Unit 4 Rockets Flashcards
The rest of the lectures (24 cards)
What distinguishes rockets from airbreather engines?
Rocket carry both fuel and oxidiser, enabling operation in space, unlike airbreathing engines which rely on atmospheric oxygen.
What is the basic principle of rocket propulsion?
Thrust is produced by accelerating mass (propellant) out of a nozzle, applying Newton’s third law.
Define monopropellant rocket.
A rocket that uses a single propellant that decomposes or reacts exothermically on contact with a catalyst.
What are the two main types of chemical rocket engines?
Solids propellant and liquid propellant rockets.
List the four main components of a solid rocket motor.
Combustion chamber, igniter , solid propellant and nozzle.
What is Vielle (Saint Robert’s) law for burn rate?
r = (alpha)*p^n
r is the burn rate
p is chamber pressure
n is combustion index.
What are three main types of solid propellants?
Double-based, composite and composite double-based propellant.
What are the types of burning patterns in solid motor?
Progressive (increasing thrust), neutral (constant thrust) and regressive (decreasing thrust).
What is a key advantage of liquid rockets over solid ones?
Throttling, restart capability and higher performance.
Why do some liquid propellant requires cryogenic storage?
Because they are gases at room temperature (e.g. liquid oxygen, hydrogen).
What affects exits velocity Ve?
Chamber temperature Te, molecular mass M, expansion ratio Ae/A*, and pressure ratio pe/pc
What is a practical limit for SSTO (single stage to orbit) with chemical propellants?
Mass ratio ~ 6
Specific impulse ~ 450s
Propellant mass fraction ~ 90%
Why is aviation challenging to decarbonise?
Due to energy density needs, long ranges, and slow tech turnover.
What are the ACARE 2020 Targets?
Reduce CO2 by 50%,
NOx by 80%
and noise by 50%
(per passenger-km vs 2000).
What is Sustainable Aviation Fuel (SAF)?
A drop in biofuel made from non-fossil sources (e.g. cooking oil) that can reduce emissions by up to 80%.
List key issues with SAF?
High cost, low production volumes and competition with food/agriculture.
What roles could hydrogen play in aviation?
Fuel cells for small aircraft; direct combustion for short / medium-haul jets; storage and material challenges exists.
What are engine noise sources in modern engine?
Mainly fan and jet noise.
How does jet engine noise scale with velocity?
Noise proportional V ^8
What material innovations are crucial for engines?
Ceramic Matrix Composites (CMCs), Titanium aluminides, powder metallurgy nickel alloys.
What are CMCs and why are they important?
Lightweight, heat-resistant materials used in turbines; improve efficiency and reduce emissions.
What are hydrogen-related material challenge in aerospace?
Embrittlement, cryogenic performance, corrosion from water vapor, sealing and fatigue testing.
Advantages and disadvantage of solid propellant
Advantages and disadvantage of liquid propellant
