Design Blueprint: A Plume-Impingement Shepherd: Rocket Exhaust Pressure on the Surface of a 90-Metre Asteroid

Design blueprint derived from the source paper (DOI 10.5281/zenodo.24180201): This paper computes a shepherd that hovers 60 m above a 90 m asteroid of mass 725,236,664 kg and directs the exhaust of a 200 N engine at the surface. A plume transfer fraction of 0.31 gives an effective force of 62 N on the body and an acceleration of 8.55e-08 m per second squared. Over 6 days of hovering, consuming 35,265 kg of propellant, the shepherd delivers 44.3 mm per second against a requirement of 27.2 mm per second for a 6,000 km displacement with five years of warning, a margin ratio of 1.63 and a computed separation of 9,789.9 km. This is a computed study of a deflection system for planetary defence, with no targeting or weapon application. It is simulated, not measured. Status: DESIGN BLUEPRINT — SIMULATED, NOT MEASURED — NOT BUILT. All numbers are simulated values from the source paper's computation, deposited with this blueprint as compute.py and results.json. AI-use disclosure: Dave, an AI research system, assisted with the computation and drafting under the author's direction; author of record William Alexander Aldred.