SBIR-STTR Award

Algorithm development for midcourse discrimination requires large libraries of signatures (i.e., time histories of reflected and/or radiated optical intensity or radar cross-section) accurately incorporating the properties of deployed objects, including low mass decoys erected or inflated from small-volume stowage. The dynamics of such objects plays a critical role in signature determination. Current signature codes model only rigid body motion, which may be inappropriate for decoys made of flexible materials, particularly after suffering an off-nominal deployment and concurrent shape distortion. Under a current Phase I SBIR contract PRA is installing the capability to automatically create ensembles of off-nominal decoy models for rapid generation of suites of signatures with appropriately varying properties. In this proposal we describe a parallel effort to develop a fully compatible non-rigid body motion (NRBM) simulation capability for PRA's VISIG signature code. When integrated with the other work, this will allow high-fidelity simultaneous modeling of both static and dynamic structural deformations, fully including effects of flexure on the rotational state of the object and vice-versa. Dynamic effects on signature through object shape changes are also included.

The majority of penetration aids (penaids) are packed to conserve volume until ready for deployment, then inflated or erected to a final shape. Such "stowable" objects are necessarily constructed from flexible materials; their post-deployment motion will include (at least) small structural vibrations and energy loss to damping, as well as the usual rotational component (tumbling, or spin and precession for an axisymmetric conic decoy, more complex rotation in the general case). Potential discrimination techniques exist employing the time-dependent signatures of rotation, vibration or both. Off-nominal deployment, in which the object fails to reach its intended size, shape and/or rotational state must also be considered. In any case (nominal or off-nominal deployment) the physical interaction among the rotational and vibrational degrees of freedom can introduce potentially exploitable signature changes. This Proposal deals with the physics and mathematics of techniques for simulating the rotation and vibration of flexible penaids, including in particular the interactions between these motions. We build on a simulation developed under Phase I and also invoke the expertise of a subcontractor with extensive experience in the modeling of flexible structures.