Journal of Aerospace Engineering

A new design of a reconfigurable multirotor is developed by employing a novel active–passive motor scheme. The scheme is based on quadrotor configuration with four additional motors placed in coaxial setup along a single axis. This unconventional design seeks to improve the general response of the system and increase the payload carrying capacity of the aerial vehicle. This paper presents an extensive mathematical model to establish the stability of the design, along with simulation and various real time tests. Simulation of the mathematical model with a proportional–integral–derivative (PID) controller shows the stability and responsiveness of the system in different configurations. Throttle response is also compared for different configurations. Finally, preliminary experimental test results with a prototype employing the same design are discussed. It is analytically and experimentally a stable system with a general improvement in throttle response.

Ignition and high altitude restarts under extreme conditions have always been key research problems due to low pressure and temperature of inlet air, so reliable ignition and wide ignition boundary is very necessary. In this study, the ignition characteristics of kerosene/air mixtures at different excess air coefficients with a plasma jet ignition and spark ignition were investigated experimentally in a model combustor. The plasma ignition system utilizes compressed air as plasma formation gas. The spontaneous emissions of O atoms (777 nm) and CH radicals (430 nm) were collected by photomultiplier tubes with corresponding filters to identify the ignition and combustion timing during the ignition process. A plasma jet can penetrate a recirculation zone and initiate flame kernel, and the larger plasma volume and the activated area is very helpful to achieve successful ignition. The results show that a plasma jet ignition delay time is much shorter than that for spark ignition in a wide range of excess air coefficients; the minimum plasma jet ignition delay time can be reduced by 88.74% compared to spark ignition in the same experimental conditions. With the increase in plasma arc current, the ignition delay time can be further reduced.

Establishing a lunar base requires the design and construction of infrastructure that can withstand the Moon’s hazardous environment. This study explores the effects of micrometeoroid impacts on a biopolymer-bound soil composite (BSC), a novel construction material that leverages in situ resource utilization to significantly reduce costs associated with resource transportation from Earth. Using a small fraction of biopolymer to bind regolith, BSC can be used to build radiation and micrometeoroid shielding for habitats, stable landing and launching pads, and pavements that help to contain dust. To determine the relationship between hypervelocity impacts and BSC material damage, 19 hypervelocity impact experiments were conducted on BSC targets. Analytical power-law relationships were derived to predict transient crater dimensions, such as volume and diameter, from projectile features, such as diameter, density, and velocity. The scaling exponents determined for BSC transient crater volume and diameter are comparable to those of quartzite, sandstone, and basalt and indicate that crater formation in BSC is largely driven by the kinetic energy of the projectile, as expected for cohesive low-porosity materials.

Fiber research in concrete construction technology has been helping to prevent catastrophic disasters due to the loss of structural integrity and service life by functioning as structural health monitoring (SHM) technology. Past studies demonstrated the use of self-consolidating carbon nanofiber concrete (SCCNFC) as a structural sensor, which led to the development of carbon nanofiber aggregates (CNFAs) to be used as strain sensors to determine localized strains in concrete structures. This paper examines the effect of temperature and hydration on CNFAs. In the temperature study, the specimens containing CNFA were monitored for temperature sensing capability through one complete cooling and heating cycle ($-20°\mathrm{C}$ to 90°C), giving the mathematical model to predict the thermal behavior of CNFAs used to monitor the temperature of embedded structures. In the hydration study of CNFAs, this paper critically examines the effect of water on the electrical resistance of CNFAs and demonstrates the necessity of the waterproof coating in embedded CNFAs for reliable SHM.