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SES 405 Power Subsystem Technical Review. By: Josh Lincoln Nick Knaus Rushi Patel. Power Requirements. Power Requirements Continued. Mission Constraints and Assumptions . Budget Discovery Class Mission - $425 million Mass Launch Vehicle - Atlas V ($90 million)
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SES 405Power Subsystem Technical Review By: Josh Lincoln Nick Knaus Rushi Patel
Mission Constraints and Assumptions • Budget • Discovery Class Mission - $425 million • Mass • Launch Vehicle - Atlas V ($90 million) • Payload mass to GEO ~ 4,750 kg • Environment • Temperature: 70 – 390 Kelvin • Gravity: 1.622 m/s^2 • Radiation • Vacuum • Time • 12 Lunar days (~ 12 Earth Months) • Assumptions • ASRG is technologically ready and will perform under lunar conditions • The ASRG’s radiation will not harm any other subsystems • The energy required for the rover to complete its mission is 280Wh for 12 lunar days • Operational day and night
Power system comparisonsRTG vs. Solar • Note: • GPHS RTG outputs 4400 Wt compared to 500 Wt from the ASRG • RTG allows operations at night, and thermal power • Mass for solar includes the mass of batteries, assuming 100Wh/kg for Li-ion batteries, with a power budget of 560W (half in use, half charging batteries).
Choosing a Power System Goal: Provide “enough” power to lunar rover for 12 lunar days A RTG based power subsystem was chosen to be the best based of the AHP trade study method
Power System – Allocation of system power(time and subsystem)
Power system Pros and Cons • RTG • Pros: Continuous power, not reliant on sun, thermal power, small volume • Cons: Requires Nuclear Material, Cost, Weight, radiation • Solar • Pros: Cost, weight, solar shielding, no radiation • Cons: Discontinuous power, volume, reliant on the sun, variable power generation
Previous Systems • Lunokhod 1 • Mass: 756 kg (rover) • Power/System: Solar cell fueled batteries • Lunokhod 2 • Mass: 840 kg (rover) • Power/System: Solar panels / batteries • Spirit • Mass: 185 kg (rover) • Power/System: Solar panels (Photovoltaic) / Rechargeable litium ion batteries • Opportunity • Mass: 185 kg (rover) • Power/System: Solar panels (Photovoltaic) / Rechargeable litium ion batteries • Curiosity • Mass: 900 kg (rover) • Power/ System: RTG
Power System Summary • System: RTG • 2 ASRGs • Power: 280Weh / 500 Wt • Voltage: 22-34 VDC (Nominal Range) • Mass: 40 kg, with 1.6kg of Pu-238 • Cost: $54 million combined • Dimensions: 0.3m in diameter, 0.75m in height each • Thermally manage rover temperature • Located on either side of rover, to balance mass • Thermal dissipation, possibly need to isolate due to emitted radiation • Powers all subsystems • Different power modes (Cruise, Roam, Focused Investigation)
Power Systems Summary cont. • Maximum power: 280W • Batteries for energy storage and discharge (high voltage instruments) • Self regulating computer system (separate from SMARTS) • Communicate with SMARTS • Integrated with SMARTS