The duties of the Aerodynamics sub-system are the aerodynamic design and trajectory analysis of the rocket, as well as the development of configurations and automatic control systems to improve its performance. To achieve the best possible results, the sub-system develops its own tools, performs CFD analysis and wind tunnel testing.

The sub-system consists of two departments:

  • Aerodynamic Design
  • Automatic Control

Aerodynamic Design department

The main goal of the Aerodynamic Design department it to design a stable rocket that reaches the target apogee precisely. The design process consists of multiple stages and constant improvements are made until the requirements are met and the desired result is accomplished.

During the first stages lower fidelity tools, like OpenRocket, are used to save time, while high fidelity ones (e.g. CFD) are utilized in the latter stages. Moreover, wind tunnel testing is performed to validate the results.

Ανάλυση ευστάθειας πυραύλου στο OpenRocket
Stabilty analysis in OpenRocket

In OpenRocket the initial configuration layout and sizing are determined and an estimation of the weights is given. Additionally, aerodynamic characteristics (e.g. drag) and stability are calculated and a trajectory analysis is performed. The best accuracy is provided by Computational Fluid Dynamics Software (CFD), through which the aerodynamic characteristics and the stability are again calculated. At the same time, the airflow around the rocket is studied. For this purpose, the sub-system uses the pre-processor ANSA from Beta CAE systems for meshing and ANSYS CFD/Fluent as solvers.

Διακριτοποίηση Nosecone στον προ-επεξεργαστή ANSA της BETA CAE Systems
Nosecone meshing in pre-processor ANSA from Beta CAE systems

The final dimensions of the nosecone and fins are determined with trade studies realized through CFD analysis.

During the design process, the members are also provided with the rare opportunity to study complicated aerodynamic phenomena, like flow separation in fins and shockwave formation at supersonic speeds.

Flow seperation over a fin
Shockwave formation on PEGASUS nosecone

Another significant part of the sub-system is the Research & Development of new configurations, mechanisms, and design tools. The most important ones until now are the:

  • Tailcone: Using project PEGASUS as a baseline, the effects of a tailcone in a rocket’s performance were studied, with the intention to used it in future projects.  Its purpose is to reduce the drag of the rocket, by minimizing vortices generated from the base of the rocket.
  • Performance assessment and trajectory analysis: The sub-system is currently developing a performance assessment and trajectory analysis tool which will replace OpenRocket. This will provide better accuracy and a more precise simulation, while maintaining the ease of use OpenRocket provides.
Ενσωμάτωση Tailcone σε πύραυλο
Tailcone intergration

Automatic Control Department

The goal of this recently formed department is to develop controllers and mechanisms, so as to improve the performance and the dynamic behaviour of the rocket. This is achieved through analysis, modeling of physical and automatic control systems and extraction of transfer functions. Necessary for the design and performance assessment of the controller is the simulation of the systems. These are realized in Matlab and Simulink.

Ενσωμάτωση Airbrakes σε πύραυλο
Airbrake intergration

An airbrake system is currently being developed, whose goal is to control the apogee of the rocket. This is achieved by controlling fins, vertical to the airflow, that increase the rocket’s drag. The first version of the controller and mechanism have already been designed, as well as the simulation software, in collaboration with the Aerodynamic Design department. A prototype remains to be built for evaluation of the airbrake system. Further on, its development will continue and its complexity will increase due to the growing number of the controlled variables and the greater accuracy of simulation software.

Some of the sub-system’s future goals include the development of a roll control system and an active fin control, which will allow full control of the rocket’s orientation.