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Thermomechanical Methodology for Stabilizing Shape Memory Alloy (SMA) Response

SMA training can be completed in a matter of minutes, rather than days or even weeks. Shape memory alloys (SMAs), sometimes known as “smart metals,” provide a lightweight, solid-state alternative to conventional actuators and switches, such as hydraulic, pneumatic, or motor-based systems. To function properly, SMAs must be “trained” to return to a previous form when heated, and innovators at NASA’s Glenn Research Center have developed a remarkable new method of completing this training at a fraction of the time and cost of conventional training techniques. Glenn’s technique uses mechanical cycling, rather than more complicated and time-consuming thermal cycling, to train SMAs before implementation. In addition, this new approach to training allows SMAs to be applied to complex geometric components, so that they may be used in a broader number of applications.

Posted in: Briefs, Materials

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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.

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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)].

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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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Polyimide Aerogels with Three-Dimensional Cross-Linked Structure

Applications for the strong, flexible material include thermal insulation and lightweight sandwich structures. John H. Glenn Research Center, Cleveland, Ohio NASA-developed polyimide aerogels are 500 times stronger than conventional silica aerogels. The innovative aerogels represent a revolutionary advance over fragile silica aerogels because they are highly flexible and foldable in thin film form. As a thin film, they can be used to insulate industrial pipelines, automotive shields, and temporary housing structures, and can be used within protective clothing such as firefighting jackets, space suits, and parkas. As a thicker part, they can be easily molded to a shape, or sanded and machined to provide insulation as well as mechanical support. No other aerogel possesses the compressive and tensile strength of the NASA innovation while still retaining its ability to be flexibly folded to contour to whatever shape is needed.

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