Chapter 13: Spacecraft Subsystems

Question 1

What is an EPS?

Answer 1

electrical power system that converts energy into usable electrical power to run the spacecraft

Question 2

charge

Answer 2

q = 1.6E-19 Coulombs

Question 3

current

Answer 3

i = dq/dt amps (C/s)

Question 4

volts

Answer 4

v = PE/q volts (J/C)

Question 5

resistance

Answer 5

R = v/i ohms (J*s/C^2)

Question 6

power

Answer 6

P = iv watts (J/s)

Question 7

What does the power supply do?

Answer 7

collects and converts energy and regulates power output

Question 8

What does the power condition and distribution do?

Answer 8

adjusts voltages to match subsystem designs

Question 9

What are common energy sources?

Answer 9

1. solar (photo electric effect)
2. chemical (electrolytes, anodes, cathodes)
3. nuclear (heat from decaying isotopes)

Question 10

Explain solar cell power

Answer 10

P=iv
peak power = Pmp
open circuit voltage = Voc
short circuit current = Isc

Question 11

What is current density?

Answer 11

J=I/A_cell

used instead of I

Question 12

What is the fill factor equation?

Answer 12

FF = VmpImp / VocIsc

Question 13

The efficiency of power is?

Answer 13

η = Pout/Pin

Question 14

What is the sun angle effect equation?

Answer 14

Pout = Pinηcos

Question 15

What are some sources of chemical energy?

Answer 15

Li ion batteries
Nicad
NiH2

Question 16

How are battery capacities rated?

Answer 16

rated against a particular discharge rate

Question 17

What are voltages based on?

Answer 17

based on current capacity (looses capacity over time)

Question 18

What in the hell is a Radioisotope Thermoelectric Generator?

Answer 18

generates voltage when radioactive decay of plutonium or uranium produces heat

Question 19

What is ADCS

Answer 19

attitude determination control system

keeps the spacecraft accurately and precisely pointed in the right direction

Question 20

What reference frame is used when determining location of a spacecraft?

Answer 20

the ECI or Earth centered inertial frame

Question 21

What reference frame is used when determining attitude of a spacecraft?

Answer 21

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)

Question 22

What is the control system layout?

Answer 22

1. sensors (where I am)
2. desired attitude (where do I want to be)
3. controller (how do I get there)
4. actuators (apply the correction)
5. dynamics (physics happen, bitch!)

Question 23

List the types of sensors

Answer 23

horizon/earth
sun sensor
star tracker
magnetometer
gyros
GPS
accelerometer

Question 24

What are some common actuators?

Answer 24

magnetorquers
reaction wheel
control movement gyros
thrusters

Question 25

What are some environmental disturbances?

Answer 25

solar radiation pressure
atmospheric drag
gravity gradient
magnetic field torque

Question 26

What are some passive stablizers

Answer 26

gravity gradient
spin stabilizer
dampers

Question 27

Determination

Answer 27

how well you know where your pointing

Question 28

Control

Answer 28

how well you can point in the right direction and get there

Question 29

What is the ADCS composed of?

Answer 29

sensors, actuators, attitude control software algorithms