DESCRIPTION: Hypersonic vehicle systems require efficient thermal insulators that are optimized to manage thermal radiation transfer and gas conduction heat transfer and offer structural protection during sustained hypersonic flight and atmospheric entry where the maximum temperature capability can exceed 2000K. This technical challenge requires theory application for radiative properties of diffusion scattering in porous media which also takes into account combined radiation and conduction heat transfer. Theoretical approaches can in principle exploit natural transparency and reflectivity properties for electromagnetic waves in the hypersonic regime provided the interplay between the surface characteristics and the porous media are designed to selectively control the emission, absorption and scattering of thermal radiation.  The objective of this solicitation is to design insulators that efficiently suppress the radiation mode of heat transfer through physics based models, demonstrate fabrication technologies, and validate the predicted response at the hypersonic regime of interest.
 

PHASE I: Design and develop thermal radiation inhibited structures for reusable applications at temperatures exceeding 1650K over one hour, and highest possible heat load configuration that is pertinent to  hypersonic platforms. Design and fabricate insulator media that validates predicted thermal transport properties.
 

PHASE II: Develop both analytical, first-principle theories, and random walk models of the radiative and conductive properties of optimized insulator media.  Establish model extrapolation strategies for the best available model that minimizes the adverse effect of length scale changes. Optimize scattering, absorption, and morphological stability of heterogeneous porous media for temperatures exceeding 1650K. Transition technology to the industrial constructs.
 

PHASE III DUAL USE APPLICATIONS: Potential transition partners include the Air Force, DARPA, NASA and the U.S. industrial sector for hypersonic application. Alternative aeronautics markets may also be possible for air-breathing applications, industrial applications such as plasma processing and micro-fabrication techniques.
 

REFERENCES:

1. Lee, S. C., White, S., and Cunnington, G. R., 1994, “Effective Radiative Properties of Fibrous Composites Containing Spherical Particles,” J. Thermophysics and Heat Transfer, 8 (3), pp. 400-405.
 

2. Tetsuo Noguchi and Takeshi Kozuka, Principles of Radiant Heat Transfer. John Wiley & Sons, Inc., New York, 1960.
 

3. Cunnington, G. R., Lee, S. C., and White, S. M., 1998, “Radiative Properties of Fiber-Reinforced Aerogel: Theory vs Experiment,” J. Thermophysics and Heat Transfer, 12 (1), pp. 17-22.  (Also, IV-10)
 

4. Oxide Reflectance Standard,” Natl. Bur. Sfd. (U.S.) Circ., No. 1.