Evaluation of using two-phase frictional pressure drop correlations for normal gravity to microgravity and reduced gravity

The calculation of two-phase frictional pressure drop (TPFPD) is required by two-phase systems operating under microgravity and reduced gravity. There are a large number of correlations for the TPFPD in tubes under normal gravity. However, it is hard to find out a TPFPD correlation obtained from microgravity and/or reduced gravity conditions, and thus people have to use TPFPD correlations for normal gravity to calculate TPFPD under microgravity and reduced gravity. It is necessary to evaluate the feasibility of such practice. This paper offers a comprehensive review of the TPFPD correlations for normal gravity and an up-to-data survey of the TPFPD experimental study under microgravity and reduced gravity. There are 23 TPFPD correlations for normal gravity reviewed and 135 experimental data under microgravity obtained from the literature. These experimental data are used to evaluate the reviewed TPFPD correlations. It is found that the smallest mean absolute relative deviation (MARD) of the correlations is greater than 34%. Using TPFPD correlations for normal gravity to reduced gravity and microgravity may be acceptable for the first approximation, but correlations intended for microgravity and reduced gravity are needed and more experiments are desired to obtain more data with high accuracy.     

Skeletogenesis in sea urchin larvae under modified gravity conditions.

From many points of view, skeletogenesis in sea urchins has been well described. Based on this scientific background and considering practical aspects of sea urchin development (i.e. availability of material, size of larvae, etc.), we wanted to know whether orderly skeletogenesis requires the presence of gravity. The objective has been approached by three experiments successfully performed under genuine microgravity conditions (in the STS-65 IML-2 mission of 1994; in the Photon-10 IBIS mission of 1995 and in the STS-76 S/MM-03 mission of 1996). Larvae of the sea urchin Sphaerechinus granularis were allowed to develop in microgravity conditions for several days from blastula stage onwards (onset of skeletogenesis). At the end of the missions, the recovered skeletal structures were studied with respect to their mineral composition, architecture and size. Live larvae were also recovered for post-flight culture. The results obtained clearly show that the process of mineralisation is independent of gravity: that is, the skeletogenic cells differentiate correctly in microgravity. However, abnormal skeleton architectures were encountered, particularly in the IML-2 mission, indicating that the process of positioning of the skeletogenic cells may be affected, directly or indirectly, by environmental factors, including gravity. Larvae exposed to microgravity from blastula to prism/early pluteus stage for about 2 weeks (IBIS mission), developed on the ground over the next 2 months into normal metamorphosing individuals.     

The SOS-LUX-LAC-FLUORO-Toxicity-test on the International Space Station (ISS).

In the 21st century, an increasing number of astronauts will visit the International Space Station (ISS) for prolonged times. Therefore it is of utmost importance to provide necessary basic knowledge concerning risks to their health and their ability to work on the station and during extravehicular activities (EVA) in free space. It is the aim of one experiment of the German project TRIPLE-LUX (to be flown on the ISS) to provide an estimation of health risk resulting from exposure of the astronauts to the radiation in space inside the station as well as during extravehicular activities on one hand, and of exposure of astronauts to unavoidable or as yet unknown ISS-environmental genotoxic substances on the other. The project will (i) provide increased knowledge of the biological action of space radiation and enzymatic repair of DNA damage, (ii) uncover cellular mechanisms of synergistic interaction of microgravity and space radiation and (iii) examine the space craft milieu with highly specific biosensors. For these investigations, the bacterial biosensor SOS-LUX-LAC-FLUORO-Toxicity-test will be used, combining the SOS-LUX-Test invented at DLR Germany (Patent) with the commercially available LAC-FLUORO-Test. The SOS-LUX-Test comprises genetically modified bacteria transformed with the pBR322-derived plasmid pPLS-1. This plasmid carries the promoterless lux operon of Photobacterium leiognathi as a reporter element under control of the DNA-damage dependent SOS promoter of ColD as sensor element. This system reacts to radiation and other agents that induce DNA damages with a dose dependent measurable emission of bioluminescence of the transformed bacteria. The analogous LAC-FLUORO-Test has been developed for the detection of cellular responses to cytotoxins. It is based on the constitutive expression of green fluorescent protein (GFP) mediated by the bacterial protein expression vector pGFPuv (Clontech, Palo Alto, USA). In response to cytotoxic agents, this system reacts with a dose-dependent reduction of GFP-fluorescence. Currently, a fully automated miniaturized hardware system for the bacterial set up, which includes measurements of luminescence and fluorescence or absorption and the image analysis based evaluation is under development. During the first mission of the SOS-LUX-LAC-FLUORO-Toxicity-Test on the ISS, a standardized, DNA-damaging radiation source still to be determined will be used as a genotoxic inducer. A panel of recombinant Salmonella typhimurium strains carrying either the SOS-LUX plasmid or the fluorescence-mediating lac-GFPuv plasmid will be used to determine in parallel on one microplate the genotoxic and the cytotoxic action of the applied radiation in combination with microgravity. Either in addition to or in place of the fluorometric measurements of the cytotoxic agents, photometric measurements will simultaneously monitor cell growth, giving additional data on survival of the cells. The obtained data will be available on line during the TRIPLE-LUX mission time. Though it is the main goal during the TRIPLE-LUX mission to measure the radiation effect in microgravity, the SOS-LUX-LAC-FLUORO-Toxicity-test in principle is also applicable as a biomonitor for the detection and measurement of genotoxic substances in air or in the (recycled) water system on the ISS or on earth in general.     

The effect of microgravity on plasma-osteocalcin

The rapid loss of bone mass is one of the serious problems which have to be solved before long-lasting manned spaceflights may be considered. In this paper we describe investigations in which we have checked whether the bone loss in astronauts as well as in osteoporotic patients may be related to abnormalities in a recently discovered calcium-binding protein, named osteocalcin. It was observed that in all subjects of a limited number of osteoporotic patients, the amount of calcium-binding groups (Gla-residues) in the circulating osteocalcin was substantially reduced. The Gla-content could be normalized, however, by the oral administration of vitamin K (1 mg/day). We also analyzed the Gla-content of plasma-osteocalcin from 4 astronauts before and after the D-1 mission. The amount of Gla-residues was reduced by more than 50% in the post-flight samples. It seems probable, that an increased vitamin K-intake by the astronauts will correct the observed abnormality, but whether this will lead to a decrease of the microgravity-induced bone-loss remains to be seen.     

Adaptive response studies may help choose astronauts for long-term space travel.

Long-term manned exploratory missions are planned for the future. Exposure to high-energy neutrons, protons and high charge and energy particles during a deep space mission, needs protection against the detrimental effects of space radiation. It has been suggested that exposure to unpredictable extremely large solar particle events would kill the astronauts without massive shielding. To reduce this risk to astronauts and to minimize the need for shielding, astronauts with highest significant adaptive responses should be chosen. It has been demonstrated that some humans living in very high natural radiation areas have acquired high adaptive responses to external radiation. Therefore, we suggest that for a deep space mission the adaptive response of all potential crew members be measured and only those with high adaptive response be chosen. We also proclaim that chronic exposure to elevated levels of radiation can considerably decrease radiation susceptibility and better protect astronauts against the unpredictable exposure to sudden and dramatic increase in flux due to solar flares and coronal mass ejections.     

Function of the cytoskeleton in gravisensing during spaceflight.

Since astronauts and cosmonauts have significant bone loss in microgravity we hypothesized that there would be physiological changes in cellular bone growth and cytoskeleton in the absence of gravity. Investigators from around the world have studied a multitude of bone cells in microgravity including Ros 17/2.8, Mc3T3-E1, MG-63, hFOB and primary chicken calvaria. Changes in cytoskeleton and extracellular matrix (ECM) have been noted in many of these studies. Investigators have noted changes in shape of cells exposed to as little as 20 seconds of microgravity in parabolic flight. Our laboratory reported that quiescent osteoblasts activated by sera under microgravity conditions had a significant 60% reduction in growth (p<0.001) but a paradoxical 2-fold increase in release of the osteoblast autocrine factor PGE2 when compared to ground controls. In addition, a collapse of the osteoblast actin cytoskeleton and loss of focal adhesions has been noted after 4 days in microgravity. Later studies in Biorack on STS-76, 81 and 84 confirmed the increased release of PGE2 and collapse of the actin cytoskeleton in cells grown in microgravity conditions, however flown cells under 1 g conditions maintained normal actin cytoskeleton and fibronectin matrix. The changes seen in the cytoskeleton are probably not due to alterations in fibronectin message or protein synthesis since no differences have been noted in microgravity. Multiple investigators have observed actin and microtubule cytoskeletal modifications in microgravity, suggesting a common root cause for the change in cell architecture. The inability of the O g grown osteoblast to respond to sera activation suggests that there is a major alteration in anabolic signal transduction under microgravity conditions, most probably through the growth factor receptors and/or the associated kinase pathways that are connected to the cytoskeleton. Cell cycle is dependent on the cytoskeleton. Alterations in cytoskeletal structure can block cell growth either in G1 (F-actin microfilament collapse), or in G2/M (inhibition of microtubule polymerization during G2/M-phase). We therefore hypothesize that microgravity would inhibit growth in either G1, or G2/M.     

Evaluation of upper body muscle activity during cardiopulmonary resuscitation performance in simulated microgravity

Performance of efficient single-person cardiopulmonary resuscitation (CPR) is vital to maintain cardiac and cerebral perfusion during the 2–4 min it takes for deployment of advanced life support during a space mission. The aim of the present study was to investigate potential differences in upper body muscle activity during CPR performance at terrestrial gravity (+1Gz) and in simulated microgravity (μG). Muscle activity of the triceps brachii, erector spinae, rectus abdominis and pectoralis major was measured via superficial electromyography in 20 healthy male volunteers. Four sets of 30 external chest compressions (ECCs) were performed on a mannequin. Microgravity was simulated using a body suspension device and harness; the Evetts–Russomano (ER) method was adopted for CPR performance in simulated microgravity. Heart rate and perceived exertion via Borg scores were also measured. While a significantly lower depth of ECCs was observed in simulated microgravity, compared with +1Gz, it was still within the target range of 40–50 mm. There was a 7.7% decrease of the mean (±SEM) ECC depth from 48 ± 0.3 mm at +1Gz, to 44.3 ± 0.5 mm during microgravity simulation (p < 0.001). No significant difference in number or rate of compressions was found between the two conditions. Heart rate displayed a significantly larger increase during CPR in simulated microgravity than at +1Gz, the former presenting a mean (±SEM) of 23.6 ± 2.91 bpm and the latter, 76.6 ± 3.8 bpm (p < 0.001). Borg scores were 70% higher post-microgravity compressions (17 ± 1) than post +1Gz compressions (10 ± 1) (p < 0.001). Intermuscular comparisons showed the triceps brachii to have significantly lower muscle activity than each of the other three tested muscles, in both +1Gz and microgravity. As shown by greater Borg scores and heart rate increases, CPR performance in simulated microgravity is more fatiguing than at +1Gz. Nevertheless, no significant difference in muscle activity between conditions was found, a result that is favourable for astronauts, given the inevitable muscular and cardiovascular deconditioning that occurs during space travel.     

航天员失重环境下运动策略与效能分析

航天员在空间执行任务过程中由于受到空间微重力环境的影响,其运动的协调性以及平衡性均会与地面环境下的表现有所差异.以研究失重环境下航天员运动特点为目标,对航天员姿态调整策略进行动力学分析,并对运动过程人体效能进行评价.具体而言,在无外力/力矩驱动下,人体必须依靠四肢按一定的协调运动策略才能实现对躯干姿态的主动控制.而运动...     

Preliminary results of space experiment: Implications for the effects of space radiation and microgravity on survival and mutation induction in human cells

In view of the concern for the health of astronauts that may one day journey to Mars or the Moon, we investigated the effect that space radiation and microgravity might have on DNA damage and repair. We sent frozen human lymphoblastoid TK6 cells to the International Space Station where they were maintained under frozen conditions during a 134-day mission (14 November 2008 to 28 March 2009) except for an incubation period of 8 days under 1G or μG conditions in a CO₂ incubator. The incubation period started after 100 days during which the cells had been exposed to 54 mSv of space radiation. The incubated cells were then refrozen, returned to Earth, and compared to ground control samples for the determination of the influence of microgravity on cell survival and mutation induction. The results for both varied from experiment to experiment, yielding a large SD, but the μG sample results differed significantly from the 1G sample results for each of 2 experiments, with the mean ratio of μG to 1G being 0.55 for the concentration of viable cells and 0.59 for the fraction of thymidine kinase deficient (TK⁻) mutants. Among the mutants, non-loss of zygosity events (point mutations) were less frequent (31%) after μG incubation than after 1G incubation, which might be explained by the influence of μG on cellular metabolic or physiological function. Additional experiments are needed to clarify the effect of μG interferes on DNA repair.     

Alkylating agent (MNU)-induced mutation in space environment.

In recent years, some contradictory data about the effects of microgravity on radiation-induced biological responses in space experiments have been reported. We prepared a damaged template DNA produced with an alkylating agent (N-methyl-N-nitroso urea; MNU) to measure incorrect base-incorporation during DNA replication in microgravity. We examined whether mutation frequency is affected by microgravity during DNA replication for a DNA template damaged by an alkylating agent. Using an in vitro enzymatic reaction system, DNA synthesis by Taq polymerase or polymerase III was done during a US space shuttle mission (Discovery, STS-91). After the flight, DNA replication and mutation frequencies were measured. We found that there was almost no effect of microgravity on DNA replication and mutation frequency. It is suggested that microgravity might not affect at the stage of substrate incorporation in induced-mutation frequency.     

Radiation hazards on space missions outside the magnetosphere.

Future space missions outside the magnetosphere will subject astronauts to a hostile and unfamiliar radiation environment. An annual dose equivalent to the blood-forming organs (BFOs) of approximately 0.5 Sv is expected, mostly from heavy ions in the galactic cosmic radiation. On long-duration missions, an anomalously-large solar energetic particle event may occur. Such an event can expose astronauts to up to approximately 25 Gy (skin dose) and up to approximately 2 Sv (BFO dose) with no shielding. The anticipated radiation exposure may necessitate spacecraft design concessions and some restriction of mission activities. In this paper we discuss our model calculations of radiation doses in several exo-magnetospheric environments. Specific radiation shielding strategies are discussed. A new calculation of aluminum equivalents of potential spacecraft shielding materials demonstrates the importance of low-atomic-mass species for protection from galactic cosmic radiation.     

An attempt to determine the ideal psychological profiles for crews of long term space missions.

This paper reviews possible psychological criteria for selection at individual level (personality, psychological stability, competence, social skills) as well as at crew level (crew size, gender, compatability, group homeostasis). Once astronauts have been selected an important effort will have to be made pre-flight to prepare the crew to the autonomy necessary for a Mars trip. During the mission psychological support will be important, but probably limited by the mission constraints. At this stage, mission success will probably rely mainly on the capacity of the crew to prevent and manage crises internally. Post-flight psychological support is necessary to help astronauts to readapt to a normal way of life on Earth.     

SJ-10 Recoverable Satellite for Space Microgravity Experiments

SJ-10 is a recoverable scientific experiment satellite specially for the space experiments of microgravity physics science and space life science. This mission was officially started on 31 December 2012, and the satellite was launched on 6 April 2016. This paper introduces briefly the SJ-10 mission, the progress of SJ-10 engineering and the project constitution of sciences experiments onboard SJ-10. The purpose of this mission is to discover the law of matter movement and the rule of life activity that cannot be discovered on the ground due to the existence of gravity, and to know the acting mechanism on organisms by the complex radiation of space that cannot be simulated on the ground.      

Parathyroid hormone-related protein is a gravisensor in lung and bone cell biology.

Parathyroid Hormone-related Protein (PTHrP) has been shown to be essential for the development and homeostatic regulation of lung and bone. Since both lung and bone structure and function are affected by microgravity, we hypothesized that 0 x g down-regulates PTHrP signaling. To test this hypothesis, we suspended lung and bone cells in the simulated microgravity environment of a Rotating Wall Vessel Bioreactor, which simulates microgravity, for up to 72 hours. During the first 8 hours of exposure to simulated 0 x g, PTHrP expression fell precipitously, decreasing by 80-90%; during the subsequent 64 hours, PTHrP expression remained at this newly established level of expression. PTHrP production decreased from 12 pg/ml/hour to 1 pg/ml/hour in culture medium from microgravity-exposed cells. The cells were then recultured at unit gravity for 24 hours, and PTHrP expression and production returned to normal levels. Based on these findings, we have obtained bones from rats flown in space for 2 weeks (Mission STS-58, SL-2). Analysis of PTHrP expression by femurs and tibias from these animals (n=5) revealed that PTHrP expression was 60% lower than in bones from control ground-based rats. Interestingly, there were no differences in PTHrP expression by parietal bone from space-exposed versus ground-based animals, indicating that the effect of weightlessness on PTHrP expression is due to the unweighting of weight-bearing bones. This finding is consistent with other studies of microgravity-induced osteoporosis. The loss of the PTHrP signaling mechanism may be corrected using chemical agents that up-regulate this pathway. In conclusion, PTHrP represents a stretch-sensitive paracrine signaling mechanism that may sense gravity.     

Structural and functional organisation of regenerated plant protoplasts exposed to microgravity on Biokosmos 9.

Preparatory experiments for the IML-1 mission using plant protoplasts, were flown on a 14-day flight on Biokosmos 9 in September 1989. Thirty-six hours before launch of the biosatellite, protoplasts were isolated from hypocotyl cells of rapeseed (Brassica napus) and suspension cultures of carrot (Daucus carota). Ultrastructural and fluorescence analysis of cell aggregates from these protoplasts, cultured under microgravity conditions, have been performed. In the flight samples as well as in the ground controls, a portion of the total number of protoplasts regenerated cell walls. The processes of cell differentiation and proliferation under micro-g did not differ significantly from those under normal gravity conditions. However, in micro-g differences were observed in the ultrastructure of some organelles such as plastids and mitochondria. There was also an increase in the frequency of the occurrence of folds formed by the plasmalemma together with an increase in the degree of complexity of these folds. In cell cultures developed under micro-g conditions, the calcium content tends to decrease, compared to the ground control. Different aspects of using isolated protoplasts for clarifying the mechanisms of biological effects of microgravity are discussed.     

载人深空探测任务的空间环境工程关键问题

对载人深空探测过程中将遭受的太阳宇宙射线、银河宇宙射线、微重力、尘与尘暴、深空微生物等环境进行分析。对不同深空环境给航天员带来的威胁进行了探讨。从物理屏蔽防护、辐射风险的监测和预警、辐射防护药物、航天员选拨等角度对采取的措施进行了阐述。从空间辐射对航天员的损伤机理、抗辐射和微重力药物开发、空间辐射屏蔽防护结构与材料、航天服自清洁、抗微生物侵蚀材料的研发等多个角度对需要进一步开展的工作进行了讨论。     

Possible actions of gravity on the cellular machinery.

Since the first flight of the ESA Biorack on the German Spacelab Mission D1 in 1985 evidence has been obtained that biological cells and small unicellular organisms function differently under conditions of microgravity. However, there is still lack of scientific proof that these effects are caused by a direct influence on the cells in the weightlessness condition. The question how normal gravity may play a role in cellular activity is being addressed and the results show that gravity may provide important signals during certain state transitions in the cell. These would be gravity-sensitive windows in the biological process. Also, by amplification mechanisms inside the cell, the cell may assume a state that is typical for normal gravity conditions and would change in microgravity. Experimental tools are discussed that would provide the conditions to obtain evidence for direct action of gravity and for the possible existence of gravity-sensitive windows.     

Finite time non-singular sliding mode control for spinning tether system with prescribed performance under artificial gravity mission

In this paper, the spinning tether system (STS) is applied to produce the artificial gravity overload with a proposed spin-up scheme in elliptical transfer orbits. To improve the comfort of the astronauts during spinning, the combined control scheme with tension and thrust is designed for spin-up. Then, based on the novel performance function and sliding mode technology, a finite time prescribed performance controller is proposed to track angular velocity for the desired artificial gravity overload. Compared with the existing works, the tracking error is controlled within the preset transient performance and converged to the origin within finite time even in the presence of unknown external disturbance. The stability of closed-loop tracking system is proved by Lyapunov theorem. Finally, the numerical simulations are given to demonstrate the effectiveness and robustness of the proposed controllers in the artificial gravity mission.