L4 - Space & Rocket Propulsion Flashcards
What is a space propulsion system for?
- Get spacecraft into space
- Move them around once they get there
- Change their attitude
How does a rocket work?
A rocket converts mass and energy into thrust.
- Energy is transferred to propellant
- The energised propellant is converted to high velocity exhaust
How can the thrust be increased?
- Increasing the mass flow rate
- Increasing the exhaust velocity
How is the total rocket operation time called?
The burn time.
What are the different types of space propulsion systems?
- Chemical (Solid, Liquid, Hybrid)
- Electric (Electrothermal, Electrostatic, Electromagnetic)
- Nuclear Fission
Describe the funtionning of a standard chemical thermodynamic rocket.
A chemical reaction gives heat, then waste products are accelerated through a nozzle. In most chemical rockets, a fuel and oxidiser combine in a combustion chamber to produce hear and by-products.
What is a cold-gas rocket?
It is the simplest form of thermodynamic rocket. The mechanical energy is the pressurised propellant.
- Very reliable
- Multiple restarts/pulsing possible
- Low Ve (~400m/s) and thrust (<1N)
Used only for attitude control on small spacecraft.
What is a solid rocket?
It is a rocket that typically contains a mixture of fuel, oxidizer and binder all in a sigle package called a motor. It is used for boosters and upper stages.
What are the different types of liquid rockets?
- Bipropellant
- Monopropellant
- Cryogenic
- Storable
- Hypergolic
What constitutes a Bipropellant rocket?
Two liquid propellants, fuel and oxidiser, react together to produce heat and echaust products.
Mainly used in launch vehicles.
What constitutes a Monopropellant rocket?
One propellant which decomposes when in contact with a catalyst.
- Usually operated in pulsed mode
- Low performance but simple
Mainly used for satellite attitude and orbit control.
What constitutes a Cryogenic rocket?
Liquid fuel/oxidiser that need refrigeration.
What constitutes a Storable rocket?
Liquid fuel/oxidiser that can be stored indefinitely.
What constitutes a Hypergolic rocket?
Liquid fuel/oxidiser that reacts spontaneously.
What are hybrid rockets?
Rockets that combine aspects of liquid and solid systems by using liquid oxidiser and a solid fuel.
How does electric propulsion work?
It uses electricity as the energy source to accelerate a propellant.
It cannot accelerate as fast a chemical propulsion but can reach higher final velocities using smaller amounts of propellants.
What are the three types of electric propulsion?
- Electrothermal
- Electrostatic
- Electromagnetic
How does Electrothermal propulsion work?
It uses electrically-produced heat (resistojet, arcjet).
How does Electrostatic propulsion work?
It uses charged particles accelerated by electric fields (gridded ion thruster, hail effect thruster, FEEP).
How does Electromagnetic propulsion work?
It uses electric and magnetic fields (MPD thrusters, PIT).
How does Nuclear fission propulsion work?
It uses a nuclear power source to provide energy to heat a propellant.
- Higher Ve than chemical (10km/s)
- But extra mass due to reactor
Difficult for launch but attractive for solar system travel.
