Microgravity Environment Of Space Research Articles

Backstepping sliding mode control strategy of non-contact 6-DOF Lorentz force platform

With the development of aerospace technology, more and more scientific activities are carried out in the universe. Due to the microgravity environment of space, the control of the 6-DOF platform is different from those on the earth. First, a virtual prototype model of the 6-DOF non-contact platform was built in ADAMS. The dynamics model was developed based on the Newton–Euler method. Then, the 6-DOF backstepping sliding mode controller and disturbance observer were designed in MATLAB/Simulink. Finally, by combining the virtual prototype model in ADAMS and the control system in MATLAB, the co-simulation model was proposed. According to the simulation results, the 6-DOF backstepping sliding mode controller can well complete the positioning, 3D trajectory tracking, and vibration isolation tasks of non-contact 6-DOF platform. Quantitatively, the spatial error of backstepping sliding mode controller’s 3D trajectory tracking is only 50% of the ordinary sliding mode control and it is 20% of the nonlinear propotional-derivative-integral.

Simulation analysis of liquid sloshing separation in spacecraft with tank based on SPH method

<p indent=0mm>The separation of spacecraft in orbit is based on multibody dynamics in a space microgravity environment, while liquid sloshing is studied based on complex nonlinear dynamics. In this study, the smoothed particle hydrodynamics (SPH) method was used to simulate liquid sloshing with a free surface in a spacecraft tank, and the separation dynamic model of the spacecraft and liquid fuel was established. Through the analysis of spacecraft separation dynamics and fluid–structure coupling dynamics, the problem of the influence of sloshing of the liquid in the fuel tank on spacecraft separation attitude was solved. The interference force and torque of liquid sloshing on the spacecraft can be obtained from the model fluid–structure coupling dynamics calculation. The separation attitude of spacecraft with liquid sloshing in the tank is different from that based on a rigid body assumption. The liquid levels affect the calculation results of spacecraft separation attitude, interference force, and torque. The analysis results provide a reference for the optimization design and separation safety design of the spring separation mechanism and improve the reliability of spacecraft attitude control design.

NUMERICAL STUDY ON THERMAL DESTRATIFICATION IN LARGE SCALE HYDROGEN PROPELLANT TANK IN SPACE BY JET INJECTION UNDER ZERO GRAVITY CONDITION1)

Liquid Hydrogen plays a vital role in the future energy system as a space propellant, but it is sensitive to heat leakage from the environment because of its low boiling point and easy evaporation. On the other hand the buoyancy convection in the space microgravity environment is significantly reduced. When there is local heat leakage on the wall of the propellant tank, temperature stratification arises around the heat leakage source causing local overheating. It seriously affects the multiphase heat and mass transfer in the propellant tank which induces the tank pressure rise and jeopardize the structural safety of the system. To prevent the tank pressure from rising above the design of limits, venting or active pressure control techniques must be implemented. The cryogenic jet mixing is an effective means to suppress temperature stratification. The cryogenic fluid is mixed with the fluid inside the tank through a jet nozzle to reduce the local high temperature and achieve uniform temperature. In present paper, the thermal stratification phenomenon caused by the local heat leakage under microgravity condition was numerically simulated by using a fully filled two-dimensional large scale tank model. This paper mainly analyzes the suppression and elimination of local thermal stratification caused by heat leakage near the bottom of the storage tank and the outlet connecting section. The influence of different cryogenic jet mixing conditions on eliminating the temperature stratification effect is analyzed. The results show that the position of jet nozzle has no obvious effect on the elimination of thermal stratification inside the tank when the circular jet nozzle is used and the cryogenic jet condition is the same. When the jet nozzles are located in the same relative position inside the tank and the incident flow rate is the same, the circular jet nozzles have more concentrated flow direction, the flow field in the tank evolves faster, so the thermal stratification elimination effect is better than the hemispherical jet nozzles.

Dynamic Modeling and Active Vibration Isolation of a Noncontact 6‐DOF Lorentz Platform Based on the Exponential Convergence Disturbance Observer

In order to study the vibration isolation and positioning performance of the noncontact 6‐DOF platform in the space microgravity environment, this paper presented a cosimulation model of a virtual prototype. Based on the model driven by biaxial noncontact Lorentz force actuators (NLFAs), an equivalent dynamic model has been established. In the meanwhile, the 6‐DOF sliding mode robust controller with exponential convergence disturbance observer is developed. The mechanical system simulation model was designed using ADAMS, and the corresponding 6‐DOF decoupling control system and disturbance observer programs were developed using MATLAB/Simulink. According to the mechatronics simulation results, the system can enable the floating platform to achieve micron‐level posture positioning within 0.5 s. In vibration isolation simulation, the disturbance observer can predict the external disturbance input and compensate the control force more accurately so that the floating platform can effectively suppress low‐frequency disturbance and step disturbance under the control of the sliding mode controller. And the displacement of the floating platform under the disturbance of 1–100 Hz frequency sweep is less than 1 μm.

Adaptive Controller Based on Spatial Disturbance Observer in a Microgravity Environment.

In this paper, a new controller for an operating manipulator work in the space microgravity environment is proposed. First, on the basis of the load variation caused by microgravity, a sliding mode control method is used to model the gravity term, and the logistic function is introduced as the approaching function. An improved sliding mode reaching law is proposed to control the manipulator effectively, and Lyapunov theory is used to deduce its closed-loop stability. A friction compensation scheme, which regards friction as disturbance, is introduced to the microgravity environment, and a space disturbance observer (SDO) is designed from the viewpoint of disturbance suppression to identify the friction characteristics of the control system accurately. To model the lagging friction phenomenon caused by velocity inversion during operation tasks, an adaptive compensation scheme based on the LuGre model is proposed. Finally, the design of a manipulator system, which consists of a robot arm, dexterous hand, teleoperation system, central controller, and visual system, is presented. On-orbit maintenance and capture experiments are carried out successively. The effectiveness and reliability of the controller are verified, and the on-orbit operation tasks are completed successfully.

The effects of geometry and heating rate on thermocapillary convection in the liquid bridge

The experimental study on thermocapillary convection in liquid bridges of large Prandtl number has been carried out on Tiangong-2 in space. The purpose of these experiments is to study the oscillation instability of thermocapillary convection, and to discover and recognize the mechanism of destabilization of thermocapillary convection in the microgravity environment in space. In this paper, the geometry of a half-floating-zone liquid bridge is featured by the aspect ratioArand volume ratioVr, and its influence on critical conditions of oscillatory thermocapillary convection is studied. More than 700 sets of space experiments have been finished. The critical conditions and oscillation characteristics of thermocapillary convection instability in theAr–Vrparameter space have been fully obtained under microgravity conditions for the first time. It is found that theAr–Vrparameter space can be divided into two regions of different critical conditions and oscillation characteristics: the region of low frequency oscillation, and the region of high frequency oscillation. More importantly, we obtain the complete configuration of these two stability neutral curves, and find that the low frequency mode is a ‘’ type curve. Based on this, we discuss the influence of heating rate on the oscillation mode. It is found that the heating rate affects the selection of critical mode, which results in a jump change of critical temperature difference. The findings of this study are helpful to better understand the critical modes and transition processes of thermocapillary convection in liquid bridges with different configurations.

Gravity scaling law of heat transfer in nucleate pool boiling

Boiling phenomenon can realize high performance heat exchange due to latent heat transportation accompanying the liquid-vapor phase change, resulting in its wide applications for high heat flux transfer both in normal gravity on the ground and in space microgravity environment. It is well known that gravity strongly affects boiling phenomenon by creating forces in the systems that drive motions, shape boundaries, and compress fluids. The study of the influence of gravity on boiling heat transfer is of great significance for relevant space applications. Our current knowledge on boiling phenomenon, however, is often composed of a great amount of empirical correlations and semi-mechanistic models for engineering applications, which are mainly depended upon empirical data obtained from elaborately designed experiments on the ground. Although many empirical correlations and semi-mechanistic models include gravity as a parameter, they usually fail when extended beyond the empirical range they were based on. Microgravity experiment offers a unique opportunity to study the complex interactions in boiling phenomenon without gravity, and thus to reveal the mechanism of gravity, or gravity scaling law, underlying boiling phenomenon by comparing microgravity experimental data with those obtained in normal gravity. Review of the up-to-data progress on gravity scaling law of nucleate pool boiling heat transfer is made in the present paper, especially focusing on the RKM (Raj-Kim-McQuillen) gravity scaling law which presents a unified framework for scaling behaviours of nucleate pool boiling heat transfer relevant to gravity based on the quasi-steady state, ground-based short-term reduced gravity experimental results acquired during transition periods of approximately 3–5 s when the acceleration varied continuously from hypergravity to low- g , or vice versa , in parabolic flights. The gravity scaling parameter for heat flux was updated based on high quality microgravity data aboard ISS (the International Space Station), and its robustness in predicting low gravity heat transfer is further demonstrated by predicting many of the trends in the pool boiling literature that cannot be explained by any single model. There are, however, some deficiencies and/or unsolved problems in the RKM gravity scaling law. The definition of the dimensionless temperature involves the temperatures of the boiling incipiency and of the CHF (critical heat flux). It was implicitly assumed that these two characteristic temperatures are constants in different gravity conditions. These assumptions, however, have no theoretical or empirical basis in fact. Moreover, recent numerical studies utilizing the lattice Boltzmann method, as well as some experimental evidences, showed that the temperature of CHF increases with the gravity level. Furthermore, the hypotheses on the asymptotic behaviours near the boiling incipiency and the critical heat flux confused the meaning of different gravity scaling parameters, which are defined clearly in the present paper. An important reason for the deficiencies of the RKM gravity scaling law is the lack of empirical data, especially experimental results in long-term, steady state pool boiling in different levels of reduced gravity. Thus, a variable gravity pool boiling experiment project utilizing CSS (the Chinese Manned Space Station) under construction, as well as systematic numerical simulations, are suggested in order to promote the research in this field.

Parameter analysis of on-orbit volumetric measurement using cavity resonance

Propellant volumetric measurement based on the cavity acoustic resonance may be a promising alternate in space microgravity environment. The present paper concentrates on the influences of the hemispherical structure of the tank, steady/unsteady non-flat continuous propellant-gas interface, and propellant's compressibility on the acoustic resonant frequency of the system. A one dimensional mathematical acoustic resonant model, where acoustic perturbation dynamics only in the axial coordinate is considered, based on conservations of mass and momentum is provided and compared with numerical simulations by COMSOL software and experiments conducted by the previous research. Results show that analytical predictions by the present model keep consistent with numerical simulations and experiments. While the structure of a hemispherical tank can influence the resonant frequency, the present model can optimizationally compensate such effect. The continuous non-flat propellant-gas interface changes the resonant frequency. A flatter interface leads to smaller influence. On the other hand, the unsteady low-frequency low-amplitude wave-like movement of the propellant-gas interface imposes negligible effluence on the resonant frequency of the tank. Finally, the propellant compressibility is quantitatively shown to be negligible for most propellants.

Experiments on Simulation Microgravity of Composite Deployable Antenna

After the satellite is launched into a special orbit in space, its space environment is zero gravity or microgravity. Therefore, in ground simulation experiments, it is necessary to consider overcoming the gravity of the earth and try to reduce or eliminate the influence of gravity. In this paper, the method of counteracting gravity by air-floating platform is used to simulate the space microgravity environment, and to do the unfolding experiments for single deployable antenna. After the deployment of the single antenna, the connection structure of single antenna is tested by modal experiment. The microgravity simulation experiment shows that the shape memory hinge can normally satisfy the folding and unfolding of a single antenna. The whole unfolding process is smooth and there is no obvious vibration. The first six modes and natural frequencies are obtained and compared with the simulation results. The comparison shows that the experimental results are in agreement with the simulation results.

Mechanical design and analysis of a gripper for non-cooperative target capture in space

Space grippers are the key devices for accomplishing space non-cooperative target capture, which has a great significance for satellite services and space debris removal. This article proposes a novel mechanical gripper device for the capture of aluminum honeycomb panels of non-cooperative satellites. The gripper was modeled and assembled in the three-dimensional modeling platform UGNX. The model was imported into the simulation software ADAMS. ADAMS is capable of analyzing the kinematic feasibility of the gripper model. Collision and penetrating power analysis of the mechanical claws into an aluminum honeycomb plate were carried out in LS-DYNA. Through non-vertical piercing experiment, the maximum approaching angle tolerance is 10°. The established rigid connection can withstand a destructive force greater than 1000 N. A prototype of the mechanical gripper is built. A ground test was carried out with this prototype, in which a test-platform simulated the space microgravity environment. The results certified that the prototype could reach the target at a relative speed of 0.5 m/s and then quickly complete the grabbing motion and establish a rigid connection. The experiment shows that this mechanical gripper can accomplish the task of repeatedly capturing the surface of non-cooperative space satellites.

3D Printed and Additively Manufactured RoboSiC™ for Space, Cryogenic, Laser and Nuclear Environments

Abstract Goodman Technologies has been directly responsive to, and focused on, 3D printing and additive manufacturing techniques, and what it takes to manufacture in zero-gravity. During a NASA Phase I SBIR project, using a small multi-printhead machine, we showed that it was possible to formulate and 3D print silicon carbide into shapes appropriate for lightweight mirrors and structures at the production rate of 1.2 square-meter/day. Gradient lattice coupons with feature sizes on the order of 0.8mm were printed and were easily machined to very fine tolerances, ten-thousandths of an inch by Coastline Optics in Camarillo, CA. To further elaborate on the list of achievements, in Phase I, Team GT demonstrated three different ceramization techniques for 3D printing low areal cost, ultra-lightweight Silicon Carbide (SiC) mirrors and structures, radiation shielding, and electronics, several of which could be employed in microgravity The Goodman Technologies briefing presented at 2017 Mirror Technology Days “3D Printed Silicon Carbide Scalable to Meter-Class Segments for Far-Infrared Surveyor: NASA Contract NNX17CM29P along with sample coupons resulted in extreme interest from both Government and the Contractor communities. Our materials, which we call RoboSiC™, is suited for many other applications including heat sinks and radiation shielding for space electronics, and we have already started to make the first parts for these applications. The successful Phase I project suggests that we will meet or exceed all NASA requirements for the primary mirror of a Far-IR Surveyor such as the Origins Space Telescope (OST) and have a high probability solution for the LUVOIR Surveyor in time for the 2020 Decadal Survey. Results indicate that printing on the ground will achieve an areal density of 7.75 kg/square-meter (~39% of a James Webb Space Telescope (JWST) beryllium segment), a cost to print of $60K/segment, and an optical surface that has nanometer-scale tolerances. Printing in the microgravity environment of space we have the potential to achieve an areal density of 1.0–2.0 kg/square meter (&amp;lt;10% of a JWST beryllium segment), with a cost to print of ~$10K/segment. The areal density is 2–15 times better than the NASA goal of 15 kg/square meter, and the costs are substantially better than the NASA goal of $100K/square meter. The encapsulated gradient lattice construction provides a uniform CTE throughout the part for dimensional stability, incredible specific stiffness, and the added benefit of cryo-damping. For the extreme wavefront control required by the Large UV/Optical/IR Surveyor (LUVOIR) the regularly spaced lattice construction should also provide deterministic mapping of any optical distortions directly to the regular actuator spacing of a deformable mirror (DM). Some of our processes will also allow for direct embedding of electronics for active structures and segments. Encapsulation of the lattice structures will allow for actively cooling with helium for unprecedented low emissivity and thermal control. Several decades of experience and testing with SiC have shown that our materials will survive, nay thrive in, the most extreme Space, Cryogenic, Laser and Nuclear Environments.

Osteoclast-derived exosomes inhibit osteogenic differentiation through Wnt/β-catenin signaling pathway in simulated microgravity model

In the microgravity environment of space, astronauts undergo osteoporosis due to an imbalance in bone remodeling. Recent studies have shown that exosomes derived from osteoclasts could mediate cell-to-cell communication in bone remodeling. However, the role of osteoclast-derived exosomes in bone remodeling in microgravity remains a mystery. Our objective is to investigate the cellular processes modulated by exosomes from RAW264.7 cell-derived osteoclasts and the underlying mechanism of action for the exosomes-mediated osteogenesis of osteoblast-like MC3T3-E1 cells in simulated microgravity. We took advantage of the random positioning machine (RPM) to simulate microgravity for the model and investigated the role of exosomes from RAW264.7 cell-derived osteoclasts in osteoclast-osteoblast communication. The results showed that this type of mature osteoclast-derived exosomes (OC-Exos) in the RPM evidently inhibited the cellular proliferation of osteoblasts via inducing cellular apoptosis and altering their cell cycle distribution. Alkaline phosphatase and mineralization activity of MC3T3-E1 cells were significantly lower after treatment with OC-Exos from RPM and mRNA expression of osteoblast-specific genes were down-regulated. Further study confirmed that OC-Exos in RPM obstructed the differentiation of MC3T3-E1 cells by interfering with Wnt/β-catenin signaling pathway. Together, these observations demonstrated that OC-Exos played an essential role in the regulation of bone remodeling in the microgravity environment. These results shed light on a novel pathway of cross-talk between osteoclasts and osteoblasts, which will be helpful to explain the possible mechanisms underlying osteoporosis in microgravity.

Laser piloted ignition of electrical wire in microgravity

This work studied the piloted ignition of electrical wires in both normal gravity and microgravity using the laser-induced spark. Unique experiments were conducted in the microgravity parabolic flight with laboratory wires under the oxygen concentration of 14–21% and external radiation of up to 15.9 kW/m2. The wire sample consists of a 2.5-mm thick core, using the solid copper (Cu) or the hollow stainless steel (SS) tube, and a 0.75-mm thick black polyethylene (PE) insulation. This is the first piloted-ignition experiment on solid fuel in microgravity with the laser-induced spark as the pilot. Experimental results show that regardless of the oxygen level, the ignition delay time is always smaller in microgravity than in normal gravity, indicating a higher fire risk in the microgravity space environment. As the heat flux and the oxygen concentration increase, auto-ignition is observed. Moreover, if the core is exposed to the external heating source, it can heat the insulation to promote the ignition, different from the heat sink found in past ignition research. This unique research provides valuable information about the fire risk of electrical wire in microgravity and future long-term space travel.

Dynamic modeling and experimental analyses of Stewart platform with flexible hinges

A new dynamic model of the Stewart platform with flexible hinges is proposed based on the Kane equation combined with the principle of virtual powers. Firstly, the model and coordinates introduced are described. Specifically, the velocity and acceleration of each part are obtained through kinematics analysis. Secondly, balance equations are subsequently formulated using the principle of virtual powers. Noting that the vibration amplitude of satellites is very small in the space microgravity environment, a linearly simplified form of the dynamic equation of the Stewart platform with flexible hinges is obtained. Finally, the validity of the equations is experimentally and numerically verified, and it is also demonstrated that the proposed platform possesses a good vibration isolation performance. All the results presented in this paper lay the foundation for further study on vibration control using a Stewart platform.

(Mechanical Speed Multiplication Bearings and Flying Bicycle and Flying Car Design)

Chinese Abstract: 为了让业余爱好者都可以通过本论文的设计图来改装制造万有斥力飞行器，特将这三种装置的设计技术参数、设计理念、制作方式向大家展示。 这是一篇基础科学研究与应用科学研究两方面兼有的论文，本论文主要在上一篇《颠覆传统科学理论的曹氏万有斥力飞行器》的基础上，对无万有引力作用下的园环的滚动情况作进一步研究，以及对有引力作用下的园环的滚动情况的研究，对自旋中的进动产生的原理及产生进动的原因进行了深入研究。同时，在此原理的基础上，从一名总设计师的角度，设计了人力骑行的离心万有斥力飞行自行车，有动力的离心万有斥力飞行汽车以及以此飞行汽车为工具，进行飞行汽车载人飞上月球取样的双人飞行器，为此需求的高速转速轴承的研究设计，以便用于对飞行器进行配套的高速转速轴承的设计制造。 本论文可以让全球任何一位普通工程师都能按本论文的设计，生产出合格的产品。能够在72小时以内，让这种飞行汽车飞上月球取样并安全返回。 本论文的总设计技术将证明，笔者作为一名总设计师，进行任何总设计的能力，不输于全球任何一位优秀的总设计师设计出来的成果。 本论文设计理念为以机械式为主，这样可以避免电子器件在复杂的电磁环境下易受到干扰，产生危险的情况发生。主要是在地球万有引力的环境中运行，在太空微重力环境下的运行可以兼容。 不同于其它许多的发明是从现象才找出其中的真理，本人是从基本理论的推导发现了现象：万有斥力飞行器。 随着统一场理论研究的逐深入，即电磁二元素存在的物质宇宙中，由于电磁的相互转换，产生了自旋，并由此产生了静质量、惯性、万有引力、万有斥力等，统一场理论系列后面的论文《论惯性引力和惯性斥力与万有引力和万有斥力的统一》，将作全面细致深入地研究分析。所以，旋转体可以被很好的利用于解决万有引力、万有斥力产生的所有结果。在统一场理论的推动下，推导出滚动离心斥力，地球上的人类将进入飞行历史的新纪元，将实现无万有引力和无万有斥力飞行和太空旅行。当10组自旋体在瞬间将离心斥力调整到同一个方向时，将产生瞬间几吨重的离心万有斥力，这是当今所有飞行器都达不到的状况，当滚动离心斥力科学技术发展到利用和控制原子核自旋的水平时，一颗子弹的所有原子核旋转离心万有斥力合力将达到几吨重，子弹的飞行速度将达到10000km/s（一万公里每秒）。 English Abstract: In order to allow amateurs can modify the design of this paper to create universal repulsion especially the design of these three devices technical parameters, design concepts, production methods to show you. This is a basic scientific research and applied science both the paper, this paper mainly in the previous article subvert the traditional scientific theory of Cao universal repulsion aircraft, based on the universal gravitation The further research on the rolling condition and the research on the rolling condition of the ring under gravitation are carried out. The principle of the precession in the spin and the reason of precession are deeply studied. At the same time, on the basis of this principle, from the perspective of a chief designer, designed a man-riding centrifugal universal repulsion flying bike, a powered centrifugal universal repulsion flying car and the use of this flying car as a tool for flight Vehicle manned flying on the moon sampling double for which the demand for high speed bearing research and design, in order to be used for aircraft supporting high speed bearing design and manufacturing. This thesis can make any ordinary engineer in the world can design and produce qualified products according to the dissertation. Be able to fly the flying car to the moon for sampling and return safely within 72 hours. The overall design techniques of this paper will prove that the author, as a chief designer, has the ability to carry out any general design without losing the design of any outstanding chief architect in the world. The design concept of this dissertation is mainly mechanical, which can avoid the danger of the electronic device being interfered in the complex electromagnetic environment. Mainly in the gravitation of the Earth environment, the operation in the space micro-gravity environment can be compatible. Different from many other inventions, the truths are found out of phenomena. I have found the phenomenon from the basic theory deduction: universal repulsion aircraft. With the deepening of the study of unified field theory, that is, in the material universe in which electromagnetic two elements exist, the spin is generated due to the mutual conversion of electromagnetic fields, and thus the static mass, inertia, universal gravitation and universal repulsion are generated, The thesis behind the theory series, On the Unity of Inertial Gravity and Inertial Repulsion and Universal Gravitation and Universal Repulsion, will be thoroughly and in-depth studied and analyzed. Therefore, the rotating body can be well used to solve all the problems caused by universal gravitation and universal repulsion. Driven by unified field theory, a new era of rolling centrifugal repulsion and the human race on earth entering a flight history will be deduced. It will achieve gravitation-free and universal repulsion and space travel. When the 10 groups of spin-bodies in a moment of centrifugal repulsion will be adjusted to the same direction, it will produce a moment a few tons of centrifugal universal repulsion, which is all the aircraft today are unattainable, when the rolling centrifugal repulsion science and technology to Utilizing and controlling the level of atomic spin, all nuclei of a bullet will spin a thousand revolutions together with a universal repulsion force that will fly at a speed of 10,000 km / s (10,000 km per second).

Persistence of plant hormone levels in rice shoots grown under microgravity conditions in space: its relationship to maintenance of shoot growth.

We investigated the effects of microgravity environment on growth and plant hormone levels in dark-grown rice shoots cultivated in artificial 1 g and microgravity conditions on the International Space Station (ISS). Growth of microgravity-grown shoots was comparable to that of 1 g-grown shoots. Endogenous levels of indole-3-acetic acid (IAA) in shoots remained constant, while those of abscisic acid (ABA), jasmonic acid (JA), cytokinins (CKs) and gibberellins (GAs) decreased during the cultivation period under both conditions. The levels of auxin, ABA, JA, CKs and GAs in rice shoots grown under microgravity conditions were comparable to those under 1 g conditions. These results suggest microgravity environment in space had minimal impact on levels of these plant hormones in rice shoots, which may be the cause of the persistence of normal growth of shoots under microgravity conditions. Concerning ethylene, the expression level of a gene for 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, the key enzyme in ethylene biosynthesis, was reduced under microgravity conditions, suggesting that microgravity may affect the ethylene production. Therefore, ethylene production may be responsive to alterations of the gravitational force.

Exploration of Microgravity by Using the Cold Atom Interferometer in Deep Space Environment

The fundamental principle of atom interferometer and the advantages of atom gravimeter in microgravity environment are introduced and the present research status and potential applications of atom gravimeters in microgravity environment are described. Compared with other gravimeters, the atomic interference gravimeter becomes a good choice for deep space gravitational field measurement, and the deep space microgravity environment can effectively prolong the interference time of the atomic interferometer and improve the gravimeter sensitivity.

Attitude control for astronaut assisted robot in the space station

Because of the limited working hours of astronauts in the space station, the in-cabin robot has high value in the technological validation and scientific research. Based on this requirement, we proposed and designed an Astronaut Assisted Robot(AAR) working in the space station. It can float in the space station cabin, fly autonomously, and hold a fixed position and/or posture. In addition, it also possesses environmental awareness capabilities and intelligence. Thus the AAR can assist astronauts to complete some special scientific experiments or technical tests. In this paper, the system architecture and experimental equipment of the AAR are designed firstly depending on the characteristics of space microgravity environment and the requirements of assisting astronauts missions. And then, the motion principles of the AAR are analyzed and the robot’s dynamic model is established by using the Newton - Euler algorithm. Since the attitude control of the robot is the basis for its free movement, the PID Neural Network( PIDNN) algorithm, which is a kind of intelligent control algorithm, is used to design the attitude controller of the AAR. Finally, the reasonability of the robot’s structural design and the availability of its attitude controllers are verified through the simulation experiments.

Astronauts in outer space teaching students science: comparing Chinese and American implementations of space-to-earth virtual classrooms

The purpose of this study was to investigate differences between science lessons taught by Chinese astronauts in a space shuttle and those taught by American astronauts in a space shuttle, both of whom conducted experiments and demonstrations of science activities in a microgravity space environment. The study examined the instructional structure and science topics coverage, as well as the methods employed for helping students conceptualize scientific laws via experimental demonstrations and activities. The analysis of the lessons sampled in this study revealed three predominant themes for how both the Chinese and the American astronauts conceptualized the science topics (i.e., Health and Life in Space, Work and Career in Space, and Exploration in Space and Earth Science). The analysis also examined how the teacher-student interactions were structured. Research findings suggest that under the appropriate conditions informal science education can play a distinct role in providing students with experiences of: (a) experiments unavailable in classroom settings, and (b) explanations of these experiments by field-based scientists conducting original research.

Microwave interrogation cavity for the rubidium space cold atom clock**Project supported by the National Natural Science Foundation of China (Grant No. 11034008), the Fund from the Ministry of Science and Technology of China (Grant No. 2013YQ09094304), and the Youth Innovation Promotion Association, Chinese Academy of Sciences.

The performance of space cold atom clocks (SCACs) should be improved thanks to the microgravity environment in space. The microwave interrogation cavity is a key element in a SCAC. In this paper, we develop a microwave interrogation cavity especially for the rubidium SCAC. The interrogation cavity has two microwave interaction zones with a single feed-in source, which is located at the center of the cavity for symmetric coupling excitation and to ensure that the two interaction zones are in phase. The interrogation cavity has a measured resonance frequency of 6.835056471 GHz with a loaded quality factor of nearly 4200, which shows good agreement with simulation results. We measure the Rabi frequency of the clock transition of the rubidium atom in each microwave interaction zone, and subsequently demonstrate that the distributions of the magnetic field in the two interaction zones are the same and meet all requirements of the rubidium SCAC.