Propulsion
The Propulsion subsystem supplies thrust for orbital changes, station-keeping, momentum dumps, and de-orbit or extended maneuvers.
Core Functions
- Generate required ΔV for mission orbit changes.
- Support attitude control / momentum management if needed.
- Ensure safe storage and reliable flow of propellant.
Key Design Drivers
| Driver | Driven By | Impact |
|---|---|---|
| ΔV | Mission trajectory | Propellant mass, tank size |
| Dry Mass | Overall s/c mass | Tank & structure design |
| Thrust Level | Maneuver timeline, ACS | Thruster sizing |
| Propellant Type | Performance & handling | Tank pressurization, thermal control |
Propulsion Elements
-
Propellant Tanks
- Must be structurally integrated.
- Thermal constraints: e.g., hydrazine near 0°C freezing point.
-
Thrusters
- For main maneuvers or reaction control.
- Arranged to provide torque about spacecraft axes.
-
Valves & Feed Lines
- Multiple valves for two-fault tolerance to hazards.
- Heat trace or insulation to keep propellant within temp limits.
Common Propellants
- Hydrazine (N2H4): Widely used for monoprop.
- Biprop (NTO/MMH): Higher performance, more complex.
- Electric (Ion, Hall): High Isp, lower thrust, extended burn times.
Interfaces
- Attitude Control: Thruster-based momentum unloading.
- Thermal Control: Propellant freeze-point management.
- Structures: Tank placement & thrust alignment loads.
Operations & Safety
- Handling and integration with toxic or cryogenic propellants require specialized procedures.
- Must maintain pressure & temperature, avoid leaks/explosions.
Cross-Links
- See Attitude Determination and Control System on thruster usage for attitude maneuvers.
- See Spacecraft Structure and Mechanisms for mounting of tanks and thrust-load paths.