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At least 199 records · Page 11

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NASA NTRS1978

Extended duration Orbiter life support definition

Extending the baseline seven-day Orbiter mission to 30 days or longer and operating with a solar power module as the primary source for electrical power requires changes to the existing environmental control and life support (ECLS) system. The existing ECLS system imposes penalties on longer missions which limit the Orbiter capabilities and changes are required to enhance overall mission objectives. Some of these penalties are: large quantities of expendables, the need to dump or store large quantities of waste material, the need to schedule fuel cell operation, and a high landing weight penalty. This paper presents the study ground rules and examines the limitations of the present ECLS system against Extended Duration Orbiter mission requirements. Alternate methods of accomplishing ECLS functions for the Extended Duration Orbiter are discussed. The overall impact of integrating these options into the Orbiter are evaluated and significant Orbiter weight and volume savings with the recommended approaches are described.

Kleiner, G. N.↗

NASA NTRS1979

Extended duration orbiter study: CO2 removal and water recovery

Two electrochemical depolarized carbon dioxide concentrator subsystems were evaluated against baseline lithium hydroxide for (1) the baseline orbiter when expanded to accommodate a crew of seven (mission option one), (2) an extended duration orbiter with a power extension package to reduce fuel cell expendables (mission option two), and (3) an extended duration orbiter with a full capability power module to eliminate fuel cell expendables (mission option three). The electrochemical depolarized carbon dioxide concentrator was also compared to the solid amine regenerable carbon dioxide removal concept. Water recovery is not required for Mission Option One since sufficient water is generated by the fuel cells. The vapor compression distillation subsystem was evaluated for mission option two and three only. Weight savings attainable using the vapor compression distillation subsystem for water recovery versus on-board water storage were determined. Combined carbon dioxide removal and water recovery was evaluated to determine the effect on regenerable carbon dioxide removal subsystem selection.

Marshall, R. D.↗

NASA NTRS1979

The effect of the duration of jet aircraft flyover sounds on judged annoyance

The effect of the duration of jet aircraft flyover sounds on humans and the annoyance factor are examined. A nine point numerical category scaling technique is utilized for the study. Changes in the spectral characteristics of aircraft sounds caused by atmospheric attenuation are discussed. The effect of Doppler shifts using aircraft noises with minimal pure tone content is reported. The spectral content of sounds independent of duration and Doppler shift are examined by analysis of variance.

Shepherd, K. P.↗

NASA NTRS1981

SEL and EPNL noise duration coefficients for the 747 and T-38 aircraft

Duration coefficient were calculated for Boeing 747 and T-38 airplanes for sound exposure level (SEL) and effective perceived noise level (EPNL) scales. The measured SEL suration coefficients were 8.4 for the Boeing 747 and 5.5 for the T-38 result was in good agreement with a previous result for a similar F-5 airplane. In EPNL, the duration coefficients were 7.2 for the Boeing 747 and 5.7 for the T-38. The difference in the results between the two airplanes is believed to be due to their different engine noise source spectra. The difference in the Boeing 747 results in the two different metric was due to the different frequency weighting of A-weighted sound pressure level, used in SEL, and tone-corrected perceived noise level, used in EPNL, when applied to the 747 spectra.

Willshire, W. L., Jr.↗

NASA NTRS1983

Planning in time - Windows and durations for activities and goals

The present general purpose automated planner/scheduler generates parallel plans aimed at the achievement of goals having imposed time constraints, with both durations and start time windows being specifiable for sets of goal conditions. Deterministic durations of such parallel plan activities as actions, events triggered by circumstances, inferences, and scheduled events entirely outside the actor's control, are explicitly modeled and may be any computable function of the activity variables. The final plan network resembles a PERT chart. Examples are given from the traditional 'blocksworld', and from a realistic 'Spaceworld' in which an autonomous spacecraft photographs objects in deep space and transmits the information to earth.

Vere, S. A.↗

NASA NTRS1985

Photometric and spectroscopic gamma-ray observations of solar transient phenomena using long duration balloons

A program currently in progress to conduct extended duration spectroscopic and photometric observation of solar X-ray phenomena from balloons is described. High photometric sensitivity to weak hard X-ray bursts is attained using a 600 sq cm array of phoswich scintillators. High spectral resolution for stronger bursts is available from an array of planar germanium detectors. These instruments are carried in a novel balloon gondola dssigned for the 15 to 20 day float durations available through using conventional zero pressure balloons in the radiation controlled (RACOON) mode.

Pelling, M. R.↗

NASA NTRS1985

Pitch change thresholds as influenced by angular rate and duration of the apparent horizon's displacement

The displacement threshold (DT) during voluntary visual tracking of a line and during fixation of a stable spot located at the initial stimulus position was determined to help in the modeling pilot manual dynamics during the nose-up 'flare' maneuver. Forty-six observers made paired comparison, forced choice judgments of the maximal downward displacements of a horizontal line moving at various speeds for the durations of 0.25, 0.50, and 1.00 sec. The results indicated that the DT is significantly lower, the confidence is higher, and the number of errors and guesses is smaller when a fixation dot is present; moreover, increasing both the stimulus velocity and duration significantly improves the accuracy of displacement discrimination and increases mean confidence.

Haines, R. F.↗

NASA NTRS1988

Crew productivity issues in long-duration space flight

Considerable evidence suggests the importance of teamwork, coordination, and conflict resolution to the performance and survival of isolated, confined groups in high-technology environments. With the advent of long-duration space flight, group-related issues of crew functioning will take on added significance. This paper discusses the influence of crew roles, status, leadership, and norms on the performance of small, confined groups, and offers guidelines and suggestions regarding organizational design, crew selection, training, and team building for crew productivity and social well-being in long-duration spaceflight.

Nicholas, John M.↗

NASA NTRS1988

Vertical displacement threshold sensitivity along the horizontal meridian as a function of stimulus rate, duration, and length

Four independent variables of visual perception during binocular viewing were studied. In 24 observers, the vertical displacement threshold (DT) sensitivity along the horizontal meridian was determined as a function of the rate, duration, and length of the stimulus. It was found that the DT increases with an increased angular separation of the stimulus image from the fovea (i.e., the stimulus must move farther in order to be correctly discriminated as having moved). In addition, it was found that the sensitivity to the stimulus displacement increases with increasing of the stimulus length, duration, and/or angular rate. These findings are related to the design optimization of dynamic attitude displays and symbology for aircraft.

Haines, Richard F.↗

NASA NTRS1989

A model for plasma volume changes during short duration spaceflight

It is well established that plasma volume decreases during spaceflight and simulated weightlessness (bedrest). The decrement in plasma volume is thought to contribute to the orthostatic intolerance that has been observed in some crew members following spaceflight. To date, no studies have evaluated the effectiveness of fluid countermeasures of varying osmolality in the restoration of plasma volume and orthostatic tolerance in a controlled study. The overall objectives of this project were to: (1) provide a model that would rapidly and safely produce a fluid loss comparable to that which occurs during short duration spaceflight; and (2) design a study that would determine the optimal drink solution to restore orthostatic tolerance and describe the mechanism(s) whereby orthostatic tolerance is restored. In summary, Lasix can be used as a way of simulating the plasma volume changes that occur during short duration spaceflight. The total loss of plasma is comparable to spaceflight. Lasix is fast acting, and has relatively few side effects. The present design for evaluating the optimal fluid countermeasures will have important implications in restoring orthostatic tolerance and function in the latter stages of spaceflight when it is essential for safe operation of the spacecraft.

Davis, John E.↗

NASA NTRS1989

Coronal mass ejections and associated X-ray flare durations

It is found that 22 percent of a sample of M1 or greater impulsive soft X-ray flares were associated with coronal mass ejections (CMEs) observed in the Solwind coronagraph. These flares were more energetic than similar impulsive flares without CMEs, and the associated CMEs were narrow (5-40 deg) in angular width. A survey of all CMEs associated with M1 or greater X-ray flares reveals a good correlation between flare duration CME angular width. The H-alpha characteristics of impulsive, CME-associated flares suggest that they are not the dynamic or eruptive flares presumed to be associated with CMEs, but rather, are confined flares. The H-alpha flare locations are neither centered under the CME legs. The disparity in size scales between the CMEs and their associated flares leaves the basis of the correlation between CME width and X-ray flare duration unresolved.

Kahler, S. W.↗

NASA NTRS1991

Results of the TTF-TCNQ- and the calcium carbonate-crystallization on the Long Duration Exposure Facility

Experiment AO139A on the Long Duration Exposure Facility (LDEF) carried four large containers into orbit for five years with crystal growth solutions for lead sulfide, calcium carbonate, and tetra thiafulvalene- tetra cyanoquino methane (TTF-TCNQ). The LDEF was in excellent condition after the long orbital stay, and although the temperature data was lost, the experiment program had been working since the valves in all containers were opened. All four experiments produced crystals; however, they were of varying quality. The calcium carbonate crystals had the best appearance. The TTF-TCNQ crystals were packed together near the valve openings of the container. When taken apart, the single crystals showed some unusual morphological properties. X-ray investigations as well as conductivity measurements on the long duration space grown TTF-TCNQ crystals are presented, and pictures of the calcium carbonate are shown. Comparisons are made with previous space solution growth experiments on the European Spacelab Mission and the Apollo-Soyuz Test Project.

Nielsen, Kjeld Flemming↗

NASA NTRS1991

Space mechanisms needs for future NASA long duration space missions

Future NASA long duration missions will require high performance, reliable, long lived mechanical moving systems. In order to develop these systems, high technology components, such as bearings, gears, seals, lubricants, etc., will need to be utilized. There has been concern in the NASA community that the current technology level in these mechanical component/tribology areas may not be adequate to meet the goals of long duration NASA mission such as Space Exploration Initiative (SEI). To resolve this concern, NASA-Lewis sent a questionnaire to government and industry workers (who have been involved in space mechanism research, design, and implementation) to ask their opinion if the current space mechanisms technology (mechanical components/tribology) is adequate to meet future NASA Mission needs and goals. In addition, a working group consisting of members from each NASA Center, DoD, and DOE was established to study the technology status. The results of the survey and conclusions of the working group are summarized.

Fusaro, Robert L.↗

NASA NTRS1990

Strategies for crew selection for long duration missions

Issues surrounding psychological reactions to long duration spaceflight are discussed with respect to the definition of criteria for selecting crewmembers for such expeditions. Two broad dimensions of personality and behavior are defined - Instrumentality including achievement orientation, leadership, and ability to perform under pressure and Expressivity encompassing interpersonal sensitivity and competence. A strategy for validating techniques to select in candidates with the optimum psychological profile to perform successfully on long duration missions is described.

Helmreich, Robert L.↗

NASA NTRS1990

Neuronal plasticity in relation to long-duration spaceflight

Exposure to microgravity leads to a marked reduction in sensory-motor stimuli to the vestibular, proprioceptive and somatosensory systems. Long-duration missions, such as those proposed for a trip to Mars, may lead to significant changes in neural function. This paper presents results based on studies of sensory deafferentation of specific brain regions and detailed changes which occur in neuronal architecture. Data from these studies emphasize the need for further research related to sensory system deprivation and the development of new unique countermeasures for long-duration space flight.

Hillman, Dean E.↗

NASA NTRS1991

Long Duration Exposure Facility (LDEF) results

This paper presents an overview of the initial observations of the Long Duration Exposure Facility and the 57 onboard experiments which were retrieved from space on January 12, 1990, during the Space Shuttle STS Mission 32. The facility and the 57 science, technology, and applications experiments had remained in space for almost 6 years. The initial and the continuing observations of this retrieved hardware have provided, and will continue to provide for a number of years in the future, a wealth of basic science data on the environments of near-earth space and a unique opportunity to observe and study long duration synergistic effects of these space environments on a large array of typical spacecraft materials and systems.

Kinard, William H.↗

NASA NTRS1991

Mathematical modeling of acute and chronic cardiovascular changes during Extended Duration Orbiter (EDO) flights

The purpose of NASA's Extended Duration Orbiter program is a gradual extension of the capabilities of the Space Shuttle Orbiter beyond its current 7-10 day limit on mission duration, as warranted by deepening understanding of the long-term physiological effects of weightlessness. Attention is being given to the cardiovascular problem of orthostatic tolerance loss due to its adverse effects on crew performance and health during reentry and initial readaptation to earth gravity. An account is given of the results of the application of proven mathematical models of circulatory and cardiovascular systems under microgravity conditions.

White, Ronald J.↗

NASA NTRS1991

Duration of liquid water habitats on early Mars

The duration of ice-covered lakes after the initial freezing of the early Mars is presently estimated via a climate model whose critical parameter is the existence of peak seasonal temperatures above freezing, and in which the variability of insolation is included. Under conditions in which meltwater was supplied by an ice source, it is found that water habitats could have been maintained under relatively thin ice sheets for as many as 700 million years after the onset of below-freezing global temperatures. The duration of such habitats on the early Mars therefore exceeds the upper limit of the time envisioned for the emergence of aquatic life on earth.

Mckay, Christopher P.↗