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Numerous applications of the NASA Structural Analysis (NASTRAN) computer program, a general purpose finite element code, are discussed. Additional features that can be added to NASTRAN, interactive plotting of NASTRAN data on microcomputers, mass modeling for bars, the design of wind tunnel models, the analysis of ship structures subjected to underwater explosions, and buckling analysis of radio antennas are among the topics discussed.
Explosive maritime cyclogenetic events are usually aligned with the warm currents off the east coasts of Japan and the U.S. One such event occurred during FGGE in an area which featured good instrumented ship and aircraft coverage. The UCLA 4th order GMC was employed to generate predictions of the event for comparisons with the real-world data. FGGE III-b data were used to initialize the model calculations. Attention was directed to the physical processes causing the onset of the cyclogenesis, particularly the heat budgets of the fluxes involved. The diabatic heating was observed to be equivalent to the horizontal temperature advection. The main source of energy around the cyclone center was identified as the conversion of energy from static energy to kinetic energy. Further analyses of similar events are required if the present results are to be validated.
Monthly summaries of atmospheric soundings taken over 17 years from 49 midocean stations at small islands and weather ships distributed over major oceans are examined. Over tropical oceans, precipitable water is found to be a better predictor of surface-level humidity than surface-level air temperature. A statistical relation in the form of a polynomial is derived; from this relation, the monthly-mean, surface-level mixing ratio can be computed from monthly-mean precipitable water. The root-mean-square differences between the measured and derived values were found to be less than 8 x 10 to the -4th over most ocean areas. Such a relation is useful in deriving large-scale evaporation and latent heat flux data from the ocean, using spaceborne observations. The temporal and spatial variabilities of data deviations from this relation are examined. This relation is found to be applicable to all major ocean basins and can be used to monitor interannual variability. Boundary-layer thermodynamics of different air masses are suggested as an explanation of some characteristics of this relation.
This paper reviews the results of several simulation investigations of rotary-wing and fixed-wing VSTOL aircraft performing terminal-area operations that include decelerating approaches under instrument conditions and recovery to either fixed landing pads or a ship. By concentrating on instrument decelerating approaches and the hover and landing, it is possible to compare directly the control and display requirements for similar tasks for aircraft with and without vectored thrust capability. Collectively, the results from these experiments, together with other simulator and flight experiments and operational experience, provide a consistent view of control and display complexity required for similar operational capability in adverse weather for the two types of VSTOL configurations. Some initial data showing influence of the transition corridor on flying qualities during transition are pesented and lead to a general discussion of the problem of operating margin definition.
Comparison with in situ measurements shows that the Nimbus/Scanning Multichannel Microwave Radiometer is useful in describing the month-to-month variability of the latent heat flux 'LE' and related parameters during the 1982-1983 El Nino event. The spaceborne measured monthly mean LE was found to be within 30 W/sq m of those derived from ship reports. Absolute accuracy could not be determined, though satellite measurements could extrapolate information on the LE both in space and in time.
Early astronomical photography of comets at perihelion encouraged the establishment of an International Halley Watch (IHW) Team for regularly photographing the Comet. The February 1986 period was particularly troublesome due to the limitations of cometary visibility in the Southern Hemisphere. Schmidt cameras were placed on Tahiti, Easter Island, Faraday Station on the Antarctic Peninsula, Reunion Island and in South Africa. Blue- and red-filter B/W images were obtained every night and color prints were occasionally shot. Each night's images were examined before the next night's photography. Several interesting anecdotes are recounted from shipping, manning and operation of the telescopes.
Observations and theoretical models of small-scale phenomena in the oceans are reviewed, with a focus on progress during the period 1983-1986. Topics examined include surface layers, equatorial turbulence, off-equator mixed layers, the scaling of mixing, turbulence concepts, laboratory results, internal waves and mixing, rings, the nature of the bottom layer, double diffusion and intrusions, salt fingers, and biological interactions. Also discussed are developments in instrumentation (fast sampling profilers with upward-profiling capability, deep profilers, ship-motion correction, horizontal samplers, small submersibles, submarines, towed packages, conductivity sensors, dissolved-oxygen sensors, and acoustic Doppler current profilers) and goals for future research.
The need for improved surface wind and wind stress data is discussed. The collection of wind data using ship reports, research buoys, and cloud motion vectors is examined. The need for data on surface-wind stress fields is emphasized. Accurate stress data are required for studying: (1) the normal seasonal cycle and the intraannual events; (2) wind stress curls and the forcing of ocean circulation; (3) El Nino events; and (4) the low response of the midlatitude ocean circulation.
Polyimide-foam airducts low in cost and light in weight. Relatively safe in fires because they resist spread of flames and generate little smoke. Polyimide-foam ducts less expensive to manufacture. Suitable for heating and air-conditioning in airplanes, ships, trains, and buildings.
Report describes an evaluation of firefighting module that delivers water at 5,000 gal/min (320 L/s). Is compact, self-contained, portable water pump. Besides firefighting, module used for flood control, pumping water into large vessels, and pump water from sinking ships.
Simplified mathematical model of coupled vibrations of vehicle and its payloads used in stability analysis for control purposes. Multiple-payload stability criterion extension of single-payload criterion based on measurements and detailed calculations of fundamental vibrational modes of vehicle and payload. Represented in simplified form by coupled masses and springs vibrating in one dimension, each spring having stiffness that gives rise to previously determined fundamental vibrational frequency associated mass in absence of coupling with other mass. Developed to avoid complexity and cost of full vibrations/stability calculations for each different combination of Space Shuttle payloads, simplified analysis technique also useful in assessing stability in loaded airplanes, ships, trucks, cranes, and conveyor systems.
A computer-simulation study was undertaken to investigate a maximum concealment guidance technique (pop-up maneuver), which military aircraft may use to capture a glide path from masked, low-altitude flight typical of terrain following/terrain avoidance flight enroute. The guidance system applied to this problem is the Fuel Conservative Guidance System. Previous studies using this system have concentrated on the saving of fuel in basically conventional land and ship-based operations. Because this system is based on energy-management concepts, it also has direct application to the pop-up approach which exploits aircraft performance. Although the algorithm was initially designed to reduce fuel consumption, the commanded deceleration is at its upper limit during the pop-up and, therefore, is a good approximation of a minimum-time solution. Using the model of a powered-lift aircraft, the results of the study demonstrated that guidance commands generated by the system are well within the capability of an automatic flight-control system. Results for several initial approach conditions are presented.
Results of a substantial body of ground-based simulation experiments indicate that a high degree of precision of operation for recovery aboard small ships in heavy seas and low visibility with acceptable levels of effort by the pilot can be achieved by integrating the aircraft flight and propulsion controls. The availability of digital fly-by-wire controls makes it feasible to implement an integrated control design to achieve and demonstrate in flight the operational benefits promised by the simulation experience. It remains to validate these systems concepts in flight to establish their value for advanced short takeoff vertical landing (STOVL) aircraft designs. This paper summarizes analytical studies and simulation experiments which provide a basis for the flight research program that will develop and validate critical technologies for advanced STOVL aircraft through the development and evaluation of advanced, integrated control and display concepts, and lays out the plan for the flight program that will be conducted on NASA's V/STOL Research Aircraft (VSRA).
The identification, quantification, computer modeling and verification of the Tomahawk nonlinear liquid spring shock isolation system in a surface ship Vertical Launch System (VLS) are discussed. The isolation system hardware and mode of operation is detailed in an effort to understand the nonlinearities. These nonlinearities are then quantified and modeled using the MSC/NASTRAN finite element code. The model was verified using experimental data from the Navel Ordnance Systems Center MIL-S-901 medium weight shock tests of August 1986. The model was then used to predict the Tomahawk response to the CG-53 USS Mobile Bay shock trials of May-June 1987. Results indicate that the model is an accurate mathematical representation of the physical system either functioning as designed or in an impaired condition due to spring failure.
Blast or penetrator-impact induced shocks are characterized by high acceleration levels, particularily in the higher frequency range and for a short time duration. These shocks are dangerous for the equipment of ships, combat vehicles, airplanes or spacecraft structures. As ballistic shock loads are insufficiently simulated by laboratory test machines, researchers designed a ballistic shock simulator. The impact induced shocks are simulated by an explosive and the vehicle to be bombarded is replaced by a simplified structure. This structure is suitable to accommodate any equipment which can be tested up to their load limits.
The formative stages of the onset of the 1979 southwest monsoon was marked by a WNW-ESE oriented band of marine convection over the South Arabian Sea. This convection was first observed on June 10, 1979 using satellite cloud imagery. The marine convection appeared during a major acceleration of the upper troposphere easterly wind field. A composite vertical meridional cross-section of upper level winds for June 11, revealed the core of the Tropical Easterly Jet (TEJ) at 115 mb, 9.5 deg N. Time analysis of the upper level wind field over the Tropical Wind Observing Ship (TWOS) polygon show a lowering of both the pressure level of maximum wind and tropopause level with acceleration of the upper level easterlies. The tropopause was as much as 20 mb lower on the equatorial side of the TEJ. Streamline analysis of the maximum observed easterly winds over India did not reveal the horizontal position of the TEJ. Careful analysis of Total Ozone Mapping Spectrometer (TOMS) data for June 11, 1979 showed relatively high values of ozone south of India. It was observed that the latitudinal position of the TEJ on June 11, at approximately 70 deg E coincided with the northern edge of relatively high ozone values. Using this as a reference, the TEJ core was identified as far as NE Bay of Bengal (the limits of the available TOMS data).
A Thematic Mapper (TM) field experiment was followed by a data analysis to determine TM capabilities for analysis of suspended matter and phytoplankton. Factor analysis showed that suspended matter concentration, atmospheric scattering, and sea surface temperature can be retrieved as independent factors which determine the variation in the TM data over water areas. Spectral channels in the near infrared open the possibility of determining the Angstrom exponent better than for the coastal zone color scanner. The suspended matter distribution may then be calculated by the absolute radiance of channel 2 or 3 or the ratio of both. There is no indication of whether separation of chlorophyll is possible. The distribution of suspended matter and sea surface temperature can be observed with the expected fine structure. A good correlation between water depth and suspended matter distribution as found from ship data can now be analyzed for an entire area by the synoptic view of the TM scenes.
The concept of circulation control was successfully demonstrated in flight using an A-6 aircraft. Circulation control can provide an aircraft with STOL performance of heavy lift capability. For ship based Naval aircraft the lower takeoff and landing velocities result in reduced deck gear and wind over the deck requirements. Circulation control airfoils can be mechanically less complex and lightweight compared to multi-element high lift airfoils.