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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.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Intensity measurements for the /2, O/ gamma-band of O2, b 1Sigma-g/+/ - X 3Sigma-g/-/

Line intensities for the P sub P and P sub Q branches of the (2-O) vibrational band of the magnetic dipole electronic transition for the oxygen red system at 6280 A were measured, and the sum of the R sub R and R sub Q branch intensities was taken. A large number of repetitive spectral scans were required for accuracy, because of low absorption values even at optical path lengths from 300 to 600 m. A total of 557 individual measurements of P-branch lines yielded an intensity value for the P-branches, and equivalent widths for 24 spectral scans yielded an intensity value for the R-branch. R-branch to P-branch intensity ratios were taken for the A-band, B-band, and gamma-band (respectively, O-O at 7620 A, 1-O at 6880 A, and 2-O at 6280 A). Intensities for some rotational lines are found, and effects of combined rotation-vibration interaction are probed.

Miller, J. H.↗
NASA NTRS1977

Influence of zero-G on single-cell systems and zero-G fermenter design concepts

An analysis was made to identify potential gravity-sensitive mechanisms that may be present in the single-cell growth system. Natural convection (density gradients, induced sedimentation, and buoyancy) is important in microbial systems. The absence of natural convection in the space-flight environment could provide an opportunity for new approaches for developments in industrial fermentation and agriculture. Some of the potential influences of gravity (i.e., convection, sedimentation, etc.) on the cell were discussed to provide insight into what experimental areas may be pursued in future space-flight research programs.

Mayeux, J. V.↗
NASA NTRS1985

(Ad/f,g/), (ad/fg/) and locally (ad/f,g/) invariant and controllability distributions

Over the past decade, it has been found that concepts from differential topology such as foliation and invariant distribution play a crucial role in the study of nonlinear systems. These concepts were first employed in studies of nonlinear controllability and observability. More recently, they have occurred in the study of decoupling and linearization via feedback. In connection with the widening area of application, requirements for a greater precision have arisen. The present paper represents an attempt to provide that precision. In this paper, an introduction is given of the basic concepts which are needed for an understanding of controllability, observability, and decoupling of nonlinear systems. Attention is given to mathematical preliminaries, aspects of invariance, nonlinear controllability and observability, disturbance decoupling, and controllability distributions.

Krener, A. J.↗
NASA NTRS1993

Modal parameters of space structures in 1 G and 0 G

Analytic and experimental results are presented from a study of the changes in the modal parameters of space structural test articles from one- to zero-gravity. Deployable, erectable, and rotary modules was assembled to form three one- and two-dimensional structures, in which variations in bracing wire and rotary joint preload could be introduced. The structures were modeled as if hanging from a suspension system in one gravity, and unconstrained, as if free floating in zero-gravity. The analysis is compared with ground experimental measurements, which were made on a spring-wire suspension system with a nominal plunge frequency of one Hertz, and with measurements made on the Shuttle middeck. The degree of change in linear modal parameters as well as the change in nonlinear nature of the response is examined. Trends in modal parameters are presented as a function of force amplitude, joint preload, reassembly, shipset, suspension, and ambient gravity level.

Bicos, Andrew S.↗
NASA NTRS1994

Heterogeneous Reaction of ClONO2(g) + NaCl(s) to Cl2(g) + NaNO3(s)

The heterogeneous reaction of ClON02 + NaCl yields Cl2 + NaNO3 (eq 1) was investigated over a temperature range 220-300 K in a flow-tube reactor interfaced with a differentially pumped quadrupole mass spectrometer. Partial pressures of ClON02 in the range 10(exp -8) - 10(exp -5) Torr were used. Granule sizes and surface roughness of the NaCl substrates were determined by using a scanning electron microscope, and in separate experiments, surface areas of the substrates were measured by using BET analysis of gas-adsorption isotherms. For dry NaCl substrates, both the decay rates of ClON02 and the growth rates Of C12 were used to obtain reaction probabilities, gamma(sub l) = (4.6 +/- 3.0) x 10(exp -3) at 296 K and (6.7 +/- 3.2) x 10(exp -1) at 225 K, after considering the internal surface area, The error bars represent 1 standard deviation. The Cl2 yield based on the ClONO2 reacted was measured to be 1.0 +/- 0.2. In order to mimic the conditions encountered in the lower stratosphere, the effect of water vapor pressures between 5 x 10(exp -5) and 3 x 10(exp -4) Torr on reaction 1 was also studied. With added H20, reaction probabilities, gamma = (4.1 +/- 2.1) x 10(exp -3) at 296 K and (4.7 +/- 2.9) x 10(exp -3) at 225 K, were obtained. A trace of HOCl, the reaction product from the ClON02 + H20 yield HOCl + HN03 reaction, was observed in addition to the C12 product from reaction 1. The implications of this result for the enhancement of hydrogen chloride in the stratosphere after the El Chichon volcanic eruption and for the marine troposphere are discussed.

Timonen, Raimo S.↗
NASA NTRS2001

Effect of Marangoni Convection Generated by Voids on Segregation During Low-G and 1-G Solidification

Solidification experiments, especially microgravity solidification experiments, are often compromised by the evolution of unwanted voids or bubbles in the melt. Although these voids and/or bubbles are highly undesirable, there is currently no effective means of preventing their formation or of eliminating their adverse effects, particularly during microgravity experiments. Marangoni convection caused by these voids can drastically change the transport processes in the melt. Recent microgravity experiments by Matthiesen (1) Andrews (2) and Fripp (3) are perfect examples of how voids and bubbles can affect the outcome of costly space experiments and significantly increase the level of difficulty in interpreting their results. Formation of bubbles have caused problems in microgravity experiments for a long time. Even in the early Skylab mission an unexpectedly large number of bubbles were detected in the four materials processing experiments reported by Papazian and Wilcox (4). They demonstrated that while during ground-based tests bubbles were seen to detach from the interface easily and float to the top of the melt, in low-gravity tests no detachment from the interface occurred and large voids were grown in the crystal. More recently, the lead-tin-telluride crystal growth experiment of Fripp et al.(3) flown aboard the USMP-3 mission has provided very interesting results. The purpose of the study was to investigate the effect of natural convection on the solidification process by growing the samples at different orientations with respect to the gravitational field. Large pores and voids were found in the three solid crystal samples processed in space. Post-growth characterization of the compositional profiles of the cells indicated considerable levels of mixing even in the sample grown in the hot-on-top stable configuration. The mixing was attributed to thermocapillary convection caused by the voids and bubbles which evolved during growth. Since the thermocapillary convection is orientation-independent, diffusion-controlled growth was not possible in any of the samples, even the top-heated one. These results are consistent with recent studies of thermocapillary convection generated by a bubble on a heated surface undertaken by Kassemi and Rashidnia (5-7) where it is numerically and experimentally shown that the thermocapillary flow generated by a bubble in a model fluid (silicone oil) can drastically modify the temperature field through vigorous mixing of the fluid around it, especially under microgravity conditions.

Kassemi, M.↗
NASA NTRS2003

Experiment Document for 01-E077 Microgravity Investigation of Crew Reactions in 0-G (MICRO-G)

The Experiment Document (ED) serves the following purposes: a) It provides a vehicle for Principal Investigators (PIS) to formally specify the requirements for performing their experiments. b) It provides a technical Statement of Work (SOW). c) It provides experiment investigators and hardware developers with a convenient source of information about Human Life Sciences (HLS) requirements for the development and/or integration of flight experiment projects. d) It is the primary source of experiment specifications for the HLS Research Program Office (RPO). Inputs from this document will be placed into a controlled database that will be used to generate other documents.

Newman, Dava J.↗
NASA NTRSDate not supplied

Space Settlement Should Use 1 g Shielded Space Platforms, Not the 1/6 or 1/3 g, Radiation Exposed Moon or Mars

Previous missions have subjected astronauts to confined space, weightlessness, and increased radiation. These impair astronaut comfort, performance, and future health. The exploration and future settlement of space will depend on the long term presence of individual humans. This requires the development of space platforms where humans can work and live in health for many years, perhaps generations. A livable space platform must provide adequate volume, gravity, and radiation shielding. This seems easier to do in deep space or Low Earth Orbit (LEO) than on the surface of the moon or Mars. Permanently habitable deep space platforms will enable scientific and technical research, space tourism, space mission preparation, space industry development, and military surveillance and operations. The first fully habitable space station would probably be located in LEO for convenience and lower cost.

Harry W Jones↗
NASA NTRS1998

High sustained +Gz acceleration: physiological adaptation to high-G tolerance

Since the early 1940s, a significant volume of research has been conducted in an effort to describe the impact of acute exposures to high-G acceleration on cardiovascular mechanisms responsible to maintaining cerebral perfusion and conscious in high performance aircraft pilots during aerial combat maneuvers. The value of understanding hemodynamic characteristics that underlie G-induced loss of consciousness has been instrumental in the evolution of optimal technology development (e.g., G-suits, positive pressure breathing, COMBAT EDGE, etc.) and pilot training (e.g., anti-G straining maneuvers). Although the emphasis of research has been placed on the development of protection against acute high +Gz acceleration effects, recent observations suggest that adaptation of cardiovascular mechanism associated with blood pressure regulation may contribute to a protective 'G-training' effect. Regular training at high G enhances G tolerance in humans, rats, guinea pigs, and dogs while prolonged layoff from exposure in high G profiles (G-layoff) can result in reduced G endurance. It seems probable that adaptations in physiological functions following chronically-repeated high G exposure (G training) or G-layoff could have significant impacts on performance during sustained high-G acceleration since protective technology such as G-suits and anit-G straining maneuvers are applied consistently during these periods of training. The purpose of this paper is to present a review of new data from three experiments that support the notion that repeated exposure on a regular basis to high sustained +Gz acceleration induces significant physiological adaptations which are associated with improved blood pressure regulation and subsequent protection of cerebral perfusion during orthostatic challenges.

Review, Tutorial↗
NASA NTRS1992

Comparisons of three anti-G suit configurations during long duration, low onset, +Gz

Little physiologic data exist on the effects of long duration, low onset, hypergravity (+G). Space shuttle crewmembers are subjected to low +G forces (less than +3G) for upwards of 30 minutes during reentry. A similar reentry profile is predicted for the National Aerospace Plane (NASP). The physiologic effects of this acceleration stress are compounded by the loss of body water experienced during microgravity. Currently, a standard 5 bladder anti-G suit is being used during shuttle reentry. There have been complaints of discomfort using this suit, mainly due to the abdominal bladder. This study compared the effectiveness of three anti-G suit configurations in volume depleted subjects during a simulated space shuttle reentry profile. Methods: Seven male subjects were given intravenous Lasix in a dose from 20-40 mg to induce a total body weight loss of 3 plus or minus 1.5 percent. Approximately six hours after the injection, the subjects donned one of three anti-G suits - a standard 5 bladder anti-G suit, an extended coverage anti-G suit (the advanced technology anti-G suit or ATAGS), or an extended coverage anti-G suit without an abdominal bladder (the reentry anti-G suit or REAGS). All subjects were exposed to a simulated space shuttle reentry profile. Non-invasive eye-level blood pressure (ELBP) was monitored throughout the +G exposure. When systolic ELBP dropped below 70 mmHg, the anti-G suit was inflated in 0.5 psig increments to the pressure required to maintain 70 mmHg ELBP. Each subject rode with all three suits. Comparisons were made between the final pressure required in each suit to maintain ELBP and subjective reports of comfort. Results: The mean final suit pressure required to maintain ELBP was 1.1 psi, in both the ATAGS and REAGS versus 1.8 psi in the standard suit. In addition, the subjects rated the REAGS suit highest on the comfort scale, citing the absence of the abdominal bladder as the main reason. Conclusions: Overall, the REAGS suit was the superior anti-G suit during long duration, low onset +G. This is based on its ability to maintain ELBP and still remain comfortable when inflated for prolonged periods of time.

Stegmann, B. J.↗
NASA NTRS1994

Comparative performance of a modified Space Shuttle Reentry Anti-G Suit (REAGS) with and without pressure socks

In a prior study, the Armstrong Laboratory (AL) demonstrated that +G(sub z) protection during simulated shuttle reentry could be improved with an extended coverage anti-G suit with pressure socks but no abdominal bladder (REAGS). In a subsequent study conducted at the NASA Johnson Space Center it was shown that REAGS had a down side which included restricted mobility (during simulated shuttle egress) and a larger boot size needed for the pressure socks. The present study was conducted using a modified REAGS to increase mobility during egress. The size of the crotch opening was increased, and the fabric covering the buttocks was replaced with more elastic material. Six healthy male members of the AL centrifuge panel served as subjects for the study. As in the earlier study, subjects received 20 to 35 mg of IV Lasix approximately 6 hours before being exposed to a simulated space shuttle reentry +G(sub z) profile on the AL centrifuge, which induced a mean weight loss of 2.8 percent, range 2.1 percent to 3.7 percent. The REAGS was inflated to 1.0 psig 10 minutes prior to G onset. The G-profile was identical to that used in the previous REAGS study. Physiologic parameters monitored were also the same, i.e., eye-level systolic blood pressure (ELBP) using the Finapres digital cuff technique and heart rate and rhythm. Subjective comments were obtained from questionnaires administered after the increased G exposure. Systolic ELBP was maintained at 60 mm Hg or above by pressurizing the anti-G suit in 0.5 psig increments up to a maximum pressure of 2.5 psig. There were no significant differences in mean G-suit pressure required to maintain systolic ELBP at 60 mm Hg or above between the REAGS worn with and without pressure socks. Maximum mean G-levels achieved during the GOR were also the same under both experimental conditions, i.e., 4.7 G with socks and 4.6 G without socks. These G-levels were essentially the same as recorded earlier with the unmodified REAGS. There were no significant differences in comfort rating during the G exposure assigned by subjects when they wore the modified REAGS with or without the pressure socks.

Krutz, R. W., Jr.↗
NASA NTRS1985

Growth and development of mice and rats conceived and reared at different G-intensities during chronic centrifugation

Prenatal and postnatal growth of rats conceived and reared at different G-intensities from 1.0G (earth gravity) to a maximum of 2.03G were compared. Prenatal growth was not generally impaired but the lung/body mass ratio of 22-day old fetuses at 2.03G was decreased significantly compared to 1.06 controls. Survival of neonatal rats was substantially reduced at 1.71G and 2.03G. Postnatal growth was decreased at the higher G-intensities and showed smaller or no effects at the lower G-intensities. Comparisons of organ/body mass ratios of hyper-G and 1.0G rats at 9 wks of age showed relatively few differences at the lower G-intensities. Postnatal growth of mice at 2.03G was suppressed during the neonatal period but recovered later so that after 9 wks the body mass of females reached and of males approached controls. Results of this preliminary study clearly show the influence of body mass in scaling the effects of hyper-G on the growth and development of and between different animal species.

Oyama, J.↗
NASA NTRS1997

Microwave Observations and Modeling of O2 (1-delta(sub g)) and O3 Diurnal Variation in the Mesosphere

The first microwave measurements of an electronically excited molecular species in the Earth's atmosphere are presented. Local thermodynamic equilibrium (LTE) rotational line emission from mesospheric O2(1-del(sub g)) was observed at a frequency of 255.01794 GHz (lambda is approx. 1.2 mm), employing the National Radio Astronomy Observatory (NRAO) millimeter facility at Kitt Peak, Arizona (32 N, 111 W). The pressure broadened line shapes of the O2(1-del(sub g)) spectra, which were obtained in January and April 1992 and in January and November 1993, are inverted to retrieve O2(1-del(sub g)) mixing profiles over the 50-70 km altitude region. The observed daytime abundances exceed ozone abundances in the lower mesosphere, which are separately retrieved with coincident O3 spectral line (249.7886 GHz) observations. The January and November 1993 observations are binned into 20-60 min time intervals to study O2(1-del(sub g)) diurnal behavior. Derived abundances of O2(1-del(sub g)) between 50 and 70 km for the four observation dates are 9%, 31%, 3%, and 26%, respectively, each +/- 10% higher than predicted, based on the simple photochemistry of lower mesospheric O2(1-del(sub g)). Modeled variation of [O2(1-del(sub g))] with time of day agrees with observed variation in that the observed difference between model and data abundances is constant throughout the daylight hours of each observation date. Model underprediction Of [02(lAg)] is consistent with similar model underprediction of mesospheric [O3]. A perturbation to the photochemical model that forces decreased ozone chemical loss brings brings both model [O3] and [O2(1-del(sub g))] into agreement with the observations. O2(1-del(sub g)) abundances derived from these 1.2 mm observations agree with [O2(1-del(sub g))] values derived from comparable SME observations of the 1.27 micrometers emission, with assumption of a 3880 sec O2(1-del(sub g)) radiative lifetime. The 6800 sec O2(1-del(sub g)) radiative lifetime proposed by Mlynczak and Nesbitt is ruled out by the similar comparison.

Sandor, Brad J.↗