This article presents an assessment of the external thermal load on the life support system of a solar aircraft under extreme operating conditions. The calculation was carried out for the maximum and minimum possible heat flows in the key points of the aircraft flight. In this article the conditions on the Earth’s surface and at the operating altitude of the aircraft were taken as calculated. The dependence of the quantitative changes in the heat load on the aircraft from altitude was revealed, taking into account changes of thermal properties of the environment and mechanisms of heat transfer.

Due to the development of technologies, alternative energy sources are becoming more widespread industry and technology. One of the most promising and widely used methods of generating heat is solar radiation. Nowadays, scientists do active research in the field of creating aircraft powered by solar panels, the so-called solar aircraft. Vehicles of this type are an innovative area for the development of aviation. One of the most important problems of the practical use of manned solar aircraft is to ensure the life of the crew of the aircraft. Due to strict weight and size restrictions, the life support system should provide a thermal regime that is comfortable for the pilot throughout all phases of flight, taking into account changes in environmental parameters and have a high degree of reliability and compactness with a minimum weight of all units. The scheme of the life support system (hereinafter referred to as the LSS) is described in the literature [1]. The paper continues the study of the problem described in [2], and an estimate of the external and internal thermal load on the LSS system of a solar aircraft under conditions at the Earth's surface and at the maximum flight altitude is given there. As a result of comparing the obtained values of heat inflows, it was revealed that the total value of the heat load can take both positive and negative values. This means that to ensure a comfort for a pilot, it is necessary to provide both heating and cooling of the pilot's suit. Considering that structural and physiological features of man can seriously affect the values of heat fluxes, the need for physiological tests was substantiated to confirm the data obtained by calculation, and the possible refinement of the design of the LSS system.