This Early Career Faculty Award will support the development of a novel phase-space coupled hybrid framework for mixed continuum/rarefied flows. Flow structures that develop around high-speed atmospheric entry vehicles often contain localized flow regions where rarefied (or non-continuum) effects, within an otherwise continuum description, lead to significant modeling uncertainty. Hybrid techniques that incorporate both continuum and kinetic computational methodologies offer an elegant balance of computational efficiency and accuracy for simulations involving mixed continuum/rarefied flow regimes. These efforts will construct a foundational hybrid framework for chemically reacting flows from Generalized Chapman-Enskog (GCE) Theory. Broad research opportunities exist in the development of this hybrid methodology, and a number of novel contributions are anticipated from these efforts including: (i) consistent state-based kinetics models for CFD/DSMC flow solvers, (ii) new set of GCE continuum breakdown parameters and assessment of continuum breakdown for reacting flows, (iii) a novel phase-space coupling procedure for improved statistics in DSMC tail-driven processes.