Thruster ICD

The purpose of this document is to describe the mechnaical, electrical, and data interfaces between the thruster subsystem and other satellite system.

Electrical Interface (UMS-0660)

The thruster subsystem interfaces electrically with the power subsystem through its Controller and Communication Assembly (CCA). The electrical connections for each component are shown in the figure below. All components are powered via onboard voltage regulators located on the thruster board, which operates from the spacecraft’s common power bus. Power is supplied from a distributed bus at an unregulated battery voltage, routed through load switches managed by the Power Module Controller.

The thruster control board receives power at the common bus voltage, typically ranges from approximately 6.5 to 7.2 Volts.
The solenoid driver receives 12 Vdc and 1.6 Vdc from the onboard voltage regulator.
The pressure transducer receives 5 Vdc± 10 mV from the onboard voltage regulator.
The MCU receives 3.3 Vdc from voltage regulator.

Figure 1- Thruster electrical interface

Data Interface(UMS-0660)

The figure below illustrates the data interfaces associated with the thruster components, as well as interfaces with other subsystems.

The Attitude and Orbit Determination and Control Subsystem (AODCS) communicates with the thruster control board via a UART interface, while the reaction wheel cluster connects to thruster board through the SPI bus. Power control is managed by CAN-Controlled Load Switches and Monitors (CCLSM) via the auxiliary CAN bus, operated by the power subsystem.

The solenoid valve driver primarily interfaces with the thruster board using a PWM signal. In addition to PWM, the driver requires a GPIO control signal that functions as an arm command. Both the PWM and GPIO signals must be active to actuate the solenoid valve. This dual-signal implementation ensures that the valve remains closed in the event of an unintended PWM activation.

The pressure and temperature transducers interface with the thruster board via analog inputs.

Figure 2- Thruster data Interfaces

Mechanical Interface

The following drawings shows the mechanical interface of the thruster.

Fuel Storage Tank (UMS-0656)

The fuel storage system consists of ten off-the-shelf CO₂ cartridges(UMS-0873) mounted to a machined block manifold (UMS-0870).

Material: The manifold is made from aluminum alloy 6061-T6, while the CO₂ cartridges are composed of carbon steel.
Connection: The cartridges are threaded directly into the block manifold. The entire assembly is secured using a support bracket fastened to the manifold with M3 × 0.5 screws. Finally, the complete assembly is mounted to the base plate, which is securely attached to the satellite’s structural shell using M3 × 0.5 hex drive screws.

Solenoid Valve (UMS-0658)

Material: 316 Stainless steel
Connections: The solenoid valve inlet is connected to the storage tank outlet using a Swagelok fitting (UMS-0781). The valve outlet is connected to a compression fitting that routes the flow from the solenoid valve to the nozzle inlet. The solenoid valve is securely mounted to the manifold using a bracket fastened with M3 × 0.5 mm thread hex screws.

Pressure Sensor (UMS-0743)

Material: 17-4PH Stainless Steel
Connection: Directly threaded into the outlet port of the storage tank .

Fill and Drain Valve (UMS-0657)

Material: stainless steel
Connected to the storage tank outlet via a fitting (UMS-0877). The valve is mounted to one of the CubeSat’s external faces using a bracket (UMS-0967), secured with M3 × 0.5 mm thread hex screws.

Nozzle (UMS-0659)

Material: Stainless steel
Connections: The nozzle is connected to the solenoid valve outlet via a compression fitting. It is mounted to the CubeSat structure using a bracket (UMS-0966) and secured with M3 × 0.5 mm thread hex screws, ensuring mechanical stability during operation.

Nozzle Orientation

The nozzle is mounted along the central rail and exits from the face of the satellite, aligned with the X direction. Its orientation is slightly offset from the satellite’s center of mass, by 15 mm in the Z direction and 9 mm in the Y direction. This offset introduces a small disturbance torque, estimated at approximately 0.150 mN.m in the Y direction and -0.090 mN.m in the Z direction. These torques are expected to be within the control authority of the reaction wheels. Figure 3 illustrates the nozzle vector configuration and its orientation within the LISSA satellite layout.