ENVIRONMENTAL TESTING
Dynamic environments and environmental testing - shock and vibration testing
ENVIRONMENTAL TESTING↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Optimal hybrid propulsion systems thrust trajectories in a patched-conic N-body force field
Euler-Lagrange equations for approximating optimal thrust trajectories for limited hybrid propulsion system in N-body dynamic environment
Pines, S.↗
Dynamic analysis of Apollo-Salyut/Soyuz docking
The use of a docking-system computer program in analyzing the dynamic environment produced by two impacting spacecraft and the attitude control systems is discussed. Performance studies were conducted to determine the mechanism load and capture sensitivity to parametric changes in the initial impact conditions. As indicated by the studies, capture latching is most sensitive to vehicle angular-alinement errors and is least sensitive to lateral-miss error. As proved by load-sensitivity studies, peak loads acting on the Apollo spacecraft are considerably lower than the Apollo design-limit loads.
Schliesing, J. A.↗
Principal sources and dispersal patterns of suspended particulate matter in nearshore surface waters of the northeast Pacific Ocean and the Hawaiian Islands
The author has identified the following significant results. ERTS-1 green and red band imagery supplemented by U-2 photographs provides synoptic views of turbid, nearshore, near-surface bodies of water which adds to the body of knowledge about the coastal ocean necessary for a thorough understanding of the dynamic environment. Tubidity and suspended sediment measurements made in the Gulf of the Farallones correlate well with water tonal patterns visible on satellite imagery. Three successively seaward zones of turbid water could be delineated. Secchi disc visibility tests were the most definitive, ranging from or = 2 meters in the main plume, to almost 3 meters in the second zone of turbid water, to 4 meters in the furthest seaward zone of turbid water measured. These variations in water clarity were reinforced by suspended sediment concentrations which ranged from 26-28 mg/1, to 20-24 mg/1, to 11-15 mg/1, respectively, in each of the three masses of water. Transmissiometer readings were basically in agreement with the suspended sediment and Secchi disc values measured. Satellite imagery and U-2 photographs of the California coastal zone taken early in April 1973 show numerous plumes of suspended sediment being deflected southward. This indicates a southward flow of the nearshore, near-surface waters, a reversal from that noted in January 1973.
Carlson, P. R.↗
Strapdown system performance optimization test evaluations (SPOT), volume 1
A three axis inertial system was packaged in an Apollo gimbal fixture for fine grain evaluation of strapdown system performance in dynamic environments. These evaluations have provided information to assess the effectiveness of real-time compensation techniques and to study system performance tradeoffs to factors such as quantization and iteration rate. The strapdown performance and tradeoff studies conducted include: (1) Compensation models and techniques for the inertial instrument first-order error terms were developed and compensation effectivity was demonstrated in four basic environments; single and multi-axis slew, and single and multi-axis oscillatory. (2) The theoretical coning bandwidth for the first-order quaternion algorithm expansion was verified. (3) Gyro loop quantization was identified to affect proportionally the system attitude uncertainty. (4) Land navigation evaluations identified the requirement for accurate initialization alignment in order to pursue fine grain navigation evaluations.
Blaha, R. J.↗
Performance characterization tests of three 0.44-N (0.1 lbf) hydrazine catalytic thrusters
The 0.44-N (0.1-lbf) class of hydrazine catalytic thruster has been evaluated to assess its capability for spacecraft limit-cycle attitude control with thruster pulse durations on the order of 10 milliseconds. Dynamic-environment and limit-cycle simulation tests were performed on three commercially available thruster/valve assemblies, purchased from three different manufacturers. The results indicate that this class of thruster can sustain a launch environment and, when properly temperature-conditioned, can perform limit-cycle operations over the anticipated life span of a multi-year mission. The minimum operating temperature for very short pulse durations was determined for each thruster. Pulsing life tests were then conducted on each thruster under a thermally controlled condition which maintained the catalyst bed at both a nominal 93 C (200 F) and 205 C (400 F). These were the temperatures believed to be slightly below and very near the minimum recommended operating temperature, respectively. The ensuing life tests ranged from 100,000 to 250,000 pulses at these temperatures, as would be required for spacecraft limit-cycle attitude control applications.
Moynihan, P. I.↗
Strapdown system Performance Optimization Test evaluations (SPOT), volume 2
A three axis inertial system is packaged in an Apollo gimbal fixture for fine grain evaluation of strapdown system performance in dynamic environments. These evaluations have provided information to assess the effectiveness of real-time compensation techniques and to study system performance tradeoffs to factors such as quantization iteration rate. The strapdown performance and tradeoff studies conducted in this program are discussed.
Blaha, R. J.↗
The response of rotating machinery to external random vibration
A high-speed turbogenerator employing gas-lubricated hydrodynamic journal and thrust bearings was subjected to external random vibrations for the purpose of assessing bearing performance in a dynamic environment. The pivoted-pad type journal bearings and the step-sector thrust bearing supported a turbine-driven rotor weighing approximately twenty-one pounds at a nominal operating speed of 36,000 rpm. The response amplitudes of both the rigid-supported and flexible-supported bearing pads, the gimballed thrust bearing, and the rotor relative to the machine casing were measured with capacitance type displacement probes. Random vibrations were applied by means of a large electrodynamic shaker at input levels ranging between 0.5 g (rms) and 1.5 g (rms). Vibrations were applied both along and perpendicular to the rotor axis. Response measurements were analyzed for amplitude distribution and power spectral density. Experimental results compare well with calculations of amplitude power spectral density made for the case where the vibrations were applied along the rotor axis. In this case, the rotor-bearing system was treated as a linear, three-mass model.
Tessarzik, J. M.↗
The development of sine vibration test requirements for Viking lander capsule components
In connection with the Viking project for exploring the planet Mars, two identical spacecraft, each consisting of an orbiter and a lander, will be launched in the third quarter of 1975. Upon arrival at the planet, the Viking lander will separate from the Viking orbiter and descend to a soft landing at a selected site on the Mars surface. It was decided to perform a sine vibration test on the Viking spacecraft, in its launch configuration, to qualify it for the booster-induced transient-dynamic environment. It is shown that component-level testing is a cost- and schedule-effective prerequisite to the system-level, sine-vibration test sequences.
Barrett, S.↗
Cost effective dynamic design and test requirements for Shuttle payloads
The results of a study examining current spacecraft dynamic design and test requirements for the cost effective design and development of Shuttle payloads are presented. Dynamic environments, payload configurations, design/test requirements, test levels, assembly level of testing, simulation methods, prototype role, load limiting, test facilities, and flight measurements are discussed as they relate to the development of a cost effective design and test philosophy for Shuttle Spacelab payloads. It is concluded that changes to current design/test practices will minimize long range payload costs. However, changes to current practices need be quantitatively evaluated before an orderly progression to more cost effective methods can be achieved without undue risk of mission failures. Of major importance is optimization of test levels and plans for payloads and payload subsystems which will result in minimum project costs.
Stahle, C. V.↗
A study to define an in-flight dynamics measurement and data applications program for space shuttle payloads
Data measurement and interpretation techniques were defined for application to the first few space shuttle flights, so that the dynamic environment could be sufficiently well established to be used to reduce the cost of future payloads through more efficient design and environmental test techniques. It was concluded that: (1) initial payloads must be given comprehensive instrumentation coverage to obtain detailed definition of acoustics, vibration, and interface loads, (2) analytical models of selected initial payloads must be developed and verified by modal surveys and flight measurements, (3) acoustic tests should be performed on initial payloads to establish realistic test criteria for components and experiments in order to minimize unrealistic failures and retest requirements, (4) permanent data banks should be set up to establish statistical confidence in the data to be used, (5) a more unified design/test specification philosophy is needed, (6) additional work is needed to establish a practical testing technique for simulation of vehicle transients.
Rader, W. P.↗
Thermo/structural design considerations to achieve the Large Space Telescope line-of-sight requirements
The Large Space Telescope (LST) which is scheduled for launch in 1982, is a long-life, precision-pointing, earth-orbiting satellite requiring a structural system that provides high dimensional stability, minimum thermal distortion, and minimum response to onboard dynamic environments (e.g., reaction wheels). The results of a detailed thermostructural finite element computer analysis show that the telescope structure, even though fabricated from a material with a zero coefficient of thermal expansion, must be isolated from the external structure by a three-point support (flex joints or spherical bearings will accomplish this). Other thermo/structural analysis of the metering structure showed that second-order deformations have a significant effect on the alignment of the primary and secondary mirrors.
Tenerelli, D. J.↗
Amplifying ribbon extensometer for measuring film and fabric strain
Variations of a low-cost amplifying linear threshold extensometer are presented in detail for high or low strain applications. Derivations of scale relationships and extraction forces are included with experimental correlations and analyses given on performance, attachment problems, gain selection, gage and base material compatibility, and zero setting techniques. Flight applications of unamplified gages on parawing deployment tests are noted. The amplified gages perform accurately in laboratory tests and further experience is needed on performance under dynamic environments.
Alley, V. L., Jr.↗
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.↗
Differential altimetry for satellite orbit determination
Differential altimetry is concerned with the employment of differenced satellite altimeter measurements at orbit ground trace intersections. The employment of this procedure makes it possible to eliminate two of the major error sources found in direct altimetry. Previous applications have not included the appropriate dynamic constraints required to account for correlations due to satellite orbit motion. A description is given of an investigation in which these correlations are included. The methodology produced is consistent with the dynamic environment. The regional or local limitations of previous approaches are overcome by extending the technique to the global scale. Attention is given to the description of the data type, the geometric topography height, altimeter errors, discretization errors, an approximate orbit determination problem, and a comparison of differenced altimeter measurements for retrograde and prograde orbits.
Hagar, H., Jr.↗
Modeling the effects of high-G stress on pilots in a tracking task
Air-to-air tracking experiments were conducted at the Aerospace Medical Research Laboratories using both fixed and moving base dynamic environment simulators. The obtained data, which includes longitudinal error of a simulated air-to-air tracking task as well as other auxiliary variables, was analyzed using an ensemble averaging method. In conjunction with these experiments, the optimal control model is applied to model a human operator under high-G stress.
Korn, J.↗
The management of energy utilization in a spacecraft tracking station and its industrial applications
The mission of a tracking station within the NASA/Jet Propulsion Deep Space Network is characterized by a wide diversity of spacecraft types, communications ranges, and data accuracy requirements. In the present paper, the system architecture, communications techniques, and operators interfaces for a utility controller are described. The control equipment as designed and installed is meant to be a tool to study applications of automated control in the dynamic environment of a tracking station. It allows continuous experimenting with new technology without disruption of the tracking activities.
Reynolds, R.↗
Recovered transient load analysis for payload structural systems
A recovered transient analysis technique is proposed wherein the results of a previous launch vehicle/payload system can be used to obtain the information on a new payload structure to be launched by an identical launch vehicle. The advantage of the proposed method is that the complete analysis can be performed within the payload organization with the same accuracy as that of a full scale, multiorganizational loads analysis. Also, the flight measured interface accelerations can be used as the forcing functions for more realistic representations of the dynamic environments.
Chen, J. C.↗