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All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

WISE 2005: LBNP Exercise and Flywheel Resistive Exercise as an Effective Countermeasure Combination

Long-term exposure to microgravity can cause a severe musculoskeletal loss and cardiovascular deconditioning in astronauts. In this report, the effectiveness of combined supine treadmill exercise in a lower body negative pressure chamber (LBNPex) and flywheel resistive exercise (Rex) countermeasures was determined to prevent bone loss, reduced aerobic upright exercise capacity and reduced muscle strength. We hypothesized that exercise subjects (EX) would show less decrease in bone mineral density (BMD), peak oxygen consumption (VO2pk) and knee extensor strength (KES) than control subjects (CON). Sixteen healthy female subjects (34 plus or minus 4yrs, 164 plus or minus 6.5cm, 58 plus or minus 5kg; mean plus or minus SD) participated in a 60-d 6 degree head-down tilt bed rest (BR) study after providing written informed consent. Subjects were assigned to one of two groups: a non- exercising CON group or an EX group performing LBNPex 2-4 d/wk and Rex every 3rd-d. VO2pk was measured with a maximal, graded, upright treadmill test performed pre-BR and on 3-d after BR. BMD was assessed pre-BR and 3-d after BR by dual energy x-ray absorptiometry total body DEXA scan (DEXA; HOLOGIC QDR 4500 Elite ). A Cybex dynamometer was employed to measure the isokinetic KES before and 5-d after BR. Two-way repeated measures ANOVA were performed with time as the repeated factor. Statistical significance was set at p less than 0.05. CON experienced a significant decrease in BMD in the trochanter (PRE: 0.670 0.045; POST: 0.646 0.352 g(raised dot) per square centimeter) and in the whole hip (PRE: 0.894 0.059; POST: 0.858 0.057 g(raised dot) per square centimeter). BMD also decreased significantly in EX in the trochanter (PRE: 0.753 plus or minus 0.0617; POST: 0.741 plus or minus 0.061 g(raised dot) per square centimeter) and whole hip (PRE: 0.954 plus or minus 0.067; POST: 0.935 plus or minus 0.069 g(raised dot) per square centimeter). BMD losses were significantly less in EX than in CON subjects. VO2pk was significantly decreased in the CON after BR (PRE: 38.0 plus or minus 4.8; POST: 29.9 plus or minus 4.2 ml(raised dot) per kilogram per minute), but not in the EX (PRE: 39.0 plus or minus 2.0; POST: 37.8 plus or minus 1.9 ml(raised dot) per kilogram per minute). KES was significantly reduced by 30% in CON (PRE: 113 plus or minus 12; POST: 78 plus or minus 8 N-m), but was not different in EX (PRE: 126 plus or minus 25; POST: 115 plus or minus 25 N-m). The combination LBNPex and Rex during 60-d BR protects against cardiovascular and musculoskeletal deconditioning and may be an efficacious countermeasure for prolonged space flight.

Meuche, S.↗
NASA NTRS1946

Performance of the Modified V-1710-93 Engine-Stage Supercharger with a Constant-Area Vaneless Diffuser

As part of an investigation to increase the power output of the V-1710-93 engine at altitude, the engine-stage supercharger was combined with a constant-area vaneless diffuser designed to improve the performance of the engine-stage supercharger at the rated engine operating point. The performance of the modified supercharger was investigated in a variable-component supercharger test rig and compared with that of the standard supercharger with an 8-vaned diffuser. A separate evaluation of the component efficiencies and a study of the flow characteristics of the modified supercharger was made possible by internal diffuser instrumentation. At the volume flow required by the engine for rated operating conditions, the modified supercharger increased the over-all adiabatic efficiency 0.05 and the over-all pressure coefficient 0.035. Furthermore, the capacity of the engine-stage supercharger was increased by replacing the standard 8-vaned diffuser with the vaneless diffuser. The peak over-all adiabatic efficiency for the modified supercharger, however, was 0.05 to 0.07 lower than that of the standard unit over the range of tip speeds investigated. The improved performance of the modified supercharger at rated engine operating conditions resulted from a shift of the point of peak adiabatic efficiency and pressure coefficient of the standard supercharger to a higher flow. The energy loss through the vaneless diffuser was found to be small. Because of the restricted diffuser diameter, however, diffusion was inadequate, which resulted in a relatively small static-pressure rise through the diffuser, high diffuser-exit velocities, and excessive collector-case losses.

Douglas, John E.↗
NASA NTRS2001

Safer Aviation Materials Tested

A series of thermally stable polymer samples were tested. These materials are called low heat release materials and are designed for aircraft interior decorative materials. The materials are designed to give off a minimum amount of noxious gases when heated, which increases the possibility that people can escape from a burning aircraft. New cabin materials have suitably low heat release so that fire does not spread, toxic chemicals are not given off, and the fire-emergency escape time for crew and passengers is lengthened. These low heat-release materials have a variety of advantages and applications: interiors for ground-based facilities, interiors of space vehicles, and many commercial fire-protection environments. A microscale combustion calorimeter at the Federal Aviation Administration's (FAA) Technical Center tested NASA Langley Research Center materials samples. The calorimeter is shown. A sharp, quantitative, and reproducible heat-release-rate peak is obtained in the microscale heat-release-rate test. The newly tested NASA materials significantly reduced the heat release capacity and total heat release. The thermal stability and flammability behavior of the samples was very good. The new materials demonstrated a factor of 4 reduction in total heat release over ULTEM (a currently used material). This information is provided in the following barchart. In other tests, the materials showed greater than a factor 9 reduction in heat-release capacity over ULTEM. The newly tested materials were developed for low dielectric constant, low color, and good solubility. A scale up of the material samples is needed to determine the repeatability of the performance in larger samples. Larger panels composed of the best candidate materials will be tested in a larger scale FAA Technical Center fire facility. The NASA Glenn Research Center, Langley (Jeff Hinkley), and the FAA Technical Center (Richard Lyon) cooperatively tested these materials for the Accident Mitigation aspects of Fire Prevention under NASA's Aviation Safety Program.

Palaszewski, Bryan A.↗
NASA NTRS1996

Relation of systemic and local muscle exercise capacity to skeletal muscle characteristics in men with congestive heart failure

OBJECTIVES. The present study was undertaken to further characterize changes in skeletal muscle morphology and histochemistry in congestive heart failure and to determine the relation of these changes to abnormalities of systemic and local muscle exercise capacity. BACKGROUND. Abnormalities of skeletal muscle appear to play a role in the limitation of exercise capacity in congestive heart failure, but information on the changes in muscle morphology and biochemistry and their relation to alterations in muscle function is limited. METHODS. Eighteen men with predominantly mild to moderate congestive heart failure (mean +/- SEM New York Heart Association functional class 2.6 +/- 0.2, ejection fraction 24 +/- 2%) and eight age- and gender-matched sedentary control subjects underwent measurements of peak systemic oxygen consumption (VO2) during cycle ergometry, resistance to fatigue of the quadriceps femoris muscle group and biopsy of the vastus lateralis muscle. RESULTS. Peak VO2 and resistance to fatigue were lower in the patients with heart failure than in control subjects (15.7 +/- 1.2 vs. 25.1 +/- 1.5 ml/min-kg and 63 +/- 2% vs. 85 +/- 3%, respectively, both p < 0.001). Patients had a lower proportion of slow twitch, type I fibers than did control subjects (36 +/- 3% vs. 46 +/- 5%, p = 0.048) and a higher proportion of fast twitch, type IIab fibers (18 +/- 3% vs. 7 +/- 2%, p = 0.004). Fiber cross-sectional area was smaller, and single-fiber succinate dehydrogenase activity, a mitochondrial oxidative marker, was lower in patients (both p < or = 0.034). Likewise, the ratio of average fast twitch to slow twitch fiber cross-sectional area was lower in patients (0.780 +/- 0.06 vs. 1.05 +/- 0.08, p = 0.019). Peak VO2 was strongly related to integrated succinate dehydrogenase activity in patients (r = 0.896, p = 0.001). Peak VO2, resistance to fatigue and strength also correlated significantly with several measures of fiber size, especially of fast twitch fibers, in patients. None of the skeletal muscle characteristics examined correlated with exercise capacity in control subjects. CONCLUSIONS. These results indicate that congestive heart failure is associated with changes in the characteristics of skeletal muscle and local as well as systemic exercise performance. There are fewer slow twitch fibers, smaller fast twitch fibers and lower succinate dehydrogenase activity. The latter finding suggests that mitochondrial content of muscle is reduced in heart failure and that impaired aerobic-oxidative capacity may play a role in the limitation of systemic exercise capacity.

Non-NASA Center↗
NASA NTRS1988

High temperature fatigue behavior of Haynes 188

The high temperature, creep-fatigue behavior of Haynes 188 was investigated as an element in a broader thermomechanical fatigue life prediction model development program at the NASA-Lewis. The models are still in the development stage, but the data that were generated possess intrinsic value on their own. Results generated to date is reported. Data were generated to characterize isothermal low cycle fatigue resistance at temperatures of 316, 704, and 927 C with cyclic failure lives ranging from 10 to more than 20,000. These results follow trends that would be predicted from a knowledge of tensile properties, i.e., as the tensile ductility varies with temperature, so varies the cyclic inelastic straining capacity. Likewise, as the tensile strength decreases, so does the high cyclic fatigue resistance. A few two-minute hold-time cycles at peak compressive strain were included in tests at 760 C. These results were obtained in support of a redesign effort for the Orbital Maneuverable System engine. No detrimental effects on cyclic life were noted despite the added exposure time for creep and oxidation. Finally, a series of simulated thermal fatigue tests, referred to as bithermal fatigue tests, were conducted using 316 C as the minimum and 760 C as the maximum temperature. Only out-of-phase bithermal tests were conducted to date. These test results are intended for use as input to a more general thermomechanical fatigue life prediction model based on the concepts of the total strain version of Strainrange Partitioning.

Halford, Gary R.↗
NASA NTRS1972

The ALOHA SYSTEM

The report provides a status report and description of THE ALOHA SYSTEM research project at the University of Hawaii. THE ALOHA SYSTEM involves the analysis and construction of advanced methods of random access communications in large computer-communication systems. The existing ALOHA SYSTEM computer-communication network uses two 24,000 baud channels in the UHF band. The system employs message switching techniques similar to those of the ARPANET, in conjunction with a novel form of random access radio channel multiplexing. By means of these techniques the system has the capacity to accommodate several hundred active users of alphanumeric consoles on the two channels available. Each of these users can transmit and receive at a peak data rate of 24,000 baud although the average data rate of the users must of course be considerably less.

Abramson, N.↗
NASA NTRS1988

Characterization of direct readout Si:Sb and Si:Ga infrared detector arrays for space-based astronomy

Preliminary test results from the evaluation of Si:Sb and Si:Ga 58 x 62-element infrared detector arrays are presented. These devices are being characterized under background conditions and readout rates representative of operation in orbiting, crogenically-cooled infrared observatories. The arrays are hybridized to silicon direct-readout multiplexers which allow random-access and nondestructive readout. Array performance optimization is being conducted with a flexible microcomputer-based drive and readoaut electronics system. Preliminary Si:Sb measurements indicate a sense node capacitance of 0.06 pF, peak (28-micron) responsivity above 3 A/W at 2V bias, read noise of 130 rms e(-), dark current approximately 10 e(-)/s, and a well capacity greater than 10 to the 5th e(-). The limited test data available on the performance of the Si:Ga array are also discussed.

Mckelvey, Mark E.↗
NASA NTRS1994

Magnetobraking: Use of tether electrodynamic drag for Earth return from Mars

It has often been proposed that a vehicle returning from Mars will use aerobraking in the Earth's atmosphere to dissipate hyperbolic excess velocity to capture into Earth orbit. Here a different system for dissipating excess velocity without expenditure of reaction mass, magnetobraking, is proposed. Magnetobraking uses the force on an electrodynamic tether in the Earth's magnetic field to produce thrust. An electrodynamic tether is deployed from the spacecraft as it approaches the Earth. The Earth's magnetic field produces a force on electrical current in the tether. If the tether is oriented perpendicularly to the Earth's magnetic field and to the direction of motion of the spacecraft, force produced by the Earth's magnetic field can be used to either brake or accelerate the spacecraft without expenditure of reaction mass. The peak acceleration on the Mars return is 0.007 m/sq sec, and the amount of braking possible is dependent on the density and current-carrying capacity of the tether, but is independent of length. A superconducting tether is required. The required critical current is shown to be within the range of superconducting technology now available in the laboratory.

Landis, Geoffrey A.↗
NASA NTRS1978

Historical evidence of importance to the industrialization of flat-plate silicon photovoltaic systems. Volume 1: Executive summary

An analysis is given of the Low-Cost Silicon Solar Array Project plans for the industrialization of new production technologies expected to be forthcoming as a result of the project's technology development efforts. In particular, LSSA's mandate to insure an annual production capability of 500 MW peak for the photovoltaic supply industry by 1986 is critically examined. The examination focuses on one of the concerns behind this goal -- timely development of industrial capacity to supply anticipated demand. Some of the conclusions include: (1) construction of small-scale pilot plants should be undertaken only for purposes of technology development; (2) large-scale demonstrations should be undertaken only when the technology is well in hand; (3) commercial-scale production should be left to the private sector; (4) the 500-MW annual output goal should be shifted to Program Headquarters.

Smith, J. L.↗
NASA NTRS1977

The standard 20 AH battery

The modular power system, which is the first intended use for the NASA standard battery, is basically a four foot by four foot by eighteen inch box which can handle a complement of three 20 ampere hour batteries or later on the intended use is for three 50 ampere hour batteries to be the full complement. The system is designed to be used as a plug on component on a multi mission modular spacecraft. It has as a design point a basically 1250 watt orbital average load. The way it breaks up in a near earth orbit it would be somewhere around 1,000 watts for everything except 10 minutes, and during any 10 minute period it may go up to a peak of 3,000 watt load. Features of the battery reviewed include criteria to store electrical energy, the battery package, the covers and cases, and electrolytes. The capacities expected are 90 percent, the average cell capacity for 24 C, 90 percent of the actual battery capacity of 19 C, and 85 percent of the actual 25 degree battery capacity at zero discharge voltage for 50 percent DOD new battery is in the vicinity expected or predicted of 26.4 volts.

Zollner, M. T.↗
NASA NTRS2007

Canopy Level Solar Induced Fluorescence for Vegetation in Controlled Experiments

Solar induced chlorophyll fluorescence (SIF) was retrieved from high resolution reflectance spectra acquired one meter above saplings of three deciduous tree species during springtime (three weeks after leaf flush) and in late summer when foliage was mature. SIF was determined by application of the Fraunhofer Line Depth (FLD) Principal to above-canopy spectra acquired with an Analytical Spectral Devices (ASD) Fieldspec spectroradiometer (3.2 nm resolution with 1.2 nm sampling interval). SIF retrievals were made at the two atmospheric oxygen (O2) absorption features that occur in the chlorophyll fluorescence (ChlF) region (660 -780 nm). These telluric features are 02V, the broader and deeper feature centered at 760 nm, but located on the shoulder of the far-red ChlF peak at 740 nm; and 023, a narrow feature centered at 688 nm that is positioned near the red ChlF peak at 685 nm. Supporting, coincident leaf level fluorescence, reflectance, photochemical and other measurements were also made. At the leaf level, these measurements included in situ photosynthetic capacity (Pmax) and light adapted total chlorophyll fluorescence (Fs') collected at steady state under high light and controlled chamber conditions (e.g., temperature, PAR, humidity, and COz); optical properties (reflectance, transmittance, absorptance); chlorophyll and carotenoid content; specific leaf mass; carbon (C) and nitrogen (N) content; fluorescence emission spectra at multiple excitation wavelengths; the ChlF contribution to red (R) and far-red (FR) reflectance; fluorescence imagery; and fluorescence excitation-emission matrices (EEMs). The tree species examined were tulip poplar (Liriodendron tulipifera L.), red maple (Acer rubrum L.), and sweetgum (Liquidambar styraczflua L.), and each had been provided four levels of N augmentation (0, 19, 37, and 75 kg Nhectare seasonally) to simulate atmospheric deposition from air pollution. Whole-plant SIF measurements of these species were compared with SIF estimates derived using FluorMOD, a radiative transfer model that includes fluorescence properties of foliage, when provided with our supporting measurements. Simulated values for SIF were also compared with similar estimates made over three years for corn (Zea mays L) crops under N treatments (20, 50,70, and 140 kg Nhectare) and with corn and pepper (Capsicum annuum L.) plants provided dimethyl urea (DCMU, 0 and 5 x 10" M) which were grown in pots and grouped in artificial canopies for spectral measurements. For near-surface measurements of healthy and stressed vegetation, red SIF retrieved at 688 nm (023) varied between 2-7 mW/m(exp 2)/nm/sr while far-red SIF retrieved at 760 nm (O2A) varied between 0.5 and 4.0 mW/m(exp 2)/nm/sr. Typical values for the SIF red/far-red ratio ranged between 1.75 and 4.0. Relationships of SIF to spectral reflectance indices and foliar photochemical indices were examined, such as photosynthetic light use efficiency. Initial investigations of the variability in these measurements at the same leaf temperature for sunlit and shaded foliage showed us that shaded foliage produced higher ChlF and light use efficiency. Other factors that affect SIF determinations are discussed. These results will assist in determine the expected intensity of the SIF signal from vegetation near the surface, as well as to identify enhancements needed for FluorMOD (or other such models), and will assist in determining relationships of SIF to reflectance indices and carbon dynamics.

Middleton, E. M.↗
NASA NTRS2005

Optimizing Parameters for Deep-Space Optical Communication

A paper discusses the optimization of the parameters of a high-rate, deep-space optical communication link that utilizes pulse-position modulation (PPM) and an error-correcting code (ECC). The parameters in question include the PPM order (number of pulse time slots in one symbol period), the ECC rate, and the uncoded symbol error rate. In simple terms, the optimization problem is to choose the combination of these parameters that maximizes the throughput data rate at a given bit-error-rate (BER), subject to several constraints, including limits on the average and peak power and possibly a limit on the uncoded symbol error rate. This is a complex, multidimensional optimization problem, the solution of which involves computation of channel capacities for various combinations of the parameters. The paper presents extensive theoretical analyses and numerical predictions that elucidate the many facets of the optimization problem. It shows how a nearly optimum solution can be obtained by choosing the optimum PPM order for the desired number of bits per slot and concatenating the PPM mapping with an error-correction code so that the decoded bits satisfy some BER threshold.

Moison, Bruce↗
NASA NTRS1997

NiH2 Battery Reconditioning for LEO Applications

This paper summarizes reasons for and benefits of reconditioning nickel-hydrogen (NiH2) batteries used for Low Earth Orbit (LEO) applications. NiH2 battery cells do not have the classic discharge voltage problems more commonly associated with nickel-cadmium (NiCd) cells. This is due, in part, to use of hydrogen electrodes in place of cadmium electrodes. The nickel electrode, however, does have a similar discharge voltage signature for both cell designs. This can have an impact on LEO applications where peak loads at higher relative depths of discharge can impact operations. Periodic reconditioning provides information which can be used for analyzing long term performance trends to predict usable capacity to a specified voltage level. The reconditioning process described herein involves discharging NiH2 batteries at C/20 rates or less, to an average cell voltage of 1.0 volts or less. Recharge is performed at nominal C/5 rates to specified voltage/temperature (V/T) charge levels selected to restore required capacity with minimal overcharge. Reconditioning is a process of restoring reserve capacity lost on cycling, which is commonly called the memory effect in NiCd cells. This effect is characterized by decreases in the discharge voltage curve with operational life and cycling. The end effect of reconditioning NiH2 cells may be hidden in the versatility, of that design over the NiCd cell design and its associated negative electrode fading problem. The process of deep discharge at lower rates by way of reconditioning tends to redistribute electrolyte and water in the NiH2 cell electrode stack, while improving utilization and charge efficiency. NiH2 battery reconditioning effects on life are considered beneficial and may, in fact. extend life based on NiCd experience. In any case, usable capacity data obtained from reconditioning is required for performance evaluation and trend analysis. Characterization and life tests have provided the historical data base used to determine the need for reconditioning in most battery applications. The following sections briefly describe the background of NiH2 battery reconditioning and testing at Lockheed Martin Missiles & Space (LMMS) and other aerospace companies.

Armantrout, J. D.↗
NASA NTRS1978

Historical Evidence of Importance to the Industrialization of Flat-plate Silicon Photovoltaic Systems, Volume 2

Problems which may arise as the low cost silicon solar array (LSSA) project attempts to industrialize the production technologies are defined. The charge to insure an annual production capability of 500 MW peak for the photovoltaic supply industry by 1986 was critically examined, and focused on one of the motivations behind this goal-concern over the timely development of industrial capacity to supply anticipated demand. Conclusions from the analysis are utilized in a discussion of LSSA's industrialization plans, particularly the plans for pilot, demonstration and commercial scale production plants. Specific recommendations for the implementation of an industrialization task and the disposition of the project quantity goal were derived.

Smith, J. L.↗
NASA NTRS1986

Computer simulation of immobilized pH gradients at acidic and alkaline extremes - A quest for extended pH intervals

Computer simulations of the concentration profiles of simple biprotic ampholytes with Delta pKs 1, 2, and 3, on immobilized pH gradients (IPG) at extreme pH values (pH 3-4 and pH 10-11) show markedly skewed steady-state profiles with increasing kurtosis at higher Delta pK values. Across neutrality, all the peaks are symmetric irrespective of their Delta pK values, but they show very high contribution to the conductivity of the background gel and significant alteration of the local buffering capacity. The problems of skewness, due to the exponential conductivity profiles at low and high pHs, and of gel burning due to a strong electroosmotic flow generated by the net charges in the gel matrix, also at low and high pHs, are solved by incorporating in the IPG gel a strong viscosity gradient. This is generated by a gradient of linear polyacrylamide which is trapped in the gel by the polymerization process.

Mosher, Richard A.↗
NASA NTRS1988

Fast Data Acquisition For Mass Spectrometer

New equipment has speed and capacity to process time-of-flight data. System relies on fast, compact waveform digitizer with 32-k memory coupled to personal computer. With digitizer, system captures all mass peaks on each 25- to 35-microseconds cycle of spectrometer.

Lincoln, K. A.↗
NASA NTRS1988

Structural optimization of turbine blade firtrees

On the basis of the present optimization equation for the structural capacity of a turbine blade attachment firtree, the optimum of the lobe circular fillet radius in the blade and in the turbine disk is determined. In order to further diminish peak stress in firtree design, an elliptical fillet radius is selected in place of the circular one. Two-dimensional stress analysis results for a three-lobe firtree with elliptical radius shows a 14-percent stress reduction in the blade necks (where cracking has been experienced) over the current, four-lobe firtree design.

Lee, R. L.↗
NASA NTRS1974

A baseline maritime satellite communication system

This paper describes a baseline system for maritime communications via satellite during the 1980s. The system model employs three geostationary satellites with global coverage antennas. Access to the system is controlled by a master station; user access is based on time-ordered polling or random access. Each Thor-Delta launched satellite has an RF power of 100 W (spinner) or 250 W (three-axis stabilized), and provides 10 equivalent duplex voice channels for up to 1500 ships with average waiting times of approximately 2.5 minutes. The satellite capacity is bounded by the available bandwidth to 50 such channels, which can serve up to 10,000 ships with an average waiting time of 5 minutes. The ships must have peak antenna gains of approximately 15.5 dB or 22.5 dB for the two cases (10 or 50 voice channels) when a spinner satellite is used; the required gains are 4 dB lower if a three-axis stabilized satellite is used. The ship antenna requirements can be reduced by 8 to 10 dB by employing a high-gain multi-beam phased array antenna on the satellite.

Durrani, S. H.↗