AEM 360 – Astronautics, Lesson 19
Communications and Data Handling
& Electrical Power Subsystems
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Overview
• Admin
• Lesson for Today:
Communications and Data Handling
& Electrical Power Subsystems
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CDHS Basic Principles
Handling Data
CDHS Systems Engineering
EPS Basic Principles
Energy Sources
EPS Systems Engineering
CDHS
Communications and
Data Handling Subsystem
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CDHS
Communications and
Data Handling Subsystem - CDHS
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CDHS
Basic Principles
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CDHS
Communications Components
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CDHS
Data Handling
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CDHS
Environmental Effects
• Single event upsets (SEUs)
• Single event latch-ups
South Atlantic Anomaly
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CDHS
Analog
vs
Digital
Data
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CDHS
CDHS Testing
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EPS
Electrical Power Subsystem
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EPS
• Charge
• Coulomb’s Law
• Voltage (aka.
electrical potential)
• Current
• Resistance
• Power
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Basic
Principles
EPS
Charge
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Can be positive (+), negative (-) or neutral
Basic unit is the coulomb (C)
Opposite charges attract and like charges repel
Coulomb’s Law describes electrostatic force
EPS
Coulomb’s Law
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EPS
Current, i
The unit for current is amperes (amps)
which equals the charges flowing per second
amps = charges / time (coulombs / s)
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EPS
Voltage
• The energy an electric field can
transmit to a unit charge
• Analogous to water pressure
• Units are volts, V
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energy per charge
= volts
= joules / coulomb
EPS
Resistance
• Opposes the flow of charges
• Unit is the ohm, Ω
• Ohm’s Law relates the current to the voltage
pushing the charge (i.e., higher resistance results
in lower current)
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EPS
Power
• Amount of energy delivered per unit time
• Unit is the watt, W
• Defined as one joule of energy per second
V = energy/charge, and i = charge/time so,
P = (energy/charge) x (charge/time) = energy/time
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EPS
Circuits and Current
Spacecraft run on DC power
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EPS
Solar
Energy
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EPS
Solar Cell
Power Output
Density
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EPS
Current Voltage Trade-off:
The i/V Curve
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EPS
Solar Arrays
Solar Array Panels
Body Mounted
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EPS
Body Mounted Array Disadvantage
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EPS
Eclipse
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EPS
Earth’s Angular Radius
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EPS
Maximum Time Spent in Eclipse
LEO: 15 eclipses per day, up to 36 minutes each (depending
on inclination) or about 5500 per year
GEO: 90 eclipses per year starting at only a few minutes and
building to a maximum of 72 minutes
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EPS
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Solar Energy Decreases with the
Square of the Distance from the Sun
Venus: 2596 W/m2
Earth: 1358 W/m2
Mars: 585 W/m2
Jupiter: 50 W/m2
(solar power impractical)
At Jupiter: 50 W/m2
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EPS
Chemical Energy: Ions
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EPS
Chemical Energy: Batteries and Fuel Cells
Nickel-hydrogen (NiH2) Batteries
Fuel Cells
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EPS
Nuclear Power:
Radioisotope Thermoelectric Generator (RTG)
New Horizons RTG
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EPS
Cassini Probe RTG
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EPS
EPS System Functions:
Power Supply and
Power Conditioning and Distribution
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EPS
EPS Example
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Questions?
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Next Lesson
• Lesson 20
Environmental Control and Life Support
• Reading:
– Sellers, Chapter 13, pp 481-499
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