Recently, engineers from Tecplot, Inc. presented a white paper entitled “Evaluation of the High Lift Prediction Workshop Data Using Simulation Analytics” to the Applied Modeling & Simulation Branch at NASA AMES.
The writers of the paper had a clear goal: Engineers must fully understand the flow physics during the separation maneuver in order to properly size the separation motors. Otherwise, the spent solid rocket boosters (SRB) could make contact with the core stage.
NASA runs thousands of simulations of how a SRB will separate from a rocket. What they’re most concerned with are possible scenarios in which something could go wrong. Because engineers work in probabilities, they want to know the degree of safety in their design. So, they ask questions like:
How does the weight, power, and shape of the SRB affect the design? Where is the center of mass of different SRB once the fuel is spent? How does that affect separation?
What is the best orientation of the rocket to begin the SRB separation phase? What happens if the attitude (orientation) of the main rocket is different from that shown in the design?
Under what scenarios could the SRB swing back and hit the main rocket? How likely is this to happen? Can we simulate that occurrence?
What happens when the boosters don’t fire at the right moment of separation? How will that change the “pitch” of the SRB moving away from the main rocket?
What happens if the mechanical connections don’t release as designed?
If we start with five different SRB designs, and then five different main rocket configurations, and each SRB/Rocket combo takes 1,000 simulations to cover the possible scenarios, are we prepared to run 25,000 simulations to understand all scenarios (5 x 5 x 1000)?
How will we understand the results of the simulations? How will we visualize the results? In a table form? In a graph? Would it help to create a (computer generated) visual image of the scenario? Would it help to be able to quickly compare one image to a hundred other images using software like Tecplot Chorus?
What are we missing?
Since NASA is a public organization that is attempting to do relatively unique tasks (i.e. put humans into space), they are under a high degree of scrutiny. So NASA engineers are highly motivated to think of every scenario that a rocket may encounter during its flight. The SRB is a critical stage, so running accurate simulations and understanding the consequences of various scenarios is what “keeps them up at night”.