Design of Chemical Propellant Thruster to Deorbit Nano satellite: StudSat II

An increase in satellite application has skyrocketed the number of satellites, especially in the low earth orbit (LEO). The major concern today is that these satellites become debris after the end of life, negatively affecting the space environment. As per the International Guidelines of the European Space Agency, it is mandatory to deorbit the satellite within 25 years of its end of life. This paper is aimed to design the solid chemical propellant thruster to deorbit the StudSat II from its original orbit to the lower orbit. StudSat II carries the heritage of StudSat I, successfully launched on 12th July 2010 AD, and is the first Pico Satellite in India by the undergraduate students of seven engineering colleges. This paper explains how a solid monopropellant thruster could be used to deorbit the satellite after the end of life with the least difficulty compared to other active and passive methods of deorbiting. The deorbiting mechanism consists of a solid propellant, Convergent Divergent nozzle, ignition system, and electronic actuators. The components of the thruster were designed in the CATIA V5, and the combustion studies and flow analysis were done in ANSYS. The concept of Hohmann transfer was used to deorbit the satellite, and STK was used to simulate it.Comment: 8 papers, 17 figures, Presented and Published at Proceedings of the XVII Vibration Engineering & Technology of Machinery Conference(VETOMAC),Dec. 15-17, 2022, DMAE, IOE, Pulchowk, Nepa

Explosive Welding Process to Clad Materials with Dissimilar Metallurgical Properties

Explosive welding is a solid-state process, which is an advanced form of joining two metal plates with dissimilar metallurgical properties, irrespective of the differences in physical and chemical properties. In this process, high pressure of explosive is used to accelerate one metal plate over another to form the bimetallic product. The pressure needs to be sufficiently high and for enough length of time to achieve inter-atomic bonds. During the explosive welding process, a jetting phenomenon occurs at the collision point which cleans the top oxide layer over metals and leaves the virgin surfaces that help in the joining process. The metals are joined without losing their pre-bonded properties with higher bond strengths than the strength of the weaker parent material. There are various critical factors such as explosive type, mass of explosive, stand-off distance, type of plate material, velocity of detonation etc. which affect the bond quality. Researchers mainly play with all these parameters to bring out the best characteristics of the bimetallic product that can be used for the desired applications such as heat exchanger, pressure vessels etc

Participatory ranking of fodders in the western hills of Nepal

Fodder is an important source of feed of the ruminants in Nepal. In the mid hills of Nepal, farmers generally practice integrated farming system that combines crop cultivation with livestock husbandry and agroforestry. Tree fodders are good sources of protein during the forage and green grass scarcity periods especially in dry season. Local communities possess indigenous knowledge for the selection of grasses and tree fodders at different seasons in mid hills of western Nepal. A study was conducted on the perception of farmers with respect to selection of fodder species in eight clusters in Kaski and Lumjung districts that range 900-2000 meter above sea level and receive average precipitation of 2000- 4500mm per annum. During the fodder preference ranking, farmers prepared the inventory of fodders found around the villages and nearby forests and selected top ten most important fodders in terms of their availability, palatability, fodder yield, milk yield and milk fat yield. In total, 23 top ranking fodders species were selected from the eight clusters. These fodder species were also ranked using pairwise ranking and weighted scoring methods and ranking was done on the basis of merit numbers obtained from weighted scores. The analysis revealed Artocarpus lakoocha as best tree fodder followed by Ficus semicordata, Thysanolena maxima and Ficus calvata. Similarly, the calendar of fodders trees for lopping season and the best feeding time was prepared on the basis of farmers’ local knowledge. This study suggests strategies for promotion of locally preferred tree fodder species and supplementing tree fodder with feed in different seasons depending on their availability and local preferences

Nutritive values of fodders at different seasons and altitudes in Gandaki River Basin of Nepal

This study aimed to assess the seasonal and ecological variation of chemical and nutritional values of locally preferred fodders in Gandaki River Basin (GRB) areas. The study was conducted in four altitudinal gradients viz. <400m, 400-800m, 800-1200m and 1200–1600m altitude above sea level in different looping seasons: rainy, spring and winter seasons. The most important five species of fodder trees Artocarpus lakoocha, Ficus roxburghii, Thysanolaena maxima, Ficus semicordata and Bauhinia purpurea were selected based on farmers’ preferences in nutritional values. Fodder samples comprised young leaves, old leaves and young twigs that were taken in July, September and December. It was revealed that nutritive value is not very much influenced by altitude but it is strongly influenced by lopping seasons. Among Thysanolaena maxima, Artocarpus lakoocha, Ficus roxburghii and Bauhinia purpurea the cellulose contents were significantly different (p<0.001) with seasons but there was no significant variation with altitudes. Similarly, Acid Detergent Fibre (ADF) contents in Thysanolaena maxima, Ficus roxburghii and Bauhinia purpurea were found significantly different with seasons. Ficus roxburghii fodder tree was found significantly different in Neutral Detergent Fibre (NDF), ADF, Cellulose and Potassium content with seasons. Similarly, fodder tree Bauhinia purpurea was found significant on Dry matter (DM), Crude fibre (CF), NDF, ADF, cellulose, tannin and potassium with seasons. The study hinted how careful planning of species selection and prudent decision in scheduling looping and feeding fodder trees can help improve animal metabolism, health, growth and productivity

Thangmi wedding ritual texts

Thangmi wedding ritual text