Search NASA⌕ Search

SEARCH · Search NASA

Results for “SUSPENSION”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Effect of suspension hypokinesia/hypodynamia on glucocorticoid receptor levels in rat hindlimb muscles

Ilyina-Kakueva et. al. (1976) conducted an investigation in which rats were exposed to weightlessness during the Cosmos program. An examination of the rats revealed a marked atrophy of hindlimb muscles. A suspension model has been developed to simulate these weightlessness-induced alterations. In agreement with the Cosmos studies, suspension hypokinesia/hypodynamia (H/H) results in differential atrophy of hindlimb muscles in rats. Recent studies have demonstrated elevated glucocorticoid receptor numbers in the gastrocnemius muscle following immobilization and denervation. One of the objectives of the present investigation was to evaluate the effect of suspension H/H on glucocorticoid receptor levels in rat hindlimb muscles. Another objective was to ascertain whether altered receptor levels reflect the differential nature of hindlimb muscle atrophy during suspension H/H. The obtained findings suggest that differential muscle atrophy resulting from H/H may result from differential alterations of glucocorticoid receptor levels.

Steffen, J. M.↗
NASA NTRS1984

A suspension model for hypokinetic/hypodynamic and antiorthostatic responses in the mouse

Hypokinetic/hypodynamic and antiorthostatic responses to weightlessness and bedrest were simulated in mice using a suspension technique. Animals were suspended for 1 or 2 weeks in an antiorthostatic posture and positioned to permit freedom of movement but eliminate load bearing by the hindlimbs. Suspended mice exhibited reduced food and water intakes and a rapid 10 percent decrease in body weight to a level which was maintained for the remainder of the suspension period. Diuresis was evident in suspended mice, but the natriuresis and kaliuresis previously observed in the suspended rat were not evident. Differential hindlimb muscle atrophy and increased excretion of urea and ammonia were also noted in suspended mice. Postsuspension recovery studies indicated that the recovery process was highly effective. These results document specific responses in the mouse and similarities in the responses of mice and rats to suspension. These studies expand the utility of the suspension model and suggest that the mouse may be useful in future studies simulating both weightlessness and bedrest.

Steffen, J. M.↗
NASA NTRS1985

Bone and muscle atrophy with suspension of the rat

In order to identify a suitable model for the study of muscle atrophy due to suspension in space, a modified version of the Morey tail suspension model was used to measure the atrophic responses of rat bone and muscle to 14-30 days of unloading of the hindlimbs. The progress of atrophy was measured by increases in methylene diphosphonate (MDP) uptake. It is found that bone uptake of methylene diphosphonate followed a phasic pattern similar to changes in the bone formation rate of immobilized dogs and cats. Increased MDP uptake after a period of 60 days indicated an accelerated bone metabolism. Maximum muscle atrophy in the suspended rats was distinctly different from immobilization atrophy. On the basis of the experimental results, it is concluded that the tail suspension model is an adequate simulation of bone atrophy due to suspension.

Leblanc, A.↗
NASA NTRS1985

Status of wind tunnel magnetic suspension research

This paper reports the status of the NASA Langley Research Center program aimed at the development of the technology required for large-scale Magnetic Suspension and Balance Systems. The use of magnetic suspension of the model in a wind tunnel is seen to be the only viable method to eliminate aerodynamic interference problems arising with mechanical model-supports. The two small-scale magnetic suspension systems in operation at Langley are the only ones now active in the U.S. The general features and capabilities of these two systems and all of the ongoing research in the use of magnetic suspension are described.

Boyden, R. P.↗
NASA NTRS1987

Effect of anabolic steroids on skeletal muscle mass during hindlimb suspension

The effect of treatment with an anabolic steroid (nandrolone decanoate) on the muscle mass of plantaris and soleus of a rats in hindlimb suspension, and on the isomyosin expression in these muscles, was investigated in young female rats divided into four groups: normal control (NC), normal steroid (NS), normal suspension (N-sus), and suspension steroid (sus-S). Steroid treatment of suspended animals (sus-S vs N-sus) was found to partially spare body weight and muscle weight, as well as myofibril content of plantaris (but not soleus), but did not modify the isomyosin pattern induced by suspension. In normal rats (NS vs NC), steroid treatment did enhance body weight and plantaris muscle weight; the treatment did not alter isomyosin expression in either muscle type.

Tsika, R. W.↗
NASA NTRS1988

Progress towards extreme attitude testing with Magnetic Suspension and Balance Systems

Progress is reported in a research effort aimed towards demonstration of the feasibility of suspension and aerodynamic testing of models at high angles of attack in wind tunnel Magnetic Suspension and Balance Systems. Extensive modifications, described in this paper, have been made to the Southampton University suspension system in order to facilitate this work. They include revision of electromagnet configuration, installation of all-new position sensors and expansion of control system programs. An angle of attack range of 0 to 90 deg is expected for axisymmetric models. To date, suspension up to 80 deg angle of attack has been achieved.

Britcher, Colin P.↗
NASA NTRS1990

Four-Wheel Vehicle Suspension System

Four-wheel suspension system uses simple system of levers with no compliant components to provide three-point suspension of chassis of vehicle while maintaining four-point contact with uneven terrain. Provides stability against tipping of four-point rectangular base, without rocking contact to which rigid four-wheel frame susceptible. Similar to six-wheel suspension system described in "Articulated Suspension Without Springs" (NPO-17354).

Bickler, Donald B.↗
NASA NTRS1989

NASA CSI suspension methods overview

New suspension techniques will be necesary for ground testing the flexible spacecraft anticipated in NASA's future space activity. The most complex spacecraft involve nonlinear maneuvering (i.e., large angle slewing) with articulating substructures such as remote manipulating systems. The NASA control-structure interaction (CSI) ground test method team has begun researching and developing methodology to suspend the future class of spacecraft. This overview describes the work completed thus far. The research objective and technical approach will be presented first. Second, will be a suspension device overview followed by an assessment of existing hardware. Two different mechanical zero-spring-rate mechanisms will be compared for optimal performance. Next, will be a description of how existing hardware can be evolved to meet more general suspension requirements. A comparison of suspending articulating structures overhead vs underneath will follow. After a few experimental results from the zero-spring-rate mechanism/air suspension cart will be concluding remarks and future work.

Woodard, Stanley E.↗
NASA NTRS1991

Torsional suspension system for testing space structures

A low frequency torsional suspension system for testing a space structure uses a plurality of suspension stations attached to the space structure along the length thereof in order to suspend the space structure from an overhead support. Each suspension station includes a disk pivotally mounted to the overhead support, and two cables which have upper ends connected to the disk and lower ends connected to the space structure. The two cables define a parallelogram with the center of gravity of the space structure being vertically beneath the pivot axis of the disk. The vertical distance between the points of attachment of the cables to the disk and the pivot axis of the disk is adjusted to lower the frequency of the suspension system to a level which does not interfere with frequency levels of the space structure, thereby enabling accurate measurement.

Reed, Wilmer H., III↗
NASA NTRS1987

Magnetic suspension and balance systems (MSBSs)

The problems of wind tunnel testing are outlined, with attention given to the problems caused by mechanical support systems, such as support interference, dynamic-testing restrictions, and low productivity. The basic principles of magnetic suspension are highlighted, along with the history of magnetic suspension and balance systems. Roll control, size limitations, high angle of attack, reliability, position sensing, and calibration are discussed among the problems and limitations of the existing magnetic suspension and balance systems. Examples of the existing systems are presented, and design studies for future systems are outlined. Problems specific to large-scale magnetic suspension and balance systems, such as high model loads, requirements for high-power electromagnets, high-capacity power supplies, highly sophisticated control systems and position sensors, and high costs are assessed.

Britcher, Colin P.↗
NASA NTRS1992

Overview of magnetic suspension research at Langley Research Center

An overview of research in small- and large-gap magnetic suspension systems at LaRC is presented. The overview is limited to systems which have been built as laboratory models or engineering models. Small-gap systems applications include the Annular Momentum Control Device (AMCD), which is a momentum storage device for the stabilization and control of spacecraft, and the Annular Suspension and Pointing System (ASPS), which is a general purpose pointing mount designed to provide orientation, mechanical isolation, and fine pointing space experiments. These devices are described and control and linearization approaches for the magnetic suspension systems for these devices are discussed. Large-gap systems applications at LaRC have been almost exclusively wind tunnel magnetic suspension systems. A brief description of these efforts is also presented.

Groom, Nelson J.↗
NASA NTRS1992

Computation of magnetic suspension of maglev systems using dynamic circuit theory

Dynamic circuit theory is applied to several magnetic suspensions associated with maglev systems. These suspension systems are the loop-shaped coil guideway, the figure-eight-shaped null-flux coil guideway, and the continuous sheet guideway. Mathematical models, which can be used for the development of computer codes, are provided for each of these suspension systems. The differences and similarities of the models in using dynamic circuit theory are discussed in the paper. The paper emphasizes the transient and dynamic analysis and computer simulation of maglev systems. In general, the method discussed here can be applied to many electrodynamic suspension system design concepts. It is also suited for the computation of the performance of maglev propulsion systems. Numerical examples are presented in the paper.

He, J. L.↗
NASA NTRS1992

Dynamics and control of a large displacement suspension system for ground testing of flexible space structures

As the development in flexible space structures expands, the need for an efficient and accurate suspension system for ground tests increases accordingly. In this article, a disk suspension system was developed. Analytical results describing the dynamics of a passive and active suspension system were generated given realistic parameters of the system. These results for the passive case, were then compared with the data obtained from an experimental model with initial displacement and random forcing inputs. The dynamics of the system was analyzed. Results show that the experimental model resembles closely the analytical model and therefore strongly suggests feasibility of such a suspension system.

Reaves, Mercedes C.↗
NASA NTRS1992

Laboratory evaluation of two advanced suspension devices for ground vibration testing of large space structures

In order to provide the advanced suspension technology needed to allow ground test measurement of free-body modal parameters, two advanced suspension devices, one passive, the other active, are evaluated on the basis of laboratory testing of each device type with rigid and flexible payloads. Rigid-body tests show the basic behavior of the devices when they are uncoupled from a test article near their bandwidth. Flexible body tests show how suspension device dynamics couple with the dynamics of a representative large space structure. For the flexible body testing, targets for the free-body modal parameters are developed from test-verified analysis of the representative structure suspended in an orientation which is only mildly sensitive to suspension constraints.

Cooley, Victor M.↗
NASA NTRS1993

Microgravity combustion of dust suspensions

Unlike the combustion of homogeneous gas mixtures, there are practically no reliable fundamental data (i.e., laminar burning velocity, flammability limits, quenching distance, minimum ignition energy) for the combustion of heterogeneous dust suspensions. Even the equilibrium thermodynamic data such as the constant pressure volume combustion pressure and the constant pressure adiabatic flame temperature are not accurately known for dust mixtures. This is mainly due to the problem of gravity sedimentation. In normal gravity, turbulence, convective flow, electric and acoustic fields are required to maintain a dust in suspension. These external influences have a dominating effect on the combustion processes. Microgravity offers a unique environment where a quiescent dust cloud can in principle be maintained for a sufficiently long duration for almost all combustion experiments (dust suspensions are inherently unstable due to Brownian motion and particle aggregation). Thus, the microgravity duration provided by drop towers, parabolic flights, and the space shuttle, can all be exploited for different kinds of dust combustion experiments. The present paper describes some recent studies on microgravity combustion of dust suspension carried out on the KC-135 and the Caravelle aircraft. The results reported are obtained from three parabolic flight campaigns.

Lee, John H. S.↗
NASA NTRS1992

The middeck active control experiment: Gravity and suspension effects

Viewgraphs on the Middeck Active Control Experiment (MACE): Gravity and Suspension Effects are presented. Topics covered include: gravity and suspension influences; gravity and suspension effects on structure; gravity effects on sensors and actuators; modeling of gravity and suspension effects on structure; geometric stiffness theory and initial static deformation calculation; modeling gravity's effect on accelerometers and PMA's; application to MACE; MACE EM configuration study; and MACE DM configuration study.

Crawley, Edward F.↗
NASA NTRS1993

Large angle magnetic suspension test fixture

Progress made under the subject grant in the period from 1 Nov. 1992 to 31 May 1993 is presented. The research involves the continued development of the Large Angle Magnetic Suspension Test Fixture (LAMSTF) and also the recommissioning of an additional piece of exisiting hardware. During the period in question, the initial configuration of LAMSTF was completed and made routinely and reliably operational. A digital phase advance controller was completed and documented. The goal of a controlled 360 deg rotation was achieved. Work started on the recommissioning of the Annular Suspension and Pointing System (ASPS). Work completed during the report period included: modeling; position sensing; controller; support of the Second International Symposium on Magnetic Suspension Technology; and recommissioning of the Annular Suspension and Pointing System.

Britcher, Colin P.↗
NASA NTRS1993

A large motion zero-gravity suspension system for experimental simulation of orbital construction and deployment

The design and implementation of a vertical degree of freedom suspension system is described which provides a constant force off-load condition to counter gravity over large displacements. By accommodating motions up to one meter for structures weighing up to 100 pounds, the system is useful for experiments which simulate orbital construction events such as docking, multiple component assembly, or structural deployment. A unique aspect of this device is the combination of a large stroke passive off-load device augmented by electromotive torque actuated force feedback. The active force feedback has the effect of reducing break-away friction by a factor of twenty over the passive system alone. The thesis describes the development of the suspension hardware and the control algorithm. Experiments were performed to verify the suspensions system's effectiveness in providing a gravity off-load and simulating the motion of a structure in orbit. Additionally, a three dimensional system concept is presented as an extension of the one dimensional suspension system which was implemented.

Straube, Timothy Milton↗