Capture Trajectory Design And Atmospheric Entry Guidance For Probing Celestial Bodies In Complex Dynamical Field

The interplanetary mission involves complex dynamics, e.g., multi-body dynamics and aerodynamics. Judicious utilization of such dynamics can reduce the fuel consumption of orbit injection and atmospheric entry missions. This thesis focuses on the capture trajectory design and atmospheric entry guidance in a complex system with multiple gravitational bodies and sensible atmosphere. The main results are as follows.1. A systematic method to construct ballistic capture orbits in general dynamics and scenarios is presented. Orbits are generated by forwardly and backwardly integrating the discretized initial conditions. A novel definition of spatial stability is introduced. This definition, together with the escape and impact conditions, allows us to categorize the orbits into four sets, i.e., weakly stable, unstable, crash, and acrobatic. Ballistic capture orbits are extracted from these sets by simple manipulation. A stability index is formulated and used to detect these ideal orbits of practical interest. Capture orbits at Mercury, Europa,and the Earth have been considered as study cases. The feasibility of the construction algorithm, as well as the usefulness of the stability index, are verified through numerical simulations.2. The role played by the dynamical model, the planetary true anomaly and eccentricity, the particle initial plane, as well as the natural moon, is analyzed. The following has been found: 1) The larger the planetary eccentricity is, the easier the particle can be ballistically captured; 2) A configuration with the planet at aphelion(perihelion) maximizes the chances of capture for prograde(retrograde) orbits; a planet true anomaly in the rangeπ/4- π/2 generates regular post-capture orbits; 3) The spatial distribution has significant effect on the capture dynamics; inclinations in the range 40- 70 deg and 150- 160 deg promote capture and regularity; initial planes that maximize the chances of capture are also those that produce regular post-capture orbits; 4) the presence of a moon can be profitably exploited to further improve the quality of the post-capture trajectories; it also makes the permanent capture of a particle with zero-cost feasible. These results provide basic guidelines for selecting initial conditions and dynamical models that derive ideal ballistic capture orbits.3. A low-cost insertion strategy by combining ballistic capture and aerobraking is presented. A baseline algorithm including two inclination correction methods is proposed.A mathematical derivative is introduced to obtain the optimal yawing angle associated with a minimum flight time. The insertion strategy is applied in three scenarios, i.e., Mars capture mission, sample return from an asteroid, and Earth-Venus transfers. Numerical simulations show the significant propellant-saving capability and promising perspective in orbit capture.4. A novel insertion strategy by combining ballistic capture and aerocapture is addressed. A baseline procedure including a semi-analytical prediction of periapsis dynamic pressure is proposed. Simulated results of Mars capture scenario show this strategy can not only reduce the peak thermal impact and therefore lower the mass factor of the thermal protection system, but also avoid the "single-point failure" of the conventional aerocapture strategy.5. A skip entry guidance algorithm by using numerical predictor-corrector and "PatchedCorridor" is developed. The bank angle magnitude is parameterized using piecewise linear segments with respect to a normalized entry energy. An analytical derivation of the lateral state in the Kepler phase is accomplished, obtaining a "Patched-Corridor" with a lateral velocity corridor in the skip phase and a lateral crossrange corridor in the final phase. An extended estimation method is introduced to compensate for aerodynamic and atmospheric uncertainties. The simulations show the guidance algorithm provides a high landing precision, produces acceptable aerodynamic loads, requires few bank angle reversals, and is easy to operate. The guidance algorithm is valuable in practical applications.In summary, this thesis extends the concept of ballistic capture with aerobraking,aerocapture, and atmospheric entry techniques. The proposed methods can capture the spacecraft into a high-elliptic orbit, a circular science orbit, and onto the target’s surface with few fuel consumption. The obtained results are to provide technical reference for future deep-space missions of China.