Gun Propulsion Concepts. Part I: Fundamentals

Modern gun propulsion techniques are driven by the desire to increase muzzle kinetic energy as a means to enhance weapon lethality, reduce costs, increase reliability, and improve vulnerability. In recent years, a significant part of research and developmental activities has been focused not only on conventional solid-propellant and novel liquid-propellant gun propulsion techniques but also on advanced concepts, particularly those offering substantial performance increase. High performance can be achieved by pure electric systems(coil or rail gun) as well as by combining chemical propulsion either with gasdynamic principles (light gas gun or ram accelerator) or with electrothermal techniques (hybrid gun). Part I of this paper deals with the fundamentals of projectile acceleration techniques. The objective is to provide the basis for understanding gun technology and to lay the basis for assessing present and future developments.     

Investigation of Liquid Gun Propellants: Electrical ignition of LGP 1846

Progress achieved in the study of the electrical ignition of the hydroxylammonium nitrate(HAN)-based liquid gun propellant LGP 1846 is described. The goal of the work is to develop an igniter system suitable for regenerative liquid propellant guns. Several igniter configurations of the one- as well as the two-stage types designed by the Ballistic Research Laboratory and the Fraunhofer-Institut EMI-AFB, have been tested. Voltage and current as well as the pressure histories were recorded. Calculations of electrostatic field distributions discussed here were obtained by a finite element code implemented at Dynamit Nobel. The theoretical analysis yielded alternative electrode designs for future testing. In addition, a specially designed igniter chamber equipped with sapphire windows was used at EMJ-AFB to study the fundamentals of the electrical discharge by means of high-speed photography.     

液体发射药的玻璃化转变温度及其体积弛豫活化焓

用ＤＳＣ测定了三种硝酸羟胺－三乙醇胺硝酸盐－水（ＨＡＮ－ＴＥＡＮ－Ｈ２Ｏ）为主成分的液体发射药的玻璃化转变温度，研究了玻璃化转变温度与升温速率的关系，导出了玻璃化转变时体积弛豫的活化焓的表达式，并计算得到了这种活化焓，为改进预测液体发射药低温粘度的方法打下了基础。     

Optimization of Liquid Gun Propellants based on nitromethane/methanol by physical and chemical modifiers

Main topics of developing and optimizing liquid gun propellants are the suppression of oscillations, and increase in performance and an improvement of electrical conductivity. Additives for the liquid system nitromethane/methanol will be described, that will change the evaporation and reaction kinetics by varying the physical and chemical properties. This will lead to an improved escillation behavior. Energetic additives, based on organic azido-compounds, will cause a significant enhancement in performance. The electrical conductivity is improved by special compounds on the base of transition metal nitrates. The investigations show a small effect of the physical modifiers. A significant suppression of oscillations is reached by mechnistical additives. Using these additives, the interaction of the specific energy with an accompanying increase in intensity of oscillation - will be minimized. As a consequence, the possibility of an additional enhancement in performance is given, due to the developed energetic additives.     

液体发射药的粘流活化焓和低温粘度的预估

测定了三种液体发射药的低温粘度，研究了粘流活化焓与温度的关系，计算了粘滞流动的活化焓。并与玻璃化转变的活化焓结合起来，对由普通方法得到的安德烈方程的几个参数进行修正，从而发展了一种改进的预测液体发射药低温粘度的方法。与常用的ＶＴＦ方程进行比较，表明这种改进的方法对于预测液体发射药的低温粘度有着更高的精度。     

Burning Rates and Thermal Behavior of Bistetrazole Containing Gun Propellants

The influence of two selected bistetrazoles, 5,5′‐bis(1H‐tetrazolyl)‐amine (BTA) and 5,5′‐hydrazinebistetrazole (HBT), on the combustion behavior of a typical triple‐base propellant was investigated. Seven propellant formulations, one reference and six others incorporating 5 %, 15 %, and 25 % of either HBT or BTA compounds, respectively, were mixed and extruded into a cylindrical, no perforations, geometry. The resulting propellants showed high burning rates, up to 93 % higher than the reference formulation at 100 MPa. However, the increase in burning rates came at the cost of higher burning rate dependency on pressure, with a pressure exponent as high as 1.4 for certain formulations. HBT‐containing propellants showed notably lower flame temperature when compared to the reference formulation, with a flame temperature reduction of up to 461 K for the propellant containing 25 % HBT. The thermal behavior of the propellants was also investigated through DSC experiments. The addition of bistetrazoles provided lower decomposition temperatures than the pure nitrogen‐rich materials, indicating that the two compounds probably react readily with the −ONO₂ groups present in the nitrocellulose and the plasticizers used in the formulation. The onset temperature of all propellants remained within acceptable ranges despite the observed decrease caused by the addition of the bistetrazole compounds.     

Oscillating Combustion of Gun Propellants in the Closed Vessel. I. preliminary investigation

The oscillating combustion, which takes place in the closed vessel when certain colloidal gun propellants are fired has been investigated. The amplitude of the oscillation depended on the geometry and flame temperature of the propellant. For propellants having the same composition but different geometry, the amplitude of the oscillation varied inversely with the maximum pressure in the vessel. This was tentatively ascribed to vortex formation during combustion.     

The Quantity/Distance Category of Gun and Rocket Propellants

The quantity/distance categorisation of explosive materials is discussed. The procedure for the standard UK laboratory-type test (large sealed vessel test) is described. The borderline, in terms of the test, between fire and explosive risks has been established by testing materials for which the nature of the hazard is previously known. Trials have established that boxed UK plastic (composite) propellants are fire risks only.     

Volumes and Sound Speeds of Two Gun Propellants at high pressure

Gun propellants are subjected to a variety of high stress states during the ballistic cycle. Attempts by constitutive modelers to describe the response of the propellant during the cycle are hampered by an almost complete lack of well-characterized experimental data at high pressures. We present quasistatic, hydrostatic pressure-volume, and compression and shear-wave-speed data on two formulations of a low porosity propellant. The hydrostat shows three distinct regions at pressures to 200 MPa. Below about 60 MPa, the response is elastic, with an effective compressibility controlled by the porosity; from ∼60 Mpa to 140 MPa the porous matrix fails and the material softens as the porosity distribution is crushed; above ∼140 MPa, the bulk modulus continues to increase to the value for the matrix. Both the hydrostat and sound speed data show significant time-dependent effects with characteristic times of ∼10³ s and > 10⁴ s.     

Burning Rate Evaluation of Composite Solid Propellants. A simplified approach

One of the principal parameters associated with a solid propellant is its linear burning rate. Many attempts have been made in the past to determine theoretically the burning rates of solid propellants by the use of appropriate combustion models. The object of the present paper is to propose a simplified theory of burning rate suitable for composite solid propellants. While the paper follows basically the scheme suggested for this purpose by Beckstead, Derr and Price using multiple flamelets, certain simplifying assumptions have been introduced with a view to make the model easier to operate. An attempt is also made in the paper to extend it to the case of aluminized solid propellants as well on the basis of a specific hypothesis regarding the role of aluminium. The relevant transcendental equations of combustion were solved on a digital computer. The burning rates and related characteristics were evaluated by this technique for two specific ammonium perchlorate-based solid propellants, one aluminized and the other non-aluminized, and the results obtained agree reasonably with the reported experimental trends.     

Combustion Behavior and Thermochemical Properties of RDX-Based Solid Propellants

The combustion behavior and thermochemical properties of two types of RDX-based composite propellants, XM39 and M43, are studied and compared in order to investigate the effect introduced by an energetic ingredient in the M43 propellant formulation. Due to the enhanced rate of heat release on the burning surface caused by the energetic material of M43 propellants, the burning rate of M43 propellants is found to be higher than that of XM39 propellants. The presence of the energetic material in the M43 propellant formulation also increases the burning surface temperature and thermal diffusivity of M43 propellants; it does not, however, introduce any observed changes in the flame structure and the heat feedback from the gas phase to the condensed phase. Based upon SEM pictures, burning-surface structures of the recovered XM39 and M43 propellant samples are found to be significantly different, indicating the strong effect of the energetic material on the surface reaction. A set of important thermochemical properties of XM39 and M43 propellants is deduced from the experimental data.     

Modeling of Ignition and Combustion of Boron-Containing Solid Propellants

Combustion, Explosion, and Shock Waves - This paper presents the results of an experimental study of the ignition and slagging characteristics for combustion of boron-containing solid propellants...     

Role of sparger design in mechanically agitated gas-liquid reactors. Part II: Liquid phase mixing

Liquid phase mixing time was measured in 0.57, 1.0 and 1.5 m i.d. mechanically agitated gas-liquid reactors. Transient conductivity technique was used for the mixing time measurement. Pitched blade downflow turbine was employed. The design details of PTD impellers such as diameter (0.22 T to 0.5 T) and blade width (0.25 D to 0.35 D) were studied. The influence of sparger types and their design on mixing time has been investigated. For this purpose, pipe, ring, conical, and concentric ring spargers were employed. The design details of the ring sparger, i.e. ring diameter, number of holes and hole size were also studied in depth. Sparger location with respect to the impeller was found to be the most important variable and, therefore, it was varied for practically all the spargers studied in this work. It was found that the liquid phase mixing time depends on the impeller design, sparger design, sparger location, impeller speed and superficial gas velocity. Correlations have been developed for the dimensionless mixing time.     

Microchemical Engineering: Components,Plant Concepts,User Acceptance – Part II

Over the last five years, many activities have focused on the unexploited field of carrying out reactions on small scales. Due to the rapid development of new components, this paper deals with recent developments only in a compressed form. An important point is the analysis of possible plant concepts for microreactors and whether these are a sensible option. Due to the enormous difference in size between the microchannels and the fluid periphery of possible components this is not just a technical question. It touches on the microtechnology concept as a whole. The direction in which the field should be developed and which measures can be taken to influence its development are questions that are addressed here with respect to the big industrial interest in microreactors.     

双基系固体推进剂热安定性及安定机理研究进展

从化学安定剂的结构、性能、应用及其作用机理等方面综述了化学安定剂在双基系固体推进剂热安定性中的作用及安定机理的研究进展,分析了近年来研究中存在的问题,包括缺乏化学安定剂本构关系的研究、化学安定剂安定机理研究不足、热安定性检测手段有待改进等。提出了今后研究的重点主要是加强化学安定剂本构关系研究、深入研究安定剂作用机理和反应动力学、拓展新方法和新技术的应用等。附参考文献74篇。     

CRT colorimetry. Part II: Metrology

The colorimetric characterization of computer-controlled CRT displays require radiometric measurements with high precision and accuracy in order to achieve acceptable colorimetric accuracy in defining stimuli generated with this type of imaging modality. Precision and accuracy requirements for photometers, colorimeters, and spectroradiometers were evaluated. When models are used to relate digital counts defining a stimulus and resulting spectral radiant exitance, displays are assumed to exhibit channel and spatial independence. A variety of tests and the results of evaluating four imaging systems are described. From these analyses, measurement accuracy is mainly limited by wavelength scale in the case of spectro-radiometers and filter fit in the case of colorimeters. Measurement precision is limited by the number of significant figures for fixed-range devices and signal-to-noise limitations for low-luminance stimuli. Display accuracy is limited by a lack of channel and spatial independence. Display precision is mainly limited by the electronic design of the display and the stability and load independence of the gun amplifiers. © 1993 John Wiley & Sons, Inc.     

Laundry Detergency of Solid Nonparticulate Soil or Waxy Solids: Part II. Effect of the Surfactant Type

In this work, methyl palmitate with a melting point around 30°C was used as a model of waxy soil. Its detergency was evaluated with a hydrophilic surface (cotton) or a hydrophobic surface (polyester) using different surfactants: alcohol ethoxylate (EO9), sodium dodecyl sulfate (SDS), methyl ester sulfonate (MES), methyl ester ethoxylate (MEE), and two extended surfactants (C_12,14-10PO-2EO-SO₄Na and C_12,14-16PO-2EO-SO₄Na). The detergency efficiency at a 0.2 wt.% surfactant and 5 wt.% NaCl gradually increased while redeposition gradually decreased with increasing washing temperature in most studied surfactant solutions; this was observed both above and below the melting point of methyl palmitate on both studied fabrics. If the methyl palmitate was heated above the melting point when deposited on the fabric, it was better able to penetrate into the fabric matrix as compared to deposition below the melting point, resulting in poorer detergency for heated deposition, particularly for washing temperatures lower than the melting point. Among the surfactants studied, the nonionic surfactant (EO9) showed the highest detergency efficiency (73–94%) at any washing temperature especially on the polyester fabric. For washing temperatures below the melting point, detergency performance correlated well with the contact angle of surfactant solution on the solid methyl palmitate surface for all studied surfactants when salinity was varied. In this work, conditions resulting in the highest detergency below the melting point corresponded to the highest detergency above the melting point, suggesting this as a systematic approach to formulating below the melting point of the soil. Charge of particles or fabric was not observed to be important to the detergency mechanism, but steric factors resulting from surfactant adsorption were observed to be important mechanistic factors in waxy solid detergency.     

High Energy Propellants for Advanced Gun Ammunition Based on RDX,GAP and TAGN Compositions

A number of gun propellant compositions based on RDX, GAP, TAGN and combinations thereof were formulated and studied with the aim to select the suitable composition for advanced gun ammunition in respect of processability and ballistic performance. Theoretical thermochemical properties of the compositions were computed using a ‘THERM’ programme and the ballistic performance was evaluated on the basis of closed vessel tests. In addition, sensitivity, thermal characterization, thermal stability and mechanical properties of the compositions were also determined for assessing the suitability for application. A composition containing 28% NC, 45% RDX, 20% TAGN, 6% GAP, 0.7% carbamite and 0.3% resorcinol was found to provide higher level of force constant at relatively lower flame temperature, reasonably good burning rate characteristics and mechanical properties.