7 Space Systems Flashcards
What are the 3 phases of a satellites lifecycle?
Attaining orbit
On-orbit operations - Maintain orbit, Maintain attitude, Mission C2
End-of-life
What are the 2 basic structures of a satellite?
Bus - The basic spacecraft and its core support functions.
Payload - Equipment that supports and delivers the required capability.
What are the 9 subsystems of a satellite?
Power Generation Payload Attitude determination and control Navigation guidance and control Propulsion Communications Command and data handling Thermal control Structures and Mechanisms
The Navigation Guidance and Control (NGC) systems looks to answer what from the satellite?
Where I am?
Where do I want to go?
How do I get there?
What is the job of the Navigation Guidance and Control (NGC) system?
To maintain and change a vehicle’s orbital trajectory - Orbital Maintenance
What are the 7 different types of thrusters?
Cold gas Liquid monopropellant Liquid bi-propellant Resisto-Jet Arc-Jet Ion Plasma
What are the adv and disadv. of a Cold Gas thruster?
Adv: Simple + Can be turned on/off and recharged repeatedly
Disadv: Low thrust (0.1 - 270 N) + Low specific impulse (60 - 150 sec)
What are the adv and disadv. of a Liquid Monopropellant thruster?
Adv:
Simple and reliable
One propellant to manage
Lower temps simplify chamber and nozzle design
Disadv:
Possible toxic propellants
Low thrust (0.1 - 600 N)
Low specific impulse (140 - 320 sec)
What are the adv and disadv. of a Liquid Bi-propellant thruster?
Adv:
Higher specific impulse (270-450 sec)
Can be self-igniting which aids reliability - Hypergolic
Scalable to high thrust (10 - 6,000,000 N)
Disadv:
Complex
Expensive
Possible toxic propellants
What are the adv and disadv. of a Resisto-Jet thruster?
Adv:
Simple
Can use any propellant
Disadv:
High power requirement
Extremely low thrust (0.0005 - 10 N)
Not suitable for LEO
What are the adv and disadv. of a Arc-Jet thruster?
Adv:
High specific impulse (500-2500 sec)
Disadv:
High power requirement
Low thrust (0.05 - 40 N)
Limited heritage
What are the adv and disadv. of an Ion thruster?
Adv:
Very high specific impulse (5000 - 10,000 sec)
Very long design life
Unlimited cycling
Disadv:
High power requirement
Very low thrust (0.02 - 2 N)
What are the adv and disadv. of a Plasma thruster?
Adv:
High specific impulse (2000 - 10,000 sec)
Very long design life
Unlimited cycling
Disadv:
High power requirement
Very low thrust (0.2 - 200 N), Hall Effect
0.00001 - 0.001 N, Pulsed Plasma
Name the 2 kinds of plasma thruster
Hall Effect
Pulsed Plasma
The Attitude Determination & Control Subsystem (ADCS) looks to answer what for the satellite?
Current state of the spacecraft (where is it pointing right now?) Desired state (where should I be pointing?) Means to achieve the desired state (how far and how to make the rotational around the 3 primary axis: pitch, yaw, roll)
What so the job the Attitude Determination and Control Subsystem (ADCS)?
Measure and control the spacecraft’s rotational behaviour around its centre of mass
What are the three attitude control sensors (most -> least accurate)
Star trackers or mapper (0.0003 deg)
Sun sensors (< 1 deg)
Earth or horizon sensors (approx 1 deg)
What are the 3 momentum control devices?
Bias momentum (0.1 deg accuracy)
Reaction wheel (0.001 deg accuracy)
Control moment gyro (CMG) (0.001 deg accuracy)
What are the 3 options for the Electrical Power Subsystem?
Solar
Chemical
Nuclear
What are the 3 basic functions of the Electrical Power Subsystem?
Power Generation
Power Conditioning and Distribution
Power Storage
What 3 things can degrade solar performance?
Temperature (colder is better)
Radiation and charged particles
Eclipses
When is max power generated by a solar panel?
When the incoming light is perpendicular to the surface of the panel
When are chemical systems used provide power to the satellite?
In the shade of the Earth
Eclipses
Specialised missions
What is the difference between primary and secondary batteries?
Primary - single use (throw away) used to launch vehicles and sometimes when solar panels aren’t generating electricity
Secondary - rechargeable with lifetime dependant on depth of discharge and number of cycles
What are the 2 main types of chemical electrical power?
Battery
Fuel cell
A Nuclear power system typically uses what fuel?
Plutonium-238
What is the benefit of a Nuclear power source on a satellite?
Extremely long-lasting
No moving parts
What does PMAD stand for in the Electrical Power Subsystem?
Power Management and Distribution
What is the PMAD designed to do?
Manage power requirements and the power shifting from active power generation via solar panels to battery discharging during eclipses
What is the TCS on a satellite?
Temperature Control Subsystem
What are the 3 principle methods of heat transfer?
Convection
Conduction
Radiation
What heat transfer mechanism is available in space?
Radiation
What are the 3 main sources of heat in space?
Direct sunlight
Albedo (sunlight reflected from the Earth’s surface)
IR radiation emitted by Earth
How do you move heat AWAY from a satellite?
Radiation
How do you move heat AROUND a satellite?
Conduction
What are the 3 different types of loads that can be experience on the structure of a satellite?
Axial
Lateral
Torsional
What are the primary requirements of a satellites structure and mechanisms?
Support a spacecraft’s key components
Protect the spacecraft’s components throughout its life
Deploy antennas, sensors and payloads through out the mission
Minimise vibrations
What is the C&DH System?
Command and Data Handling system
This is the ‘brains’ of the satellite.
What are the 3 main components of the C&DH system?
CPU
Memory
Input/Output
What will the C&DH do?
Manage and command all the onboard bus and payload systems.
Receive and manage commands from the ground.
Collect health and status telemetry then prep for transmission to ground.
Retrieve onboard payload data, process and format, and arrange for delivery to comms systems.
Provide error detection and recovery functions.
Support NGC functions to maintain spacecraft position and manoeuvring, as required.
