Chapter 13: Spacecraft Subsystems Flashcards
What is an EPS?
electrical power system that converts energy into usable electrical power to run the spacecraft
charge
q = 1.6E-19 Coulombs
current
i = dq/dt amps (C/s)
volts
v = PE/q volts (J/C)
resistance
R = v/i ohms (J*s/C^2)
power
P = iv watts (J/s)
What does the power supply do?
collects and converts energy and regulates power output
What does the power condition and distribution do?
adjusts voltages to match subsystem designs
What are common energy sources?
- solar (photo electric effect)
- chemical (electrolytes, anodes, cathodes)
- nuclear (heat from decaying isotopes)
Explain solar cell power
P=iv
peak power = Pmp
open circuit voltage = Voc
short circuit current = Isc
What is current density?
J=I/A_cell
used instead of I
What is the fill factor equation?
FF = VmpImp / VocIsc
The efficiency of power is?
η = Pout/Pin
What is the sun angle effect equation?
Pout = Pinηcos
What are some sources of chemical energy?
Li ion batteries
Nicad
NiH2
How are battery capacities rated?
rated against a particular discharge rate
What are voltages based on?
based on current capacity (looses capacity over time)
What in the hell is a Radioisotope Thermoelectric Generator?
generates voltage when radioactive decay of plutonium or uranium produces heat
What is ADCS
attitude determination control system
keeps the spacecraft accurately and precisely pointed in the right direction
What reference frame is used when determining location of a spacecraft?
the ECI or Earth centered inertial frame
What reference frame is used when determining attitude of a spacecraft?
LVLH/ORB
local vertical, local horizon / orbiting frame
z axis towards center of earth (yaw)
y axis perpendicular to orbital plane (pitch)
x axis tangent to orbital plane (roll)
What is the control system layout?
- sensors (where I am)
- desired attitude (where do I want to be)
- controller (how do I get there)
- actuators (apply the correction)
- dynamics (physics happen, bitch!)
List the types of sensors
horizon/earth sun sensor star tracker magnetometer gyros GPS accelerometer
What are some common actuators?
magnetorquers
reaction wheel
control movement gyros
thrusters
What are some environmental disturbances?
solar radiation pressure
atmospheric drag
gravity gradient
magnetic field torque
What are some passive stablizers
gravity gradient
spin stabilizer
dampers
Determination
how well you know where your pointing
Control
how well you can point in the right direction and get there
What is the ADCS composed of?
sensors, actuators, attitude control software algorithms
