Unguided airdrop typically relies on a precise release point to achieve accurate results. Such systems typically use round parachutes and follow a ballistic trajectory, pushed by the wind as they fall. Guided airdrop systems using steerable ram-air parafoils, on the other hand, are able to actively control themselves to a target point. Due to their significant glide slope capability, they can be dropped from significant offsets with much less concern for the actual release point. However, significant glide slope implies significant forward velocity. This can cause problems on landing, and can result in damaged or rolled-over payloads. Before landing, guided airdrop systems flare, attempting to reduce their velocity. Recent developments with in-canopy bleed air actuators have led to systems controlled without any trailing-edge control at all. Such systems cannot flare, but instead enter a deep sink at the end of flight by opening all of the bleed air vents. In this way, they impact more vertically than they otherwise would, although their total speed does not change much. Airdrop system impact requirements are typically set as a threshold total impact speed, rather than impact accelerations, since impact accelerations vary depending on what surface the system lands upon, if it lands level, impact attenuation hardware on the cargo, and other factors. Nonetheless, acceleration evaluation is important because high acceleration can damage the cargo being delivered. In this paper we develop a multibody dynamic simulation of an MC-5 guided airdrop system that can be used to analyze the effects of guidance strategies, landing maneuvers, and system configurations on the survivability of the cargo upon landing. This system has flexible connections between the payload, AGU, and canopy. The model can reproduce landing maneuvers with trailing edge control (flare) and bleed air control (deep sink). Landings are simulated at all angles with respect to the wind in order to examine the effects of landing into the wind. Through snapshots of landings during flight testing, we show that this model can reproduce characteristics of those landings such as payload toppling and AGU swing-down over the payload. A Monte Carlo study was performed using this model so that various systems, landing maneuvers, and final guidance strategies can be compared. The modeled bleed air systems matched the flight data in that they impact with higher total velocity than similarly weighted trailing edge systems after flare, but their near vertical landings prevent the payload from rolling over even at higher velocities. The study showed that impact velocity and peak payload acceleration increase if the system lands with the wind vs. against it, yet there is a wide region where the system lands somewhat against the wind in which the peak acceleration is not highly affected. This implies the systems has some bandwidth in which it could steer during final approach to improve accuracy without increasing the risk of cargo damage significantly.
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