Ground Effects for Widely Spaced, Supersonic, Vertical Retrorockets

摘要

A scenario for creating acceptable touchdown velocity on land for the Orion Crew Excursion Vehicle employsnretrorockets for final landing u0001V. To capture the ground effects due to the interaction of the retrorockets and thenvehicle, detailed computationalmodelingwas used to determine the effective thrust at several different firing heights.nThese results were then used to determine the change in impulse for a wide range of possible firing altitudes. For anCrew Excursion Vehicle retrorocket firing time of 0.5 s, the steady-state effective vertical thrust of the modulenchanges fromu000113:2tou000211:8%for altitudes from152 to 15.2 cm, respectively. A simple descent analysis shows thatnground effects will impart a net decrease or increase in impulse, depending on ignition altitude. In this analysis, thenground effects serve to increase the optimal firing height and increase the ignition altitude margin for a givennmaximum landing velocity.