rarefied gas dynamics

Rarefied gas dynamics studies how gases behave when their molecules are sparsely spread out, so they rarely collide. This typically happens in very thin environments like outer space or high-altitude flight. Unlike in normal air where molecules constantly bump into each other, in rarefied gases, these collisions are infrequent, causing deviations from standard fluid behavior. Understanding this helps design spacecraft, satellites, and vacuum systems, as it models gas flow where traditional assumptions about pressure and turbulence no longer apply. It combines principles from thermodynamics, kinetic theory, and fluid mechanics to describe how such gases move and interact.