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There are no author-identified significant results in this report.
A quadrilateral shell element, CQUAD4, was added to level 15.5 and subsequently to level 16.0 of NASTRAN. The element exhibited doubly curved surfaces and used biquadratic interpolation functions. Reduced integration techniques were used to improve the performance of the element in thin shell problems. The creation of several new bulk data items is discussed, along with a special module, GPNORM, to process SHLNORM bulk data cards. In addition to the theoretical basis for the element stiffness matrix, consistent mass and load matrices are presented. Several potential sources of degenerate behavior of the element were investigated. Guidelines for proper use of the element were suggested. Performance of the element on several widely published classical examples was demonstrated. The results showed a significant improvement over presently available NASTRAN shell elements for even the coarsest meshes. Potential applications to two classes of practical problems are discussed.
An explicit adaptive controller, which makes direct use of on-line parameter identification, has been developed and applied to both the linearized and nonlinear equations of motion for the F-8 aircraft. This controller is composed of an on-line weighted least squares parameter identifier, a Kalman state filter, and a real model following control law designed using single-stage performance indices. The corresponding control gains are readily adjustable in accordance with parameter changes to ensure asymptotic stability if the conditions of perfect model following are satisfied, and stability in the sense of boundedness otherwise. Simulation experiments with realistic measurement noise indicate that the controller was effective in compensating for parameter variations and capable of rapid recovery from a set of erroneous initial parameter estimates which defined a set of destabilizing gains.
The Synthetic Aperture Radar (SAR) onboard the Seasat-A satellite will conduct a number of experiments involving deep ocean waves, coastal wave patterns, polar ice and land forms. The SAR will have a 25 m by 25 m resolution over a swath of 100 km width centered about 300 km to the right of the spacecraft track. The SAR's high data rate limits operations to times when Seasat-A is in view of a few ground stations with special SAR receiving equipment. However, the SAR will collect much useful data about deep ocean and coastal waves in the Atlantic and Pacific Oceans; about ice in the Northwest Atlantic, in the Great Lakes and off the coast of Alaska; and about land over much of the United States and Canada.
A description is presented of the instrument system which is needed for the Earth Radiation Budget Satellite System (ERBSS). The system is to be composed of instruments on two of NOAA's near-polar sun-synchronous Tiros-N/NOAA A through G series of operational satellites and on a NASA midinclination satellite of the Applications Explorer Mission (AEM) type referred to as ERBS-A/AEM. The Tiros-N/NOAA satellites will be in nominal 833 km altitude circular orbits with orbital inclinations of 98 deg. The AEM satellite will be in a circular orbit with an inclination of approximately 56 deg and a nominal altitude of 600 km. Each satellite will carry wide field-of-view (WFOV) and medium field-of-view (MFOV) sensors, a sensor for measuring the solar constant, and a narrow field-of-view (NFOV) cross-track scanner. The conceptual design of the W/MFOV instrument is discussed along with the conceptual design of the scanner.
Throughout the aircraft development process flight simulators are used to evaluate design concepts, 'handling' qualities, and operational procedures. A modern flight research simulator comprises a cockpit equipped with flight instruments and controls, subsystems to provide visual, motion, and other flight cues, and a digital computer. REPLAY is a computer program which enables a user to reproduce the multidimensional flight cues for an entire simulation 'run'. Attention is given to simulation fidelity improvement, simulation data recovery, simulation quality assurance, and aircraft systems research. It is pointed out that each of the applications discussed supports aircraft systems research by improving the realism, efficiency, or reliability of the simulation facility.
There are no author-identified significant results in this report.
There are no author-identified significant results in this report.
There are no author-identified significant results in this report.
There are no author-identified significant results in this report.
There are no author-identified significant results in this report.
There are no author-identified significant results in this report.
Development of ARIS - Alabama Resources Information System is summarized. Development of data bases, system simplification for user access, and making information available to personnel having a need to use ARIS or in the process of developing ARIS type systems are discussed.
The elimination of Ampholine from the system by establishing the pH gradient with simple ampholytes is proposed. A mathematical model was exercised at the level of the two-component system by using values for mobilities, diffusion coefficients, and dissociation constants representative of glutamic acid and histidine. The constants assumed in the calculations are reported. The predictions of the model and computer simulation of isoelectric focusing experiments are in direct importance to obtain Ampholine-free, stable pH gradients.
The interfaces between the Ku-band system and the TDRSS, between the S-band system and the TDRSS, GSTDN and SGLS networks, and between the S-band payload communication equipment and the other Orbiter avionic equipment were investigated. The principal activities reported are: (1) performance analysis of the payload narrowband bent-pipe through the Ku-band communication system; (2) performance evaluation of the TDRSS user constraints placed on the S-band and Ku-band communication systems; (3) assessment of the shuttle-unique S-band TDRSS ground station false lock susceptibility; (4) development of procedure to make S-band antenna measurements during orbital flight; (5) development of procedure to make RFI measurements during orbital flight to assess the performance degradation to the TDRSS S-band communication link; and (6) analysis of the payload interface integration problem areas.
Structural design procedures are described for a large antenna system to meet performance requirements under gravity and wind loading. A computational method is shown for the evaluation of performance in response to wind loading. Cumulative probability distribution curves for wind loading gain reductions for 100-m-diameter antennas are developed to compare a relatively heavy baseline reflector backup structure with two lighter-weight structures; all have equivalent, acceptable performance for gravity loading.
This paper describes an approach for relay of data-modulated subcarriers from Shuttle payloads through the Shuttle Ku-band communications subsystem (and subsequently through a tracking and data relay satellite system to a ground terminal). The novelty is that a channel originally provided for baseband digital data is shown to be suitable for this purpose; the resulting transmission scheme is referred to as a narrowband bent-pipe scheme. Test results demonstrating the validity of the narrowband bent-pipe mode are presented, and limitations on system performance are described.
The earth-orbiting satellite provides a platform, outside the earth's atmosphere, which is capable of simultaneously monitoring the outgoing reflection of the sun's energy from the earth's surface and atmosphere, and the longwave radiation emitted by the earth and its atmosphere. These capabilities provide the opportunity to conduct detailed studies of the variations in the earth's radiation budget, the effects of natural and manmade changes in the environment on this budget, and the effects which changes in the energy budget produce on earth's weather and climate. A description is presented of the instrument system requirements and a conceptual design of an instrument approach to meet these requirements for providing the earth radiation budget data.