N151-079 TITLE: Ultra-low Diffusivity High Temperature Capable Insulation

TECHNOLOGY AREAS: Air Platform, Materials/Processes, Weapons

ACQUISITION PROGRAM: Navy Conventional Prompt Global Strike, DARPA Tactical Boost Glide Demo

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 section 5.4.c.(8) of the solicitation. 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: Hypersonic flight induces severe heat loads into airframe, control surfaces and internal assemblies. Thermal insulation must be stable at temperatures up to 1000�C, be compact, must resist evaporation and erosion/oxidation, and have low thermal diffusivity to limit heat transfer to support structures and internal electronics.

DESCRIPTION: A thermal protection system (TPS) is used to maintain the aerospace vehicle�s structural temperature within acceptable limits during sustained flight of hypersonic vehicles. Thermal barrier coatings are complex, multi-layered, and multi-material systems with many variants related to composition, processing and microstructure. Reduction in required insulation volumes are needed to fit internal systems into volume-constrained hypersonic vehicles. Reduction in thermal diffusivity below 8 E-8 m2/sec is needed. Ceramic matrix composite (CMC) TPSs have been investigated and are similar to metallic TPSs, but use CMC components which have a higher temperature capability. Metallic and CMC TPSs and blankets can utilize various types of non-load bearing insulations. The use of new materials, innovative textile architectures, and/or high-temperature multilayer insulations (MLI) in either blanket, metallic or CMC TPSs are possible solutions.

Partially Yttria Stabilized Zirconia (YSZ) is the state-of-the-art material used for ceramic TPSs due to its good mechanical and thermal properties. YSZ has thermal diffusivity of 8.8 E-8 m�/sec. At temperatures higher than 1200�C, YSZ thermal barriers are affected by accelerated sintering and by phase transitions. Exposure above 1200�C results in partial decomposition of metastable zirconia and transformation to monoclinic phase during cooling. This transformation results in volume change and cracking.

PHASE I: Develop proof of concept for diffusivity achievable through combinations of current state-of-the-art insulation materials to achieve the diffusivity not currently achievable with a single material system. Similarly, define approaches for diffusivity reduction achievable through further opacification.

Develop an assessment of the reduction in diffusivity achievable through foams and gels based on high density metals and metal-oxides as well as an assessment of diffusivity reductions achievable in increasing of phonon scattering through addition of dopants. Feasibility of the best approaches will be shown through small-scale material fabrication used in small-scale proof of concept demonstrations.

In the Phase I Option, if awarded, high temperature integration options will be developed allowing attachment of the insulation to metal and Ceramic Matrix Composite materials. These options will provide compliancy sufficient for ambient to 1200�C operation without gaps or tears caused by differences in thermal expansion between the insulation and the parent structure.

PHASE II: Using the best alternative identified in Phase I, produce lots of small-scale insulation bats from which thermal and mechanical properties will be measured. Testing at elevated temperatures will be conducted to determine extent of outgassing and particulate formation. Measure the extent of hydrophilic absorption of moisture. Investigate coating and processing alternatives to reduce water absorption. Develop a plan for accelerated aging testing. Identify fabrication methods for both prototype development of 10 to 50 5lb bats and small scale production of 1000 bats per year. Develop a safety assessment of fabrication methods. Using labor intensive fabrication methods, an initial lot of 10 5lb bats will be fabricated for quality assessment and small sample statistics of performance will be provided. Conduct thermal and mechanical property measurements on the 10 bats. Bat size and shape will be optimized for ease of missile installation. Key cost, size and performance attributes will be developed for commercial application. Designs for commercial application be will be developed and demonstrated.

PHASE III: Using the missile specific design, non-recurring and recurring unit costs will be developed. A lot of 20 bats will be produced of the missile optimized insulation bats. Combined thermal and mechanical property measurements will be conducted on the missile optimized bats. The remaining bats will be provided to the DARPA Tactical Boost Glide demonstration program for evaluation and for incorporation into the Tactical Boost Glide demonstration vehicles. Identify large scale production alternatives. Develop a cost model of expected large scale production to provide estimates of non-recurring and recurring unit production costs. A production concept for commercial application will be developed addressing commercial cost and quality targets.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Improvements to reduce diffusivity of insulation allows reduction of insulation size in space-limited applications such as commercial satellites, rockets for space launch, and long duration capable airplane engines.

REFERENCES:
1. Hu, et. al, Journal of Materials Science Volume 45 2010 pp. 3242-3246. "Porous yttria-stabilized zirconia ceramics with ultra-low therma conductivity."

2. Schlichting, et al,Journal of Materials Science, 36 (2001) pp. 3003-30101. "Thermal conductivity of dense and porous yttria-stabilized zirconia."

3. Kim, et al, Applied Energy, 94 (2012) pp. 295-302. "Combined heat transfer in multi-layered radiation shields for vacuum insulation panels: Theoretical/numerical analysis and experiments."

4. Gomez, et el, Journal of Materials Science, 44 (2009) pp. 3466-3471. "ZrO2 foams for porous radiant burners."

5. Quadbeck, et al, CellMat 2010 Conference. "Open Cell Metal Foams � Application-oriented Structure and Material Selection."

KEYWORDS: Insulation; Diffusivity; Ultra High Temperature Ceramic Composites (UHTC); Metal Foams; Aerogel; Microporous Gel; Ceramic Foams; Foil Multi-Layer Insulation

** TOPIC AUTHOR (TPOC) **

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