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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Photorefractor ocular screening system

A method and apparatus for detecting human eye defects, particularly detection of refractive error is presented. Eye reflex is recorded on color film when the eyes are exposed to a flash of light. The photographs are compared with predetermined standards to detect eye defects. The base structure of the ocular screening system is a folding interconnect structure, comprising hinged sections. Attached to one end of the structure is a head positioning station which comprises vertical support, a head positioning bracket having one end attached to the top of the support, and two head positioning lamps to verify precise head positioning. At the opposite end of the interconnect structure is a camera station with camera, electronic flash unit, and blinking fixation lamp, for photographing the eyes of persons being evaluated.

Richardson, John R.↗
NASA NTRS1987

Role of orientation reference selection in motion sickness, supplement 2S

Previous experiments with moving platform posturography have shown that different people have varying abilities to resolve conflicts among vestibular, visual, and proprioceptive sensory signals. The conceptual basis of the present proposal hinges on the similarities between the space motion sickness problem and the sensory orientation reference selection problems associated with benign paroxysmal positional vertigo (BPPV) syndrome. These similarities include both etiology related to abnormal vertical canal-otolith function, and motion sickness initiating events provoked by pitch and roll head movements. The objectives are to explore and quantify the orientation reference selection abilities of subjects and the relation of this selection to motion sickness in humans. The overall objectives are to determine: if motion sickness susceptibility is related to sensory orientation reference selection abilities of subjects; if abnormal vertical canal-otolith function is the source of abnormal posture control strategies and if it can be quantified by vestibular and oculomotor reflex measurements, and if it can be quantified by vestibular and oculomotor reflex measurements; and quantifiable measures of perception of vestibular and visual motion cues can be related to motion sickness susceptibility and to orientation reference selection ability.

Peterka, Robert J.↗
NASA NTRS1987

The rationale for an aeroassist flight experiment

The states of several technologies are reviewed which are critical to the design of an aeroassisted orbital transfer vehicle. In these technologies, advancements are needed which hinge on obtaining new flight data. While some of the work can be done with the wind tunnel and computational disciplines, much of the required new data are tied to finite chemical reaction rates, possible thermal nonequilibrium, high flow enthalpy, and strong viscous effects. Because these effects cannot be modeled adequately in ground-based facilities, computational methods lack adequate verification to allow committing to the design of an aeroassist vehicle. Thus a new flight experiment is being planned by NASA to gather the required data. The flight experiment and associated instrumentation which NASA is proposing is discussed briefly.

Jones, Jim J.↗
NASA NTRS1987

Rate effects on delamiantion fracture toughness of a toughened graphite/epoxy

The objective of this study was to determine the effects of loading rate on interlaminar fracture toughness of T300/F-185 graphite/epoxy composite, having an elastomer-modified epoxy resin matrix. Mode I interlaminar fracture was investigated by means of uniform width and width-tapered double cantilever beam (DCB) specimens. Hinged tabs were used to insure unrestrained rotation at the free ends. Specimens were loaded at quasi-static deflection rates of up to 8.5 mm/s corresponding to crack extension rates of up to 21 mm/s. Crack extension was monitored by means of strain gages mounted on the surface of the specimen. Continuous records were obtained of load, deflection, and crack extension for determination of the strain energy release rate. The latter was calculated by means of the area method and beam analysis method, and expressed as a power law of the crack extension velocity. Results indicate that the strain energy release rate decreases with crack velocity by over 20 percent over three decades of crack velocity.

Daniel, Isaac M.↗
NASA NTRS1987

A study of some approximations in the modeling of a coupled rotor/fuselage aeromechanical system

Equations of motion for a three-bladed hingeless rotor coupled to a gimbal-supported fuselage are developed. A brief derivation of the equations is presented, including the assumptions made, the ordering scheme, and a discussion of both the source of the aerodynamic axial load term and the reason for differences due to hinge sequence. The solution of the equations is discussed, including linearization, the use of multiblade coordinates to eliminate periodic coefficients, and specialization to a root-sprung model. The treatment of the blade root offset by using an ordering scheme to neglect higher-order terms is found to affect results in pitch and roll. A small aerodynamic loading term in the blade axial direction has a significant effect at large collective pitch settings, as does the choice of a flap-lag or a lag-flap transformation sequence for blade motion. The results for a hingeless rotor also differ significantly from those for the root-sprung model when the nonrotating natural frequencies are matched.

Blelloch, P. A.↗
NASA NTRS1988

Folding Truss Structure

Concept for foldable and deployable truss offers advantages of strength, rigidity, and mechanical simplicity. Structure consists of series of boxlike bays with 9-ft sides. Each box has panels on top and bottom and two sides. Two remaining sides open. Panels hinged at connecting edges. Adapted to terrestrial transportable structures, scaffolds, cranes, and rows of cubicles.

Warren, Aubrey D.↗
NASA NTRS1988

Tool Extracts Smooth, Fragile Tubes

When laterally compressible tube too slippery to pull, simple tool does job. Consists of three linked sections of steel tube with sticky rubber on inside and handles on outside. Hinged sections encircle tube to be pulled. User pulls on handles to extract tube.

Sanders, Fred G.↗
NASA NTRS1986

An experimental investigation of the aerodynamics of a NACA 64A010 airfoil-flap combination with and without flap oscillations. Part 1: Steady-state characteristics

A NACA 64A010 airfoil with a sealed-gap 1/4-chord flap was tested between splitter plates in the NASA Ames 11- by 11-Foot Transonic Wind Tunnel at Mach numbers from 0.50 to 0.85, and Reynolds numbers based on chord from 3 to 13 million. Although the main purpose of the test was to obtain unsteady pressure data with the flap oscillating, no unsteady data are presented in this paper. The steady-state data are presented and compared with other test data to provide a basis for evaluating the results. Pressure data at two span stations are used to deduce early boundary-layer transitions at the midspan at higher Mach numbers, angles of attack, and flap angles. The effects of flap angle on pressures, normal force, pitching moment, and hinge moment are also presented in the report. Mach number errors caused by the splitter-plate configuration and the angle of attack are evaluated using pressure measurements near the floor and ceiling of the wind tunnel.

Buell, Donald A.↗
NASA NTRS1986

Computational design of natural laminar flow wings for transonic transport application

Two research programs are described which directly relate to the application of natural laminar flow (NLF) technology to transonic transport-type wind planforms. Each involved using state-of-the-art computational methods to design three-dimensional wing contours which generate significant runs of favorable pressure gradients. The first program supported the Variable Sweep Transition Flight Experiment and involves design of a full-span glove which extends from the leading edge to the spoiler hinge line on the upper surface of an F-14 outer wing panel. Boundary-layer and static-pressure data will be measured on this design during the supporting wind-tunnel and flight tests. These data will then be analyzed and used to infer the relationship between crossflow and Tollmein-Schlichting disturbances on laminar boundary-layer transition. A wing was designed computationally for a corporate transport aircraft in the second program. The resulting wing design generated favorable pressure gradients from the leading edge aft to the mid-chord on both upper and lower surfaces at the cruise design point. Detailed descriptions of the computational design approach are presented along with the various constraints imposed on each of the designs. Wing surface pressure distributions, which support the design objective and were derived from transonic three-dimensional analyses codes, are also presented. Current status of each of the research programs is included in the summary.

Waggoner, Edgar G.↗
NASA NTRS1988

Preliminary investigation of stability of a fin-stiffened slender strut

A fin-stiffened strut concept which possesses high bending stiffness and low packaged volume has been identified for use on large space structures. The concept incorporates three curved fins which deploy from a core tube to increase the effective cross-sectional moment of inertia, the buckling load, and the vibration frequency of the strut. A strut design incorporating welded fin connections provides an upper bound of the strut buckling load. A strut design which allows the individual fins and core to move independently in the strut axial direction provides a lower bound of the strut buckling load which is approximately 20 to 25 percent of the upper bound. A practical strut design, incorporating hinge assemblies which constrain the fins to move together but independently of the core tube in the strut axial direction, provides a buckling load which is 75 to 80 percent of the upper bound. Euler's equation can be used to accurately predict buckling loads for the bounding designs. Flat plate finite element models of all designs give results that agree to within 10 percent of the experimental values. Equivalent beam models of the strut give results which are slightly less accurate.

Lake, Mark S.↗
NASA NTRS1988

The X-beam as a deployable boom for the space station

Extension of antennas and thrust modules from the primary structure of the space station will require deployable beams of high stiffness and strength, as well as low mass and package volume. A square boom cross section is desirable for interface reasons. These requirements and others are satisfied by the X-beam. The X-beam folds by simple geometry, using single-degree-of-freedom hinges at simple angles, with no strain during deployment. Strut members are of large diameter with unidirectional graphite fibers for maximum beam performance. Fittings are aluminum with phosphor bronze bushings so that compliance is low and joint lifetime is high. The several beam types required for different applications on the space station will use the same basic design, with changes in strut cross section where necessary. Deployment is by a BI-STEM which pushes the beam out; retraction is by cables which cause initial folding and pull the beam in.

Adams, Louis R.↗
NASA NTRS1986

Computational wing design studies relating to natural laminar flow

Two research studies are described which directly relate to the application of natural laminar flow (NLF) technology to transonic transport-type wing planforms. Each involved using state-of-the-art computational methods to design three-dimensional wing contours which generate significant runs of favorable pressure gradients. The first study supported the Variable Sweep Transition Flight Experiment and involves design of a full-span glove which extends from the leading edge to the spoiler hinge line on the upper surface of an F-14 outer wing panel. A wing was designed computationally for a corporate transport aircraft in the second study. The resulting wing design generated favorable pressure gradients from the leading edge aft to the mid-chord on both upper and lower surfaces at the cruise design point. Detailed descriptions of the computational design approach are presented along with the various constraints imposed on each of the designs.

Waggoner, Edgar G.↗
NASA NTRS1988

Low-speed wind-tunnel test of a STOL supersonic-cruise fighter concept

A wind-tunnel investigation was conducted to examine the low-speed static stability and control characteristics of a 0.10 scale model of a STOL supersonic cruise fighter concept. The concept, referred to as a twin boom fighter, was designed as a STOL aircraft capable of efficient long range supersonic cruise. The configuration name is derived from the long twin booms extending aft of the engine to the twin vertical tails which support a high center horizontal tail. The propulsion system features a two dimensional thrust vectoring exhaust nozzle which is located so that the nozzle hinge line is near the aircraft center of gravity. This arrangement is intended to allow large thrust vector angles to be used to obtain significant values of powered lift, while minimizing pitching moment trim changes. Low speed stability and control information was obtained over an angle of attack range including the stall. A study of jet induced power effects was included.

Coe, Paul L., Jr.↗
NASA NTRS1988

Expandable pallet for space station interface attachments

Described is a foldable expandable pallet for Space Station interface attachments with a basic square configuration. Each pallet consists of a series of struts joined together by node point fittings to make a rigid structure. The struts have hinge fittings which are spring loaded to permit collapse of the module for stowage transport to a Space Station in the payload bay of the Space Shuttle, and development on orbit. Dimensions of the pallet are selected to provide convenient, closely spaced attachment points between the node points of the relatively widely spaced trusses of a Space Station platform. A pallet is attached to a strut at four points: one close fitting hole, two oversize holes, and a slot to allow for thermal expansion/contraction and for manufacturing tolerances. Applications of the pallet include its use in rotary or angular joints; servicing of splints; with gridded plates; as instrument mounting bases; and as a roadbed for a Mobile Service Center (MSC).

Wesselski, Clarence J.↗
NASA NTRS1988

Aeroelastic tailoring for oblique wing lateral trim

Composite material aeroelastic tailoring is presently explored as a means for the correction of the roll trim imbalance of oblique-wing aircraft configurations. The concept is demonstrated through the analysis of a realistic oblique wing by a static aeroelastic computational procedure encompassing the full potential transonic aerodynamic code FLO22 and a Ritz structural plate program that models the stiffness due to symmetrical-but-unbalanced composite wing skins. Results indicate that asymetric composite tailoring reduces the aileron deflection needed for roll equilibrium, and reduces control surface hinge moment and drag. Wing skin stresses are, however, very high.

Bohlmann, Jonathan D.↗
NASA NTRS1987

A shared position/force control methodology for teleoperation

A flexible and computationally efficient shared position/force control concept and its implementation in the Robot Control C Library (RCCL) are presented form the point of teleoperation. This methodology enables certain degrees of freedom to be position-controlled through real time manual inputs and the remaining degrees of freedom to be force-controlled by computer. Functionally, it is a hybrid control scheme in that certain degrees of freedom are designated to be under position control, and the remaining degrees of freedom to be under force control. However, the methodology is also a shared control scheme because some degrees of freedom can be put under manual control and the other degrees of freedom put under computer control. Unlike other hybrid control schemes, which process position and force commands independently, this scheme provides a force control loop built on top of a position control inner loop. This feature minimizes the computational burden and increases disturbance rejection. A simple implementation is achieved partly because the joint control servos that are part of most robots can be used to provide the position control inner loop. Along with this control scheme, several menus were implemented for the convenience of the user. The implemented control scheme was successfully demonstrated for the tasks of hinged-panel opening and peg-in-hole insertion.

Lee, Jin S.↗
NASA NTRS1988

Deep crustal deformation by sheath folding in the Adirondack Mountains, USA

As described by McLelland and Isachsen, the southern half of the Adirondacks are underlain by major isoclinal (F sub 1) and open-upright (F sub 2) folds whose axes are parallel, trend approximately E-W, and plunge gently about the horizontal. These large structures are themselves folded by open upright folds trending NNE (F sub 3). It is pointed out that elongation lineations in these rocks are parallel to X of the finite strain ellipsoid developed during progressive rotational strain. The parallelism between F sub 1 and F sub 2 fold axes and elongation lineations led to the hypothesis that progressive rotational strain, with a west-directed tectonic transport, rotated earlier F sub 1-folds into parallelism with the evolving elongation lineation. Rotation is accomplished by ductile, passive flow of F sub 1-axes into extremely arcuate, E-W hinges. In order to test these hypotheses a number of large folds were mapped in the eastern Adirondacks. Other evidence supporting the existence of sheath folds in the Adirondacks is the presence, on a map scale, of synforms whose limbs pass through the vertical and into antiforms. This type of outcrop pattern is best explained by intersecting a horizontal plane with the double curvature of sheath folds. It is proposed that sheath folding is a common response of hot, ductile rocks to rotational strain at deep crustal levels. The recognition of sheath folds in the Adirondacks reconciles the E-W orientation of fold axes with an E-W elongation lineation.

Mclelland, J. M.↗
NASA NTRS1988

Structural relations of charnockites of South India

The structural features of the Peninsular gneisses were discussed and compared with those in the charnockitic rocks. On this basis, three types of charnockite occurrences can be recognized: those involved in isoclinal folds that were later boudinaged and refolded, those affected by migmatization synkinematic with early isoclinal folding, and incipient charnockites formed in low-pressure zones of fold-hinges and boudin-necks (e.g., Kabbaldurga). It was concluded that at least two, if not three, stages of charnockite formation are required by these structural data.

Naha, K.↗