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Alternate Lubrication Mechanisms for Small UAV and Attritable Weapon Systems


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Renewable Energy Generation and Storage 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 new and innovative lubricating fluid (oil, fuel, and/or grease) supply/delivery system technologies for rolling element bearings in small Unmanned Aerial Vehicle (UAV) engines and/or attritable/expendable weapon systems to replace current architectures–thereby reducing overall system weight, cost, complexity, and maintenance requirements/burden due to fluid leaks and lubricant shelf life during extended storage. DESCRIPTION: While numerous efforts have been made into enabling oil-free technologies [Ref 1] and alternative bearings (including air [Ref 2] and magnetic bearings [Ref 3]), rolling element bearings utilizing fluid lubrication remain prevalent within U.S. Navy platforms. Fluid-lubricated rolling element bearings provide excellent load-carrying capacity, low friction operation, and damping properties when properly lubricated [Ref 4]. Novel delivery methods for lubricants could allow for realization of the advantages of rolling element bearings without the drawbacks of the supporting hardware typically required to provide lubrication supply [Ref 5]. Traditional flow-through and recirculating rolling element bearing lubrication systems which utilize pressurized oil and/or fuel require parts such as supply/scavenge pumps, reservoirs, sumps, plumbing/pipes, and seals, which can account for up to 30% of overall propulsion system weight, volume, and cost in small limited-life engines. In addition, the shelf-life limitations of lubricants used in these systems (such as oil, fuel-oil mixtures, grease) can lead to corrosion or increased maintenance actions during long-term storage. Innovative technologies which enable replacement of traditional lubrication schemes for small, limited-life engines and attritable weapon systems are being sought to reduce total system ownership cost. It is recommended that the small business partner with a component or engine manufacturer, with aerospace experience in UAV and/or attritable systems, to increase potential of tech transition and future commercialization. Transition will require collaborating with small engine Original Equipment Manufacturers (OEMs) interested in drop-in replacements, modifying current designs, or incorporating new lubrication mechanisms within new engine designs. PHASE I: Develop and subscale test a proof-of-concept mechanism which has potential to eliminate traditional lubrication schemes. Design approaches should demonstrate, through tribological experimentation, modeling, and/or subscale testing, the ability to prevent adverse surface deterioration such as overheating, galling, spalling or seizure ofrotating mechanical systems under relevant operating conditions for a representative UAV or attritable engine system architecture mission cycle. Relevant applications of interest include mechanical systems supporting ranges of 150-1500 lbs of equivalent load which can rotate anywhere between 15,000 to 75,0000 rpm at up to 250 degrees Fahrenheit for durations of 5 hours or greater depending on application. PHASE II: Contractors are encouraged to collaborate with commercial OEM’s for UAV and/or attritable engine systems for Phase II activities. Develop detailed design of the concept(s) developed in Phase I with a focus on development, design, and demonstration of a full-scale prototype UAV or attritable engine system utilizing the novel lubrication mechanism proposed. Validation testing should be performed under relevant engine operating conditions including loads, speeds, and temperatures expected for intended applications. Testing should provide comparison data against traditional fuel, oil, and/or grease lubricated architectures and assess the feasibility of the designed system to replace these architectures. A preliminary assessment shall be made of potential long-term storage benefits. PHASE III DUAL USE APPLICATIONS: Continue to improve upon any deficiencies in the technology noted within Phase II. Analyze and test the manufacturability, ease of installation, and logistical burden of the lubrication method. The commercial small UAV market is much larger than the military and would benefit equally from these technologies. REFERENCES: 1. Taylor, K.M.; Sibley, L.B. and Lawrence, J.C. "Development of a ceramic rolling contact bearing for high temperature use." Wear, Volume 6, Issue 3, (1963): 226-240. 2. Radil, Kevin; Howard, Samuel and Dykas, Brian. "The role of radial clearance on the performance of foil air bearings." Tribology Transactions, Volume 45, Issue 4, (2002): 485-490. 3. Clark, Daniel J.; Jansen, Mark J. and Montague, Gerald T. “An overview of magnetic bearing technology for gas turbine engines.” NASA/TM—2004-213177 and ARL–TR–3254, August 1, 2004. 4. DellaCorte, Christopher. "Oil-Free shaft support system rotordynamics: Past, present and future challenges and opportunities." Mechanical Systems and Signal Processing 29, 2012, pp. 67-76. 5. Wongseedakaew, Khanittha, et al. “Thermo Elastohydrodynamic Lubrication with Liquid-Solid Lubricant.” Advanced Materials Research, vol. 1025-1026, 2014, pp. 32–36., doi:10.4028/ KEYWORDS: Lubrication systems, rolling element bearings, mechanical systems, engines, small Unmanned Aerial Vehicle, UAV, attritable propulsion, fuel, oil, grease, long-term storage
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