Approximate analytical models for landing energy absorption, including the effect of penetration by the payload into its crushable casing

Abstract : Two approximate analytical models are defined for a landing configuration in which a spherical payload can sometimes penetrate into its crushable casing. Results for both models are found to agree reasonably well with two previous experimental measurements. Design examples are presented for an impact velocity of 300 ft per sec. These are based on choices of zero or 'perfect' payload bonding, and of either a balsa-like or honeycomb-like class of crushable material. The greatest difference between the models for these examples is a 29-percent discrepancy in the required maximum crushing stress. A particular pair of examples gives the unexpected result that penetration can provide a decrease in crushable material weight by a factor greater than 4 when the honeycomb-like class of material is required without penetration, but the more efficient balsa-like class is feasible with penetration.