1. Orbital Transfer Vehicle (OTV) Power Systems
Ian Meginnis
February 12, 2009
Group Leader - Power Systems
Phase Leader - Translunar Injection
Ian Meginnis Power Systems

2. OTV Solar Arrays
Two, circular Ultraflex solar arrays from Able Engineering
Based on 2kW power needs:
Total Deployed Area = 6.67m2
Total Stowed Volume = 0.068m3
Total Mass = 13.3kg
Total Cost = $2 million
Structural Requirements
Stowed Maximum Acceleration: 25g normal; 30g lateral
Deployed Maximum Acceleration: 0.1g (all axes)
Lunar lander batteries can support 2kW of OTV operations for up to 50mins during periods of darkness
Ian Meginnis
Power Systems

3. OTV Power Configuration
PPU
(Electric Propulsion)
PCDU
Battery
(LL)
100V
DC-DC Converters
Individual OTV
Components
Solar Array
<200V
Solar Array
Acronym Definitions:
PCDU - Power Conditioning and Distribution Unit
PPU - Power Processing Unit
LL - Lunar Lander
DC - Direct Current
Note: Not to scale
Ian Meginnis
Power Systems

4. Backup Slide Calculation of Solar Array Dimensions Solar Array Mass:
Total Power Consumption: 2kW
Solar Array Power Density: 150W/kg
2000W / 150W/kg = 13.3kg
Solar Array Storage Volume:
Thickness: 0.102m
Height: 0.326m
Radius: 1.03m
0.102m x 0.326m x 1.03m = m3
Solar Array Cost:
Cost/Watt: $1000/W
2000W x $1000/W = $2 million
Ian Meginnis
Power Systems

5. Backup Slide (cont.) PCDU Specifications
Terma Power Management and Distribution System
Power Capacity: 2kW
Voltage Output: 100V
Mass: 14kg
Volume: m3
Ian Meginnis
Power Systems

6. Backup Slide (cont.) DC-DC Converter Information
100 VDC Input Spacecraft Bus, Radiation Hardened
Produced by Modular Devices Incorporated
Available power output: 6.5W-80W
Various output voltages available
Separate DC-DC converter used for each device
All converters integrated into single-box design
Ian Meginnis
Power Systems