Lightweight Hypersonic Thermal Protection Material

Materials and Coatings
Lightweight Hypersonic Thermal Protection Material (LAR-TOPS-322)
Flame and hypersonic flow resistant boron nitride nanotube (BNNT) mat
State of the art high temperature shielding materials are not flexible. This technology forms the structurally robust, thermally stable BNNT into a low weight, flexible mat. BNNT advancements are highly sought after because they are as strong as carbon nanotubes, but they have a much higher resistance to heat, high voltage, and neutron radiation. The flexible BNNT mat can provide temperature protection up to 1300oC with density of 200-400 kg/m3.

The Technology
Originally developed as a flexible thermal protection system (FTPS), this BNNT mat was designed to shield a 40-ton craft from the high aerothermal flux of atmospheric entry, descent, and landing. The novel lightweight flexible BNNT mat is an excellent flame retardant material and has shown excellent thermal stability and shielding capabilities under a hypersonic thermal flux test in air. The novel BNNT mat or fabric creates an in-situ passivation layer under high thermal flux which minimizes penetration of the atmosphere (air or gas) as well as heat and radiation through the thickness. BNNT effectively diffuses heat throughout the mat or fabric laterally and radially to minimize localized excessive heat. In addition, the lightweight flexible BNNT mat can efficiently alleviate the heat via radiation because of its high thermal emissivity. This invention offers a lightweight, simple, single layer BNNT FTPS with better thermal protection and flame retardation performance in extreme environments while providing structural robustness. The novel BNNT materials can also serve as flame retardants and flame retardant additives in composite systems that are also potentially more colorable compared to carbon nanotube additives.
Sample of BNNT mat under torch, shown unscathed after test - Image Credit: NASA
  • Withstands 1300 C with thermal flux rate of 50 W/cm1300 square
  • Flexible mat
  • Process forms a protective boron oxide passivation layer
  • Electrically non-conductive
  • White base color that can be dyed
  • Can be used to make woven and non-woven flexible fabrics
  • Resists high temperatures and direct flame
  • Self-extinguishing
  • High thermal emissivity

  • High temperature electrical insulation
  • Fire resistant structural cabling
  • Thermal insulation in aircraft & jet engines
  • Piezoelectric applications
  • Reinforced high temperature composite materials
  • Lightweight radiation shielding
  • Aerospace thermal shielding
  • Building insulation
  • Personal protective clothing
  • Appliance, automotive, and industrial high temperature insulation applications
Technology Details

Materials and Coatings
Boron Nitride Nanotube (BNNT) and BNNT Composites: Overview, Cheol Park, Sang-Hyon Chu and Catherine Fay. NSTRF Student Meeting at JPL, Pasadena, CA, August 4-6, 2019.
Similar Results
PICA being tested in Arcjet Facility
Creating Low Density Flexible Ablative Materials
The low density flexible ablator can be deployed by mechanical mechanisms or by inflation and is comparable in performance to its rigid counterparts of the same density and composition. Recent testing in excess of 400W/cm2 demonstrated that the TPS char has good structural integrity and retains similar flexibility to the virgin material, there by eliminating potential failure due to fluttering and internal stress buildup as a result of pyrolysis and shrinkage of the system. These flexible ablators can operate at heating regimes where state of the art flexible TPS (non-ablative) will not survive. Flexible ablators enable and improve many missions including (1) hypersonic inflatable aerodynamic decelerators or other deployed concepts delivering large payload to Mars and (2) replacing rigid TPS materials there by reducing design complexity associated with rigid TPS materials resulting in reduced TPS costs.
A New Family of Low-Density, Flexible Ablators
The invention provides a family of low density, flexible ablators comprising of a flexible fibrous substrate and a polymer resin. The flexible ablators can withstand a wide range of heating rates (40-540 Watts/cm2) with the upper limit of survivable heat flux being comparable to the survivable heat flux for rigid ablators, such as PICA and Avcoat. The amount and composition of polymer resin can be readily tailored to specific mission requirements. The material can be manufactured via a monolithic approach using versatile manufacturing methods to produce large area heat shields, which provides a material with fewer seams or gaps. The goals of the work are primarily twofold: (i) to develop flexible, ablative Thermal Protection System (TPS) material on a large, blunt shape body which provides aerodynamic drag during hypervelocity atmospheric entry or re-entry, without perishing from heating by the bow shock wave that envelopes the body; and (ii) to provide a relatively inexpensive TPS material that can be bonded to a substrate, that is unaffected by deflections, by differences in thermal expansion or by contraction of a TPS shield, and that is suitable for windward and leeward surfaces of conventional robotic and human entry vehicles that would otherwise employ a rigid TPS shield. This technology produces large areas of heat shields that can be relatively easily attached on the exterior of spacecraft.
Rover Large
New Methods in Preparing and Purifying Nanomaterials
Sometimes called white graphite, affordable and plentiful hBN possesses the same kind of layered molecular structure as graphite. In graphite, this structure has allowed next-generation nanomaterials like carbon nanotubes and graphene to be produced. With hBN, however, the process of converting the substance into boron nitride nanotubes (BNNT) has been too difficult to yield commercial quantities. Glenn innovators have created several new methods that could enable greater adoption of this unique nanomaterial. In the initial stage, the starter reactant is mixed with a selected set of chemicals (a metal chloride, for example) and an activation agent (such as sodium fluoride). This mixture causes hBN to become less resistant to intercalation. The intercalated product can then be exfoliated by heating the material in air, and giving the material a final rinse with a liquid-phase ferric chloride salt to dissolve any embedded impurities without damaging its internal structure. These efficiently exfoliated nanomaterials can be used to form advanced composite materials (e.g., layered with aluminum oxide to form hBN/alumina ceramic composites). Nanomaterials fabricated from hBN can also take advantage of the material's unique combination of being an electrical insulator with high thermal conductivity for applications ranging from microelectronics to energy harvesting. Glenn's innovations have enabled a significantly improved matrix composite material with the potential to make a significant impact on the commercial materials market.
CHIEFS Material
Multilayered Fire Protection System
The Multilayered Fire Protection system uses technology from the space craft flexible heat shield for future planetary missions. By optimizing this material for the fire environment, utilizing heat shield test methods, and experimenting with different materials, the NASA team developed a multilayered fire protection system. This system includes an outer textile layer which reflects over 90 percent of the radiant heat, an insulated layer which protects against convective heat and hot gases, and a non-porous film layer which is a gas barrier layer.
front from NETL
Soft Magnetic Nanocomposite for High-Temperature Applications
Commercial soft magnetic cores used in power electronics are limited by core loss and decreased ferromagnetism at high temperatures. Extending functional performance to high temperatures allows for increased power density in electric systems with fixed power output and elevated operating temperature. The innovators at Glenn developed a unique composition and process to improve the temperature capability of the material. Nanocomposite soft magnetic materials are typically comprised of a combination of raw materials including iron, silicon, niobium, boron, and copper. Instead of niobium, NASA's material utilizes small cobalt and tantalum additions. The raw materials are combined to form an amorphous precursor through melt spinning. NASA&#39s innovation with the fabrication lies in the thermal annealing step, which nucleates and crystallizes the precursor to form the composite structure of the material. By adjusting the temperature and magnetic field of the thermal annealing step, Glenn's process results in good coupling between the crystalline and amorphous matrix phases. Innovators at Glenn demonstrated the temperature robustness using small test cores of their material and are investigating additional quality attributes compared to other well-known soft magnetic materials (see two Figures below).
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