The rapid growth in the population of objects orbiting the Earth has led to increased congestion and collision risk. Solar-sail missions have been proposed as a means of debris removal by harnessing the perpetual force from sunlight to perform maneuvers; however, their capability to avoid collisions under the combined effects of solar radiation pressure and atmospheric drag remains to be investigated.

To address this gap, a framework was developed to simulate conjunctions between a sail and debris using representative uncertainties to compute collision risk. Analytical and numerical locally-optimal control laws were applied to steer the sail away from conjunctions and minimize maneuver durations while safely reducing the collision risk. The results revealed patterns in the applicability of specific control laws, with maneuver durations ranging from minutes to hours and showing strong dependence on orbital, physical, and conjunction parameters. ... Read more

Weather balloons have been used for decades as a means of measuring atmospheric properties. Balloons are launched twice a day from almost 900 locations worldwide, carrying measurement instruments called radiosondes. Along with data from ground-based sensors, aircraft, and remote-sensing satellites, the collected meteorological data is fed into numerical weather forecasts and climate models. The weather balloons typically burst at altitudes of around 33 km, after which the radiosonde falls back with a parachute but without any control. This leads to large amounts of waste scattered over land and sea. While the balloon material itself is fully biodegradable, the loss of radiosondes and their associated electronics can be an environmental threat. Furthermore, the loss of the filling gases such as helium and hydrogen also poses a threat to the environment – helium is a non-renewable resource and hydrogen indirectly causes warming effects when released in the upper atmosphere. These factors present the need to develop sustainable and reusable alternatives to current weather balloons. In response to this pressing need, the BRAVO family of gliders has been developed, which is short for “Balloon-Released Aerial Vehicle for weather Observation”. This report provides a comprehensive overview of the design process of creating these gliders. It introduces the detailed final design and outlines the logistical and operational procedures associated with their usage. Furthermore, the report encompasses meticulous analyses of cost and market factors, technical risks, and sustainability considerations. To ensure reliability, the gliders undergo thorough verification and validation processes. Finally, the report concludes with gained insights, recommendations, and directions for future work.F ... Read more