73348 - Aerospace Propulsion Systems

Learning outcomes

The student acquires information required to understand the behavior of all rocket engines (both liquid and solid) and of electric propulsion systems. This is done starting from the analysis of the propulsion requirements needed for each mission, then approaching the general design of rocket engines, and finally studying each component characteristics.

Course contents

Introduction to propulsion
Rocket and space vehicle performance; thrust and specific impulse.
Motion equation for a space vehicle with propulsion; trajectory limitations. Gravity and drag losses.
Single and multi-stage vehicle performance; Chemical rockets (liquid, solid and hybrid propellant) performance.
Electric propulsion: evaluation of the optimal specific impulse.
Definition of the propulsion requirements to fulfil a space mission.

Chemical rockets
Thrust chambers, nozzle behavior. Performance characteristics: thrust coefficient, characteristic velocity. Over and under expansion. Conical nozzles, shaped nozzles, nozzle length. Plug and expansion deflection nozzles, aerospike. Friction and back-pressure effects.
Propellants combustion. Equilibrium composition and temperature. Nonequilibrium expansion.
Liquid-propellant combustion chambers. Fuel and oxidant injection. Chamber length. Chamber cross-sectional area.
Solid propellants combustion chambers. Burning rates. Combustion pressure, burning stability, erosive burning. Two-phase flow and expansion in the nozzle.
Rocket heat transfer. Regenerative cooling of liquid-propellant rockets. Heat sinks and solid propellant nozzle design.

Electrothermal rockets
Nuclear rocket
Resistojet: propellant choice, performance.
Arcjet: propellant choice, arc stabilization problems, electrode degradation.

Electrical rocket propulsion
Ion thrusters. Bombardment ionization, acceleration and neutralization of the ion beam. Propellant choice.
MPD thrusters. Performance, limitations

Readings/Bibliography

Sutton - Rocket Propulsion - John Wiley & Sons, New York

Hill & Peterson - Mechanics and Thermodynamics of Propulsion -Addison-Wesley Publishing Company - New York

Jahn - Physics of electric propulsion - McGraw Hill - New York

Stuhlinger - Ion propulsion for space flight - McGraw Hill - New York

Teaching methods

The lessons are frontal in the classroom. All the information and the material that is needed in order to successfully pass the exam are presented by the teacher at the board.

Attendance is strongly recommended for an improved learning of concepts and notions, but does not affect the final evaluation process.

Assessment methods

Final exam will be a discussion during which students will be asked theoretical questions about the subjects explained during the course.

In the course of the examination it will be also assessed student's ability to resolve new problems or at least to set up the correct resolutive strategy.

The evaluation, expressed in thirtieths, will be higher the more the student is:

• autonomous in articulating responses to the two questions;
• exhaustive in explaining the arguments;
• precise in representing the functionality of the free-hand sketches.

Teaching tools

Usually a visit to a factory that produces rockets is organized during the two months the class is given.

Office hours

See the website of Fabrizio Ponti