Engineering topics
Kern, D. L.
Publications and source records attributed to Kern, D. L..
JPL standard for spacecraft system dynamic and static testing
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Effective mass of fluid tank vibration testing
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The Proposed NASA Pyroshock Test Criteria Standard - Part I
The National Aeronautics and Space Administration has traditionally left the task of specifying design and test criteria to each of the several NASA Centers. Faced with the wide variety fo resulting criteria used for resolving similar or identical problems, the NASA Office of Chief Engineer initiated a program to develop consistent NASA-wide standards if the various NASA Centers could agree to a set of common requirements.
Summary of Cassini Acoustic Criteria Development Using Titan IV Flight Data
The Cassini spacecraft is being developed by the Jet Propulsion Laboratory (JPL) for theNational Aeronautics and Space Administration (NASA) to orbit and explore the planet Saturn, itsrings and satellites. Cassini will be launched on a Titan IV and boosted out of earth orbit by aCentaur. This paper discusses the development of Cassini acoustic criteria using Titan IV flight data. The Titan IV flight acoustic measurements and the different flight data processing techniquesemployed by Martin Marietta and The Aerospace Corporation are described in Reference 1, as wellasthe methods employed by JPL for identifying and correcting for instrumentation system transients.
Transient vibration test criteria for spacecraft hardware
Transient vibration test criteria, developed for spacecraft hardware, provide a test rationale to verify the capability of the hardware to withstand the low and mid frequency transient vibration environments induced by launch vehicle events. A test method, consisting of a series of discrete frequency, limited cycle, modulated sine wave pulses, was developed to avoid the slow swept sine drawbacks, yet provide a repeatable test that would excite all frequencies. The shape of the waveform is that of the classic response of the mass of a one degree of freedom system when it is base-excited by an exponentially decayed sine wave transient. Criteria were developed to define pulse amplitudes, shapes, and center frequencies from spacecraft loads analyses. Test tolerance criteria were also developed and specified. The transient vibration test criteria were implemented on spacecraft flight hardware and provided a more realistic test simulation (i.e., less conservative) for qualification of spacecraft hardware without risk of undertest.
Tailoring dynamic qualification tests for interplanetary spacecraft
It is pointed out that the word 'tailoring' has become quite popular in the past few years. Thus, two recently revised environmental test documents make frequent mention of test tailoring. 'Tailoring' is defined by MIL STD 810D (Environmental Test Methods and Engineering Guidelines). The word refers to 'the process of choosing or altering test procedures, conditions, values, tolerances, measures of failure, etc., to simulate or exaggerate the effects of one or more forcing functions to which an item will be subjected during its life cycle...'. This paper is concerned with requirement level test tailoring. Attention is given to examples of dynamic qualification test tailoring for an interplanetary spacecraft program. These examples are to provide ideas for test tailoring which can be applied to other space flight programs.
Acoustic environments for JPL shuttle payloads based on early flight data
Shuttle payload acoustic environmental predictions for the Jet Propulsion Laboratory's Galileo and Wide Field/Planetary Camera projects have been developed from STS-2 and STS-3 flight data. This evaluation of actual STS flight data resulted in reduced predicted environments for the JPL shuttle payloads. Shuttle payload mean acoustic levels were enveloped. Uncertainty factors were added to the mean envelope to provide confidence in the predicted environment.
Test program to develop vibroacoustics test criteria for the Galileo bus
In order to define random vibration test requirements for Galileo bus-mounted hardware, an extensive vibroacoustics test program was conducted on hardware available from the previous Voyager spacecraft development program. The Galileo test program consisted of acoustic tests on three configurations of the Voyager Dynamic Test Model bus and shaker random vibration tests on two flight-like bus equipment bay assemblies and one dummy equipment bay assembly. The primary goal of the acoustic tests was to define vibration levels at locations on the bus structure representative of inputs to bus equipment bay assemblies and to obtain response data on bus bay subassemblies for correlation with the vibration tests response data. The primary purpose of the vibration tests was to determine if the vibration tests excited subassembly responses at least as severely as the bus acoustic tests.
Dynamic environments for space shuttle payloads
Payload bay dynamic data from the first two space shuttle flights are summarized and evaluated. Development of dynamic environment design and test criteria for shuttle payloads from measured flight data is discussed. Factors that must be considered are flight to flight variations, spatial variations, temporal variations, measurement bias errors and the degree of confidence desired that a predicted environment will not be exceeded in flight. Summary and conclusion reports will be published after STS-4 and at appropriate intervals thereafter. The nature of these future reports and their impact on the user community is discussed.