced into the propellant in the form of a colloidal suspension are investigated. It is shown that the possibility of changing the burning rate by means of applying the catalyst on the oxidizer crystal surface is determined by the chemical nature, the content of the compounds deposited on the oxidizer surface, and by the structure of the coating formed on the ammonium perchlorate surface. Excluding the agglomeration of the catalytic additives using the developed methods, the variation in their dispersivity and the nature of localization in the propellant are the indicators of the propellant's performance efficiency within the region of small additive concentrations (up to 0.5%) in the propellant. Scientific Research Institute for Physicochemical Problems, Belorus State Univ., 220050 Minsk. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 6, pp. 82–88, November–December, 1995.     

Kinetic Description of Mass Loss Data for the Assessment of Stability,Compatibility and Aging of Energetic Components and Formulations Exemplified with ε‐CL20

The efficiency of the assessment and of the development of energetic materials can be increased by modelling stability, compatibility, ageing and thermal decomposition of the used components and formulations. All four terms have in common that chemical reactions are the dominating processes, besides for example migration of mobile components. These chemical reactions are only in part controlled by thermodynamics, to a great extend they are controlled kinetically. Kinetic models are formulated and used for mass loss measurements with isothermally operated ovens and TGA (Thermogravimetric Analysis). The models include autocatalytic decomposition and evaporation or decomposition of a minor component beside a main component. A formulation of a general bimolecular reaction in terms of mass loss is useful in compatibility studies. Approximations and simplifications of the autocatalytic models are discussed. The shown applications include new data on hexanitrohexaazaisowurtzitane crystallized in ε‐phase (ε‐HNIW, ε‐CL20) and rocket propellant formulations of type HFK containing ε‐CL20 as main component. The kinetic data for the decomposition of ε‐CL20 are given and discussed with data from literature.     

彩涂胶辊用聚氨酯弹性体的研制

合成了一种彩涂胶辊用聚氨酯弹性体材料,考察了聚酯多元醇、异氰酸酯、扩链剂、催化剂、操作工艺等因素对材料性能的影响。所制聚氨酯弹性体具有较高的力学性能、良好的耐溶剂性能、较好的切削加工性和较长的使用寿命。     

推进剂药粒干燥过程的安全性分析

分析了推进剂药粒在干燥过程中发生热分解、燃烧或热爆炸的起因。通过比较几种典型干燥方法,了解其干燥过程的优缺点。根据推进剂干燥过程中所发生的物理化学变化,讨论了干燥过程中硝化甘油蒸发及推进剂热分解、燃烧或热爆炸的机理。通过烘箱法模拟热分解,找到了发生热分解、燃烧或热爆炸的时间和温度点。最后分析了推进剂药粒在干燥过程中的危险性。     

The properties of 1,3,3,5,7,7-hexanitro-1,5-diazacyclooctane (HCO) and its application in propellants

The properties of HCO and its application as a monopropellant were described. In comparison with HMX, it is also a high energetic explosive with high thermostability and can be used as an oxidizer in solid rocket propellants. Theoretical specific impulse of HCO-double base propellant systems were calculated and the burning rates and thermostability of propellant were experimentally determined. Propellants were prepared with a spray-casting process. As an oxidizer in solid rocket propellant, HCO shows better characteristics under certain aspects compared with HMX.     

Investigation of the Decomposition Processes in Single-Base Propellants under vacuum using a minicomputer-controlled automated apparatus

There is described the application of an automated vacuum stability test in following the decomposition and the stability of single base propellants. The relations of the propellant decomposition rate, evaluated from the loss of stabilizer, to the decomposition rate measured at the stability test were verified. The data obtained indicate the applicability of the vacuum test to check the chemical stability of propellants.     

CL-20含量及其粒度级配对NEPE推进剂燃烧性能的影响

采用静态与水下声发射法测试了CL-20含量及其粒度级配对NEPE推进剂燃速与压强指数的影响;采用DSC与TG-IR联用研究了CL-20对NEPE推进剂热分解行为的影响。结果表明,随着CL-20质量分数由42%增至50%,推进剂燃速与压强指数上升,燃烧效率提高,表明CL-20氧化能力高于GAP/硝酸酯含能黏合剂体系;随着CL-20/HMX、CL-20/Al质量比增高,推进剂燃速上升,燃烧效率上升;CL-20对推进剂燃速和压强指数的贡献高于HMX;随着CL-20/AP质量比增高,CL-20/AP混合体系分解产物氧化能力降低,燃烧反应速率降低,燃速降低;CL-20粒度级配对NEPE推进剂燃烧行为影响显著,当CL-20的粒径(d50)在5~50μm时,随着细粒度CL-20含量增高,推进剂燃速与燃速压强指数下降;当体系中存在超细粒度CL-20(d50=500nm)时,推进剂燃速与燃速压强指数随着超细粒度CL-20含量的增加而有所增加,4种粒度CL-20对NEPE推进剂燃速的贡献顺序为:粗粒度>中粒度>超细粒度>细粒度。     

Synthesis and Application of Borate Ester Bonding Agents for a Four‐Component Hydroxy‐Terminated Polybutadiene Propellant

Low molecular weight interconnection monomers including polyepichlorohydrin, poly(propylene oxide), poly(ethylene glycol adipate), and poly(butylene adipate) were synthesized to evaluate the effects of the molecular structure of interconnection monomers on the bonding efficiency of borate ester bonding agents (BEBA) applied in four‐component hydroxy‐terminated polybutadiene (HTPB) propellants. The monomers were characterized by IR spectroscopy, elemental analysis, and gel permeation chromatography. A series of new borate ester bonding agents were synthesized using the as‐synthesized interconnection monomers as well as poly(ethylene glycol) and applied in the preparation of four‐component HTPB propellants. The application results showed that BEBA‐4 prepared from poly(butylene adipate) could significantly improve the mechanical properties of the four‐component HTPB propellant, reduce the slurry viscosity leading to improvement of processing properties and aging resistant performance, while no significant effect on the burning characteristics of the propellant was observed.     

Influence of an Electric Field on the Burning Behavior of Solid Fuels and Propellants

An experimental study on the effects of an applied external electric field on the combustion behavior of solid fuels and solid propellants has been conducted. In an opposed flow burning configuration, application of an electric field was shown to extinguish a paraffin fuel and gaseous oxygen flame over a broad range of operating conditions. When subjected to the electric field, burning paraffin fuel strands were found to extinguish at various axial locations relative to the exit of the oxidizer gas jet. Extinguishment location was found to be a function of field strength as well as electrode surface area, while changes in polarity did not significantly alter the results. In addition, the combustion behaviors of two composite solid rocket propellants were studied while subjected to an external electric field. Both propellants were based on HTPB/AP combinations, with one propellant containing aluminum and the other being non‐aluminized. Application of an electric field to the composite solid rocket propellant strands demonstrated decreases in propellant burning rate under all operating conditions for both propellants including changes in polarity. The flame structure of the aluminized propellant was examined closely as the luminosity, flame length, and flame width varied significantly with field strength and burning location of the strand relative to the electrodes.     

Infrared Irradiance Reduction in Minimum Smoke Propellants by Addition of Potassium Salt

One of the plume characteristics of minimum smoke propellant is the infrared (IR) radiation signature, which may be useful for detection of rocket. The IR irradiance is known to be reduced by afterburning suppression in rocket plume by addition of potassium salt in propellant. The minimum smoke propellant with nitrate ester polyether (NEPE) binder system and nitramine oxidizers was researched for the afterburning and IR irradiance difference according to the content of potassium salt as afterburning suppressant in propellant formulation. The propellants were formulated to satisfy the level of AGARD smoke class AA and potassium sulfate was selected as afterburning inhibitor suitable for NEPE propellant. The afterburning flame length and mid‐range IR intensity were measured, while conducting static firing tests of 6 inch (15.24 cm) standard rocket motors loaded with minimum smoke propellants of the different contents of potassium sulfate. The total IR irradiance of HMX/RDX propellant with 1.1 % potassium sulfate was reduced to about 23 % compared to the propellant without afterburning suppressant due to the inhibition of afterburning. Also, the total IR irradiance of the HNIW (30 %)/RDX propellant was found to be almost three times more than that of the HMX/RDX propellant although the content of potassium sulfate was the same of 1.1 % in both propellants.     

Short-Action Solid Rocket Motors with Double-Base Propellants

Due to various reasons double-base solid propellants have been replaced increasingly by composite propellants in the past years. However, the ALARM rocket motor of the Bayern-Chemie GmbH is one exception. Applications ideal for double-base propellants are short-action rocket motors with burning times ranging from some milliseconds up to approximately 200 ms. Various rocket motors of this type were developed at Dynamit Nobel GmbH for different kinds of application. Based on multiple-tube grains improved designs and manufacturing methods have been developed to enable cost-effective solutions even at low production rates. This includes also simplified test procedures to supervise the propellant fabrication.     

Temperature profile in the combustion wave of low calorific value propellants

Combustion wave temperature profiles are determined for two low calorific value propellants (Q _c = 2189 and 2518 kJ/kg). It is shown that the structure and parameters of the combustion wave differ significantly from those for previously studied propellants of medium (propellant N) and high (propellant NB) calorific values. At a relatively short distance from the burning surface, the temperature is significantly (180–270 K) higher than the calculated value due to fact the combustion products contain carbon black from the decomposition of heat-resistant dibutyl dinitrotoluene and dibutyl phthalate. Then, part of carbon black reacts endothermically with CO₂ and H₂O, leading to a decrease in temperature, which for the first sample is nevertheless 100–140 K higher than the thermodynamic value. For the investigated propellants, the activation energy of the leading reaction is the same as for the previously studied propellants, suggesting a common decomposition kinetics of the condensed phase regardless of the propellant composition. However, a uniform dependence of the burning rate on surface temperature is not observed. For low calorific value propellants, the surface temperatures are close to those for propellant N although their burning rate is significantly (2–2.2 times) lower. The causes of this fact are considered.     

Quantitative Measurement of Propellant Stabilizers with tlc and liquid-crystalline method of visualization

Basic compounds of propellants, nitrate esters decompose forming nitrogen oxides as the catalytic products. To inhibit further decomposition, stabilizer reacts with nitrogen oxides, and finally non-catalytic products are formed, so autocatalytic decomposition is minimized. In this way, chemical stability of propellant increases, but the content of stabilizer decreases. In this paper, the possibility of quantitative analysis of the weight loss of propellant stabilizer using the TLC method and the liquid crystal method of visualization is presented. The advantages of solid phase extraction (SPE) application in such analysis are also shown.     

Ballistic Modification of Nitramine Propellants with Special Reference to NG‐PE‐PCP‐Based High Energy Propellants

The burning rate pressure relationship is one of the important criteria in the selection of the propellant for particular applications. The pressure exponent (η) plays a significant role in the internal ballistics of rocket motors. Nitramines are known to produce lower burning rates and higher pressure exponent (η) values. Studies on the burning rate and combustion behavior of advanced high‐energy NG/PE‐PCP/AP/Al‐ and NG/PE‐PCP/HMX/AP/Al‐based solid rocket propellants processed by a conventional slurry cast route were carried out. The objective of present study was to understand the effectiveness of various ballistic modifiers viz. iron oxide, copper chromite, lead/copper oxides, and lead salts in combination with carbon black as a catalyst on the burning rate and pressure exponent of these high‐energy propellants. A 7–9 % increase in the burning rates and almost no effect in pressure exponent values of propellant compositions without nitramine were observed. However, in case of nitramine‐based propellants as compared to propellant compositions without nitramines, slight increases of the burning rates were observed. By incorporation of ballistic modifiers, the pressure exponents can be lowered. The changes in the calorimetric values of the formulations by addition of the catalysts were also studied.     

Evaluation of Mechanical Properties of Solid Propellants in Rocket Motors by Indentation Technique

It is essential to evaluate the mechanical properties of propellants in a solid propellant rocket motor (SPRM) for structural integrity and its performance evaluation before the flight test. Conventionally, uni‐axial tensile testing on an universal testing machine (UTM) is used to evaluate the mechanical properties of solid propellant carton which is cast along with SPRM. Propellants in rocket motors experience various types of loading during storage, transportation, and environmental conditions over the period of time before actual flight whereas the propellant carton doesn’t experience the same as it is stored in magazine. At present, the mechanical properties of propellant cast in a carton are considered to be the mechanical properties of propellant in a rocket motor, which is not truly representative. Therefore, a non‐destructive indentation technique has been used to establish a method for evaluating the mechanical properties of solid propellants in rocket motors based on hydroxyl terminated polybutadiene. The test results obtained using the penetrometer indentation technique was analyzed comprehensively and compared with UTM results. The mathematical correlations were also developed using least square method and established by conducting the penetrometer indentation test on similar propellant composition. Further, the developed correlation was used to evaluate the mechanical properties of propellant in flight SPRM by penetrometer indentation technique.