The current paper presents a new model for the simulation of a prospective nitrous oxide (N 2 O) monopropellant thruster operation. The specific impulse performance expected by the N 2 O monopropellant is suitable for spacecraft station-keeping and small orbit manoeuvres. This thruster is presently at a lab-scale prototype firing stage of research and development. The N 2 O monopropellant operation is simulated during the most important, start-up transient and steady-state, thruster modes. A good fit between experiment and simulation has been achieved during model validation. This demonstrates that the assumptions made in the model are feasible for accurate representation of the processes and phenomena occurring inside the N 2 O monopropellant thruster during operation so that the model is applicable for practical design problem solution. Further development of the existing model is expected to provide more detailed understanding of the decomposition process along the thruster.

For a mission to constantly watch geostationary (Orbital inclination isn’t 0, GEO) spacecraft by an optical satellite during a whole fly-around cycle, study the relative position relationship between the two and sun during fly-around mission; design the trajectory of the optical satellite, on which, the optical satellite keeps facing to the spacecraft in the direction opposite the Sun. Firstly, for constant surveillance to geosynchronous (Orbital inclination is 0) spacecraft, study from the Keplerian orbit elements, analyze its geometric relationship with the sun and the optical satellite. Then calculate the initial phase interval that meets the requirements of the mission. Compared with Clohessy-Wiltshire equation (CW equation), this method is more concise and the spatial physical meaning is clearer. However, the orbital inclination of GEO spacecraft is usually not 0. Secondly, taking GEO spacecraft with 1° inclination as an example, calculate the initial phase interval of the mission. Thirdly, select an initial phase in the initial phase interval, and design the fly-around trajectory based on CW equation. Lastly, the optical satellite’s position when it receives the mission is initial position, and the position when the fly-around mission starts is final position. The optical satellite’s approach trajectory is summarized as spacecraft's Lambert trajectory optimization. Take the time of two orbital maneuvers as optimization variables, and the fuel consumption as optimization objective. Optimize the plan of orbital maneuvering. The total pulse thrust velocity required for orbital maneuver after optimization in the example is 18.2514m/s, which is highly feasible in engineering. This method can be used for space situational awareness and in-orbit services of GEO spacecraft.

In this paper, a new angle-of-attack(AOA) guidance law and controller with multi-control surface and reaction control system (RCS) are designed to reduce normal acceleration in suborbital re-entry phase. First, the six-degree-of-freedom (6 DOF) nonlinear dynamic model of sub-orbital vehicles established, and the overload characteristics is analyzed under traditional AOA guidance law. Second, an AOA guidance law added height element is proposed to reduce the Normal accelerate peak value during re-entry. Furthermore, an Inverse-PIDA control law and composite control strategy are designed to control multi-aerodynamic surface and RCS. Finally the proposed approach is applied in a sub-orbital vehicle re-entry flight, validation simulation are conducted by using the proposed guidance law and controller with the 6 DOF nonlinear dynamic model , Monte-Carlo statistical analysis shows it can get well control performance with ±20% aerodynamic elements uncertainty and random wind.