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Purpose This paper aims to optimize the mass of a tethered aerostat to achieve optimum hull volume, and fins to generate aerodynamic lift to reduce the blow-by. Design/methodology/approach The design code of aerostat involving structure, aerostatics, aerodynamics and stability has been developed using MATLAB®. The design code is used to obtain the baseline configuration for a tactical aerostat mission by using the statistical values of the hull fineness ratio and the fin parameters of in-service aerostats. The effect of the design variables that include the hull fineness ratio, fin area and fin position on the aerostat mass and blow-by is determined through sensitivity analysis. The aerostat is optimized with an objective function of minimization of mass for the bounded values of design variables and taking blow-by limit as a constraint. Findings This study reveals that the simultaneous optimization of the aerostat hull fineness ratio, fin area and fin position results in an improvement in the design. The aerostat design with optimum values of these parameters helps in a reduction in its size and mass without compromising the blow-by limits. Research limitations/implications This study has been conducted by keeping the hull shape constant by selecting standard National Physics Laboratory envelope shape. The aerodynamic model used in the design code is based on empirical relationships that can be improved in future studies that can use high fidelity aerodynamic models using CFD based surrogate models. Originality/value The previous studies on optimization of aerostats are limited to hull envelope shape only, whereas this paper presents the optimization of the hull and fin together. The optimized configuration obtained has a reduced mass and can operate within the specified blow-by limits.

The Aerostats are lighter-than-air (LTA) systems that are used to carry important payloads at specified altitudes. Tethered aerostats are connected to the ground via a tether that maintains the position and provides power. Aerostats have to operate in various atmospheric conditions depending on their mission. This paper presents a literature review on the different envelope shapes of the tethered aerostats. Aerostat envelope contains the LTA gas that provides the lift force to carry the payload in the air. This research paper presents a comprehensive literature review on the different shapes of aerostat envelopes. The review has been presented to highlight the design process of the different aerostat envelope shapes that includes sizing, aerodynamics and stability. In addition to the design factors, this paper also presents a review on the applications of different aerostat envelope shapes. Information related to the different design parameters and limitations of aerostat envelopes is also provided.

Regression testing is performed to see if any changes introduced in software will not affect the rest of functional software parts. It is inefficient to re-execute all test cases every time the changes are made. In this regard test cases are prioritized by following some criteria to perform efficient testing while meeting limited testing resources. In our research we have proposed value based particle swarm intelligence algorithm for test case prioritization. The aim of our research is to detect maximum faults earlier in testing life cycle. We have introduced the combination of six prioritization factors for prioritization. These factors are customer priority, Requirement volatility, implementation complexity, requirement traceability, execution time and fault impact of requirement. This combination of factors has not been used before for prioritization. A controlled experiment has been performed on three medium size projects and compared results with random prioritization technique. Results are analyzed with the help of average percentage of fault detection (APFD) metric. The obtained results showed our proposed algorithm as more efficient and robust for earlier rate of fault detection. Results are also revalidated by proposing our new validation equation and showed consistent improvement in our proposed algorithm.