Optimization and Manufacturing of Opacified Fibrous Insulation (OFI)

HeetShield Inc. (Flagstaff, Arizona) is developing an advanced thermal insulation to increase mission capability for civilian and military spacecraft.  During the Phase I STTR, researchers at Virginia Tech University successfully proved that nanofibers of silicon carbide could be produced in a custom diameter by 1) preparing a polymethyl methacrylate (PMMA) solution containing silicon nanoparticles, 2) electrospinning nanofibers from that solution, and 3) carburizing the electrospun fibers in a vacuum furnace filled with a carbon-based gas to convert the Si particles to SiC.  The resulting SiC nanofibers were self-supporting, even in the absence of the PMMA carrier.  The fiber diameter of the fibers produced matched the target fiber diameter, which was developed to demonstrate a thermal insulation specifically optimized for heat flux peaking at 900C.  Unfortunately, not enough material was made to verify that performance matched the model. From Phase I, we determine that another method of making nanofibers is preferred.  The Phase I method developed a beaded nanofiber that would likely have a muted optical transmittance pattern, which may not be ideal for an insulation designed for a specific heat flux.  Therefore, Phase II will include efforts by 3 separate teams to electrospin carbon-based nanofibers, thereby reducing the risk associated with electrospinning and most likely improving fiber attenuation characteristics.  Carbon nanofibers will be converted to silicon carbide using a process developed by Idaho National Labs and being commercialized by Advanced Ceramic Fibers.  These fibers will be used to produce an advanced thermal insulation known as Gen 3 Opacified Fibrous Insulation (OFI) using wet laid nonwoven methods.  Optical transmittance measurements will determine which fibers have the best radiant heat flux attenuation properties, and thermal diffusivity will measure thermal performance of the Gen 3 OFI at designated temperatures and pressures.  Methods being validated for Gen 3 OFI optimized for 900C can be applied to other missions up to 1700C.  Improved, high temperature insulations, like the one advanced under this program, are needed for cost-efficient launch and re-entry vehicles. The 2-year Phase II effort is supported by 3 research institutions including University of Houston, Lorain County Community College and Arizona State University.  At each institution, one or two students will be invited to work on specific aspects of the research effort with guidance from faculty and staff, and support from HeetShield Inc.