I. Introduction olar powered aircrafts began their flight in 1974 by Sunrise I1. However, their main achievements were reached by NASA series of solar aircrafts beginning by Pathfinder in 1993 and ending with Helios in 20032. Great successes were reaching altitude of 96,863 ft by Helios and commercial remote sensing mission on coffee harvest in Hawaii by Pathfinder-plus3. In 2005, a small solar aircraft created by AC Propulsion company named Solong could fly for 48 hours. Also, Zephyr built by Qinetiq company, set an unofficial endurance record in August 2008 by staying airborne for three and half days to a maximum altitude of 58,355 ft. This aircraft modified its performance by setting an official endurance record of 14 days and 24 minutes in July 2010 and reviviscenced the hopes for ‘Eternal Flight’.

The advantages of solar aircrafts are as following: low pollution, low cost, flight capability in polluted areas or other planets, high altitude, and long endurance. Their disadvantages are structural flexibility and sensitivity to atmospheric conditions, sensitivity to solar radiation level, and low Wpay. This challenges are still noticeable and great research and technology development in the areas of solar cells, energy storage systems, and aircraft design are still needed to design and build safe, reliable, and efficient solar aircrafts so that disatsers such as helios mishap2 will not occur again. With technology progress we can have more capable solar aircrafts and the future for these aircrafts is very thriving. However there has not been much work done on solar aircraft design in the literature4-12. Most of those designs are suffering from the brevity and are based on power sizing for multi-day endurance capability. For power sizing, they use the equation for total power available by the solar cells during day light equal to power