The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

Noise is an environmental pollutant with recognized impacts on the psychological and physiological health of humans. Many porous materials are often limited by low sound absorption over a broad frequency range, delicacy, excessive weight and thickness, poor moisture insulation, high temperature instability, and lack of readiness for high volume commercialization. Herein, an efficient and robust lamella-structure is reported as an acoustic absorber based on self-assembled interconnected graphene oxide (GO) sheets supported by a grill-shaped melamine skeleton. The fabricated lamella structure exhibits ≈60.3% enhancement over a broad absorption band between 128 and 4000 Hz (≈100% at lower frequencies) compared to the melamine foam. The enhanced acoustic absorption is identified to be structure dependent regardless of the density. The sound dissipation in the open-celled structure is due to the viscous and thermal losses, whereas it is predominantly tortuosity in wave propagation and enhanced surface area for the GO-based lamella. In addition to the enhanced acoustic absorption and mechanical robustness, the lamella provides superior structural functionality over many conventional sound absorbers including, moisture/mist insulation and fire retardancy. The fabrication of this new sound absorber is inexpensive, scalable and can be adapted for extensive applications in commercial, residential, and industrial building structures.

/pdf/graphene-oxide-based-lamella-network-for-enhanced-sound-4ja09aylz8.pdf

Graphene Oxide-Based Lamella Network for Enhanced Sound Absorption

Review of pyroshock wave measurement and simulation for space systems

Rather than enjoying a fine book when a mug of coffee in the afternoon, then again they juggled later some harmful virus inside their computer. spacecraft structures and mechanisms from concept to launch the space technology library is easily reached in our digital library an online entry to it is set as public thus you can download it instantly. Our digital library saves in merged countries, allowing you to acquire the most less latency era to download any of our books in the manner of this one. Merely said, the spacecraft structures and mechanisms from concept to launch the space technology library is universally compatible subsequent to any devices to read.

Spacecraft Structures and Mechanisms-From Concept to Launch

Low frequency active acoustic attenuation is examined for the payload fairing of a representative small launch vehicle. The feasibility of using structural sensors and actuators for active acoustic control is assessed with a numerical model of the fairing. The results of the numerical analysis indicate that broadband damping decreases the interior overall sound pressure level between 4 dB and 10 dB, depending on the amount of structural damping that is added to the vibration modes. Singular value analyses demonstrate that point force actuators and in-plane strain actuators have the control authority for active acoustic control. Control studies indicate that local velocity feedback reduces the average vibration level of the fairing by roughly 50%, and that the force levels required of the control system are within the range of conventional point force and piezoceramic actuators.

Vibroacoustic modeling of a launch vehicle payload fairing for active acoustic control

Energy analysis methods are commonly used to predict the vibroacoustic response of a spacecraft inside a launch vehicle payload fairing during liftoff. The payload fairing wall is often lined with acoustic blankets which can be difficult to model. This paper shows the development of a practical working method for accurately representing acoustic blankets in a VAPEPS statistical energy analysis model. A clear scaling relationship between the acoustic absorption coefficient and the blanket thickness is established. The scaling procedure is demonstrated using two sets of data for different absorption materials. The absorption data are implemented in VAPEPS by converting them to frequency-dependent damping loss factors. A post-processing procedure is derived to account for the increase in transmission loss due to the addition of the blanket layer. The entire process is used to predict the noise reduction in a VAPEPS model of the Atlas 14-ft-diameter payload fairing. Comparisons to ground-test and flight data ...

Implementation of Acoustic Blankets in Energy Analysis Methods with Application to the Atlas Payload Fairing

VAPEPS (VibroAcoustic Payload Environment Prediction System) is a computer program used to predict the vibroacoustic response of a structure. An alternate VAPEPS modeling technique, the Modified NASA Lewis Method, is an improvement for modeling unreinforced mass loaded honeycomb panels. The Modified NASA Lewis Method prediction is compared to the standard ASMS VAPEPS prediction, and the acoustic test data for three spacecraft panels. An analytical method of computing variance is presented and used to compute 95 percent confidence levels. These levels are compared to the standard VAPEPS confidence levels and to the envelope of the test data. As a result of using the new methodology suggested in the paper, both the mean prediction and the 95 percent confidence level prediction agree well with the test data in both spectral shape and magnitude. Therefore, the Modified NASA Lewis Method prediction methodology may be used to define more realistic random vibration test levels.

A modified VAPEPS method for predicting vibroacoustic response of unreinforced mass loaded honeycomb panels

Numerous vibroacoustics advances and impacts in the aerospace industry have occurred over the last 15 years. This article addresses some of these that developed from engineering programmatic task-work at the NASA Glenn Research Center at Lewis Field.

/pdf/recent-advances-in-vibroacoustics-4um4dk64rk.pdf

Recent advances in vibroacoustics

The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) is leading the design and build of the new world-class vibroacoustic test capabilities at the NASA GRC's Plum Brook Station in Sandusky, Ohio, USA. Benham Companies, LLC is currently constructing modal, base-shake sine and reverberant acoustic test facilities to support the future testing needs of NASA s space exploration program. The large Reverberant Acoustic Test Facility (RATF) will be approximately 101,000 ft3 in volume and capable of achieving an empty chamber acoustic overall sound pressure level (OASPL) of 163 dB. This combination of size and acoustic power is unprecedented amongst the world s known active reverberant acoustic test facilities. The key to achieving the expected acoustic test spectra for a range of many NASA space flight environments in the RATF is the knowledge gained from a series of ground acoustic tests. Data was obtained from several NASA-sponsored test programs, including testing performed at the National Research Council of Canada s acoustic test facility in Ottawa, Ontario, Canada, and at the Redstone Technical Test Center acoustic test facility in Huntsville, Alabama, USA. The majority of these tests were performed to characterize the acoustic performance of the modulators (noise generators) and representative horns that would be required to meet the desired spectra, as well as to evaluate possible supplemental gas jet noise sources. The knowledge obtained in each of these test programs enabled the design of the RATF sound generation system to confidently advance to its final acoustic design and subsequent on-going construction.

/pdf/the-development-of-the-acoustic-design-of-nasa-glenn-mhjjwvb9rv.pdf

The Development of the Acoustic Design of NASA Glenn Research Center's New Reverberant Acoustic Test Facility

The NASA John H. Glenn Research Center and the U.S. Department of Energy are currently developing a Stirling convertor for use as an advanced spacecraft power system for future NASA deep-space missions. As part of this development, a Stirling Technology Demonstrator Convertor (TDC) was recently tested to verify its survivability and capability of withstanding its expected launch random vibration environment. The TDC was fully operational (producing power) during the random vibration testing. The output power of the convertor was measured during the testing, and these results are discussed in this paper. Numerous accelerometers and force gauges were also present which provided information on the dynamic characteristics of the TDC and an indication of any possible damage due to vibration. These measurements will also be discussed in this paper. The vibration testing of the Stirling TDC was extremely successful. The TDC survived all its vibration testing with no structural damage or functional performance degradation. As a result of this testing, the Stirling convertor's capability to withstand vibration has been demonstrated, enabling its usage in future spacecraft power systems.

https://ntrs.nasa.gov/api/citations/20010019633/downloads/20010019633.pdf

Vibration Testing of an Operating Stirling Convertor

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