1. Ian Meginnis January 29, 2009 Group Leader - Power Systems
Power Systems Sizing
Ian Meginnis
January 29, 2009
Group Leader - Power Systems
Ian Meginnis Power Systems

2. Battery Sizing
Secondary batteries used for lunar lander (LL) and rover
Size of LL batteries dictated by power requirement for 2 weeks of darkness
LL battery mass =~ 23kg
Based on requirement of 10 Watts for 2 weeks
Mass of rover batteries based how much power is needed prior to solar array deployment
Occurs soon after landing
Rover battery mass =~ 0.5kg
Ian Meginnis
Power Systems

3. Data from Busek Co. Inc.
Ian Meginnis
Power Systems

4. Backup Slide Calculation of battery size for LL:
Li-ion Energy Density: 145 Wh/kg
Thermal Power Requirement: ~10 Watts
Total Time in Darkness: 2 weeks (336 hr)
Battery Mass = 336hr * 10W / 145Wh/kg = 23 kg
Calculation of solar array sizing for rover:
Need to power several devices:
Turn on and operate computer (RAD6000): ~10W; 1.0hr
Egress LL: ~10W; 1.0hr
Solar array deployment: ~6W; 1.0hr
Ian Meginnis
Power Systems

5. Backup Slide (cont.)
Solar arrays comprised of triple-junction Gallium Arsenide (GaInP2/GaAs/Ge)
Produce ~300W/m2
Busek Hall-Effect Thrusters:
Model
Input Power (W)
Thrust (mN)
Solar Array Size (m2)
BHT-200
200
12.8
0.7
BHT-600
600
42.0
2.0
BHT-1000
1000
58.5
3.3
BHT-1500
1700
102.0
5.7
BHT-8000
8000
512.0
26.7
BHT-20k
20250
1080.0
67.5
Data from Busek Co. Inc.
Ian Meginnis
Power Systems