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Integral Fuel Tank Self-sealing Protection


OBJECTIVE: Develop technology capable of providing lightweight self-sealing capability to prevent fuel loss from ballistic impacts for combat aircraft fuel tanks. DESCRIPTION: Lightweight self-sealing capability to prevent fuel loss from ballistic impacts is a critical combat aircraft performance objective. Currently, fuel tanks are protected with ballistic liners, internal self-sealing layers or self-sealing bladders with limited success. The bladders consist of multiple layers. The internal (sandwiched) layer of material swells upon contact with fuel, with the intended result of resealing the bladder, after puncture, to prevent fuel loss. The current specification required resealing within 2 minutes after puncture. Issues with current technology include excessive weight and unreliable reproducibility in self-sealing layer resulting in poor ballistic wound closure and additional fuel loss. As ballistic impact most typically occurs on the underside of the aircraft, protection is not necessary on the top of the fuel tank. Reduction of material to cover only the vulnerable areas could result in reduced weight. Additionally, a more reliable and consistent method of ballistic protection is sought. The goal of this STTR is installation/application of a lightweight ballistic protection technology to vulnerable areas of existing integral fuel tank structure. Design concerns include balancing level of ballistic protection with aircraft weight and stiffness. Ballistic protection includes impacts from both tumbled and fully aligned small caliber Armor Piercing (AP), AP Incendiary (API), Ball rounds and missile warhead fragments. New technologies should be capable of providing fuel containment within 2 minutes (threshold), with 30 seconds the ultimate goal, at -40 degrees F and at ambient temperatures. New technologies should perform with commercial Jet A (including military additives) and a 50/50 blend of current jet fuel and bio fuel with minimum aromatic content of 8%. Design should not interfere with fuel purity, fuel transfer and surrounding aircraft structure or equipment. Threshold leak rates from new approaches will be tested using existing aircraft fuel tanks after a simulated penetration by a 50 caliber round at -40 degrees F and at ambient temperatures. PHASE I: Develop approaches to provide lightweight ballistic protection capable of meeting required specifications for existing aircraft fuel tanks. Demonstrate the feasibility of the recommended approach. Identify concepts and methods to be used to install/apply this new technology to existing fuel tanks. PHASE II: Develop and demonstrate prototype ballistic protection capabilities using a panel from a current fuel tank design under a range of ballistic rounds, meeting desired leakage limits. PHASE III: Complete validation and verification of ballistic protection technology. Transition technology for implementation on existing fixed wing aircraft or auxiliary fuel tank. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Lightweight fuel tank protection can transfer to commercial aviation, automotive and transportation industries, providing protection of tanks containing fuel, hazardous materials and other liquids.
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