Notetaker: Electrical Power Subsystem Flashcards
Identify
Generates, stores and distributes power throughout the spacecraft
Subsystem
Electrical Power Subsystem (EPS)
Identify
Most common source of power for earth orbit satellite
Solar Panels
What are the solar panel configurations?
- Body Mounted
- Sun Tracking
- Roll Out
Identify
Simpler and more robust, but less effective at producing power
Solar Panel Configurations
Body Mounted
Identify
Not always within visibility of the sun; only capable of producing limited power for limited time
Solar Panel Configurations
Body Mounted
Identify
Effective for spin-stabilized satellites with lower power requirements
Solar Panel Configurations
Body Mounted
Identify
More complex than body mounted solars panels
Solar Panel Configurations
Sun Tracking
Identify
Provides higher level of power-to-weight efficiency, compared to body mounted
Solar Panel Configurations
Sun Tracking
Identify
Successfully tested 2017 on ISS, can be deployed and retracted
Solar Panel Configurations
Roll Out
Identify
20% lighter, 4x smaller, boost
Solar Panel Configurations
Roll Out
What are the Solar Panel Deployments?
- Low Cycle
- High Cycle
Identify
Exploding Bolts Solar Arrays
Solar Panel Deployment
Low Cycle
Identify
Deployed once and are never retracted (for sun-tracking solar panels)
Solar Panel Deployment
Low Cycle
Identify
Repeatable Deployment Solar Arrays
Solar Panel Deployment
High Cycle
Identify
High strain composite boom on both sides of solar arrays use stored energy, no motor, to change from a coil shape into a support arm
Solar Panel Deployment
High Cycle
Identify
Can use a motor to retract solar array
Solar Panel Deployment
High Cycle
Identify
Roll-out Solar Array
Solar Panel Deployment
High Cycle
Identify
Solar cells produce most power when directly facing the sun; perpendicular to source of radiation
Solar Panel Operations
Incidence Angle
Identify
Incidence angle and materials directly effect effectiveness of solar cells
Solar Panel Operations
Efficiency
What are the two tasks of Solar Array Drive Mechanism (SADM)?
- Positioning: Positions solar arrays to face the sun as directly as possible
- Tracking: Constantly operate to track the sun while spacecraft maintains operational, earth-pointing attitude
Solar Array Drive Mechanism (SADM) is also “how to maintain it” in terms of solar panels.
What are the two tasks of Sun Sensors?
- Evaluation: Solar cells produce most power when directly facing the sun; perpendiculat to source of radiation
- Determination: Incidence angle and materials directly affect effectiveness of solar cells
Sun Sensors are also “how to get feedback” in terms of solar panels.
Identify
Supply power to components when needed
Batteries
Identify
Capable of more power than batteries wired in parallel
Battery Configuration
Series
Identify
If a single cell fails, the entire series of cells is nonfunctional
Battery Configuration
Series
Identify
Hold a charge longer than batteries in series
Battery Configuration
Parallel
Identify
Inherently redundant; failure of a single cell will not affect any other cells which require higher temperatures
Battery Configuration
Parallel
Identify
First battery used in space
Battery Cell Material
Nickel Cadmium (NiCd)
Identify
Large and susceptible to memory effect
Battery Cell Material
Nickel Cadmium (NiCd)
Identify
Store a relatively small amount of power relative to mass and volume
Battery Cell Material
Nickel Hydrogen (NiH2)
Identify
Solved the memory effect issue
Battery Cell Material
Nickel Hydrogen (NiH2)
Identify
Not susceptible to memory effect
Battery Cell Material
Lithium Ion (Li-ion)
Identify
Significantly lighter and more efficient than Nickel Hydrogen batteries
Battery Cell Material
Lithium Ion (Li-ion)
Identify
Highly volatile and have the potential to explode if exposed to extreme heat or pressure
Battery Cell Material
Lithium Ion (Li-ion)
Identify
During an eclipse: Solar arrays are unable to produce power, so batteries must be used to continue satellite operations
Battery Use and Material
Operational Usage
Identify
When power demand is greater than generation: Batteries temporarily supplement until power load is decreased
Battery Use and Material
Operational Usage
Identify
The life of battery is repeatedly overcharged, it builds up electrolyte crystals on the cathodes; results in lower discharge voltage
Battery Use and Material
Voltage Depression
Identify
Combated by only charging the batteries when they need to be charged and stopping when they are fully charged
Battery Use and Material
Voltage Depression
Identify
Mitigate effects of memory effect, voltage depression, and deep discharge
Battery Use and Material
Reconditioning
Identify
Process of completely discharging then recharging
Battery Use and Material
Reconditioning
What is responsible for allocating power in the correct voltages and current to the rest of the satellite?
Power Management Distribution (PMaD) System
What is the process of prioritizing components and shutting off power to less vital components?
Load Shedding
