TECHNOLOGY AREAS: Materials/Processes, Weapons

ACQUISITION PROGRAM: PMA-259 Air-to-Air Missile Systems

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: Develop methods to apply antireflection coatings to the inside of deep concave surfaces including a tangent ogive infrared dome.

DESCRIPTION: Future infrared-guided missiles may use aerodynamically shaped seeker domes instead of hemispheric domes used today. An aerodynamic shape such as a tangent ogive reduces drag and also permits increased field of regard for the infrared seeker. The dome shape requires efficient antireflection coatings to reduce reflections from off-normal angles of incidence. An ideal coating will have variable thickness to provide optimum antireflection performance at different look angles.

A candidate tangent ogive seeker dome will be made of transparent polycrystalline alumina. It will have a base diameter of 5 inches and a height of 7.5 inches. The tip of the ogive will be cut off and so can serve as an inlet or outlet for gas flow during coating. The dome and its coating must be capable of withstanding temperatures up to 1000 C in the air.

PHASE I: Develop a method to apply an antireflection coating to the inside of an ogive dome made of polycrystalline alumina. The coating should provide broadband antireflection performance in the 3 to 5 micrometer wavelength region. The Government will provide coupons of transparent polycrystalline alumina for coating development. For an initial demonstration, apply a uniform coating to the inside of a fused silica tube with a diameter of 5 inches. For a second demonstration, the Government will provide a metal ogive dome with several flat disks of polycrystalline alumina mounted in holes to simulate an ogive-shape alumina surface. Coat the inside of the metal ogive and measure the transmittance of the alumina disks to demonstrate the performance of the coating.

PHASE II: Optimize the coating for antireflection performance and adherence to alumina. Apply the coating to the inside of an alumina ogive to be provided by the Government. Develop a method to verify the performance of the coating in a production environment. Develop a method to apply a continuously varying coating to provide optimal antireflection performance at different look angles through different regions of the dome.

PHASE III: Implement a commercial process capable of coating aerodynamic domes on the internal and external surfaces. The external coating must be resistant to erosion as well as providing antireflection performance.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The coating technology developed in this effort has potential applications for heat-resistant coatings where durability and stability at extreme temperatures is required. For example, medical-lighting systems that use hot mirrors, cold mirrors and ultraviolet-blocking filters need to withstand high thermal loads (high temperature) and high ultraviolet flux. Currently available medical-lighting systems have short lifetimes and require frequent maintenance. Coatings that have better heat and ultraviolet radiation resistance and that could be deposited uniformly onto the interior and exterior of the bulbs would greatly extend the lifetimes of these medical-lighting systems.

The telecommunications industry uses ball lenses for fiber-optic interconnects. Antireflection coating uniformity is an issue on these types of lenses. The ability to coat a small spherical lens uniformly and economically would be an important commercial application.

Other commercial markets that could benefit from durable, heat-resistant coatings are solar reflectors, infrared- and ultraviolet-curing filters, optical-projection systems, and satellite and space-based optical systems that are subjected to high thermal loads.

REFERENCES:
1. P. W. Baumeister, "Optical Coating Technology," SPIE Press, Bellingham, Washington, 2004.

2. J. D. Rancourt, " Optical Thin Films: User Handbook," SPIE Press, Bellingham, Washington, 1996.

3. M. V. Parish, M. R. Pascucci, and W. H. Rhodes, "Aerodynamic IR Domes of Polycrystalline Alumina," Proc. SPIE, 5786, 195-205 (2005).

KEYWORDS: antireflection coating; optical coating; infrared dome; optics; thin film; missile dome

** TOPIC AUTHOR (TPOC) **

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