Convective Motions in Near-Critical Fluids under Real Zero-Gravity Conditions

The results of processing and interpreting the data of joint Russian–French experiments for studying the heat and mass transfer in near-critical fluids are presented. The experiments were carried out with the ALICE-1 instrument during an orbital flight of the Mirstation from September 30 to October 2, 1995 [1]. For such fluids with a point-like source of heat, when they are placed in the field of uncontrolled inertial accelerations of the spacecraft, the influence of thermovibrational and thermogravitational mechanisms of convection on the propagation of the region of optical irregularity is investigated. It is shown that, near the thermodynamic critical point, local heating of the medium leads to generation of either intense thermogravitational convection or averaged vibroconvective flow, depending on the frequency of variations of the microaccelerations. The structure and characteristics of discovered motions are studied. The results of numerical simulations are presented that confirm the conclusion about a possibility of generation of an averaged convective flow of a vibrational type by the high-frequency component of microaccelerations.     

Cave biosignature suites: microbes,minerals, and Mars

Earth's subsurface offers one of the best possible sites to search for microbial life and the characteristic lithologies that life leaves behind. The subterrain may be equally valuable for astrobiology. Where surface conditions are particularly hostile, like on Mars, the subsurface may offer the only habitat for extant lifeforms and access to recognizable biosignatures. We have identified numerous unequivocally biogenic macroscopic, microscopic, and chemical/geochemical cave biosignatures. However, to be especially useful for astrobiology, we are looking for suites of characteristics. Ideally, "biosignature suites" should be both macroscopically and microscopically detectable, independently verifiable by nonmorphological means, and as independent as possible of specific details of life chemistries--demanding (and sometimes conflicting) criteria. Working in fragile, legally protected environments, we developed noninvasive and minimal impact techniques for life and biosignature detection/characterization analogous to Planetary Protection Protocols. Our difficult field conditions have shared limitations common to extraterrestrial robotic and human missions. Thus, the cave/subsurface astrobiology model addresses the most important goals from both scientific and operational points of view. We present details of cave biosignature suites involving manganese and iron oxides, calcite, and sulfur minerals. Suites include morphological fossils, mineral-coated filaments, living microbial mats and preserved biofabrics, 13C and 34S values consistent with microbial metabolism, genetic data, unusual elemental abundances and ratios, and crystallographic mineral forms.     

Success criteria and risk management for the new millennium program

The National Aeronautics and Space Administration (NASA) New Millennium Program (NMP) is a technology development and validation program that will flight-validate advanced, new technologies with space flight applications. NMP's purpose is twofold. First, it will develop technologies that will enable future spacecraft to be smaller, more capable and reliable, and to be launched more frequently. Second, it will validate the technologies in flight to reduce the risks to future science missions that fly these technologies for the first time. To measure the program's success, NMP has devised a set of criteria that stresses the relevance of technologies selected for flight validation to NASA's 21st-century science mission needs. Also, NMP has instituted a ‘risk management’ policy, where, through a combination of adequate resources and early risk assessment and risk mitigation plans for the technologies, the overall risk of the NMP flights can be rendered acceptable.     

Efficacy of Doppler ultrasound [correction of utrasound] for screening symptoms of decompression sickness during simulated extravehicular activities

Doppler ultrasound is frequently used for monitoring circulating microbubbles during decompression to assess the symptoms of Decompression Sickness (DCS). This analysis was carried out to evaluate its effectiveness for screening symptoms of DCS during simulated extravehicular activities (EVA). The information from various hypobaric chamber studies carried out at the NASA Johnson Space Center, Houston, TX was used in this analysis (n = 516). The circulating microbubbles were detected in the precordial area in 42% (218/516), and symptoms were reported in 16% (81/516) of these exposures. The accuracy of Doppler-detectable bubbles (Spencer grades) on all symptoms of DCS was examined by calculating measures of sensitivity and specificity. The efficacy of Doppler as a screening device was examined by calculating their positive predictive value (PPV) and negative predictive value (NPV). The results of these analyses indicated that the sensitivity of Doppler decreased, and the PPV increased with higher Spencer grades. However, the likelihood of detecting true negative cases (NPV) was consistently higher with all bubble grades. Due to the high false-positive rate and low prior probabilities of the risk of DCS, Doppler was found to be more useful to identify those who did not develop DCS, than to detect positive cases of DCS in the simulated EVA exposures.     

Main medical results of extended flights on space station Mir in 1986-1990

During 1986-1990 seven prime spacecrews (16 cosmonauts) have flown on-board the Mir orbital complex. The longest space mission duration was 366 days The principal objectives of the medical tasks were the maintenance of good health and performance of the spacecrews and conducting medical research programs which included study of the cardiovascular, motor, endocrine, blood, immune, and metabolic systems. Results obtained point to the ability of humans to readily adapt to a year-long stay in space and maintain good health and performance. Readaptation had a similar course as after other previous long-term space flights of up to 8 months in duration. Primary body system changes were not qualitatively different from findings after flights aboard the Salyut 6 and 7 space stations. In this case, during and after an 11-12 month flight, body system alterations were even less severe which was a result of adequate countermeasure use, their systematic and creative employment and maintenance of required environments to support life and work in space.     

Electrostatic Noise Spectrum at the Electron Cyclotron Frequency and Electromagnetic Emission in the Inhomogeneous Plasma of the Topside Ionosphere

Measurements of the wave emission of the topside ionosphere made onboard the APEX satellite using the electric component of the wave field in the 0.1–10 MHz frequency band are presented. At middle latitudes a wave intensity decrease was observed in the broad-band spectrum of the electrostatic noise at the electron cyclotron frequency. It is shown that a break in the spectrum of electrostatic modes at the electron cyclotron frequency (the absence of the plasma eigen-frequencies) may be a cause of the observed effect. The increase of the intensity at the electron cyclotron frequency in the ionospheric trough and at latitudes above the trough region as compared to middle latitudes may be explained by the capture by plasma irregularities of the electromagnetic emission of the auroral electron fluxes.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 3, 2005, pp. 201–208.Original Russian Text Copyright © 2005 by Izhovkina, Prutensky, Pulinets, Kiraga, Klos, Rothkael.     

A new method of determining the spectral index for protons in the energy range about 10<Superscript>13</Superscript> eV

We consider a relationship between the difference in spectral indices of the spectra of single hadrons and all hadrons (_sngl – _h) and the difference in the indices of the spectra of galactic cosmic ray (GCR) protons and nuclei. It is demonstrated that at the mountain level the ratio (_p – _Z)/(_sngl – _h) is always larger than unity, if (_sngl – _h) > 0.1. From the experimental value _sngl – _h = 0.4 ± 0.05 we derive that, in the vicinity of E = 10 TeV, _p – _Z 0.49 ± 0.06 , i.e., _p 3.09 ± 0.06.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 2, 2005, pp. 83–87.Original Russian Text Copyright © 2005 by Grigorov, Tolstaya.     

Vibration and pulsation processes in feed systems of liquid rocket engines

Pulsation and vibration process in high speed centrifugal pumps and feed lines were investigated. Linear and quadratic relations between pulsation parameters and main factors were obtained. The investigation of turbopump low frequency oscillations showed that the intensity of pulsations is proportional to the pump specific linear size. Linear mathematic models with lumped parameters fairly well demonstrate the vibration influence on low frequency flow pressure vibrations in pumps and feed lines. It is shown that, in some conditions, the pressure oscillation amplitude distribution by the vibrating feed lines length may be characterized by the presence of a node in an intermediate section. A one-dimensional mathematic model based on wave equations proved to be suitable for calculations of vibration and pulsation parameters within a wide frequency range.     

Future investigations onboard Soviet biosatellites of the Cosmos series.

Many rat experiments onboard Cosmos biosatellites have furnished information concerning the effects of weightlessness, artificial gravity, and ionizing radiation combined with weightlessness on structural and biochemical parameters of the animal body. The necessity to expand the scope of physiological investigations has led to the project of flight primate studies. It is planned to carry out the first primate experiments onboard the Cosmos biosatellite in 1982. At present investigations of weightlessness effects on the cardiovascular and vestibular systems, higher nervous activity, skeletal muscles and biorhythms of two rhesus monkeys are being developed and tested. It is also planned to conduct a study of weightlessness effects on embryogenesis of rats and bioenergetics of living systems onboard the same biosatellite. Further experiments onboard Cosmos biosatellites are planned.     

Diuretic as a means for rapid adaptation to weightlessness

In a number of flights, cosmonauts and astronauts have experienced aggravation of their health status and general condition in the initial hours and days in a weightless environment. One of the trigger mechanisms for the onset of these unfavourable conditions at the start of space flight is a redistribution of body fluids and a blood shift towards the head. To ensure controlled hypohydration as a countermeasure to the deleterious effects of 0-g and to investigate the feasibility to control adaptation, six cosmonauts were administered lasix once a day during the first 3 days of a mission. All data of the experiment (correction test, questionnaire, hematocrit) were recorded on a special form in the logbook and transmitted to the control centre for processing. Results showed that the diuretic weakened the sensation of discomfort and improved the cosmonauts' general condition. Objective indices of the correction test indicate an increased work ability of cosmonauts. After hypohydration, circulating plasma volumes in the group were reduced by 6.8 + 1.0% on average.