Coupling Collapse as a Thermodynamic Precursor in Space Systems: A Causal Entropy Framework for Mission, Trajectory, and Health Engines (KA-Space)

We present KA-Space, an early warning framework grounded in information thermodynamics—distinct from physical heat-flow thermodynamics—for three coupled space-system engines: Mission (risk-weighted utility), Trajectory (Keplerian specific energy), and Health (kernel density entropy). The central claim is: Structural coupling collapse between subsystems—measured by mutual information decay precedes observable metric degradation and constitutes a thermodynamically interpretableearly warning signal. We formalise this via Proposition 1 (a variational interpretation, not a fully proved the-orem under measure-theoretic conditions), which maps the fused fCER signal to a variational upper bound on the local entropy production rate of the coupled system under weak-coupling and approximate separability assumptions. The C2 channel is grounded in the Parrondo–Horowitz–Sagawa information–thermodynamics inequality ̇σ ≥ −dI/dt. An ablation study confirms that C2 provides the primary lead-time contribution (lead of 8.7 steps with full model vs. 1.3 steps without C2), but does not render C1 and C3 redundant across all failure scenarios. Synthetic proof-of-concept simulations across six failure scenarios and N=1 000 stochastic realisations provide distributional lead-time estimates. All results are preliminary; real-telemetry validation is required.