Trajectory simulation
This is a 6 degree of freedom trajectory simulation to determine the controls requirements for high altitude sounding rockets. The simulation is based on CFD and experimental inputs and runs on a framework within Simulink. The simulation was used to compute the trajectory and recovery pattern for the Boston University Rocket Propulsion Group's Starscraper sounding rocket.
The project arose from the limitations of trajectory modelling software available to a university group. Commercial packages were either incapable of modelling the intricacies of the Starscraper rocket, such as thrust vector control (TVC) and reaction control systems (RCS), or were prohibitively expensive.
The project arose from the limitations of trajectory modelling software available to a university group. Commercial packages were either incapable of modelling the intricacies of the Starscraper rocket, such as thrust vector control (TVC) and reaction control systems (RCS), or were prohibitively expensive.
The simulation was grounded against a RASAero case. RASAero projected the Starscraper rocket to reach 122 km and a maximum speed of 1,311 m/s. The in-house simulation projects an altitude of 119 km with a burnout velocity of 1,272 m/s. This constitutes a 3.2% difference. The difference lies in the extra features of the simulation that RASAero does not have:
- Upon burnout, the rocket is at a non-zero angle of attack when the TVC stops functioning, which pushes the rocket slowly over to create some very slight extra drag. - The rocket has more protrusions that cannot be modelled in RASAero that cause some extra drag. The use of custom derived drag coefficients stemming from both theory and CFD allows greater flexibility in fine-tuning the simulation. - The simulation has the capacity to model the mass element from TVC fluid usage, pressurization gas and RCS gas usage. |
The computed landing pattern for the Starscraper sounding rocket launched from Black Rock, Nevada
|
Recent additions to the trajectory simulation now allow simulations to take the curvature of the Earth into account, allowing even more advanced rockets to be simulated. A further benefit is the ability to directly get latitude-longitude information of the rocket's position at any point in the flight, which proves especially useful when mapping potential landing zones from boundary analysis on a rocket's performance.