Dynamics
Meet Our Dynamics Team!
The dynamics team, headed by Riley Kuhlman, worked to model the flight of the rocket and keep the overall design up to date. After the brunt of the simulation was done, Saylor Sherrodd transitioned to focus on payload. Jase Sandefur focused on the stability of flight and was, of course, our resident variable gravity expert.
Five DOF Python Model
A correct 1 DOF model (the point mass simulation that everyone makes in Excel at the start of the year) should be within 1-5% of the actual apogee, given that all inputs are correct and the wind is minimal. However, a 5 DOF model will improve the accuracy, account for the effect of the wind, and accurately model the dynamic stability. So, I wrote one in Python, and the sprawling mess of code is publicly available.
"Don't use rocksim" - Jase Sandefur
Propulsion Simulation
The propulsion of a hybrid rocket can be broken down into ox tank state, injector flow rate, fuel grain regression, combustion/chamber properties, and nozzle expansion. I wrote an algorithm in Python to simulate each of those phases, focusing most heavily on the simulation of self-pressurized nitrous blowdown and fuel grain regression.
Randomized Simulations
Rockets have a lot of variability, especially when you are custom manufacturing a motor without a full-scale test. To account for that, I set up a program that runs 100 simulations, generating a new motor thrust curve for each one based on random deviation in the temperature at launch, combustion efficiency of our propellants, and regression rate of the fuel (among other things). I tried to document the evolution of these simulation ranges here.
Dynamic Stability
Calculating dynamic stability requires that you know a good amount about the rocket. Stability is a function of the size and shape of the rocket itself, with great emphasis on the fins, and the center of mass of the rocket, which is dependent on the oxidizer and fuel. This figure is incredibly important, as it will allow you to tell how the rocket will behave at a certain point during its flight. Two necessary things are a concrete design, for CP data, and accurate propulsion model, for CM data.
CFD
In order to minimize the drag on the rail guides of the rockets, an airfoil is being designed and evaluated using computational fluid dynamics, or CFD. Using the same cell-based simulation as FEA, we can locate and minimize low-pressure regions, hopefully reducing the drag on the rocket.