Newsletters: 2003, Issue 2

Missile Defense Activities at PSI

PSI has a long history and distinguished background in missile defense technology.

Homeland defense has become a major national priority, and the science and technology community has been mobilized to provide some of the answers to this complex challenge. Physical Sciences Inc. has been involved in aspects of homeland defense for several years, developing both point and remote sensors to detect chemical and biological agents, designing urban bio-agent surveillance systems, and testing advanced decontamination systems.

Our company's heritage in homeland defense actually dates from its founding, thirty years ago. We have made notable contributions to ballistic missile defense through modeling, data analysis, ballistic range simulation and discrimination algorithm development. As this issue reports, PSI is actively engaged in missile defense technology for a system that will soon be deployed to protect our nation against a new spectrum of threats. To learn more about our historical contributions and current missile defense capabilities, please contact Bob Weiss at weiss@psicorp.com.

Missile Re-Entry Modeling

Dr. Hart Legner

The accurate modeling of the hypersonic flow enveloping re-entry and interceptor vehicles, including the chemical reactions that are occurring in the shock layer and boundary layer, combined with the mass loss behavior from ablating heat shields, is challenging and complex. This has been accomplished at PSI over several decades of government-sponsored research programs, using first principle and engineering models that capture the appropriate level of physical details.

Recent activities, led by Dr. Hart Legner, have continued these efforts as well as associated materials development and other technologies related to the missile defense area.

Interceptor Windows

PSI has made significant progress in developing an entirely unique approach to IR interceptor windows. There are two novel features of the concept. First, it is a passive window material that responds to an aerodynamic thermal load by releasing hydrogen at low temperatures, thereby cooling the material. Second, the window relies on sparse aperture imaging using distributed optical ports to see through the opaque material. Taken together, these two features of the window make it applicable to future kinetic energy interceptors with much higher speed requirements for boost phase and trans-atmospheric intercept. Continued development of this innovative interceptor window is anticipated from the Missile Defense Agency. Alan Gelb originally conceived the hydride material concept. Recent efforts have been led by Hart Legner, Principal Research Scientist, with support from Jeff Boehme, Dave Rosen, and others.

Comparison of optical images obtained by looking through a clear aperture and a sparse aperture with only a 10% open area.

Multi-Layer Heatshield Materials

Heatshield materials provide protection from excessive thermal loads that could prevent a hypersonic atmospheric interceptor, an earth re-entry vehicle or a planetary probe from achieving its mission. PSI has developed low-cost, low-density multi-layer materials for heatshield and structural applications. This material combines thermal protection features with excellent structural properties and provides a material that can be used to fabricate an aero shell with integral thermal protection.

Fabricated dual layer materials are low-density for the heatshield version and higher density as a structural composite.

The Air Force effort was led by Vic DiCristina, with significant contributions by Hart Legner, who subsequently led the development of the structural composite material. This work was performed in PSI's Thermal Technology Area, led by Bill Laughlin. The material has been fabricated by Textron Systems Division in Wilmington, MA.

Rail-Sled Aerodynamics

Full-scale ground tests of weapon system effectiveness can be conducted at the Holloman High Speed Test Track facility located at Holloman Air Force Base, NM. PSI is in the process of developing an engineering analysis tool, The Rapid Aerodynamic Interaction Load (RAIL) Code, as part of an Air Force SBIR effort. The overall goal of the program is to compute accurate aerodynamic forces, moments and heat transfer in a rapid, PC-based environment to ultimately aid in the engineering sled design process.

Photograph of generic missile payload during rocket sled test.

PSI's approach fills an important niche between approximate calculations of aerodynamic behavior and time-consuming Computational Fluid Dynamic (CFD) simulations. The PSI method is typical of the technical approach we've taken in many re-entry programs. John Cronin, who maintains the PSI flow field codes, is developing the software and user manual.

Fuel-Spill Wakes

Ballistic missiles observed during theater conflicts have been observed to have visible optical signature trails. It is very important to understand this enhanced signature since interceptor aim point algorithms require accurate knowledge of the missile heating profile and optical signature. PSI has used its suite of hypersonic flow field models to obtain wake signature predictions for liquid propellant venting and fuel release scenarios. The starting point for these simulations was the validated flow field model that PSI developed during two decades of ICBM re-entry physics programs. These results were presented at several national meetings and became an important component of the Battlespace Study for Theatre Missile Defense scenarios. Hart Legner has also led these efforts with support from John Cronin, Terry Rawlins, Mike Finson, and George Caledonia.

Flow field models for hypersonic atmospheric vehicles.

A publication of
Physical Sciences Inc.
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