Numerical Cumputation Of Upper Stage External Heat Flux

With the further development of space missions, higher requirements on launch vehicle upper stage have been put forward. The calculation of external heat flux of upper stage is the foundation of the designing of its thermal control system and its thermal analysis, at present, domestic algorithms and foreign commercial software have many defects, severely affecting the design and verification of upper stage thermal control system. Based on this, this thesis presents a deep insight into the calculation of external heat flux of the upper stage, with the following achievements:Firstly, the upper stage application and external heat flux algorithms development was summarized, and the deficiencies of existing methods were analyzed. Then, a systematic research of external heat flux theory was carried out. To resolve the shortcomings of the conventional definition, the concept of the external heat flux view factor was redefined, and the concept of external heat flux radiative transfer coefficient was put forward, to consider the absorption of external heat flux after multiple reflections, basing on radiative heat transfer theory, Monte Carlo methods and Gebhart methods.Secondly, the algorithms of upper stage external heat flux were researched. Core algorithms, such as energy beam emission models, orbital parameters and sun vector determination, external heat flux view factors calculations, were elaborated, based on the algorithms procedure. The geometric properties of the energy beam in Monte Carlo methods were described. The local coordinate and geometric parameters of upper stage common surface elements were defined. The energy beam emission models of surface elements were established. Advantages and disadvantages of intersection judgement of the beams and elements in different coordinate were analyzed, and intersection judgement in local coordinate was put forward. Algorithms of orbital parameters, coordinate transformation matrix, solar vector and eclipse considering perturbation basing on SGP4/SDP4 model were put forward. Improvement was achieved to solve the problems encountered using conventional Monte Carlo methods to calculate external heat flux, higher efficiency was achieved, and the algorithm procedures were introduced. Algorithms of external heat flux radiative transfer coefficient and total absorbed external heat flux after multiple reflections were introduced.Finally, modules were divided in the upper stage external heat flux algorithms, and upper stage external heat flux solver was realized, basing on the designing of orbital module, external heat flux view factor module, external heat flux radiative transfer coefficient module, and external heat flux module. External heat flux simulation of a simple model was made, by comparing the results of the solver and commercial software Thermal Desktop, effects of the perturbation, solar vector variation and multiple reflections were analyzed, and the distinction and the validity of the algorithms was proved. Then, external heat flux simulation of a virtual upper stage was made, by comparing the results of the solver and Thermal Desktop, it was proved that computing requirements of external heat flux of common upper stage surface could be fulfilled, and that the algorithms was applicable.