Interplanetary transfer optimization using cost function with variable coecients

In this paper,the optimal interplanetary transfer including planetary escape and capture phases is investigated in the heliocentric frame.Based on primer vector theory,a modi ed cost function with variable coecients is developed to re ect the gravitational e ect more precisely.The necessary conditions as well as the transversality conditions of the new cost function are derived to search the optimal solution in xed-time.By introducing the initial and nal coasts,the optimal interplanetary transfer is extended to the time-free situation.Finally,the proposed method is applied to the Earth-Mars and Earth-Asteroid transfer.Comparisons with existing methods show that the proposed method can provide better transfer performances with high eciency.The proposed method extends the application of primer vector theory and provides a fast and accurate reference for preliminary mission design in spacecraft planetary exploration.

Propagation of a strong cylindrical shock wave in a rotational axisymmetric dusty gas with exponentially varying density

Non-similarity solutions are obtained for one-dimensional isothermal and adiabatic flow behind strong cylindrical shock wave propagation in a rotational ax-isymmetric dusty gas, which has a variable azimuthal and axial fluid velocity. The dusty gas is assumed to be a mixture of small solid particles and perfect gas. The equi-librium flow conditions are assumed to be maintained, and the density of the mixture is assumed to be varying and obeying an exponential law. The fluid velocities in the ambient medium are assumed to obey exponential laws. The shock wave moves with variable velocity. The effects of variation of the mass concentration of solid particles in the mixture, and the ratio of the density of solid particles to the initial density of the gas on the flow variables in the region behind the shock are investigated at given times. Also, a comparison between the solutions in the cases of isothermal and adia-batic flows is made.

Fuel consumption for interplanetary missions of solar sailing

The orbits of solar sails can be changed by adjusting the sail’s attitude through external control torques.The resulting momentum will be changed,either provided by a typical attitude control subsystem or by a propellantless device.This paper investigates the extra momentum input and fuel consumption for a typical attitude control subsystem.The minimum-time transfer trajectories are designed for two rendezvous missions using both indirect and direct methods,generating continuous and discrete attitude histories,respectively.The results show that the momentum variation is almost wholly due to the solar radiation pressure.The feasibility of using tip-mounted microthrusters for attitude control is evaluated.The results show that less than0.1 kg of propellant are required for an interplanetary transfer mission when pulsed plasma thrusters with a specific impulse of700 s and a thrust of 150 mN are mounted at the tip of a 20 m square solar sail.The fuel consumptions of two transfer missions indicate that a tip-mounted pulsed plasma thruster is a viable technique for the attitude control of a solar sail.

Optimal interplanetary trajectories for Sun-facing ideal diffractive sails

A diffractive sail is a solar sail whose exposed surface is covered by an advanced diffractive metamaterial film with engineered optical properties. This study examines the optimal performance of a diffractive solar sail with a Sun-facing attitude in a typical orbit-to-orbit heliocentric transfer. A Sun-facing attitude, which can be passively maintained through the suitable design of the sail shape, is obtained when the sail nominal plane is perpendicular to the Sun–spacecraft line. Unlike an ideal reflective sail, a Sun-facing diffractive sail generates a large transverse thrust component that can be effectively exploited to change the orbital angular momentum. Using a recent thrust model, this study determines the optimal control law of a Sun-facing ideal diffractive sail and simulates the minimum transfer times for a set of interplanetary mission scenarios. It also quantifies the performance difference between Sun-facing diffractive sail and reflective sail. A case study presents the results of a potential mission to the asteroid 16 Psyche.