Variable Structure Feedback Control with Application to Spacecraft with Small Thrust Propulsion Systems

Small spacecrafts requiring small propulsion systems are becoming more popular for low Earth orbit. It is important for these research satellites to have accurate guidance and control systems. Small propulsion systems will also be beneficial for multiple small spacecrafts used future exploration expeditions beyond low Earth orbit. These small spacecrafts benefit from the simplicity of low thrust cold gas propulsion systems. Additionally, large spacecrafts using low thrust, high specific impulse propellants for main propulsion systems, such as ion engines, allow longer and more flexible missions, including Earth orbiting spacecraft and interplanetary spacecraft. In order to extend the life of future planetary exploration missions, it becomes necessary to use In-Situ Resource Utilization (ISRU) to be able to extract resources such as water, oxygen, propellants, and building materials from the local target environment. Small free flying vehicles can be used for quickly surveying planetary surfaces in order to search for potential resource locations. These surveying vehicles can also use such extracted propellants if their propulsion system is designed for it. Cold gas propulsion provides a flexible system to use locally extracted or manufactured propellants. This dissertation investigates nonlinear feedback control techniques for spacecraft with low thrust, cold gas thrust, and spacecraft with cold gas thrust. A model for a cold gas propulsion system is developed for designing control systems for multiple types cold gas thrusters. The model is also used for testing control algorithms in simulation. The cold gas model is validated from a cold gas propulsion hardware testing, and a control law is tested on hardware

Time Optimal State Feedback Control with Application to a Spacecraft with Cold Gas Propulsion

A cold gas propulsion system is well suited to provide the required thrust for a small surveyor spacecraft operated near an asteroid or planetary surface. The cold gas propellant can obtained in-situ from local surface or atmospheric constituents. For small spacecraft, the cold gas system may be limited to only on-off control of the main tank where the generated thrust is directly dependent on the tank pressure. As such the thrust will slowly decrease as the propellant is expended. A state feedback, time optimal, control law is developed for a vehicle with propellant is expended. A state feedback, time optimal, control law is developed for a vehicle with decreasing thrust in translational motion. The success of the control law is shown in simulation

Time Optimal State Feedback Control with Application to a Spacecraft with Cold Gas Propulsion

A cold gas propulsion system is well suited to provide the required thrust for a small surveyor spacecraft operated near an asteroid or planetary surface. The cold gas propellant can obtained in-situ from local surface or atmospheric constituents. For small spacecraft, the cold gas system may be limited to only on-off control of the main tank where the generated thrust is directly dependent on the tank pressure. As such the thrust will slowly decrease as the propellant is expended. A state feedback, time optimal, control law is developed for a vehicle with propellant is expended. A state feedback, time optimal, control law is developed for a vehicle with decreasing thrust in translational motion. The success of the control law is shown in simulation