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At least 163 records · Page 9

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NASA NTRS1986

Analytical determination of space station response to crew motion and design of suspension system for microgravity experiments

The objective of this investigation is to make analytical determination of the acceleration produced by crew motion in an orbiting space station and define design parameters for the suspension system of microgravity experiments. A simple structural model for simulation of the IOC space station is proposed. Mathematical formulation of this model provides the engineers a simple and direct tool for designing an effective suspension system.

Liu, F. C.↗

NASA NTRS1985

Effects of suspension hypokinesia/hypodynamia on rat skeletal muscle

The effects of suspension hypokinesia/hypodynamia (H/H) on properties of soleus and plantaris muscles of rats were studied. The objective was to compare the effects of this model to those of disuse atrophy. After 12 d of H/H, there were significant decreases in soleus and plantaris muscle wet weight and citrate synthase activity. Soleus muscle was affected to a greater extent than plantaris muscle. There was a significant decrease in noncollagen protein content of H/H soleus muscle. Triceps brachii muscles did not display significant changes in any parameters measured, suggesting that observed changes were not due to systemic factors. There was no significant change in the water content of H/H soleus or plantaris muscles. Suspension H/H causes muscle changes different from those secondary to limb immobilization, in which soleus and plantaris muscles are equally affected.

Max, S. R.↗

NASA NTRS1985

Responses of amino acids in hindlimb muscles to recovery from hypogravity and unloading by tail-cast suspension

Amino acids were assayed in muscles from rats exposed to 7 days of hypogravity and 12 h of gravity (F) or 6 days of suspension with (R) or without (H) 12 h of loading. In these groups, lower aspartate was common only to the soleus (SOL) relative to control muscles, the smallest difference being in group R. This difference in aspartate for F and H, but not for R, correlated with lower malate suggesting diminution of citric acid cycle intermediates. The R SOL value was increased over the H SOL. Therefore desite 12 h of loading, the F SOL was more comparable to the H SOL. The role of stress in preventing recovery of the F SOL was apparent from the ratios of glutamine/glutamate. Synthesis of glutamine is enhanced by glucocorticoids and is reflected by an increased ratio. In 5 of the 6 F muscles studied, this ratio was greater than in controls. In contrast, the ratio in all R muscles was similar to controls and showed recovery from the values in H muscles. Hence the post-flight treatment of F rats may have produced additional stress. Despite this stress, in some respects the SOL responses to hypogravity were similar to its responses to unloding by suspension.

Tischler, M. E.↗

NASA NTRS1987

Analytical determination of space station response to crew motion and design of suspension system for microgravity experiments

Liu, Frank C.↗

NASA NTRS1987

Airfoil flutter model suspension system

A wind tunnel suspension system for testing flutter models under various loads and at various angles of attack is described. The invention comprises a mounting bracket assembly affixing the suspension system to the wind tunnel, a drag-link assembly and a compound spring arrangement comprises a plunge spring working in opposition to a compressive spring so as to provide a high stiffness to trim out steady state loads and simultaneously a low stiffness to dynamic loads. By this arrangement an airfoil may be tested for oscillatory response in both plunge and pitch modes while being held under high lifting loads in a wind tunnel.

Reed, Wilmer H.↗

NASA NTRS1987

Electrokinetic properties of particles in concentrated suspensions

The electrokinetic behavior of concentrated suspensions is studied under conditions where the double layer is thin. Bulk electrical conductivity and single particle electrophoretic mobilities were studied as functions of the particle concentration in the suspension. It is found that the interactions between particles affect the conduction processes.

Zukoski, C. F.↗

NASA NTRS1988

Large-Angle Magnetic Suspension (LAMS)

Spherical LAMS is magnetic syspension that provides dual functions of magnetic bearing and rotorgimbal system. Provides two degrees of angular freedom within single magnetic suspension system. Approach employs spherically-shaped magnetic-gap surfaces to achieve much-larger angular freedom than available from previous suspensions.

Oglevie, Ronald E.↗

NASA NTRS1986

Status of magnetic suspension technology

The reasons for the continuing interest in the Magnetic Suspension and Balance System (MSBS) are highlighted. Typical problems that can arise because of model-support interference in a transonic wind tunnel are shown to illustrate the need for MSBS. The two magnetic suspension systems in operation at Langley are the only ones active in the U.S. One of these systems is the 13 inch MSBS which was borrowed from the Air Force Arnold Engineering Development Center. The other system is the 6 inch MSBS which was developed by MIT Aerophysics Laboratory with NASA and DOD funding. Each of these systems is combined with a subsonic wind tunnel. Ongoing research in both of these systems is covered. Last year, Madison Magnetics, Inc., completed a contractual design and cost study utilizing some advance concepts for a large MSBS which would be compatible with an 8 foot transonic wind tunnel and the highlights of the study are presented. Sverdrup Technology, Inc., recently performed a study under contract for Langley on the potential usefulness to the aerospace industry of a proposed large MSBS combined with a suitable transonic wind tunnel. The results of that study are discussed. Langley has partially funded the MSBS work at the University of Southampton for about 6 years under a grant arrangement and the major results are summarized.

Boyden, Richmond P.↗

NASA NTRS1987

Physiological comparison of rat muscle in body suspension and weightlessness

Hind limb unloading is achieved with whole body suspension (WBS) and with tail suspension (TS). Comparable levels of muscle mass loss and decreases in protein levels result during one to three weeks of exposure to microgravity (microG), WBS, and TS. Losses are most apparent in soleus (S), intermediate in gastrocnemius (G) and least in extensor digigorum longus (EDL). Comparison of S and EDL type I and II fiber changes (numbers and area) after seven days of microG flight and WBS showed, in S, an increase in Type I and Type II fiber density and a decrease in area. Except for a decrease in Type I fiber density in EDL, all other parameters remained comparable. The general conclusions were that the S under microG and WBS responds in a similar manner. The EDL, for the most part, shows little change under both conditions.

Musacchia, X. J.↗

NASA NTRS1987

Debarment and suspension

The changing Government attitude toward contractor debarment and suspension is examined, with emphasis on the fact that the Government is more alert to fraud, waste, and abuse. Consideration is given to causes of debarment or suspension, procedures and due process hearings, settlement agreements, compliance programs, and recent related legislation. It is concluded that the change in the Government contracting environment in recent years should be sufficient incentive for contractors to monitor their operations more closely.

Whelan, Thomas J.↗

NASA NTRS1988

The nonlinear behavior of a passive zero-spring-rate suspension system

Various concepts for advanced syspension systems have been proposed for counteracting gravity loads in ground vibration testing of large space structures. Approximating the flight modes of a low-frequency flexible structure in a ground test requires a very soft suspension system. The dynamic behavior of a passive zero-spring-rate mechanism, sometimes used for such ground testing, is analyzed. This mechanism reduces the stiffness inherent in suspending a test specimen by cables. However, the mechanism is shown to be sensitive to imperfections. Imperfections can initiate nonlinear behavior which becomes more pronounced at lower operating frequencies. Furthermore, large pendular motion of the suspension system couples with the vertical motion, producing additional nonlinearity.

Woodard, Stanley E.↗

NASA NTRS1988

A forecast of new test capabilities using Magnetic Suspension and Balance Systems

This paper outlines the potential of Magnetic Suspension and Balance System (MSBS) technology to solve existing problems related to support interference in wind tunnels. Improvement of existing test techniques and exciting new techniques are envisioned as a result of applying MSBS. These include improved data accuracy, dynamic stability testing, two-body/stores release testing, and pilot/designer-in-the-loop tests. It also discusses the use of MSBS for testing exotic configurations such as hybrid hypersonic vehicles. A new facility concept that combines features of ballistic tubes, magnetic suspension, and cryogenic tunnels is described.

Lawing, Pierce L.↗

NASA NTRS1988

Adaptation of bone and tendon to prolonged hindlimb suspension in rats

The effect of a sustained deprivation of ground reaction forces on mineralized and soft connective tissues was investigated in rats subjected to 28-d-long hind-limb suspension. The results of morphological and biochemical studies carried out on femurs and patellar tendons obtained from suspended and nonsuspended 110-d-old rats showed that prolonged suspension led to an increase of the minimum diameter of the femur middiaphysis (by 12 percent), without any significant alterations in cortical area, density, mineral and collagen concentrations, femur wet weight, length, and DNA and uronic acid concentrations. However, in the patellar tendons of suspended rats, the collagen and proteoglycan concentrations were 28 percent lower than in tendons obtained from nonsuspended animals. These results suggest that ground reaction forces are important for the maintenance of cortical bone and patellar tendon homeostasis during weight-bearing conditions.

Vailas, Arthur C.↗

NASA NTRS1988

Periodic weight support effects on rat soleus fibers after hindlimb suspension

The morphological and histochemical properties of rat soleus muscles were investigated following one week of hindlimb suspension. Short-duration daily weight support activity is shown to ameliorate, but not prevent, soleus atrophy induced by hindlimb suspension. The results indicate that fiber cross-sectional area is more responsive to periodic weight support in dark than light ATPas fibers, and that muscle fiber atrophy need not be associated with a loss in succinate dehydrogenase activity.

Hauschka, Edward O.↗

NASA NTRS1989

Analytical model of a five degree of freedom magnetic suspension and positioning system

An analytical model of a five degree of freedom magnetic suspension and positioning system is presented. The suspended element is a cylinder which is composed of permanent magnet material and the magnetic actuators are air core electromagnets mounted in a planar array. The analytical model consists of an open loop representation of the suspension and positioning system with electromagnet currents as inputs and displacements and rates in inertial coordinates as outputs. The uncontrolled degree of freedom is rotation about the long axis of the suspended cylinder.

Groom, Nelson J.↗

NASA NTRS1988

Design of ground test suspension systems for verification of flexible space structures

A simple model demonstrates the frequency-increasing effects of a simple cable suspension on flexible test article/suspension systems. Two passive suspension designs, namely a negative spring mechanism and a rolling cart mechanism, are presented to alleviate the undesirable frequency-increasing effects. Analysis methods are provided for systems in which the augmentations are applied to both discrete and continuous representations of test articles. The damping analyses are based on friction equivalent viscous damping. Numerical examples are given for comparing the two augmentations with respect to minimizing frequency and damping increases.

Cooley, V. M.↗

NASA NTRS1988

Fluid flow phenomena in the generation of boron carbide suspensions in magnesium melts

A mathematical representation is developed for the behavior of moderately concentrated magnesium-boron carbide suspensions when subjected to electromagnetic stirring or mechanical agitation. A power-law relationship is employed for the apparent non-Newtonian viscosity of the suspension.

Ilegbusi, O. J.↗

NASA NTRS1989

Very low frequency suspension systems for dynamic testing

Specifications for a Space Station suspension system which can provide rigid-body translation frequencies on the order of 0.1-0.2 Hz for a 50-foot payload weighing about 3400 lb and having a number of highly flexible appendages are discussed. Two suspension devices are considered, an all-mechanical passive device based on coil springs and a device using a combination of a passive pneumatic system and an active electromagnetic system. Test results show that both devices meet the initial requirements.

Kienholz, David A.↗