To break out of Earth's lower orbit, hypersonic vehicles must reach speeds greater than Mach 5.
At these hypersonic speeds, the air particles and gases that flow around the vehicle and interact with the surfaces generate heat and create shock waves that disturb the flow's equilibrium.
At each of those junctures, you can have very strong recirculation, which leads to unsteadiness.
Levin said she studies flow at a very fundamental level to understand the flow, the forces that the flow can create, and the length of time the flow remains stable in terms of microseconds to milliseconds--faster than the blink of an eye.
The gas no longer remains 79 percent nitrogen and 21 percent oxygen like we have in our atmosphere.
It's a phenomenon that occurs as the air gets thinner as you move faster," Levin said.