Results for “random vibration testing” — Page 8

NASA NTRS1988

Design and dynamic testing of an instrumented spacecraft component

Details relating to the design and subsequent vibration and shock tests of a spacecraft component for a severe vibration and shock environment are presented. The design process and analysis method involve the use of finite element analysis coupled with the Modal Strain Energy method with risk graphs to determine the adequacy of the design. The vibration levels experienced by box parts are reduced by the application of passive constrained layer viscoelastic treatments that significantly improve component reliability. All significant internal components were fully instrumented in both the random vibration and shock tests, the latter being done on a mechanical impact pyro simulator. Correlation between analysis and test data is good, validating the modeling and analysis techniques.

Dwyer, Thomas J.↗

NASA NTRS1994

VAPEPS Management Center

A VibroAcoustic Payload Environment Prediction System (VAPEPS) Management Center is established and being maintained at JPL. VAPEPS is a computer program that utilizes statistical energy analysis (SEA) theory and SEA extrapolation methods to predict the vibroacoustic environments of complex systems. The program is commonly utilized to establish random vibration and acoustic test requirements for aerospace components exposed to launch environments. It can also be used in the payload or launch vehicle design process for control or mitigation of the launch or on-orbit vibration and acoustic environments, as well as to calculate acoustically induced stresses in structures such as solar panels and reflectors.

VAPEPS↗

NASA NTRSDate not supplied

How to Educate Decision Makers on the Value and Necessity of Modal Testing and Model Correlation: Tips for Young Engineers

Engineers need to effectively communicate the justification and value of their modal testing and model correlation in terminology familiar to decision makers as it relates to the program’s risk tolerance. This communication must relate to the program’s risk tolerance and the metrics used to judge the performance of both the program and individual decision makers. The challenge is the terminologies familiar to engineers and decision makers are quite different and seemingly unrelated. The engineering profession has developed a specific terminology to solve highly technical issues, which are many times themselves unique to very specific engineering problems. It is all too easy for engineers to believe that everyone in their organization, including the decision makers, has an intrinsic understanding of what they do and the value it brings to the program’s success. This is especially true for young engineers who have recently spent the last four plus years in an academic engineering learning environment, which has a highly technical research oriented atmosphere. Effective communication with decision makers is increasingly important as the technical breadth and practical program and project experience level for up and coming decision makers diminishes. It is not unusual for the decision makers to have technical knowledge in a domain different from structural dynamics (e.g., electronics or systems). Competition among satellite manufactures has increased the focus on programmatic cost and ability to deliver on schedule. NASA programs are also seeing more restrictive programmatic cost and schedule constraints, which impact both analysis and testing. It should also be noted that a comprehensive suite of tests are required to verify a satellite’s design capability with some margin. These tests include static strength verification tests, shock, acoustic, and vibration tests (sine and random) of systems, subsystems, and components. Each of these verification tests provide opportunities for model correlation and risk reduction. It is important to recognize dynamic loads/modal test models may not include all of the flight hardware (i.e., harness, coax, waveguides, connectors, etc.) and the previously mentioned tests are still required for qualification/verification of the design. This paper provides tips to young engineers on how to bridge this communications gap, have a better understanding of the environment in which decision makers operate, and assist them to better support successful missions. While this paper primarily focuses on modal testing and model correlation as related to spacecraft missions, the concepts and recommendations presented here are equally applicable to other fields such as aeronautics, automotive, power generation, etc.

Decision Maker↗

NASA NTRSDate not supplied

How to Educate Decision Makers on the Value and Necessity of Modal Testing and Model Correlation: Tips for Young Engineers

Engineers need to effectively communicate the justification and value of their modal testing and model correlation in terminology familiar to decision makers as it relates to the program’s risk tolerance. This communication must relate to the program’s risk tolerance and the metrics used to judge the performance of both the program and individual decision makers. The challenge is the terminologies familiar to engineers and decision makers are quite different and seemingly unrelated. The engineering profession has developed a specific terminology to solve highly technical issues, which are many times themselves unique to very specific engineering problems. It is all too easy for engineers to believe that everyone in their organization, including the decision makers, has an intrinsic understanding of what they do and the value it brings to the program’s success. This is especially true for young engineers who have recently spent the last four plus years in an academic engineering learning environment, which has a highly technical research oriented atmosphere. Effective communication with decision makers is increasingly important as the technical breadth and practical program and project experience level for up and coming decision makers diminishes. It is not unusual for the decision makers to have technical knowledge in a domain different from structural dynamics (e.g., electronics or systems). Competition among satellite manufactures has increased the focus on programmatic cost and ability to deliver on schedule. NASA programs are also seeing more restrictive programmatic cost and schedule constraints, which impact both analysis and testing. It should also be noted that a comprehensive suite of tests are required to verify a satellite’s design capability with some margin. These tests include static strength verification tests, shock, acoustic, and vibration tests (sine and random) of systems, subsystems, and components. Each of these verification tests provide opportunities for model correlation and risk reduction. It is important to recognize dynamic loads/modal test models may not include all of the flight hardware (i.e., harness, coax, waveguides, connectors, etc.) and the previously mentioned tests are still required for qualification/verification of the design. This paper provides tips to young engineers on how to bridge this communications gap, have a better understanding of the environment in which decision makers operate, and assist them to better support successful missions. While this paper primarily focuses on modal testing and model correlation as related to spacecraft missions, the concepts and recommendations presented here are equally applicable to other fields such as aeronautics, automotive, power generation, etc.

Decision Maker↗

NASA NTRSDate not supplied

Design, Fabrication, Testing and Validation of a Ruggedized Fiber Optic Sensing System (FOSS) for Launch Application

Fiber-optic sensors based on fiber Bragg grating (FBG) is desirable for structural health monitoring and is used for various aerospace applications such as measuring strain and temperature, where a single optical fiber can multiplex hundreds of FBG sensors. The National Aeronautics and Space Administration (NASA) Armstrong Flight Research Center (AFRC) (Edwards, California) has been developing an optical fiber-based sensing suite called Fiber Optics Sensing System (FOSS) over the past two decades. Successful strain monitoring flight demonstrations such as the NASA Ikhana (General Atomics, San Diego, California) remotely piloted aircraft and the X-56A Multi-Utility Technology Testbed (Lockheed Martin Corporation, Bethesda, Maryland) remotely piloted subscale aircraft have been performed. Interest in adapting fiber-optic sensors for aerospace applications has led to commissioning the development of a ruggedized FOSS system for spaceflight through the NASA Launch Services Program (LSP) at the NASA Kennedy Space Center (KSC) (Merritt Island, Florida). In this paper, a ruggedized FOSS suitable for a launch environment is discussed in detail. Thermal analysis and enclosure design will be discussed as well as environmental testing such as shock, random vibration, thermal vacuum, and electromagnetic interference/electromagnetic compatibility (EMI/EMC). With all relevant environmental testing completed, a ruggedized FOSS unit has successfully passed all testing and is now deemed space-launch ready.

Allen R. Parker, Jr↗

NASA NTRS1986

Simulation efficiency in acoustic testing of Shuttle payloads

Comparative evaluations of payload vibration responses from ground acoustic tests and Shuttle flights of several payloads indicate that ground acoustic testing will generally underestimate the Shuttle flight vibrational response of a payload, particularly in the low frequency range. This underestimation is found to be primarily due to the lack of simulation during the acoustic test of the in-flight mechanical energy transmission normally transmitted through the Orbiter-payload structural interface. It is suggested that test efficiency corrections be applied when developing random vibration criteria based on ground acoustic test data.

On, Frank J.↗

NASA NTRS1972

Magnetic control assembly reports

Results are summarized of the qualification level vibration tests performed on the magnet control assembly (MCA) for Nimbus and ERTS satellites. The MCA electronics and probe units have demonstrated the capability to survive qualification sinusoidal and random vibration levels. The functional testing indicated normal operation of the units after each axis of vibration. Visual inspection indicated no evidence of degradation. Post vibration acceptance testing verified normal operation of the MCA.

Stickler, A. C.↗

NASA NTRS2019

Structural Dynamic Testing Results for Air-Independent Proton Exchange Membrane (PEM) Fuel Cell Technologies for Space Applications

In 2016, the NASA Advanced Exploration Systems (AES) project office funded research at the NASA Glenn Research Center to evaluate the maturity of the Proton Exchange Membrane (PEM) fuel cell technology and its viability for supporting launch vehicle and space applications. This technology evaluation included vibration, reactant purity, and vacuum exposure sensitivity testing. The evaluation process did not include microgravity testing. This paper discusses the vibration sensitivity testing of two air-independent fuel cell stacks provided by different vendors to assess the ability of currently available fuel cell stack hardware to survive the projected random vibrational environment that would be encountered in an upper stage launch vehicle. Baseline performance testing was utilized to quantify stack performance and overboard leak rate at standard atmospheric conditions in order to provide a reference for post-test comparison. Both fuel cell stacks were tested at a random vibration qualification level of 10.4 grms for five minutes in each axis. Low-level sinusoidal sweeps were conducted before and after each random vibration level run to see if any significant change in resonances were detected. Following vibration facility testing, the baseline performance testing was repeated. Test results demonstrated no measurable change in fuel cell electrochemical or mechanical performance, indicating that the two evaluated PEM fuel cell stacks may be suitable for space applications pending microgravity testing.

Gilligan, Ryan P.↗

NASA NTRS1975

Seminar on Understanding Digital Control and Analysis in Vibration Test Systems

The advantages of the digital methods over the analog vibration methods are demonstrated. The following topics are covered: (1) methods of computer-controlled random vibration and reverberation acoustic testing, (2) methods of computer-controlled sinewave vibration testing, and (3) methods of computer-controlled shock testing. General algorithms are described in the form of block diagrams and flow diagrams.

Source record↗

NASA NTRS1973

Development and application of vibroacoustic structural data banks in predicting vibration design and test criteria for rocket vehicle structures

A method of predicting broadband random vibration criteria for components on space vehicles is presented. Large amounts of vibration and acoustic data obtained from flights and static firing tests of space vehicle were formulated into vibroacoustic data banks for structural categories of ring frame, skin stringer, and honeycomb. The vibration spectra with their associated acoustic spectra are normalized to a reference acoustic spectrum. The individual normalized spectra are grouped according to definite structural characteristics and statistically analyzed to form the vibroacoustic data banks described in this report. These data banks represent the reference vibration criteria available for determining the new vehicle vibration criteria.

Bandgren, H. J.↗

NASA NTRS1976

Vibration testing of the JE-M-604-4-IUE rocket motor (Thiokol P/N E 28639-03)

The NASA International Ultraviolet Explorer (IUE) rocket motor (TE-M-604-4), a solid fuel, spherical rocket motor, was vibration tested in the Impact, Vibration, and Acceleration (IVA) Test Unit of the von Karman Gas Dynamics Facility (VKF). The objective of the test program was to subject the motor to qualification levels of sinusoidal and random vibration prior to the altitude firing of the motor in the Propulsion Development Test Cell (T-3), Engine Test Facility (ETF), AEDC. The vibration testing consisted of a low level sine survey from 5 to 2,000 Hz, followed by a qualification level sine sweep and qualification level random vibration. A second low level sine survey followed the qualification level testing. This sequence of testing was accomplished in each of three orthogonal axes. No motor problems were observed due to the imposition of these dynamic environments.

Alt, R. E.↗

NASA NTRS1966

An impedance-compensated random equalizer.

Parallel-filter automatic random equalizer for improved vibration testing

Electric Network↗

NASA NTRS1974

Digital vibration control techniques

Analog vibration control techniques are reviewed and are compared with digital techniques. The advantages of the digital methods over the analog methods are demonstrated. The following topics are covered: (1) methods of computer-controlled random vibration and reverberation acoustic testing; (2) methods of computer-controlled sinewave vibration testing; and (3) methods of computer-controlled shock testing. Basic concepts are stressed rather than specific techniques or equipment. General algorithms are described in the form of block diagrams and flow diagrams. Specific problems and potential problems are discussed. The material is computer sciences oriented but is kept at a level that facilitates an understanding of the basic concepts of computer-controlled induced environmental test systems.

Chapman, P.↗

NASA NTRS1988

Predicted and measured strain responses of isotropic panels to base excitation

The accuracy of classical linear theory for predicting acceleration and strain for cantilevered and Clamped-Free-Clamped-Free (C-F-C-F) panels excited through the base is studied. Aluminum, steel and titanium plates of various dimensions and thicknessess were vibration tested, using a broadband random signal applied through a shaker mounting fixture. The strains were measured at 9 locations on the cantilevered panels and at 5 locations on the C-F-C-F panels. Predictions were based on the Ritz method. The measured accelerations of the base were input to the analysis for the forcing function. Comparisons between predicted and measured strain acceleration spectra were within an average error of 20 percent for both the cantilevered and C-F-C-F panels.

Lyle, Karen H.↗

NASA NTRS1998

Twelve Channel Optical Fiber Connector Assembly: From Commercial Off the Shelf to Space Flight Use

The commercial off the shelf (COTS) twelve channel optical fiber MTP array connector and ribbon cable assembly is being validated for space flight use and the results of this study to date are presented here. The interconnection system implemented for the Parallel Fiber Optic Data Bus (PFODB) physical layer will include a 100/140 micron diameter optical fiber in the cable configuration among other enhancements. As part of this investigation, the COTS 62.5/125 microns optical fiber cable assembly has been characterized for space environment performance as a baseline for improving the performance of the 100/140 micron diameter ribbon cable for the Parallel FODB application. Presented here are the testing and results of random vibration and thermal environmental characterization of this commercial off the shelf (COTS) MTP twelve channel ribbon cable assembly. This paper is the first in a series of papers which will characterize and document the performance of Parallel FODB's physical layer from COTS to space flight worthy.

Ott, Melaine N.↗

NASA NTRS2009

Advanced Development Program for a 625 lbf thrust engine for Ares First Stage Roll Control System

NASA's new Ares Launch Vehicle will require twelve thrusters to provide roll control of the vehicle during the first stage firing. All twelve roll control thrusters will be located at the inter-stage segment that separates the solid rocket booster first stage from the second stage. NASA selected a mono propellant hydrazine solution and as a result awarded Aerojet-General a contract in 2007 for an advanced development program for an MR-80- series 625 Ibf vacuum thrust monopropellant hydrazine thruster. This thruster has heritage dating back to the 1976 Viking Landers and most recently for the 2011 Mars Science Laboratory. Prior to the Ares application, the MR-80-series thrusters had been equipped with throttle valves and not typically operated in pulse mode. The primary objective of the advanced development program was to increase the technology readiness level and retire major technical risks for the future flight qualification test program. Aerojet built on their heritage MR-80 rocket engine designs to achieve the design and performance requirements. Significant improvements to cost and lead-time were achieved by applying Design for Manufacturing and Assembly (DFMA) principles. AerojetGeneral has completed Preliminary and Critical Design Reviews, followed by two successful rocket engine development test programs. The test programs included qualification random vibration and firing lite that significantly exceed the flight qualification requirements. This paper discusses the advanced development program and the demonstrated capability of the MR-80C engine. Y;

Dawson, Matt↗

NASA NTRS2020

Characterization Testing of Space-Flight Lockheed Martin Micro1-2 Cryocooler for the Mapping Imaging Spectrometer for Europa (MISE)

The Mapping Imaging Spectrometer for Europa (MISE) instrument on the Europa Clipper mission uses a Lockheed Martin “high-power” Micro1-2 pulse tube cryocooler with a heat rejection temperature around 220 K to provide cooling at 80 K. This paper describes the thermal performance and exported forces characterization testing and results of the space-flight Lockheed Martin Micro1-2 cooler optimized for these conditions. Prior to these characterization tests, the cooler passed random vibration and thermal vacuum cycling at Lockheed Martin.

Rodriguez, Jose↗

NASA NTRS2018

Investigation of Multi-Input, Multi-Output (MIMO) Random Control Applied to Direct Field Acoustic Testing

Direct Field Acoustic Testing (DFAT) offers potential cost and time savings over reverberant chamber acoustic testing of spacecraft. The NASA Multi-Purpose Crew Vehicle (MPCV) Program recently directed a series of acoustic tests on Orion structural test articles comparing DFAT and reverberant testing of the same test article with a view to qualifying DFAT for manned space flight vehicles. The verification process compared four parameters noise level compliance with the one third octave test specification, spatial uniformity of the acoustic field, spatial correlation of the acoustic field and vibration response of vehicle structure, including representative solar array panels. While the results of the verification were encouraging, MPCV Loads and Dynamics engaged Quartus Engineering to investigate whether alternative MIMO random control strategies might improve the spatial uniformity and/or the spatial correlation of the DFAT acoustic field. This paper presents the results of acoustic field simulations of the DFAT test and provides a better understanding of how MIMO random control systems originally developed for vibration and structural durability testing can be expected to perform in DFAT testing.

Direct Field↗