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.     

Combustion-Front Non-One-Dimensionality in Single- and Double-Base Propellants

Parameters of transverse waves propagating over the surface of specimens pressed from colloxylin and double-base propellants A and N are studied. By means of microvideofilming and thermocouple measurements, it is shown that the burning sites on the specimen surface are formed by a set of transverse waves. Under atmospheric pressure, the transverse-wave front has the form of a step 0.5–1.1 mm high and decreases with increasing pressure or initial temperature of the specimen. The front propagates with variable velocities in the horizontal and vertical directions. The mean velocity of the transverse wave is three to eight times higher than the normal burning rate of the specimen as a whole (with a wide spread of local values) and increases with increasing pressure. Behind the front, combustion can be interrupted till the arrival of the next transverse wave. As in the SHS process, the reason for the emergence of the transverse waves is combustion-wave spatial instability.     

Experimental study of Double-Base Propellants Combustion Mechanisms

Experimental results about r_b(P) laws of double-base propellants are presented. The influence of many parameters (calorific potential, fabrication process, additives) is studied. With surface structure examination, we show that the first super-rate (P < 100 bar) is in relation with the presence of a carbon layer which increases chemical reactions. The second super-rate (200 bar < P < 400 bar), more physical than chemical, is in relation with the presence of globules (probably PbO) which increase the thermal conductivity near the propellant surface.     

Organic Fillers for Smokeless Insulations of Double-Base Propellants

The number of organic fillers for smokeless polyurethan-insulations hitherto known is rather small. In this paper two general formulae, expanding the range of organic fillers, are described. The first formula describes molecules with linear structures, the second one those with cyclic structures. A common feature of the fillers mentioned above their high (N + O)/C ratio.     

The Interrelation Between the Thermal Decomposition of Lead Salt and the Platonization Mechanism of Double-Base Propellants

The effects of carbon black, cupric adipate and RDX on the thermal decomposition behaviour of lead flake in double-base system are investigated by DSC measurement. The results show that the thermal decomposition peak of lead flake decomposition shifts to lower temperature with the addition of carbon black, cupric adipate and RDX, and the exotherm heat of lead flake increases with the addition of carbon black and RDX. DSC results are compared with the burning characteristics of practical plateau propellants, the chemical reactions involving lead salts near the burning surface are assumed. The mechanism of the effects of ballistic modifiers and RDX on the phenomenon of platonization are discussed.     

Combustion Mechanism of Double-Base Propellants with lead burning rate catalysts

On the basis of relevant experimental phenomena and results, which also include the results on the domain of non-propellant combustion, this paper has determined basic reactions caused by lead burning rate catalysts in the combustion process and their approximate reaction temperature. In the presence of carbonaceous matter on the burning surface the partial NO is reduced to N₂ through six reactions occurred on the carbonaceous matter instead of the reaction between NO and CO. As a result of changing the reducing path of a part of NO the burning rate rises through increasing the temperature gradient in the fizz zone at the burning surface. The reactions between PbO and C and between PbO and CO check the burning rate to rise through expending carbonaceous matter on the burning surface and causing char particles to “fly off” the burning surface. The super-rate, plateau and mesa effects are perfectly explained with these reactions and the fundamentals of heat transference. The production of the effects arises from the competing of two actions to increase burning rate and to check the burning rate enhancement of lead burning rate catalysts and the effect of the pressure on the burning rate. Because of the fact that the chance to form carbon nuclei and the time of the carbon deposit, the covering ratio of the carbonaceous matter on PbO particles, and the temperature increasing rate and the lagging temperature difference in C-PbO interfaces depend on the pressure, the ability by the reaction between PbO and C and between PbO and CO checking the burning rate to rise makes a great difference in different ranges of the pressure. In addition, according to the combustion mechanism advanced in the paper the effects of the physical and chemical properties of lead burning rate catalysts, especially their ability to absorb the ultraviolet light, on the rate-increased values and the pressure ranges of the plateau and the mesa regions have been expounded.     

Ballistic Modification of Composite Modified Double-Base Propellants containing ammonium perchlorate

The effect of certain lead and copper salts of organic acids and metallic oxides was studied on the burning rates and heat of explosion of CMDB propellants containing AP. Among lead and copper salts, basic lead salicylate gave increased burning rates, whereas lead methylene disalicylate and basic copper salicylate did not produce catalytic effect. In the case of metallic oxides, ferric oxide and cobalt oxide gave better catalytic activity than copper and chromium oxides. On crosslinking of nitrocellulose with an isocyanate, catalytic activity of ballistic modifiers was reduced. Burning rates obtained in a rocket motor (2-kg propellant) were higher by about 15%-20% than by strand burner (Crawford Bomb) method.     

Burning of Nano-Aluminized Composite Rocket Propellants

Several aluminum nanopowders were examined and compared with the final goal to evaluate their application in solid rocket propulsion. A detailed investigation of pre-burning properties by the Brunauer-Emmet-Teller method, electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy was carried out. Ballistic properties and the combustion mechanism of several aluminized propellant formulations were investigated. In particular, aggregation and agglomeration of metal particles at and near the burning surface were analyzed by high-speed high-resolution color digital video recordings. All tested nano-powders are of Russian production; their physical characterization was carried out at the Istituto Donegani (Novara, Italy); ballistic studies were performed at the Solid Propulsion Laboratory (Milano, Italy) using laboratory and, for comparison, industrial composite propellants based on ammonium perchlorate as an oxidizer. Results obtained under a fair variety of operating conditions typical of rocket propulsion indicate, for increasing nano-Al mass fraction or decreasing nano-Al size, larger steady burning rates with essentially the same pressure sensitivity. While aggregation and agglomeration phenomena still occur, their significance may be reduced by using nano-Al instead of micro-Al. __________ Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 6, pp. 80–94, November–December, 2005.     

Determination of the Decomposition Behavior of Double-Base Propellants at Low Temperatures

Thermal and mechanical stability are very important characteristics of energetic materials used as ingredients of propellants compositions. For the determination of the thermal decomposition behavior of solid double base propellants, usually gravimetric, calorimetric, and chemical methods are being employed. At ICT, the decreasing rates of stabilizers determined by high-performance chromatography at different temperatures are successfully used as a mean to forecast the chemical life time of propellants containing nitric esters. On the other hand, the mechanical properties are evaluated by measuring the tensile strength with a more or less accuracy. In the last years, the increasing performance of the gel-permeation chromatography enabled the determination of the molecular weight and the molecular weight distribution of nitrocellulose in different propellants. In this connection a linear relationship between temperature and depolymerization rate was obtained. This relationship corresponds fairly well with the stabilizer depletion rate and the drop in the mechanical properties.     

Propellants Reactivity Enhancement with Nanothermites

Propellant grains (Vectan A1) were coated with a thin and stable layer (50 μm, 10 wt‐%) of a “green” sulfate‐based nanothermite (Na₂SO₄/Al). This flash composition was used herein as an internal pyrotechnic lighter to accelerate the ignition and the combustion of the propellant. The combustion of the modified propellant, which was tested in one‐end open tubes, propagates four orders of magnitude faster than the one of pristine Vectan A1. This tremendous effect was tuned by varying the proportion of coated Vectan A1 grains from 20 to 100 % in the samples. The percolation threshold is in between 20 and 40 %. Beyond this point, the effect can be improved by increasing the proportion of nanothermite‐coated propellant grains in the charge.     

Nitramine Solid Rocket Propellants with Reduced Signature

Solid rocket propellants containing nitramine are considerably superior to doublebase propellants, both as regards their performance and mechanical properties. The pressure exponent of non-modified nitramine propellants is n ≥ 0.9. The possibility of changing the burning rate or, respectively, the pressure exponent has, however, only been realisable to a restricted extent up till now in propellants with an increased nitramine content. In the following propellant system containing nitramine, the effects of ammonium perchlorate on burning behaviour are studied:

• ammonium perchlorate (AP)
• hexogen (RDX)
• nitroglycerin (NG), or trimethylolethane trinitrate (TMETN)
• polyurethane binder (PU)

AP concentrations already as great as 10% produce considerable changes in the burning behaviour of the propellants described above. It is possible to reduce the pressure exponent by the addition of ammonium perchlorate from n ≥ 0.9 to n ≤ 0.65. The burning rates may also be influenced with AP concentrations ≤ 20% and by varying the AP particle size by the factor of 2. All the propellants prepared were easily castable and showed exceptionally good viscoelastic properties (strain at break ε_R > 200%) in the temperature range between −40 °C to + 50 °C. The thermal chemical stability is not influenced negatively in any way by the combination of nitric acid esters and ammonium perchlorate.     

Manometric Stability Tests of Double-Base Propellants in vacuum,air, and oxygen

The decomposition process of several types of double-base propellants before and after artificial aging at 75 °C for 20 days was measured in vacuum, air, and oxygen. The results are confronted with those of the test at 100 °C and with the stabilizer content before and after aging. Effects of the sample surface area were also considered.     

固体火箭推进剂快速洗井器设计原理

根据固体火箭推进剂释放能量高、燃气量大的特点 ,设计出一种新型、高效、快速水井洗井器 ,并从洗井原理、洗井效率、固体火箭推进剂性能等方面对其可行性进行了详细分析和经济评估。采用该洗井器可减少洗井设备、简化现场操作、减少辅助工作量、缩短施工时间 ,提高洗井综合效益。该洗井器在煤田、油田钻井工艺方面也有一定的使用价值。     

Sensitivity of Solid Rocket Propellants for Card Gap Test

Card gap test, which is standardized in Japan Explosives Society, was modified in order to apply it to solid rocket propellants and carried out to evaluate sensitivities against shock stimuli. Solid propellants tested here were mainly azide polymer composite propellants, which contained ammonium nitrate (AN) as a main oxidizer. Double base propellant, composed nitroglycerin and nitrocellulose (NC), and ammonium perchlorate (AP)-based composite propellants were also evaluated in order to compare with the azide polymer propellants. It is found that the sensitivity was dominated by the oxidizer characteristics. AP-and AN-based propellant had less sensitivity and HMX-based propellant showed higher sensitivity, and the adding of NC and TMETN were contributed to worse sensitive for the card gap test. Good relationship was obtained between the card gap sensitivity and the oxygen balance of propellants tested here.     

评估固体推进剂压强温度系数的方法

提出了目前评价压强温度系数所存在的问题,较系统地分析了压强温度系数的变化规律,建立了参比压强温度系数的计算方法。     

Rocket Propellants with Reduced Smoke and High Burning Rates

Rocket propellants with reduced smoke and high burning rates recommend themselves for use in a rocket motor for high accelerating tactical missiles. They serve for an improved camouflage on the battle field and may enable guidance control due to the higher transmission of their rocket plume compared to traditional aluminized composite propellants. In this contribution the material based ranges of performance and properties of three non aluminized rocket propellants will be introduced and compared to each other. The selected formulations based on AP/HTPB; AP/PU/TMETN and AP/HMX/GAP/TMETN have roughly the same specific impulse of I_SP = 2430 Ns/kg at 70:1 expansion ratio. The burning rates in the pressure range from 10–18 MPa vary from to 26–33 mm/s for the AP/HTPB propellant, 52–68 mm/s for the formulation based on AP/PU/TMETN and 28–39 mm/s for the propellant based on AP/HMX/GAP. With 58% and 20% AP-contents the propellants with nitrate ester plasticizers create a much smaller secondary signature than the AP/HTPB representative containing 86% AP. Their disadvantage, however, is the connection of high performance to a high level of energetic plasticizer. For this reason, the very fast burning propellant based on AP/PU/TMETN is endowed with a low elastic modulus and is limited to a grain configuration which isn't exposed too much to the fast and turbulent airstream. The mechanical properties of the AP/HMX/GAP-propellant are as good or better as those of the AP/HTPB propellant. The first one exhibits the same performance and burn rates as the composite representative but produces only one fifth of HCl exhaust. For this reason it is recommended for missile applications, which must have high accelerating power together with a significantly reduced plume signature and smoke production.     

双基系推进剂用生态安全的含铋催化剂

综述了生态安全的含铋催化剂对双基和ＲＤＸ－ＣＭＤＢ推进剂燃烧性能的影响,分析比较了铋化物和铅化物的催化作用。分析结果表明,粒度小、分散性好的铋化物能够取代生态安全性差的含铅燃速催化剂用于双基系推进剂中。     

NEPE推进剂中聚氨酯的热分解行为

采用ＴＧ和ＤＳＣ两种热分析方法研究了ＮＥＰＥ推进剂中各种填料和助剂对聚醚聚氨酯粘结剂热分解行为的影响。     

Ultrasonic Investigation of Mechanical Properties of Double Base Rocket Propellants

For a series of double base rocket propellants and for poly- methylmethacrylate (PMMA) the longitudinal and transverse sound wave velocities are measured at a frequency of 0.351 MHz in t h e temperature range of −40°C to +60°C. The relations between these acoustic properties and mechanical properties are given and the principal independent elastic constants are calculated. With increasing temperature these constants of the propellants decrease gradually, which points to a softening of the material. This is important for the functioning of the propellant grains in the rocket motors.     

固体推进剂燃烧波结构研究

设计了一套分析燃烧波结构的数值计算方法,可以利用热偶数据有效地分析均质推进剂固相反应的细节,为了解固体推进剂机理提拱了一种重要的手段;提出了均质推进剂也没有明显的固气界面的观点,因而也无表面温度可言;设计了固相反应热计算模型,提出了固相反应机理的观点,并指出压力不同固相反应机理基本相同,但固相放热程度不同;提出Π型热偶不宜测量非均质推进剂燃烧波结构的观点。