Tech Briefs

Flexible Ablator for Thermal Protection

Simple and versatile manufacturing approach to produce heat shields. NASA has developed a class of low-density, flexible ablators that can be fabricated into heat-shields capable of being packaged, stowed, and deployed in space. The key characteristics of this new ablative thermal protection system (TPS) are its flexibility, conformability, and tailor-ability. Flexibility allows the material to be stowed in the shroud of a launch vehicle and deployed in space, without compromising functionality. Conformability allows the material to be attached to a curved surface without precise and expensive machining. Tailor-ability allows the density and composition to be optimized for the requirements. This flexible TPS can be used to cover and thermally protect a large, blunt shape that provides aerodynamic drag during hyper-velocity atmospheric flight. It can be used with minimal modification for large aeroshells whose deployment relies mainly on mechanical means and through inflation. Such devices are called Hypersonic Inflatable Aerodynamic Decelerators (HIADs). Large blunt body aeroshells may be used to deliver large payloads (40 metric tons) to the surface of Mars.

Posted in: Briefs, Materials

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Resistive Heating Method for TPS Property Measurements

A unique ultrasonic-based technique has been developed to measure temperature profiles in materials used in thermal protection systems (TPS). The technology requires measurements of the thermal expansion coefficient and the ultrasonic velocity for these materials as a function of temperature in order to determine the variation of ultrasonic propagation speed with temperature. Generally, this is done by slowly heating materials to a set temperature so that the samples are isothermal.

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Measuring Bond Site Concentration on the Intrinsic Aerogel Surface Through Chemisorption of Chlorosilanes

This work involves development of aerogel to be used as a passive absorption media — effectively a concentrator of trace organics — that can be detected by optical techniques. Such a trace organic detection scheme is very different from all other current techniques, and has the potential to significantly enhance the sensitivity of detection of volatile species. The aerogel concentrator provides an integrated measurement over long periods of time (months, years), as opposed to mass spectroscopy, which tests at a given moment.

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Toughened Uni-piece Fibrous Reinforced Oxidation-Resistant Composite (TUFROC)

This technology has potential applications in aircraft, turbine engines, automobiles, and any application requiring thermal protection surfaces. The Toughened Uni-piece Fibrous Reinforced Oxidation-Resistant Composite (TUFROC) allows for much more affordable and sustainable operations involving Space Launch Services and other systems that utilize Earth re-entry vehicles. TUFROC has an exposed surface design and appropriate materials combination that will allow a space vehicle to survive both the mechanical stresses during launch and the extreme heating and stress of re-entry. It provides a thermal protection tile attachment system that is suitable for not only spacecraft applications, but also could be used where there are extreme heating environments [up to 3100 °F for 5 to 10 minutes and 3600 °F, and possibly higher, for very short time intervals (one-minute or less)].

Posted in: Briefs, Materials

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Effects of Postcure and Associated Design Allowables for M55J/RS-3C Polycyanate Composite

M55J/RS-3C resin composite structures on the James Webb Space Telescope (JWST) sunshield will concurrently maintain loads and be exposed to temperature extremes throughout the life of the observatory. Increasing the glass transition temperature (Tg) is intended to decrease the elevated temperature creep of the composite structures (increase dimensional stability). Also, material allowables for RS-3C at temperatures other than ambient had not been previously published at NGAS.

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Airfoil System for Cruising Flight

Biologically inspired wing flow control uses flexible extended trailing edge. Flaps can significantly alter wing aerodynamics for high lift generation. Conventional flaps are mainly deployed for takeoff and landing, but are not suitable for in-cruise flight. It is widely speculated that birds and insects utilize their wing flexibility, particularly at the trailing edges, for effective control in different regimes. For example, the avian wing geometries of mergansers and owls possess a single layer of feathers extended from an airfoil section of their wings, which improves the global aerodynamic characteristics. Avian wing geometry inspired the concept of a static extended trailing edge (SETE), where the main airfoil is extended at the trailing edge by attaching a flexible polymer membrane with suitable length and rigidity. Based upon experimental results and CFD simulation, it was determined that if SETE was implemented on a fixed-wing aircraft, it had the potential to improve cruise flight aerodynamic efficiency up to 10% and reduce fuel consumption up to 5%.

Posted in: Briefs, Aeronautics

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Conditionally Active Min-Max Limit Regulators

The control system in modern commercial aircraft engines is designed to operate the engine in a safe manner throughout its operating envelope. In order to utilize the existing safety margins more effectively, innovators at NASA’s Glenn Research Center have developed a modification to current min-max engine control logic. This architecture is referred to as a conditionally active (CA) limit regulator. This concept uses the existing min-max architecture with the modification that limit regulators are active only when the operating point is close to a particular limit, improving engine response while preserving all necessary safety limits. An improvement in thrust response, while maintaining all necessary safety limits, was also demonstrated.

Posted in: Briefs, Aeronautics

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