Spacecraft Power Systems

Spacecraft Power Systems Power Source Table 11-33 compares common s/c power sources Photovoltaic Cells Cell types Sizing (Peak and Average Power) Radiation Environment Thermal Environment Shadowing Mission life Degradation characteristics

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

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

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

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.

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