Parachute Drag Model

DTV-SIM is a computer program that implements a mathematical model of the flight dynamics of a missile-shaped drop test vehicle (DTV) equipped with a multistage parachute system that includes two simultaneously deployed drogue parachutes and three main parachutes deployed subsequently and simultaneously by use of pilot parachutes. DTV-SIM was written to support air-drop tests of the DTV/parachute system, which serves a simplified prototype of a proposed crew capsule/parachute landing system.

The DTV-SIM model is of a point-mass trajectory-integrator type and includes detailed submodels of the staged deployment of, inflation of, and aerodynamic drag on, the parachutes. The model simulates (1) the forces on the parachutes and the DTV and (2) the motion of the DTV/parachute system from release until landing. Before a planned test, DTV-SIM is used to predict the flight of the DTV/parachute system in order to devel- op a flight envelope for the test. After the test, DTV-SIM is used to reconstruct the flight on the basis of data acquired during the test and, while so doing, to optimize parameters in the parachute-inflation sim- ulation submodels.

This program was written by Peter Cuthbert of Johnson Space Center. For further information, contact the Johnson Commercial Technology Office at (281) 483-3809. MSC-24361-1

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