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At least 721 records · Page 40

Fire safety - An achievable goal

NASA program fire safety goals, discussing development of nonflammable materials covering fibrous asbestos, glass, polymides, Teflon, metallics and halogenated materials

Radnofsky, M. I.↗

Noise reductions achieved on a 720-023B aircraft using a two-segment approach

A flight investigation to determine the operational feasibility of two-segment approaches as a means for reducing airport community noise has been conducted. The effective perceived noise level (EPNL) associated with these approach profiles, using a 720-023B jet aircraft, has been obtained. The tests were designed to determine an operationally optimum approach profile and to quantify the reduction in noise level at predetermined locations on the ground beneath the flight track. The acoustic aspects of the test program are examined. An analysis of the optimum and reference profiles was made using a group of pilots. Information was also obtained on the types of pilot operational procedures used for the optimum profile.

Glass, R. E.↗

NASA's quality program - Achievements and forecast.

The NASA quality assurance program during the preceding decade is reviewed, with emphasis on those events and accomplishments which bear on the improvement of quality assurance technology, practice, and management. The nature of the space program is discussed to help understand the significance of past quality assurance events and to anticipate future trends. Potential benefits are revealed which are not necessarily limited to the aerospace field.

Weiss, H. M.↗

Computational efficiency achieved by time splitting of finite difference operators.

A technique is presented for computing multidimensional time-dependent flow fields that avoids much of the inefficiency typically found in finite difference calculations. The technique initially divides the flow field into regions, each containing a mesh of general quadrilateral cells chosen to provide spatial resolution of the local features of the flow. A finite difference operator of second order accuracy, consisting of a sequence of one-dimensional operators (each operating at near maximum Courant-Friedrich-Lewy number) is then constructed for each region. Numerical results illustrating the technique for inviscid flows about simple bodies that generate shock waves, embedded shock waves, and expansion fans are presented and compared with exact theory.

Maccormack, R. W.↗

Responses of blind fish to gravitational changes as achieved in parabolic flight

Blind fish, during parabolic flight, display a measurable and consistent behavior. The most spectacular new behavioral response is the forward looping of blind fish in or near weightlessness. This response shows no measurable adaptation during the entire period of weightlessness of about 30 sec. During the entrance and exit of weightless parabolas (pushover and pullout) respectively, the fish assumes a forward tilted diving position. Parabolic flight with negative g in the range between 0g and -1g causes similar diving responses of the fish with the only difference being that the dive is directed toward the top of the fish tank. When the response to a g value less than 1g is compared to the response to increased g load on the ground (escape of darting response) an essential difference is seen: higher horizontal acceleration or jerk on the ground causes fish to swim, or even dart, against the direction of inertial force; fish during weightless parabolas move into the direction of the inertial or gravitational force. Since the vestibular system of fish is homologous to that of man, the observed behavior of fish in weightless flight could help to better understand human performance and sensations in comparable situations.

Vonbaumgarten, R. J.↗

Modeling of a bubble-memory organization with self-checking translators to achieve high reliability.

Study of the design and modeling of a highly reliable bubble-memory system that has the capabilities of: (1) correcting a single 16-adjacent bit-group error resulting from failures in a single basic storage module (BSM), and (2) detecting with a probability greater than 0.99 any double errors resulting from failures in BSM's. The results of the study justify the design philosophy adopted of employing memory data encoding and a translator to correct single group errors and detect double group errors to enhance the overall system reliability.

Bouricius, W. G.↗

Achieving ultrahigh accuracy with a body pointing CMG/RW control system.

The purpose of the Large Space Telescope (LST) program is to place a three-meter diffraction limited telescope in a 270-nautical mile orbit in order to perform astronomical observations that are not presently possible with earth bound telescopes due to atmospheric obscuration. In order to determine whether the stringent pointing requirements could be met, a complex simulation model was defined which consisted of detailed dynamic representations of control moment gyros (CMGs) and reaction wheels including their noise characteristics, dynamic sensor representations with sensor noise, shock mounts for the CMG actuators, and a detailed flexible body structural model with all significant vehicle and solar panel bending modes. On the basis of both stability and performance studies utilizing this model, it was determined that a body pointing system will meet LST requirements.

Rybak, S. C.↗

The planetary quarantine program: Origins and achievements, 1956 - 1973

United States effort in planetary quarantine is outlined, beginning with the expressions of alarm by biologists, then discussing how a program was put together and implemented, and finally indicating the academic, governmental, institutional, and industrial agencies and people involved. It ends with a brief summary of the accomplishments and present status of the Planetary Quarantine Program and will serve as a partial explanation of how the planetary quarantine effort evolved and reached its present position.

Phillips, C. R.↗

Automated Mars surface sample return mission concepts for achievement of essential scientific objectives

Mission concepts were investigated for automated return to Earth of a Mars surface sample adequate for detailed analyses in scientific laboratories. The minimum sample mass sufficient to meet scientific requirements was determined. Types of materials and supporting measurements for essential analyses are reported. A baseline trajectory profile was selected for its low energy requirements and relatively simple implementation, and trajectory profile design data were developed for 1979 and 1981 launch opportunities. Efficient spacecraft systems were conceived by utilizing existing technology where possible. Systems concepts emphasized the 1979 launch opportunity, and the applicability of results to other opportunities was assessed. It was shown that the baseline missions (return through Mars parking orbit) and some comparison missions (return after sample transfer in Mars orbit) can be accomplished by using a single Titan III E/Centaur as the launch vehicle. All missions investigated can be accomplished by use of Space Shuttle/Centaur vehicles.

Weaver, W. L.↗

Progress in laser ranging to satellites - Achievements and plans

Theoretical and mathematical considerations involved in the design of retroreflectors for the GEOS-C and Timation III laser ranging satellites are described, laser ranging systems used by the Goddard Space Flight Center are reviewed, and planned systems changes are outlined. Equations are derived for the design of a cube corner array on a gravity gradient stabilized satellite in a circular orbit, and the required cube corner for GEOS-C is computed. Use of fixed threshold triggers and electronic and analytic pulse height compensation in present laser ranging systems is discussed. Proposed changes are outlined, including the incorporation of split gate triggers and trackers into the ranging systems and the use of analog and digital centroid measurement techniques. A theoretical consideration of the effects of velocity aberration on the reflected light beam is appended.

Plotkin, H. H.↗

Ways of achieving continuous service from computers

This paper outlines the methods used in the real-time computer complex to keep computers operating. Methods include selectover, high-speed restart, and low-speed restart. The hardware and software needed to implement these methods is discussed as well as the system recovery facility, alternate device support, and timeout. In general, methods developed while supporting the Gemini, Apollo, and Skylab space missions are presented.

Quinn, M. J., Jr.↗

Achieving equal opportunity in NASA: An assessment of needs and recommendations for action

Measures designed by NASA to improve its equal opportunity program are reported. Attempts made to increase the ratios and level of placement of women and minority men in the work force were emphasized, upward mobility for those employees already in the work force was also studied. Ways for improving the track record for NASA's equal opportunity profile are recommended.

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