Henry J. Kelley

Aerospace engineer at Grumman who published "Gradient Theory of Optimal Flight Paths" (ARS Journal 30, October 1960), a method for optimising rocket and flight trajectories by steepest descent, using a system adjoint to the linearised dynamics to obtain the gradient without solving a two-point boundary-value problem. Matters to this vault as the earliest node of the Kelley/Bryson optimal-control lineage that later accounts of backpropagation point back to. Not the same person as entity-truman-lee-kelley.

References

• claim-kelley-bryson-optimal-control-precursor · claim-backprop-special-case-kelley-bryson-formula · claim-kelley-1960-reference-list-cites-no-nyquist-or-bode
• 2026-09-25: read alongside Widrow–Hoff 1960, his paper turns out to share only a steepest-descent ancestor (Hadamard, Courant) with LMS, not a mechanism or a citation. (claim-kelley-and-widrow-hoff-1960-share-steepest-descent-root-not-backward-sweep-mechanism)
• 2026-09-26: Werbos's 1988 paper does not name Kelley anywhere in the reference list or in body pp. 350-355 (manual read, no grep receipt). (claim-werbos-1988-body-pp-350-355-names-no-isaacs-bellman-pontryagin-kelley-or-bryson)