Research On Responsive Space Lift Transfer Orbit Design And Guidance Approach

The development of responsive space lift could be significant to the rapid deployment, reconfiguration, expansion and maintenance of space systems. Taking that as the background, this thesis makes effort on the technologies of transfer orbit design and vehicle guidance, expecting to meet the new requirements proposed by responsive space lift.Firstly, transfer orbit design and optimization of responsive space lift are investigated, and the rapid design approach of transfer orbit, when the oblateness of the earth is taken into account, is presentd. (1) The ground waiting time during launch to satisfy the constraints of the orbit plane and the phase in the plane is discussed. The approach to design phasing orbit, both forward and backward, is addressed, which could improve the launch responsive capability with regard to an immovable range. (2) The two impulses minimum time transfer orbit design with fixed initial and terminal ends is studied, using an analytical method. Based on the Lagrange coefficient equation and the theorem of chord velocity, a one-unknown algebraic equation of eight degree is deduced to determine the optimum solution. Some assumptions are made to simplify the equation to get an approximate solution which is theoretically instructive. (3) A hybrid genetic algorithm (HGA) is chosen to design the four impulses minimum time transfer orbit with energy constraints. An adaptive annealing penalty function is contrived to deal with the energy constraints during orbit transfer, and two different hybrid algorithms, the serial HGA and the embed HGA, are designed. The HGAs both successfully dispose of the problem that the genetic algorithm usually converges on a probabilistic solution. Consequently, an optimum algorithm that has both local and global search competence is acquired. (4) Inspired by shooting method and virtual target, the equal-time deviation iterating approach is presented to rapidly design the transfer orbit when the oblateness of the earth is taken into account. Subsequently, the convergence conditions and singular points are discussed theoretically, based on which the improved equal-time deviation iterating approach is put forward. The two approaches both use analytical means to compute the influence of the earth's oblateness, resulting in fast convergence and high precision. Thus, they are both competent for onboard tasks, such as fast mission programming, demanded velocity calculation.Secondly, the ascending phase guidance scheme of responsive space lift is explored, and stellar/inertial composite guidance technology is selected to conquer the challenge. (1) With regard to the single star/inertial platform composite guidance system, the models with respect to platform leveling and decline are established. Besides the relations between the platform error angles and the inertial errors as well as the inertial instrument errors, the measurement equation of star sensor and the modification equation are also included. (2) Base on the analysis of ballistic missile composite guidance system working principles, two accuracy indices correction policies of the carrier rocket are put forward. One group of the indices is the local slope angle of trajectory and orbit inclination, and the other one is the semi-major axis and orbit inclination. The determination of the best correction coefficients is discussed. The numerical simulation results show that, with the same orbit injection precision, the two policies addressed in the thesis both need fewer requirements on the preparation before launch and the precision of inertial instruments. In other words, the composite guidance technology is fit for the responsive space lift. (3) With respect to the platform leveling scheme, the concept of equivalent information compression is presented, with which analytical and partly analytical approaches are derived to determine the optimum stellar direction. An optimum index that can compromise the performance of accuracy indices which have different properties is proposed, intending to get the best navigation star of the platform decline scheme,. The simplex method is chosen to do the optimization, and a best navigation star table under simple conditions is proposed to reinforce the global optimize capability of simplex method.Finally, according to the requirements of rapid space application, a combined explicit guidance shceme for orbit transfer phase, including the close-loop guidance and the iterative guidance, is studied. (1) The close-loop guidance approach is selected to steer the initial orbit maneuver. The velocity-to-gain guidance scheme and the cutoff demanded velocity prediction guidance scheme are discussed and compared. The best thrust direction of velocity-to-gain guidance scheme is surveyed, and a cutoff concept with smaller integral step and cutoff time linear forecasting is proposed. (2) The iterative guidance scheme is selected to steer the terminal orbit maneuver. With the simplification of motion equations and gravitation calculation, the iterative guidance equation is derived, using optimal control theory. The guidance algorithm is verified by numerical simulations finally.Along with the extension of space system application and development of astro- nautical technology, the responsive space lift will be the trends of space entrance and space application. The research conclusions of this thesis could be helpful in the development of our country's related space vehicles, theoretically and technically.