Expectations vs. Reality: Modeling the Rocket via Simulations
It’s 2022 and besides the ongoing pandemic, the one thing that changed the world is the new Spider-Man movie, Spider-Man: No Way Home. With fan-favorites Zendaya and Tom Holland, it’s no surprise that the movie has an 8.7 IMDB score. However, one of the most memorable characters is, of course, Ned: the guy in the chair. Peter, or Spider-Man, may be whom Ned is the “guy in the chair” for, but for the DPF rocket, it is Redshift’s very own Simulations (Sims) team.
The Sims team, up in the many rooms of the Forsyth building, has been actively working on the uses of Computational Fluid Dynamics (CFD) via a software known as ANSYS. CFD, as the name suggests, deals with fluids and lets the team predict how and where they (fluids) will flow without the use of a wind tunnel or any other costly equipment. Essentially, the Sims team is trying to measure pressures, forces, and other necessary values of the rocket in order to allow for the other AeroNU teams to make changes in time for the actual launch.
How?
The Naver-Stokes equations, a set of partial differential equations regarding fluid motion, are notorious for being convoluted, even when simplified and set up using ideal conditions. One can only imagine how it is under normal circumstances! That is where the Simulations team comes in. Using ANSYS, the team breaks parts of the rocket or even the entire thing into smaller, more manageable pieces through meshing. The fluid, such as air, is then defined around the model. Afterwards, the team sets boundary conditions and lets the software do the calculations.
As simple as the aforementioned sounds, it is by no means easy. The team first makes assumptions intelligently regarding the fluid and its surroundings. This ensures the complex problem is manageable.
Subsequently, the team meshes; when “breaking things into small, infinitesimal boxes, there are truncation errors and errors in how we solve equations iteratively,” according to lead Bjorn Kierulf. During meshing, errors are often present due to the fact that higher order terms are removed and the solution becomes discrete instead of continuous. All these simplifications can lead to the simulation not being true to reality. Due to all these complications, the Sims team is working to find a balance between too many assumptions so that the simulation is in a too ideal state and enough that forces can be approximated.
“Breaking things into small, infinitesimal boxes, there are truncation errors and errors in how we solve equations iteratively.”
Why?
As explained above, the Sims team is trying to predict forces and torques that the rockets will experience during flight… before actually flying them. In order to cover all bases, Kierulf has created any different projects for each team member to tackle. For example, team member Broderick Kelly is currently working on the relationship between the rotational forces on the Marmon clamp (a part of the rocket developed by the Internal Mechanics team that is responsible for deploying the parachutes) due to air and the counteracting forces created due to spinning fins. Another team member Mya Karinchak is focusing on predicting forces and moments when the rocket is at its maximum angle.
Albeit theoretical, the results from the simulations are extremely useful to the entire Redshift Team. The entire philosophy of Sims is getting as many accurate measurements as possible in order to ensure the final rocket will be safe. This saves an incredible number of resources, including time, energy, and money.
In Spider-Man: No Way Home, Ned may be behind the scenes, but in AeroNU, the Sims team predicts all the aspects of the scenes before they even take place!