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Cost Effective Aerodynamic Missile Domes

Description:

 
 

TECHNOLOGY AREA(S): Weapons

OBJECTIVE: Develop optical materials and novel methodology to produce an infrared-transmitting dome with high optical quality and enough design flexibility to simultaneously minimize cost and aerodynamic drag for missile seeker applications. Produce a low-drag dome for demonstration in an imaging missile seeker to prove the design and manufacturing technology developed in this effort.

DESCRIPTION: Executive Summary Statements:

 

1.) The US Army desires the ability to operate imaging sensors behind a non-spherical dome at the front of a missile.

 

2.) This effort shall develop novel materials, fabrication processes, and assembly methods which shall allow for the production of transparent domes for missiles at a minimized cost which is favorably compared to the cost of current, traditional, spherical domes.

 

3.) Exterior dome shape must remain variable in order to allow for tailoring of aerodynamic characteristics to fit various missile platforms.

 

4.) Dome materials must simultaneously transmit 1.06-micron laser radiation and either mid-wave infrared (MWIR) or long-wave infrared (LWIR), while not significantly affecting transmission of Ka-band radar. A solution for each infrared band is preferred.

 

5.) This effort shall consider dome maximum base diameters of 2.75, 5, and 7 inches.

The US Army employs imaging and non-imaging sensors on a variety of missile platforms to provide precision guidance to targets. The Army now places a strong emphasis on decreasing cost in its missiles, while simultaneously increasing the effective range of those missiles. Aerodynamic drag must be reduced on current missile platforms in order to extend the range of the missiles in an efficient manner. A key drag component of a missile with an imaging seeker is the front-end dome.

Aerodynamic drag varies with missile speed. Therefore, the shape of minimal-drag domes must be tailorable to suit different missile platforms.

Domes must also be resistant to abrasions and other environmental effects typically seen by missiles in tactical environments. The Army requires novel research of highly-transparent and robust optical materials. Novel dome materials must allow favorable transmission and wavefront quality for imaging missile seekers. Dome material research must couple with fabrication and alignment innovation in order to realize the cost minimization desired under this effort.

Platforms of interest to the Army are those with outside missile diameters of 2.75-inches, 5-inches, and 7-inches. Transparent dome base diameters are typically slightly smaller than the missile outside diameter. This effort shall expect length to diameter ratios of the aerodynamic domes to be greater than 0.5 (spherical), but likely less than 1.5. The smallest platform of interest (2.75-inch diameter) is likely to have a stationary, non-gimbaled sensor operating behind the dome. The larger platforms (5 and 7 inch diameters) are more likely to be gimbaled. These gimbaled sensors will rotate behind the dome as much as 10-degrees in angle from the longitudinal axis of the missile and dome. This motion significantly complicates dome wavefront quality metrics.

Larger diameter missile platforms may also be required to operate while transmitting both 1.06-micron laser radiation as well as Ka-band radar through the dome. The Army consequently prefers dome materials which might allow for such transmission. The Army shall regard this as lower in priority for this effort than the goal of infrared wavefront transmission and low cost.

Past efforts have developed techniques for both optical correction [1], [2], and dome fabrication and measurement [3], [4], [5], [6], for gimbaled seekers. These techniques have either not considered gimbaled imaging quality, or have proven to be prohibitively expensive for current missile programs.

Relatively recent work in chalcogenide materials [7] and molding technology [8] imply that more unique lower-cost infrared materials and novel approaches to dome technology may exist. The Army also recognizes that fresh approaches to older concepts, like plastics [9] [10], might now be made feasible.

Consider missile speeds for this effort to be subsonic. Dome abrasion is likely due to external mounting on aircraft. The Army may entertain the idea of hardened coatings, possibly even shielding the dome until launch if it is necessary, or any other novel concept to improve the lifetime of any domes developed in this effort.

The Army is primarily interested in domes which are transparent in the mid-wave infrared (MWIR) and long-wave infrared (LWIR). Of secondary interest is the near-infrared (NIR). These correspond to wavelengths 3 to 5 microns, 7 to 13 microns, and 0.7 to 1.5 microns, respectively. The dome materials in this study only have to transmit one waveband at a time. However, the Army prefers the ability to operate seekers on these missile platforms in a dual-mode configuration with a 1.06 micron laser designator sensor. Therefore, preference will be given to dome materials which exhibit simultaneous transmission in one of the aforementioned wavebands as well as at 1.06 microns.

Minimized materials and production costs are just as important to the Army as the ability to tailor domes to aerodynamic shapes with high-quality optical performance. This SBIR effort exists in order to produce domes which cost less than ones currently produced with traditional materials and methods. The Army’s goal for this effort shall be to produce domes at 25% or less than the total cost of a missile seeker. An example production cost goal would be $3,000 for a dome on a large (7-inch diameter) missile platform. Smaller platform dome cost goals would be significantly less than this example.

Phase I proposals will be technically evaluated on the perceived ability of the technology to meet the previously-stated desired system performance goals as well as achieve future cost goals.

PHASE I: Deliverable Summary:

 

Prior to conclusion of Phase I, the Army requires:

 

1.) Documented optical materials and fabrication process research to prove feasibility and quantify the likelihood to successfully achieve a dome prototype exhibiting previously-described qualities.

 

2.) Formulaic descriptions of dome shapes which are achievable by the proposed materials and methods, and which prove adaptability of the novel technology to the range of previously-described dome shapes.

 

3.) Analysis of expected transmitted wavefront quality with consideration for the novel materials and methods and dome shapes.

 

4.) Demonstration of feasible operation and scalability of any key technology components which must be achieved to prove feasibility of the proposed technology.

 

5.) A defined and documented incremental research plan to reduce technical risk as well as achieve cost goals.

Detailed Description of the expected Phase I effort:

 

The goal of the Phase I effort is to demonstrate the feasibility of a missile seeker dome with the desired properties as described in the previously stated description.

The Phase I effort shall demonstrate concept feasibility through optical design and process fabrication design, proven with calculations, references of direct experience, and component technology prototyping and/or lab experimentation. The Phase I effort shall be formulated to significantly reduce the risk to the success of future research to occur in Phase II and beyond.

A successful Phase I shall demonstrate a good understanding of manufacturing tolerances and alignment procedures which may be required to produce a seeker using such a dome.

Dome cost is often the most costly single component in a missile seeker. This SBIR effort exists primarily to solve this problem. A well-designed Phase I effort will show a clear path to low cost of fabricated, mounted, and aligned domes in quantities of several hundred to only a few thousand per year. Phase I shall define an incremental path of research to develop the technology and achieve the cost goals.

A successful Phase I shall demonstrate dome technology intended for domes exhibiting length-to-diameter ratios in the range described in the solicitation, but show some variability such that small design changes for aerodynamic reasons might be possible in the future.

Transmitted optical wavefront is a key consideration for this effort. Phase I shall examine transmitted wavefronts for proposed dome designs and produce a metric and limiting parameters by which dome optical quality can be assessed.

A well-received Phase I proposal will declare the missile diameters and wavebands which will be investigated in the SBIR effort. The Army will favor a well-formulated proposal which shows technology that might address several or all of the platforms of interest. A Phase I effort may also be formulated to demonstrate a scaled-down version of the novel dome technology, provided that the effort also establishes a well-designed incremental path to a full-scale prototype in later phases.

PHASE II: The Phase II effort shall produce and deliver prototypes of cost-efficient, aerodynamic missile domes. A successful Phase II will develop the technology that was proven to be feasible in Phase I. Detailed optical designs and manufacturing tooling designs shall occur in Phase II. Detailed fabrication and alignment processes shall be developed in Phase II. The Phase II effort shall also investigate and develop methods by which the dome will be held in place on a missile body. Phase II shall produce a functioning imaging seeker optical assembly which can be integrated with a camera to record video and test. The Phase II effort shall allow the Army to make a make a full assessment of the ability of the technology to be developed to a point where it can be integrated onto a missile platform.

In Phase II, the investigating firm shall deliver to the Army no less than two (2) prototype domes, integrated with imaging lenses. The domes shall have different shapes in order to demonstrate the design versatility of the novel technology. Measured data on dome optical and mechanical quality shall be delivered, and shall use any novel quality metrics developed as a part of this effort. Materials discoveries and novel process steps shall be documented and reported. Any early parts which illustrate manufacturing process development shall also be delivered to the Army in order to provide evidence of low-cost production methods. The Phase II shall provide well-justified cost estimates for producing domes in production quantities.

A Phase II effort should also include marketing of the technology to missile prime contractors, and establishing relationships for potential integration of the dome technology into real missile platforms.

PHASE III DUAL USE APPLICATIONS: Simultaneously develop technology for integration into a specific missile platform as well as develop spin-off commercial applications for any materials, fabrication methods and processes, or novel design processes which were developed through the SBIR effort.

 

Potential commercial technology areas might be in commercial optics fabrication or software for design, assessment and/or fabrication of similar commercial optical components.

REFERENCES:

  • Trotta, P. A., “Precision Conformal Optics Technology Program,” Proceedings of SPIE Vol. 4375, pp 96-107 (2001)
  • Zhang, W., Zuo, B., Chen, S., Xiao, H., Fan, Z., “Design of fixed correctors used in conformal optical system based on diffractive optical elements,” Applied Optics Vol. 52, No. 3, pp461-466 (2013)
  • Parish, M., Pascucci, M., Corbin, N., Puputti, B., Chery, G., Small, J., “Transparent Ceramics for Demanding Optical Applications,” Proceedings of the SPIE Volume 8016 (2011).
  • Bambrick, S., Bechtold, M., DeFisher, S., Mohring, D., “Ogive and free-form polishing with UltraForm Finishing,” Proceedings of the SPIE Vol. 8016 (2011)
  • Shorey, A., Kordonski, W., Tricard, M., “Deterministic, Precision Finishing of Domes and Conformal Optics,” Proceedings of the SPIE Vol. 5786 (2005)
  • Ditchman, C., Diehl, D., Cotton, C., Burdick, N., Woodlock, J.Z., “Advances in freeform optical metrology using a multibeam low-coherence optical probe (Quad-Probe),” Proceedings of SPIE Volume 8016 (2011)
  • Schott, Inc., “Infrared Chalcogenide Glasses”. http://www.us.schott.com/advanced_optics/english/products/optical-materials/ir-materials/infrared-chalcogenide-glasses/index.html. (11/4/2015)
  • Nam, M., Washer, J., Oh, J., “Breaking the Mold: Overcoming Manufacturing Challenges of Chalcogenide Glass Optics,” Photonics Spectra, http://www.photonics.com/Article.aspx?AID=57309 (11/4/2015)
  • Taylor, C., Borden, M. “LWIR-transmitting windows,” US Pat. No. 5493126A, 20 Feb 1996
  • Borden, M., Bitting, H., Taylor, C., Lurier, J., “Composite infrared windows using silicon and plastic,” US Pat. No. 5851631, 22 Dec 1998

KEYWORDS: dome, seeker, optics, infrared, missile, optical materials, molding, assembly

 

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