Tools from the Indian space programme for observing and forecasting extreme weather events - Retrospect and prospect

Extreme weather events (EWEs) cause hardship, economic loss and have severe socio-economic consequences. It is necessary to develop forecast capability for such events so as to minimise losses and take appropriate measures for combating. Methods relying on only ground based weather observation networks are not adequate. Observations from space platforms offer regular and frequent measurements over a wide area. Observations from geostationary platforms provide information on atmospheric parameters and processes, while low earth orbiting platforms provide global observations at higher spatial resolutions. This paper describes the evolution of space programme in India, consisting of the space segment, data processing and products, and science and applications for observing and monitoring weather systems. Emphasis is on developing end-to-end capacity in weather monitoring. Forecasting of EWEs is illustrated with a few case studies. With the integration of space technology inputs, it is expected that forecast skill and lead time of the forecast will improve. Some of the future Indian space missions planned to enhance the capacity are also described. A multidisciplinary approach comprising the use of space technology, ground based measurement network and high speed computing power, can form a backbone for observing and forecasting EWEs.

Understanding India’s International Space Cooperation Endeavour: Evolution, Challenges and Accomplishments

India has now emerged as a major space-faring nation with notable accomplishments in the launch vehicle, satellite, space application and space exploration domains in spite of beginning its space programme from a disadvantageous position vis-à-vis other space-faring nations of the day, besides endeavouring entirely in the civilian domain. International cooperation played an important role during the genesis and the early evolution of the Indian space programme and has played a complimentary role during the progressive accumulation of India’s current space capabilities. Once a recipient of assistance in the domain of space, in the new millennium, India has achieved the status of an equal and even a major partner in some of the joint space endeavours with its erstwhile benefactors and has established facilities for training space personnel from developing countries of the Asia-Pacific region. This article critically reviews India’s international space cooperation endeavour in the past five decades and its influence on the country’s current space capabilities.

Improvement in Mechanical Properties of Standard 15CDV6 Steel by Increasing Carbon and Chromium Content and Inoculation with Titanium during ESR

The AFNOR 15CDV6 steel is high-strength steel with relatively low-level alloy content. In an earlier work, by processing the steel through ESR with inoculation, a marginal increase in strength and further increase in ductility and notch toughness were obtained. But the strength of the steel is inadequate for its use in fabrication of rocket motor casing in the Indian space programme. The present work aimed to increase the strength of the steel by increasing both carbon and chromium content of the AFNOR 15CDV6 steel at the expense of increased ductility and toughness due to processing through ESR. The increase in chromium content is expected to retard the bainite reaction resulting in an increased volume fraction of martensite in the mixed microstructure. Further, addition of chromium also causes secondary hardening during tempering. Another major objective was to study the effect of inoculation during ESR on grain size and mechanical properties. Titanium was used as inoculant in the present work.

Non Destructive Metallographic Technique Used in Indian Space Programme

Metallography technique is used as an important tool in designing and development of materials. The technique is destructive and hence has its own limitations. Non destructive metallography emerged as a solution for its limitations. The microstructure of the component in the field/service can be replicated and observed under microscope. In the recent past, this technique has drawn the attention of quality control personals due to its non destructive nature. This paper explains the use of nondestructive metallography technique for Ti-6Al-4V alloy domes and low carbon steel static test bed exposed to high temperature.

Microstructural Characterisation of Copper-Stainless Steel Brazed Joint with Copper Based Filler Metal

Copper to stainless steel brazed components are used in the thrust chamber of cryogenic propulsion system of Indian Space Programme. Temperature and time play a major role in the optimization of brazing cycle. An effort has been made to study the influence of the above parameters and correlate with the microstructure and shear strength achieved. In the present work, brazing was performed using Cu based filler metal. Temperature selected was within the range of 1010-1045 °C for two different time durations (20 minutes and 30 minutes) under high vacuum (10-5 Torr). Extensive scanning electron microscopy with energy dispersive spectrometry was carried out to understand the kinetics of elemental diffusion and phase formation at and near the brazed joint. Microhardness was evaluated across the joints to facilitate further understanding of the joint chemistry. The optimized shear strength of the joints was as high as 155 MPa for the joint brazed at 1030 °C for 30 minutes against the required strength of 150 MPa. The joint could retain strength at cryo temperature and meet the minimum expected value of 320 MPa. At the same time, it exhibited good mechanical properties at elevated temperatures. This paper brings out details of the investigation carried out.

Metallurgical Studies on Explosive Welded Aluminium Alloy-Stainless Steel Bimetallic Plates

Aluminium alloys and austenitic stainless steels are often used for construction of cryogenic pressure vessels owing to their attractive properties at cryogenic temperatures. Indian space programme requires AA2219/ICSS1218-SS321 bimetallic components which are machined from explosive welded plates. Pure aluminium sheet is used as an interlayer between aluminium alloy and steel to achieve a satisfactory bond. Internal soundness of the joint is evaluated through ultrasonic testing (UT). The present paper discusses bonding trials carried out by varying the explosive parameters using facilities and expertise of Terminal Ballistic Research Laboratory (TBRL), Chandigarh and M/s Giridhari Explosives Private Limited (GEPL), Hyderabad. The welded joint is extensively characterised with respect to Lap Shear and Ultimate Tensile Strength at ambient temperature and for metallographic analysis.