Microgravity Environment Of Space Research Articles

Spreading Dynamics and Interfacial Characteristics of Sn-3.0Ag-0.5Cu-xBi Melting on Cu Substrates

The effects of Bi addition on the properties of Sn-3.0Ag-0.5Cu molten alloy on Cu substrates are discussed using wettability and interface microstructure analysis. The changes of the contact angles between Sn-3.0Ag-0.5Cu-xBi and Cu substrates with the spreading time are described by Dezellus model. It indicates that the spreading process is governed by the interfacial reaction during the dwelling time. The interface microstructure is observed to clarify the effects of reactions on the spreading behavior. It is found that Cu6Sn5 is formed adjacent to the solder and Cu3Sn appears over the substrate with Bi added at 613K, indicating that Bi exists between the intermetallics and the addition of Bi can hinder the diffusion of copper towards the interior of the solder. Therefore the existence of Bi decreases the agglomeration of Cu-Sn grains. The growth of intermetallics is thus limited and the shape of intermetallics transforms from scallop to zigzag consequently. However, the segregation phenomenon appears when the additive amount of Bi is more than 5.5mass %, which could lead to the occurrence of fracture and degrade the performance of Sn-3.0Ag-0.5Cu-xBi alloy. The results of the present study provide basic physical and chemical data for the application of lead-free solder in the future microgravity space environment.

Parameter estimation of a three-axis spacecraft simulator using recursive least-squares approach with tracking differentiator and Extended Kalman Filter

Spacecraft simulators are widely used to study the dynamics, guidance, navigation, and control of a spacecraft on the ground. A spacecraft simulator can have three rotational degrees of freedom by using a spherical air-bearing to simulate a frictionless and micro-gravity space environment. The moment of inertia and center of mass are essential for control system design of ground-based three-axis spacecraft simulators. Unfortunately, they cannot be known precisely. This paper presents two approaches, i.e. a recursive least-squares (RLS) approach with tracking differentiator (TD) and Extended Kalman Filter (EKF) method, to estimate inertia parameters. The tracking differentiator (TD) filter the noise coupled with the measured signals and generate derivate of the measured signals. Combination of two TD filters in series obtains the angular accelerations that are required in RLS (TD-TD-RLS). Another method that does not need to estimate the angular accelerations is using the integrated form of dynamics equation. An extended TD (ETD) filter which can also generate the integration of the function of signals is presented for RLS (denoted as ETD-RLS). States and inertia parameters are estimated simultaneously using EKF. The observability is analyzed. All proposed methods are illustrated by simulations and experiments.

Development of an ultra-high vacuum system for space cold atom clock

Space cold atom clock (SCAC) is developed for a series of experiments related to laser cooling of atoms and cold atom clock in space microgravity environment. An ultra-high vacuum (UHV) system is the key element for SCAC. This paper presents the design of the UHV system and also shows the status of an initial UHV system prototype with the design and a series of special vacuum treatments whose pressure distribution satisfies the special requirements for SCAC. A dual pumping system, including ion pump and getter, is introduced, and pressures of different positions have been calculated. Experiments have been carried out to acquire the performances of the initial prototype. It is proved that the initial prototype can not only self-sustain an equilibrium pressure for more than 2 months without power but also withstand the mechanical vibration test and space environment simulation test. Furthermore, an optimization design is used to get pressures which are much lower than the desired pressure (∼×10−8 Pa) in the interaction zone of the system has been demonstrated.

Effect of Oenothera odorata Root Extract on Microgravity and Disuse-Induced Muscle Atrophy.

Muscle atrophy, a reduction of muscle mass, strength, and volume, results from reduced muscle use and plays a key role in various muscular diseases. In the microgravity environment of space especially, muscle atrophy is induced by muscle inactivity. Exposure to microgravity induces muscle atrophy through several biological effects, including associations with reactive oxygen species (ROS). This study used 3D-clinostat to investigate muscle atrophy caused by oxidative stress in vitro, and sciatic denervation was used to investigate muscle atrophy in vivo. We assessed the effect of Oenothera odorata root extract (EVP) on muscle atrophy. EVP helped recover cell viability in C2C12 myoblasts exposed to microgravity for 24 h and delayed muscle atrophy in sciatic denervated mice. However, the expressions of HSP70, SOD1, and ceramide in microgravity-exposed C2C12 myoblasts and in sciatic denervated mice were either decreased or completely inhibited. These results suggested that EVP can be expected to have a positive effect on muscle atrophy by disuse and microgravity. In addition, EVP helped characterize the antioxidant function in muscle atrophy.

Space Program SJ-10 of Microgravity Research

SJ-10 program provides a mission of space microgravity experiments including both fields of microgravity science and space life science aboard the 24th recoverable satellite of China. Scientific purpose of the program is to promote the scientific research in the space microgravity environment by operating the satellite at lower earth orbit for 2 weeks. There are totally 27 experiments, including 17 ones in the field of microgravity science (microgravity fluid physics 6, microgravity combustion 3, and space materials science 8) and 10 in the field of space life science (radiation biology 3, gravitational biology 3, and space biotechnology 4). These experiments were selected from more than 200 applications. The satellite will be launched in the end of 2015 or a bit later. It is expected that many fruitful scientific results on microgravity science and space life science will be contributed by this program.

How to stimulate a space microgravity environment or effect on Earth: From the viewpoint of responses of space cell growth to microgravity

Little is known about the effects of a microgravity environment in space on biological, chemical, and physical processes. It also remains unclear if it is possible to simulate a space microgravity environment or effect on Earth. This paper discusses, according to the mechanical/physical principles of the basic processes of cell growth in space, the issues of what gravitational change is, how a space microgravity environment or effect can be simulated, and how biological responses to a simulated microgravity environment can be mimicked. It aims to elucidate relevant concepts in space life science and biotechnology, as well as in space physiology and medicine, and to present the scientific merits of related ground-based investigations.

Queer in Zero G: An interview with Frank Pietronigro

<span>American interdisciplinary artist Frank Pietronigro’s work explores issues that arise from two seemingly disparate fields: queer culture, and the culture of space travel. His writing and artwork – some of it created on parabolic flights simulating the microgravity environment of outer space – interrogate the relationships, existing and potential, between the queer and the extra-terrestrial. Pietronigro was kind enough to agree to be interviewed for this special issue on the horizons of contemporary queer theory. In the interview, we discuss his life as a queer artist, his work in microgravity spaces, and intersections of sexuality, class, art, the body, and queer possibilities in extra-terrestrial space.</span>

空间微重力下离轴三反相机离焦范围

The mirror interval and radius of curvature of optical system including three mirrors are often changed due to the impact of space microgravity,which has a greater impact on the back focal length,and causes camera defocus and imaging quality reduction.Through the equivalent Gauss optical system analysis of three-mirror system,back focal length formula can be obtained.By homogeneous coordinate transformation,the reflection mirror rigid-body displacement formula is obtained,and a mirror radius is obtained in the microgravity environment using the least squares fitting algorithm.Finally,by calculating the camera in space microgravity environment,the defocusing amount is 0.04 mm.Results provide a theoretical basis for the design of focusing mechanism.

Adaptive Compensation Control for Ground Simulation Equipment of Space Microgravity Environment Base on Neural Sliding-model

Difficult problems of simulation the space microgravity environment for big and middle experimental objects with complex move are considered. A novel system is proposed and the adaptive compensation control method based on neural sliding mode is designed. The equipments combine machine transmission、motor drive and air-bearing to realize three-dimension spatial microgravity simulation. Force feedback controller counteracts gravity real timely as controller. The scheme dispenses with accurate dynamical model. Friction non-linearity of machine system and outside disturbance are considered. Controller is designed based on state feedback. Sliding model controller is employed to compensate uncertainty model to guarantee robust. RBF neural network is used to adaptive study uncertainty up bound to reduce "chattering". The stability is proved based on Lyapunov theory. The simulation shows that the design of test system can achieve higher simulation accuracy, has important engineering value.

Using space-based investigations to inform cancer research on Earth

Experiments conducted in the microgravity environment of space are not typically at the forefront of the mind of a cancer biologist. However, space provides physical conditions that are not achievable on Earth, as well as conditions that can be exploited to study mechanisms and pathways that control cell growth and function. Over the past four decades, studies have shown how exposure to microgravity alters biological processes that may be relevant to cancer. In this Review, we explore the influence of microgravity on cell biology, focusing on tumour cells grown in space together with work carried out using models in ground-based investigations.

The effect of the space flight environment on mucin production in the mouse uterine tube

Numerous studies have indicated that the microgravity environment of space has harmful effects on several tissues throughout the body. Although this phenomenon is well documented, research in this area is still in its relative infancy. This study investigates the effects of space flight on mucin production of the uterine tubes of mice. This study examined the epithelium of the uterine tubes from female mice that were flown on the space shuttle Endeavour for 13days in August, 2007 and their concomitant controls. The tissue was qualitatively analyzed for the type of mucin produced, i.e., acidic, neutral, acidic/neutral mixture. Further, the tissue was quantitatively analyzed for the amounts of mucins produced by measuring the thickness of the mucin layer for each region of the uterine tube: isthmus, ampulla, and infundibulum. One way ANOVA tests were used to compare mucin thickness between all three sets of animals. Results indicate similar but not identical results between the three regions of the uterine tube. The Baseline tissue had the thickest mucin layer regardless of treatment group. In the ampulla the mucin layer was the thinnest in the Flight tissue, followed by the Ground Control, with the Baseline being the thickest. Analysis of the mucin layer of the infundibulum of the three treatment groups indicated no difference in its thickness between the three regions of the uterine tube. These results indicate a trend toward thinning of the mucin layer of the uterine tube in space flight, but also indicate an influence by the housing environment.

Disruption of NF-κB1 prevents bone loss caused by mechanical unloading

Mechanical unloading, such as in a microgravity environment in space or during bed rest (for patients who require prolonged bed rest), leads to a decrease in bone mass because of the suppression of bone formation and the stimulation of bone resorption. To address the challenges presented by a prolonged stay in space and the forthcoming era of a super-aged society, it will be important to prevent the bone loss caused by prolonged mechanical unloading. Nuclear factor κB (NF-κB) transcription factors are activated by mechanical loading and inflammatory cytokines. Our objective was to elucidate the role of NF-κB pathways in bone loss that are caused by mechanical unloading. Eight-week-old wild-type (WT) and NF-κB1-deficient mice were randomly assigned to a control or mechanically unloaded with tail suspension group. After 2 weeks, a radiographic analysis indicated a decrease in bone mass in the tibias and femurs of the unloaded WT mice but not in the NF-κB1-deficient mice. An NF-κB1 deficiency suppressed the unloading-induced reduction in bone formation by maintaining the proportion and/or potential of osteoprogenitors or immature osteoblasts, and by suppression of bone resorption through the inhibition of intracellular signaling through the receptor activator of NF-κB ligand (RANKL) in osteoclast precursors. Thus, NF-κB1 is involved in two aspects of rapid reduction in bone mass that are induced by disuse osteoporosis in space or bed rest.

Mastering Cryogenic Propellants

AbstractThe National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) began experimentation with cryogenic propellants in the early 1950s to understand the potential of these high-performance propellants for use in liquid propellant rocket engines. Supporting these tests required learning how to both design cryogenic systems and develop procedures to safely and reliably work with cryogenic fuels and oxidizers. This early work led to the development of a skill set that has been core to the center ever since. When NASA was formed and the exploration missions were defined, it became clear that the ability to use cryogenic propellants in the thermal and microgravity environment of space was critical to mission success, and the agency was tasked with enabling this capability. To support development of the Centaur upper stage and the Saturn S-IVB stage, GRC researchers and engineers initiated extensive technology development for the in-space application of cryogenic fluid management (CFM)...

Perception of smooth and perturbed vection in short-duration microgravity

Successful adaptation to the microgravity environment of space and readaptation to gravity on earth requires recalibration of visual and vestibular signals. Recently, we have shown that adding simulated viewpoint oscillation to visual self-motion displays produces more compelling vection (despite the expected increase in visual-vestibular conflict experienced by stationary observers). Currently, it is unclear what role adaptation to gravity might play in this oscillation-based vection advantage. The vection elicited by optic flow displays simulating either smooth forward motion or forward motion perturbed by viewpoint oscillation was assessed before, during and after microgravity exposure in parabolic flight. During normal 1-g conditions subjects experienced significantly stronger vection for oscillating compared to smooth radial optic flow. The magnitude of this oscillation enhancement was reduced during short-term microgravity exposure, more so for simulated interaural (as opposed to spinal) axis viewpoint oscillation. We also noted a small overall reduction in vection sensitivity post-flight. A supplementary experiment found that 1-g vection responses did not vary significantly across multiple testing sessions. These findings: (i) demonstrate that the oscillation advantage for vection is very stable and repeatable during 1-g conditions and (ii) imply that adaptation or conditioned responses played a role in the post-flight vection reductions. The effects observed in microgravity are discussed in terms of the ecology of terrestrial locomotion and the nature of movement in microgravity.

Al2O3 nanoparticle reinforced Fe-based alloys synthesized by thermite reaction

It is very difficult to manufacture oxide nanoparticle strengthened alloys through the conventional casting in the gravity field or even in the space microgravity environment. A thermite reaction process was used to produce molten metal that was then solidified in a graphite mold in super gravity field caused by centrifugal force; we were able to obtain Al2O3 nanoparticle reinforced Fe-based alloys. The formation of Al2O3 nanoparticles was related to the addition of TiO2 xerogel to the thermite mixture, and their uniform distribution in the alloy can be explained by their assembly in (Ni, Fe)Al intermetallics during solidification owing to the low interfacial energy between them.

Thermophysical Property Measurements of High Temperature Melts Using an Electrostatic Levitation Method

Thermophysical properties of high temperature melts are important to better understand material processes such as casting, welding, and crystal growth. Containerless processing techniques combined with non-contact diagnostic methods play significant roles in thermophysical property measurements of high temperature melts because these methods can circumvent problems which arise from a reaction between container and melts. The electrostatic levitation method can measure density, surface tension, and viscosity of high temperature materials. Most of refractory metals including tungsten have been melted and their thermophysical data have been taken with this method. This paper briefly explains the technique and discusses the future measurements using microgravity environment in space.

A combined transport-kinetics model for the growth of renal calculi

Renal stone disease is not only a concern on the Earth but could conceivably pose a serious risk to the astronauts' health and safety in Space. In this study, a combined transport-kinetics model for the growth of calcium oxalate (CaOx) crystals is presented. The model is used to parametrically investigate the growth of renal calculi in urine with a focus on the coupled effects of transport and surface reaction on the ionic concentrations at the surface of the crystal and their impact on the resulting growth rates. It is shown that under nominal conditions of low solution supersaturation and low Damköhler number that typically exist on the Earth, the surface concentrations of calcium and oxalate approach their bulk solution values in the urine and the growth rate is most likely limited by the surface reaction kinetics. But for higher solution supersaturations and large Damköhler numbers that may be prevalent in the microgravity environment of Space, the calcium and oxalate surface concentrations tend to shift more towards their equilibrium or saturation values and thus the growth process may be limited by the transport through the medium. Furthermore, it is shown that as the crystal size increases a shift towards a transport-limited growth process is likely. In this situation beyond a critical radius that is a function of the physiochemical parameters of the renal environment, the growth rate will not be independent of the radius as in a reaction-limited situation but will decrease as the crystal size increases.

Experimental approaches to study thermodiffusion – A review

A detailed review of the experimental investigations of the thermodiffusion/thermophoresis process in liquid and gaseous mixtures is presented. Experiments in the laboratories on earth as well as studies in a microgravity environment in space have been described. The former include the non-optical apparatus such as the classical Soret cell, thermodiffusion column, two-chamber thermodiffusion cell and the thermal field-flow fractionation, as well as the optical techniques, viz., classical Soret cell with beam deflection, thermal diffusion forced Rayleigh scattering, thermal lens method and the microfluidic fluorescence method. These methods are discussed along with their advantages and disadvantages. Experiments performed in the microgravity environment are also discussed.

Modeling and Verification of an Astronaut Handling Large-mass Payload

The experiments on astronaut motions are difficult to conduct due to the limitation and high cost of constructing or simulating the microgravity environment of space. Therefore, the method of computer simulation on astronaut extravehicular activity is broadly promoted. However, validations and verifications for these simulations stated in related literatures are incomplete such as comparing with the limits of human body movements or reconstructing a three-dimensional movement for some parts of EVA video. Novel modeling and verification methods for the task of an astronaut handling large-mass payload during EVA were revealed. A simplified model of an astronaut was constructed, and the astronaut motion was conceived as a planar movement of a multi-body system which includes seven segments with six revolute joints in the human body sagittal plane. The inverse kinematics method was used to calculate joint angles, joint velocities, and joint accelerations in time domain. The solution of joint torques using the inverse recursive dynamics was achieved. Furthermore, a virtual model with the ADAMSTM software was developed and implemented to verify the results by adding the kinematical data calculated to joints in order to achieve the trace of the center of mass of the hand. Additionally, the joints kinematics and kinetics data with time in the virtual model were obtained and compared with the corresponding calculated data. This result indicates that the modeling methods proposed can be employed as a solid algorithm to conduct the simulation of astronaut’s tasks in EVA, and verification using the virtual model can be easily operated and has a good accuracy. This study provides an effective and economical way of modeling and simulation for extravehicular missions.

Study on Actuators of Magnetic Suspension Platform Under Microgravity Environment in Space

摘要: 为满足空间实验室的科学实验载荷对微重力环境水平的要求,需要保证空间微重力实验载荷平台的振动隔离性能,即需要平台激励器能在控制系统的作用下适时地产生抑制平台扰动的激励力.本文提出了平台激励器的初步指标,从磁悬浮基本原理出发设计出多种结构形式,在此结构基础上完成有限元磁路仿真和激励器的线圈设计,并对各种结构形式进行比较,根据比较结果总结出各结构形式的优缺点,为激励器的具体设计提供了依据. 关键词: 磁悬浮平台 / 磁悬浮激励器 / 结构形式 / 有限元仿真 / 线圈设计