Power
The Power subsystem generates, stores, and distributes electrical power to all spacecraft subsystems and payloads.
Core Functions
- Generate power (e.g., solar array, RTG).
- Store energy in batteries for eclipse/night.
- Regulate and distribute power to loads.
Key Design Drivers
| Driver | Driven By | Impact |
|---|---|---|
| Peak & Average Power | Payload, ACS, TT&C loads | Array sizing, battery capacity |
| Bus Voltage | Spacecraft design | Harness size, distribution losses |
| Duty Cycle | Operational constraints | Battery cycles, array design |
| Eclipse Duration | Orbit geometry | Battery capacity, depth-of-discharge |
Major Elements
-
Solar Arrays
- Photovoltaic cells (multi-junction).
- Often require a mechanical deployment mechanism.
-
Batteries
- Typically Lithium-Ion; must manage charge/discharge to avoid overheat or explosion.
- Provide power during eclipses or high-load surges.
-
Power Electronics
- Control battery charge.
- DC/DC converters & distribution.
- Protective circuits (over-current, under-voltage protections).
Bus Voltages
- ~28 V is standard for many satellites.
- Higher voltages (50-160 V) sometimes used for large power demand (reduces harness mass).
Thermal & Safety
- Excess heat from power distribution requires thermal design (heatsinks, conduction paths).
- Batteries are high-energy devices requiring fault protection (fuses, circuit-breaker function) and careful charging profiles.
Cross-Links
- See Spacecraft Thermal Control System on radiator sizing for power dissipation.
- See Spacecraft Structure and Mechanisms for solar array deployment structures.