A Flight Path Generation Approach for Mission Simulation of Low Speed Aircraft in Strong Wind Fields

Abstract

Mission simulation environments are used to assess the ability of the investigated aircraft to fulfill specific flight missions. Such simulation environments are of particular interest for aircraft designed to fly persistently on high altitude and draw the necessary energy from the sun. These aircraft fly very slowly due to their very low wing loading and must cope with wind speeds that extend up to and beyond their flight speed. Additionally, these aircraft are highly limited in maneuverability, as they can only navigate very large turn radii. The assessment of mission capability for such aircraft poses a particular challenge due to the complex dependence on the availability of solar energy, especially based on the location, position, and altitude of the aircraft, as well as the time of the year. While simple flight performance calculations can provide indications of mission capability, they are generally insufficient as a planning basis. In addition to solar energy availability, the significantly variable wind at different altitudes and geographical locations, in particular, plays an important role and must be taken into account when calculating the flight path, as it has an high impact on the mission due to the slow flight speeds of solar-electric high-altitude aircraft, which are in the range of the expected wind speed. To simulate deployment missions globally for a solar powered high-altitude platform, which is currently under development, a suitable mission simulation environment has been developed. In this context, this publication describes the generation of the flight path based on a mission plan, taking into account the aircraft’s performance limitations, especially minimum turning radii. In this process, the spatial orientation and position of the aircraft can be determined for each simulation step. The calculation algorithm assumes a steady flight condition at each simulation step and is suitable for large step intervals to achieve short simulation durations for investigations of long-duration missions lasting several weeks or month. Starting with a short overview about the current aircraft development project, the requirements on the flight path generation are derived. Based on a state of the art review for optimal flight path generation algorithms, the chosen approach for the developed simulation environment is described in detail. The paper concludes with simulation results for an example mission.