1. Spacecraft Power Systems

2. Spacecraft Power Systems
Power Source
Table compares common s/c power sources
Photovoltaic Cells
Cell types
Sizing (Peak and Average Power)
Radiation Environment
Thermal Environment
Shadowing
Mission life
Degradation characteristics

3. Spacecraft Power Systems
Power Source
Radioactive Power Sources
Radioisotope Thermoelectric Generators (RTGs)
Nuclear Reactor
Dynamic Power Sources
Brayton, Stirling, Rankine cycles
Fuel Cells
Energy from oxidation reactions
High efficiency, short duration missions

4. Spacecraft Power Systems
Energy Storage
Physical Constraints
Size
Mass
Operating position
Static and dynamic environments
Programmatic Constraints
Cost
Mission
Power required, eclipse frequency and length
Reliability
Maintainability

5. Spacecraft Power Systems
Energy Storage
Electrical Constraints
Voltage
Current Loading
Duty cycles (length and frequency)
Depth of discharge
Activation time

6. Spacecraft Power Systems
Power Distribution
Cabling
10-25% of power system mass
Volume and location constraints
Fault Protection
Detection
Isolation
Correction
Switching
Subsystems require different amounts of power at different times
Power from batteries, arrays, RTG’s etc.

7. Spacecraft Power Systems
Power Regulation and Control
Peak Power Tracking (PPT)
Non-dissipative
DC-DC converter in series with solar arrays
Direct Energy Transfer (DET)
Dissipative
Shunt regulator in parallel with arrays