Performance Estimation by Varying the Grain Port Alignment Position in a Hybrid Rocket Motor

A Hybrid Rocket Motor (HRM) is a type of chemical rocket propulsion in which the propellants are stored in different physical states. To counter the low regression rate characteristic of HRM different grain configurations with innovative port techniques has been evolved with time. It creates better mixing and combustion of fuel with oxidizer without having any special injector and energetic additives. A similar technique has been used in the present study. The fuel used in the present study is a solid grain made from polyvinyl chloride with di-butyl phthalate in the 50:50 ratios with gaseous oxygen as an oxidizer. In this paper, analyses are made to study the performance of a hybrid rocket motor by varying the axial alignment of the grain port at varying locations along the length. Due to the offset of the fuel port at varying locations, recirculation zone were created that enhanced the pressure in the combustion chamber by around 1-2 bar. The thrust generated was increased in the range of 10 to 25 N. Regression rate as well as efficiency was also observed to be increased with the use of this port alignment techniques

Conceptual Design Process of a Missile Model and Production Using Additive Manufacturing Method

This study focuses on air-to-ground missile systems, which are widely used in Turkey and around the world and are becoming increasingly important. The development of missile systems takes into account various requirements defined by the end user. It is important to identify a system and its subcomponents that fully meet the requirements. This study analyzes an air-to-ground missile system and its main subcomponents identified through the conceptual design method based on the systematic design approach proposed by Pahl and Beitz. The aim is to determine the feasibility of obtaining an optimal solution that meets the requirements set by the conceptual design method. The missile design’s optimal solution was modeled using SolidWorks software. A three-dimensional (3D) printer with FDM production technology was used to produce a prototype of the computer-modeled design. ABS and ABS-plastic blend filaments were preferred due to their material properties in the FDM production process. During the printing stage, the filament and output settings of the model were determined using the 3D printer’s interface program. The filaments were then extruded through a nozzle, following the cross-sectional geometry of the part. The resulting model was printed in pieces and assembled with a tolerance of 0.1mm. This process resulted in a 3D model of the missile, which was created to represent the system structure in different colours. The study demonstrates that the conceptual design method can be used to develop innovative and meaningful missile models

Experimental and Numerical Investigation of Bodywork Effect on High Hardness Armour Steel Against a 7.62 x 51 mm NATO Ball M80 Projectile

Small arms ammunition like the 5.56×45 mm NATO Ball and 7.62×51 mm NATO Ball projectiles constitute a significant threat to light armoured vehicles. These vehicles are mostly comprised of single-layered metallic high-hardness steel armour, but as an essential vehicle design feature, mild steel bodywork is externally mounted in certain areas for fenders, toolkit boxes, storage boxes, etc. over the main armour, i.e., high-hardness steel armour. These are necessary design features of vehicles, so they can’t be neglected regarding ballistic protection against threats. Also, to provide better ballistic protection in up-armoured vehicles, armour consisting of high-hardness steel armour is integrated or mounted just behind the existing bodywork of the car. Thus, this paper experimentally and numerically investigated the “bodywork effect,” which is also called the “K-effect,” and found that the configuration where the bodywork of mild steel is placed in front of high-hardness steel armour plate failed to provide better ballistic protection against the 7.62×51 NATO Ball M80 projectile fired at 0° angle of impact with a velocity of 833±20m/s from 10 m distance. However, the single high-hardness armour steel plate provided better ballistic protection than the configuration consisting of bodywork. For the validation of the experimental investigations, the arrangements were numerically simulated. The main aim of this work was to check the bodywork effect against this particular projectile and investigate factors contributing to the phenomenon

A Unified Mechanics Theory based Damage Model for Creep in Nickel based Superalloys

Unified Mechanics Theory’s (UMT) entropy-based damage parameter, also known as the “Thermodynamic State Index” has been proven to be consistent and useful in predicting the fatigue life of different metal alloys. In recent times, studies have also demonstrated its applicability towards creep damage in nickel-based superalloys under a limited set of conditions. However, the usefulness of the “Thermodynamic State Index” in estimating damage at different temperatures, and creep loads for different metal alloys has not been evaluated yet. In this paper, creep in INCONEL 600 alloy is modeled using Norton’s creep law modified with entropy-based damage (Thermodynamic State Index). The model is calibrated to predict both damage and creep strains for any given input of stress, temperature, and time. The available database on INCONEL 600 is used in parts to both calibrate and validate the prescribed model. The damage evolution for different cases is compared and imminent conclusions are drawn

Mitigating GHG Emissions from Military Supply Chain by Use of Aerial Cable Way

The transportation sector being one of the significant contributors to greenhouse gas (GHG) emission, there is growing concerns about environmental sustainability, and reducing GHG emissions which has prompted re-evaluation of transportation systems. The 1.5 million strong Indian defence forces have huge transport fleet and this study delves into the potential of Aerial Cableway (ACW) as a promising alternative mode of transport that can significantly reduce emissions of military supply chain in mountainous terrain. The study takes a case of Himalayan terrain to investigate how ACWs offer a low-impact, energy-efficient, and environmentally friendly solution compared to conventional ground-based transportation. It takes a case of Pharkian Pass in North Kashmir where defence forces has presence and this pass is often exposed to frequent landslides, snowfall and avalanches. Every year, on an average, approximately 12,000 trucks cross Pharkian pass in a year for purpose of logistics and sustenance. Without touching sensitive issues and by using a multi-criteria-based cost-benefit analysis, the study establishes that even if 75 % of road transport trips are shifted to ACWs, the reduction of GHG emissions is by 57.7 % in addition to significant benefits of the social cost of carbon, environmental costs, economic savings and ensuring strategic advantage like all-weather connectivity

Prediction of Mechanical Response of Nickel based Superalloy Subjected to Creep Fatigue Interaction Loading using Unified Mechanics Theory

In order to simulate and predict material's real-time responses for a component under complex mechanical and thermal loads, continuum damage mechanics (CDM) is employed. However, majority of the models found in the literature are phenomenological and primarily based on curve fitting, which offer limited understanding of the underlying physics of the problem. A few physics-based models have been developed that provide greater insights. Unified mechanics theory (UMT) is one such approach that captures entropy generation due to various dissipative mechanism which aims to explain the physics of the problem. During hold time in strain-controlled creep-fatigue interaction loading, stress relaxation is observed. This study attempts to capture stress relaxation response due to creep-fatigue interaction of nickel-based superalloys using UMT, which is regarded as a more scientific method than simply fitting curves. The evolution of creep strain energy with hold time is used to understand how material ages over time due to stress relaxation during creep-fatigue interaction loading

An Efficient Spoofing Attack Detection Using Deep Learning Based Physical Layer Security Technique

Spoofing attack detection plays a crucial role in the defence field, involving critical and highly secured data processing. The accurate attack detection mechanism prevents unauthorised access to sensitive information, thereby protecting National security. Physical Layer Security (PLS) is a promising emerging technique that uses the wireless channel’s randomness to secure the communication network. The spoofing attack is one of the severe threats to the wireless network, where the attacker imitates the legitimate user to launch an attack against the network. This paper investigates the channel characteristics-based physical layer technique to detect spoofing attacks. For static radio environments, the two-sample independent hypothesis testing is used to identify the spoofing attack, showing an improvement in detection accuracy of 97 %. The attack detection problem is considered a Reinforcement Learning (RL) based classification problem for a challenging dynamic radio environment. It is simulated using the actor-critic-based Deep Reinforcement Learning (DRL) technique with the help of the Reformed Deep Deterministic Policy Gradient (Re-DDPG) algorithm. The simulated results show that the proposed method performs better than the existing strategies and achieves a Receiver Operating Characteristics (ROC) value of 0.96. The detection accuracy of the proposed method can reach up to 98 %, with precision and recall of about 98 % and 99 %, respectively. &nbsp

MILP Based Differential Cryptanalysis on IVLBC and Eslice 64

Lightweight block ciphers provide security to resource-limited devices. However, many of these ciphers lack security analysis against basic attacks. This paper provides a detailed security analysis of two lightweight block ciphers, IVLBC and Eslice-64, against differential attack. The designers of IVLBC and Eslice-64 claimed that their ciphers were secure against differential attack. In this paper, to substantiate existing cryptanalysis’s claims, we perform differential attack on these two ciphers using the mixed-integer linear programming (MILP) method. We incorporate the difference distribution table (DDT) probabilities into MILP models. We discover differential distinguishers up to seven and 15 rounds for IVLBC and Eslice-64, respectively. We improve the known distinguishers for Eslice-64 by one round. Further, we mount the key recovery attack on an eight-round IVLBC and a 16-round Eslice-64 with data/memory/time complexities of 249/ 250.59/249 and 263/212.58/263 respectively

Impact of Solid Rocket Propellant Grain Manufacturing Limitations on Launch Vehicle Capability

It is examined if any limitations in existing solid rocket propellant grain manufacturing methods adversely affected the payload capability of recent space launch vehicles. It is seen if the transition from heavy, segmented metal rocket motor casings to lightweight monolith composite casings is possible without loss of ability to design and realize high-performance grain configurations using simple and safe methods. Considering payload fraction as the comparative performance metric, recently flown solid rocket-propelled, small-lift launch vehicles were surveyed and ranked. Solid rocket boosters of underperforming launch vehicles were investigated for manufacturing factors influencing payload fraction by comparing them to boosters of better-performing launch vehicles in their weight class. Relationships between payload fraction and the solid boosters’ mass fractions, casing construction, shape of thrust profile, propellant grain configuration and method employed to manufacture the grain were analysed. It is shown that those launch vehicles that did not possess or use the technology necessary to manufacture high-performance grain configurations like undercut finocyl in monolith composite casings ended up having boosters delivering poor thrust profiles with high inert mass ultimately leading to low payload fractions

Development of Micromechanics Based Constitutive Model for Alumina Using Unified Mechanics Theory Role of Microcracks in Damage

Ceramic materials used in mechanical applications show variations in their properties due to the difference in the presence of cracks and various defects. The micro-crack length, orientation, geometry and wing crack formation and propagation within the ceramic material define the strength of the ceramic material. In this study, a micro-mechanics-based model that accounts for micro-cracks is developed. Unlike other micromechanics-based models, the current model defines failure based on entropy. Entropy generated with various micro-crack lengths, orientations and wing crack extensions is calculated using the energy approach.The Unified Mechanics Theory (UMT) is used to define the damage in the ceramic material, which can include all possible failure mechanisms. A representative volume element (RVE) with a pre-existing flaw is simulated to generate stress-strain curves. The effect of different initial crack lengths and orientations on alumina peak strength is also investigated