Function srp_total_axial_force_coefficient_kernel 

pub fn srp_total_axial_force_coefficient_kernel<R>(
    c_t: R,
    mach: R,
) -> Result<R, PhysicsError>
where
    R: RealField + FromPrimitive,

Total axial force coefficient of the central-nozzle SRP configuration

$$ C_{A,total} = C_T + f(C_T) \cdot C_{A0} $$

composed from the sibling kernels (srp_preserved_drag_fraction_kernel and jarvinen_adams_baseline_axial_coefficient_kernel); no correlation is restated here. At M = 2.0 this reproduces the report’s Fig. 56 directly (C_A0 = 1.25); at other Mach numbers in [0.6, 2.0] the M = 2.0 preserved-drag shape is scaled by the local baseline — an approximation the report’s M = 1.5 data (Fig. 33) supports in shape, labeled here as such. The composition carries the measured non-monotone band: the total axial force dips below the unpowered value for low C_T (minimum ≈ 0.73 vs 1.25 unpowered at C_T ≈ 0.46, M = 2.0) before thrust dominates — lighting the engine gently buys less deceleration than coasting.

References

• Jarvinen & Adams (1970), Figs. 32/56; Conclusion 5, p. 145: “as the thrusting coefficient increases (C_T ≥ 1), the total retroforce becomes approximately equal to the retrothrust.”