Enjie Luan

A rapid uncertainty propagation method for pre-parachute phase of Mars entry

In this paper, a novel approach is proposed for analyzing evolution of uncertainty in state trajectories of a Mars entry vehicle due to uncertainties in initial conditions and other system parameters. By introducing uncertainty factors, the stochastic dynamical systems are converted into equivalent deterministic dynamical systems in higher dimensional space. And then based on the local linearization and linear system theory, a rapid uncertainty propagation method can be get. Applying the method to a representative entry scenario taken from the NASA MSL-class mission, Simulation results indicate that the proposed method is able to predict evolution of uncertainty, compared with Monte Carlo method, with little degraded accuracy, but with much more computational efficiency.

Optimal-fuel, low-thrust Earth-Ivar transfer trajectories with Venus gravity assist

In this paper, fuel-optimal low-thrust trajectory with Venus gravity-assist is presented for exploring Ivar asteroid. The problem formulation treats the spacecraft mass as a state variable, thus coupling the spacecraft design to the trajectory optimization. To avoid numerical sensitivity, the equinoctial elements are utilized to describe spacecraft motion, and the optimization problem is divided into three subproblems, the solution of the last subproblem is taken as the primary guess for the next one. A hybrid optimization method is utilized to solve them, which method utilizes the costate time histories to parameterize the thrust steering angles time histories. Numerical results are presented for the optimal three-dimensional Earth-Ivar with Venus gravity-assist trajectory

Study of Design and Optimization of Low-Thrust Transfer Trajectory with Planetary Aerogravity Assist

In this paper, the design and optimization problem of low-thrust transfer trajectory with planetary aerogravity assist is studied. To avoid numerical sensitivity, the equinoctial elements are utilized to describe spacecraft motion. The matching condition for design of aerogravity assist trajectory is presented through analyzing the characteristics of aerogravity assist. Then we have discussed the problem formulation of AGA trajectory optimization, and presented a hybrid optimization method, which combines direct with indirect method, and utilizes the costate to parameterize the thrust steering angles time histories. Finally, Taking rendezvous with a Ceres asteroid as an example, the preliminary scheme of transfer trajectory with Mars aerogravity assist is design and optimized by using this approach

Design and optimization of interplanetary low‐thrust trajectory with planetary aerogravity‐assist maneuver

Purpose – The purpose of this paper is to study the application of the planetary aerogravity‐assist (AGA) technique to the interplanetary transfer mission with low‐thrust engine, and the design and optimization approach of low‐thrust AGA trajectory.Design/methodology/approach – In the research, the transfer trajectory with planetary AGA maneuver is analyzed first, the maximum atmospheric turn angle and the matching condition for AGA trajectory is derived out, which is the significant principle for AGA trajectory design and studies. Then, a design and optimization approach for interplanetary low‐thrust trajectory with AGA maneuver is developed. The complicated design problem is transformed into a parameter optimization problem with multiple nonlinear constraints by using calculus of variations and the matching condition associated with AGA trajectory. Furthermore, since the optimization problem is very sensitive to the launch date and AGA maneuver parameters, three ordinal sub‐problems are reformulated to ...

Search the Optimal Rendezvous Opportunities for Manned Mars Mission

Various mission and trajectory designs have been proposed to achieve the first human mission to Mars. NASAs current study for sending humans to Mars is known as the design reference mission (DRM). It selected the long-stay mission profile. In this paper, according to the DRM scenario, we investigated the optimal rendezvous opportunity for manned Mars trip. At here, three transfer strategies were taken into account. Firstly, we use the contour map and optimal algorithm to search the optimal opportunities with two-impulse and employed the patched-conic method to analyze and propagate trajectories. Then, gravity assist technique is used to search the low energy trajectory. Finally, we also make use of the aerogravity assist technique, which is the novel concept in the interplanetary exploration missions, to analyze and search the possible rendezvous opportunities.