In this paper, the problem of drogue-to-main parachute transition altitude optimization in high altitude, low opening (HALO) ballistic airdrops is studied. A probabilistic technique is employed to determine the optimal transition altitude, taking into account uncertainties due to wind disturbances, release point errors and impact point dispersion. An optimal transition surface for a pre-determined release location and altitude is computed and uploaded to the airdrop package prior to its release from the aircraft. During the drogue descent, the package position is periodically compared to the optimal transition surface. Once the transition surface is reached, the main parachute opens. A major advantage of this technique is that each point on the surface is optimized to impact the most desirable location for the given nominal wind profile, thereby reducing the sensitivity to roll out errors, wind disturbances, etc. Results show that the proposed method not only has the ability to reduce dispersion and improve accuracy but also robust and significantly less compute-intensive compared to the existing methods.
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