Passive PCB-Mounted Thermal Switch

One inner insulative layer, and one outer robust ablative layer comprise the AMTPS technology. When applying the heat shield to the surface of a spacecraft, the insulative layer is printed first and primarily functions to reduce the amount of heat soak into the vehicle. The formulation of the insulative layer has a slightly lower density (as compared to the robust layer) and is adjusted using a differing constituent ratio of phenolic and/or glass microballoon material. Both formulations combine a phenolic resin with various fillers to control pre- and post-cure properties that can be adjusted by varying the carbon and/or glass fiber content along with rheology modifiers to enhance the fluid flow for deposition systems. The robust layer is applied next and functions as the ablative layer that ablates away or vaporizes when subjected to extremely high temperatures such as those achieved during atmospheric entry. The formulation of the robust layer produces a gas layer as it vaporizes in the extreme heat that acts as a boundary layer. This boundary prevents heat from further penetrating the remaining robust material by pushing away the even hotter shock layer. The shock layer is a region of super-heated compressed gas, positioned in front of the Earth-facing bottom of the spacecraft during atmospheric entry, that results from the supersonic shockwave generated. Commercial space applications for this AMTPS technology include use on any spacecraft that transits a planetary or lunar atmosphere such as Mars or Saturn’s moon Titan. Additionally, the invention may be useful for launch system rockets to provide heat shielding from atmospheric reentry or to protect ground equipment on the launch pad from rocket exhaust plumes. As the number of government and commercial space missions to primary Earth orbits, the Moon, and the Solar System increase, there will be a growing need for cost-effective, on-demand, and timely fabrication of heat shields for space-related activities. AMTPS Formulations – Insulative and Robust Variation is at a technology readiness level (TRL) 5 (component and/or breadboard validation in laboratory environment) and is now available for patent licensing. Please note that NASA does not manufacture products itself for commercial sale.

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.

There has been much interest in developing polymeric nanocomposites with ultrahigh thermal conductivities, such as with exfoliated graphite or with carbon nanotubes. These materials exhibit thermal conductivity of 3,000 W/mK measured experimentally and up to 6,600 W/mK predicted from theoretical calculations. However, when added to polymers, the expected thermal conductivity enhancement is not realized due to poor interfacial thermal transfer. This technology is a method of forming carbon-based fillers to be incorporated into highly thermal conductive nanocomposite materials. Formation methods include treatment of an expanded graphite with an alcohol/water mixture followed by further exfoliation of the graphite to form extremely thin carbon nanosheets that are on the order of between about 2 and about 10 nanometers in thickness. The carbon nanosheets can be functionalized and incorporated as fillers in polymer nanocomposites with extremely high thermal conductivities.

The Cryostat-500 provides laboratory measurement of the steady-state thermal transmission properties of thermal insulation systems under conditions below ambient temperature. Liquid nitrogen is used as a direct measure of the energy going through the test specimen. Thermal insulation systems may be composed of one or more materials that may be homogeneous or non-homogeneous at boundary conditions from 77 K to 373 K and in environments from high vacuum (10E-7 torr) to ambient pressure (10E+3 torr). The Cryostat-500 provides a much wider range of thermal performance and covers the full range of environmental conditions for applications below ambient temperature. The instrument has been proven through extensive testing of foams, composite panels, multilayer insulation (MLI) systems, aerogel blankets, fiberglass, and many other types of materials. Both the quality and quantity of the thermal performance data for insulation materials and systems have increased even as the process and method has become more time efficient and cost effective. Further guidelines on the test method and equipment for the Cryostat-500 are given in ASTM C1774, Annex A3.

The thin film sensor’s principal advantage lies in its potential to take high frequency temperature measurements from the surface of a reentering spacecraft while simultaneously withstanding the high temperature and oxidizing environment encountered. This data provides engineers with operational phase measurements used to refine the spacecraft’s operational envelope and track flight hardware behavior in addition to providing high frequency temperature measurements that can inform the physics of a boundary layer. Mismatches in coefficients of thermal expansion (CTE) are expected in TPS-based sensor applications because the metallic materials used for temperature sensing have thermal expansion rates that differ from the rates of the substrate and coating materials in the TPS. At high temperatures during reentry, this mismatch in CTE can create a significant strain differential between the metallic sensor, sensor leads, and the materials to which the sensor and leads are bonded. High frequency response temperature measurements on the surface of entry spacecraft are not currently possible above ~700 F with existing measurement capabilities. This shortcoming is primarily due to the need for robust sensor behavior at temperatures of several thousand degrees F. The sensor design of this technology preserves the integrity of sensor components while enhancing its high temperature functionality. The thin film temperature sensor has a technology readiness level (TRL) 5 (Component and/or breadboard validation in relevant environment) and is now available for patent licensing. Please note that NASA does not manufacture products itself for commercial sale.