Apollo Capsule Capsize Stability During Splashdown: Application of a Cavity Collapse Model

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R. D. Lorenz (2011), JBIS, 64, 289-295

Refcode: 2011.64.289
Keywords: Splashdown, water landing, hydrodynamics, stability, testing

Some 9 of the 19 Apollo capsules that made splashdown in the open ocean went into an inverted (`Stable II') orientation. The wind and wave conditions associated with these inversions are summarized - all but one of the capsize events were in winds >6 m/s. The flight data are reviewed in the context of a series of scale-model tests and a physical model is proposed for the dominant, but apparently hereteofore-unrecognized, mechanism of inversion, wherein the resurging central jet of the transient cavity catches the edge of the capsule under certain conditions of horizontal velocity and attitude and applies an overturning moment. This model explains how further increases of horizontal velocity avoid capsize. The model is applied to the Orion capsule and to splashdown in Titan's hydrocarbon seas.

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