Definition
Plain language
Moving faster than about five times the speed of sound.
As stated in the literature
A flow regime above roughly Mach 5, marked by strong shock waves and intense aerodynamic heating; the setting for re-entry simulations like the Apollo command module case.
Why it matters: At these speeds the intense heating and shock waves make designing and simulating vehicles extremely hard, so getting the physics right is critical.
For example, a space capsule slamming back into the atmosphere at many times the speed of sound experiences hypersonic flight, glowing from the heat.
Heard on the show
“There's a formalization team that takes the user's request — "simulate hypersonic flow around Apollo" — and turns it into a well-posed problem with explicit physics, geometry, and observables.”Episode 042 — An Agentic Scientific Computing System That Actually Remembers What It Learns