N221-043 TITLE: Enhanced Performance Radome Materials for High Speed Missiles

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Materials / Processes

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

OBJECTIVE: Develop a common radome architecture for multiple future missile systems which provides a significant increase in thermo-structural capability while maintaining electrical performance across wide frequency bands.

DESCRIPTION: Evolving weapons technology is driving advanced missiles (supersonic and hypersonic) and other flight vehicles to greater speeds and higher accelerations. Consequently, existing materials do not exist to answer the problems being caused. The result of increased speed and acceleration is higher temperatures and thermal stresses. For instance, vehicles traveling over Mach 4 reach surface temperatures of 1,500�C or higher. Rapid acceleration results in extreme thermal gradients, translating to high stresses. Flight through adverse weather such as rain or sleet, and sand and dust add additional environmental hazards which must be survived. These conditions, resulting from the evolving technologies, will require changes in materials to meet or exceed requirements to negate the effects on missile radomes. There are specific material properties, namely dielectric constant and loss tangent, which need to be low (preferably below 5 and .05 respectively). An innovative solution may consider both advanced materials and existing state-of-the-art materials. Existing materials include slip cast fused silica, oxide ceramic matrix composites, and various forms of silicon nitride. Current materials suffer inadequacies including low thermostructural robustness, excessive electrical property variation with temperature, and excessive heat conduction through the radome. Radome materials must provide for stable performance over the duration of its flight. Thermal shock is particularly difficult and can cause expansion of the outer surface during acceleration, thereby impacting both electrical performance and material structural integrity.

A critical component of future Navy missile concepts is a radome that will operate while exposed to high temperatures (~2400K) in a harsh flight environment while maintaining legacy strength and Radio Frequency (RF) transmission properties, surpassing both the capabilities of legacy radomes and current commercially available materials. It is desired that this future radome will have a common design architecture which will allow use across multiple missile types, and reduce production costs by eliminating multiple radome types. With these objectives in mind, the U.S. Navy seeks a radome design that utilizes proven materials and manufacturing methods, but also material innovations to provide increased thermal survivability while minimizing temperature-related RF performance loss.

Concepts are sought to significantly enhance the survivability of radomes while maintaining the required RF performance. Novel constructs are envisioned that build upon current state-of-the-art with material additions, substitutions, or layering. Novel new materials, or novel combinations of known appropriate materials, may be considered. It is preferred that materials with known properties be incorporated into the proposed solution to potentially reduce the time to meet the technology readiness. Proven manufacturability and properties will be favorably considered. Advanced and novel materials could be integrated into the basic structure and/or added as additional elements or layers.

Selection and fabrication of these advanced materials to achieve novel constructs is desired. In-depth characterization and testing are critical for elucidating the mechanisms to achieve advanced survivability. Some critical considerations for any such RF radome system include electrical properties (dielectric constant, loss), thermal properties (conductivity, emissivity), structural properties across the service temperature range, and a manufacturing approach which allows for tight control of shape, size, and thickness. The awardee must propose adequate test protocols to demonstrate suitability of the proposed technology to satisfy Navy requirements. Testing can be conducted on coupons combined with modeling, or on notional prototypes. The solution must show resiliency in high temperature mechanical tests, thermal shock tests, electrical tests, non-destructive testing, and microstructural examinations.

High temperature RF property measurements of the radome materials will be needed for use in radome-level models. Tradeoffs between materials that are optimal for thermal survivability and those that are optimal for radome function will likely be encountered, requiring material development iterations. To optimize performance in all aspects, materials can be tailored in chemistry, thickness, and density.

PHASE I: Develop a concept for a common radome architecture that meets the parameters in the Description. Demonstrate that the concept can feasibly meet the requirements through analysis, modeling, and experimentation of materials of interest. The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a prototype solution in Phase II.

PHASE II: Develop and deliver notional full-scale prototypes (minimum of two) that demonstrate functionality under the required service conditions including thermal and mechanical stresses. Demonstrate the prototype performance through the required range of parameters given in the Description.

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the technology to Navy use in the STANDARD Missile program. Support the manufacturing of the components employing the technology developed under this topic and assist in extensive qualification testing defined by the Navy program. It is likely that the Phase III will involve classified information.

Potential commercial uses for high temperature radome performance improvements exist in the commercial spacecraft and aircraft industries and satellite communications.

REFERENCES:

1. Kasen, Scott D. Thermal Management at Hypersonic Leading Edges. PhD Thesis, University of Virginia, 2013. https://www2.virginia.edu/ms/research/wadley/Thesis/skasen.pdf.
2. Walton, J.D. "Radome Engineering Handbook: Design and Principles." Marcel Dekker, Inc., New York, 1970.
3. "Predictions Of Aerodynamic Heating On Tactical Missile Domes," NSWC TR 79-21, T. F. Zien and W. C. Ragsdale, Naval Surface Weapons Center Dahlgren, Virginia 22448/Silver Spring, Maryland 20910. April 25, 1979 https://apps.dtic.mil/dtic/tr/fulltext/u2/a073217.pdf.

KEYWORDS: Radomes; Advanced Missiles; Thermal Shock; Radio Frequency; RF; RF Transmission; Supersonic; Hypersonic