  This paper presents a numerical algorithm for computing 6-degree-of-freedom
free-final-time powered descent guidance trajectories. The trajectory
generation problem is formulated using a unit dual quaternion representation of
the rigid body dynamics, and several standard path constraints. Our formulation
also includes a special line of sight constraints that is enforced only within
a specified band of slant ranges relative to the landing site, a novel feature
that is especially relevant to Terrain and Hazard Relative Navigation. We use
the newly introduced state-triggered constraints to formulate these range
constraints in a manner that is amenable to real-time implementations. The
resulting non-convex optimal control problem is solved iteratively as a
sequence of convex second-order cone programs that locally approximate the
non-convex problem. Each second-order cone program is solved using a
customizable interior point method solver. Also introduced are a scaling method
and a new heuristic technique that guide the convergence process towards
dynamic feasibility. To demonstrate the capabilities of our algorithm, two
numerical case studies are presented. The first studies the effect of including
a slant-range-triggered line of sight constraint on the resulting trajectories.
The second study performs a Monte Carlo analysis to assess the algorithm's
robustness to initial conditions and real-time performance.
