simultaneous optimal design of future space transportation system with ascent and reentry trajectories
- Paper number
IAC-08.D2.5.8
- Author
Mr. Hirokazu SUZUKI, Japan Aerospace Exploration Agency (JAXA), Japan
- Year
2008
- Abstract
Many studies of optimization for reusable space transportation systems have addressed the ascent trajectory, but we can not ignore the weight of the thermal protection system (TPS), which occupies about 20% of the dry weight. Previous studies have estimated TPS weight assuming the average density of the TPS weight based on the Space Shuttle and multiplied it by the body wetted area. The vehicle is not permitted reentry flight if the estimated TPS weight is less than the required weight for reentry. However, overestimation of the estimated weight might increase operation costs and/or make the vehicle heavier than necessary. Therefore, we must estimate the TPS weight according to simultaneous optimization of the ascent and the reentry trajectories. This paper describes optimal design for TSTO reusable system using rocket propulsion with consideration of both ascent and reentry trajectories. The TPS weight estimation is performed using two steps. First, the aerodynamic heating rate is estimated for typical points. Six points are set as typical point, namely the nose, strake portion, wing tip, and at 25%, 50%, and 75% positions from the nose on the undersurface. Second, the TPS weight is estimated by dividing the TPS into two parts. The weight of the first, the hot structure, is estimated using a database of carbon/carbon material of the HOPE-X and the Space Shuttle. The weight of the second, the heat insulator, is estimated as follows. One-dimensional finite element method is performed on their points; then the required thickness is calculated. The newly proposed hybrid algorithm incorporating gradient-based and genetic algorithm methods simultaneously optimizes the ascent and reentry trajectories. In the ascending trajectory, the first stage obtains only potential energy; the second stage then accelerates to orbital speed. In the reentry trajectory, suppression of the flight time is important to reduce the TPS weight because the skin structure temperature under the TPS must not exceed the permitted temperature. However, excessive deceleration maneuvers increase the load factor, thereby augmenting the main structure weight. They have a tradeoff relationship.
- Abstract document
- Manuscript document
IAC-08.D2.5.8.pdf (🔒 authorized access only).
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