OBJECTIVE: The objective is to develop materials and associated manufacturing methods for advanced tactical missile radomes that achieve requirements for electrical, structural, and thermal performance. DESCRIPTION: Radomes on tactical missiles have exacting requirements for electrical, structural, and thermal performance (Ref. 1, 2, 3). The flight environment subjects the radome to severe thermal shock, high temperatures, and possible encounters with hydrometeors (Ref. 4) and other particles such as sand. Polymer matrix composite materials are used on radomes for lower-speed vehicles; however, missiles flying faster than Mach 2 for long flight times experience high temperature increases. Materials that are stable at high temperatures (i.e. radome ceramics) are used for radomes under these extreme conditions. Current materials include slip cast fused silica (SCFS) and Pyroceram (a glass-ceramic material manufactured by Corning). These current materials offer marginal resistance to rain impact and little growth potential for extending missile flight speeds and times. Future missiles will exceed the current standards and will require improved radomes that meet the new standards. Future missile speeds will exceed Mach 4+ and their flight times will be longer, exceeding ninety seconds. New materials and low-cost manufacturing methods are sought for radomes to meet the extended capabilities of these future missiles, and improve survivability and performance in severe environments such as those produced by weather conditions. New radome materials will require a low and thermally stable dielectric constant ( less than 5, approximately 3 preferred), low loss tangent (less than 0.01), high strength, thermal stability, and high thermal shock resistance. They should also provide a hermetic seal (preventing diffusion of water into the radome cavity) and resistance to degradation by impact with particles, including hydrometeors and sand, while in captive-carry and free flight regimes. One of the challenges encountered in developing radome materials is simultaneously addressing all of the requirements. For example, increased porosity may lower dielectric constant, but reduces particle impact resistance. Innovative uses of multiphase materials, ceramics, ceramic matrix composites, coatings, and structures may provide ways to address the suite of requirements. In addition to materials development, it is necessary to address all aspects of the radome. Some of these include attachment to the airframe, integration of possible tip inserts, and manufacturing processes. Low-cost manufacturing methods, which produce radomes at high precision, are required. Total production numbers may range from hundreds to tens of thousands, at rates up to 100 per month. The Phase I effort will not require access to classified information. If need be, data of the same level of complexity as secured data will be provided to support Phase I work. The Phase II effort will likely require secure access, and the contractor will need to be prepared for personnel and facility certification for secure access. PHASE I: The company will develop concepts for improved radomes that meet the requirements described above. The company will demonstrate the feasibility of the concepts in meeting Navy needs and will establish that the concepts can be feasibly developed into a useful product for the Navy. Feasibility will be shown through material testing, and analytical modeling. Pilot experiments demonstrating feasibility of producing radome shapes will be conducted on the most promising compositions. Sub scale or full-scale/sub-section rough prototypes will be produced and suitability of the proposed materials and processes will be evaluated by a combination of laboratory data and numerical modeling. The company will provide a Phase II development plan with performance goals and key technical milestones and that will address technical risk reduction. PHASE II: Based on the results of the Phase I and the Phase II development plan, the most appropriate material composition and approach will be scaled-up in batch size. The company will produce article prototypes (sub-scale or sub-section) for evaluation as appropriate and will produce a scaled prototype after testing and validation of the articles, meeting the performance goals defined in the Phase II development plan and the Navy requirements for radomes. Uniformity of properties of the full-scale and sub-scale prototypes will be evaluated by the use of non destructive methods. Additional modeling will be conducted on a notional radome design, predicting survival and proper functioning of the radome through a notional flight. A manufacturing plan and development plan will be prepared. The company will prepare a Phase III development plan to transition the technology to Navy use. It is probable that the work under this effort will be classified under Phase II. PHASE III: If Phase II is successful, the company will be expected to support the Navy in transitioning the technology for Navy use. The company will develop a radome for a Navy tactical missile for evaluation to determine its effectiveness in an operationally relevant environment. The company will support the Navy for test and validation to certify and qualify the radome for Navy use. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The combination of properties required for tactical missile radomes is somewhat unique, and there is little potential for commercial applications requiring the exact combination; however, there are domestic applications for ceramic materials and structures using a subset of the required radome material properties. Generally, the low dielectric constant and low loss tangent may be exploited in microelectronics, and the high temperature structural properties may be exploited in a variety of engine applications. REFERENCES: 1. Harris, Daniel C."Materials for Infrared Windows and Domes,"SPIE Optical Engineering Press, Bellingham, Washington, 1999. 2. Walton, J.D."Radome Engineering Handbook,"Marcel Dekker, Inc. 1970. 3. Volakis, John."Antenna Engineering Handbook, 4th ed."McGraw Hill Publishing, 2007. 4. Progress in Aerospace Sciences, Volume 47, Issue 4, May 2011, Pages 280-303.