Space Systems 1

Example of Earth Orbiter Spacecraft

Communication Satellites, Broadcast, Weather Satellites, Earth Observers, Navigation

Example of Science Spacecraft

Astronomy, Space Physics

Example of Military Spacecraft

Surveillance, Early Warning, Nuclear Detection, Intelligence, Anti-Satellite

Example of Additional Spacecraft

Planetary Explorers, Manned Spacecraft

Satellite Propulsion Subsystem

Responsible for orienting the spacecraft and performing orbital manoeuvres in response to control commands

Satellite Power Subsystem

Generates, stores and distributes power to other subsystems and payload. Often includes solar batteries to generate electric energy.

Command and Data Subsystem

Provides uplink for commands from the ground and downlink for satellite housekeeping parameters and data.

Attitude Control Subsystem

Determine satellite attitude, evolution and control manoeuvres.

Thermal Control Subsystem

Keeps satellite within operational tolerances

Thermal Propulsion

Based on increase of thermal energy of a working body. Consists of Chemical and Solar. Solar can be used directly or converted into electric current via solar solar cells.

Cold Gas Propulsion

Controlled, pressurised gas source and nozzle. The simplest form, used when simple is needed over high performance.

Electricthermal Propulsion

Resistojet, propellant heated by passing over tungsten heating element

Electrostatic Propulsion

Thrust from direct acceleration of positively charged particles in a static electric field - must be neutralised to avoid charge build up

Hall or Lorentz Propulsion

Hall force or Lorentz force used instead of electrostatic

Nuclear Propulsion

Solid Phase or Gaseous Phase Reactor

Photon / Laser Propulsion

Laser power beam can provide momentum directly to spacecraft. Feasibility has been demonstrated by US Air Force project. Lightcraft have reached 100 feet altitude. Lightcraft are funnel-shaped. This shape allows them to channel heat to centre, leading to strong heating of the air below. Expansion of the air underneath generates thrust.

Solar Sails

Large sheets of thin film, one side is covered by reflective coating to reflect solar radiation. Photons hit the sails which transfer their momentum to the spacecraft

Rocket Propulsion

Based on Newtons 3rd Law. The system forces out working body by applied force, the reaction fore then acts on the rocket and accelerates it

Liquid Propulsion Advantages

Restartable, Control, Throttle

Solid Propulsion Advantages

Simple, Reliable (Single Use)