Aerial Vehicles on Mars : Perpetual Endurance

The problem of quantifying a design requirement for perpetual endurance of solar-powered unmanned aerial vehicles (UAVs) is treated. The design requirement is formulated as a threshold of the Power Ratio, a non-dimensional number that characterizes the ability of an aircraft to fly while solar-powered. This socalled Perpetuity Threshold is identified, derived and shown to be related to the duration of daylight and length of the solar day. A lower bound on the Perpetuity Threshold is given and comparisons are made of this threshold between Earth and Mars. To illustrate the difference of requirements for perpetual flight between these two planets, specific aircraft examples are characterized with respect to perpetual flight and discussed.