Zero-gravity Environment Research Articles

Designing clinical trials for future space missions as a pathway to changing how clinical trials are conducted on Earth.

The project aims to build a framework for conducting clinical trials for long-term interplanetary missions to contribute to innovation in clinical trials on Earth, especially around patient involvement and ownership. We conducted two workshops in which participants were immersed in the speculative scenario of an interplanetary mission in which health problems emerged that required medical trials to resolve. The workshops used virtual reality and live simulation to mimic a zero-gravity environment and visual perception shifts and were followed by group discussion. Some key aspects for the framework that emerged from the workshops included: (a) approaches to be inclusive in the management of the trial, (b) approaches to be inclusive in designing the research project (patient preference trials, n-of-1 trials, designing clinical trials to be part of a future prospective meta-analysis, etc), (c) balancing the research needs and the community needs (eg, allocation of the participants based on both research and community need), (d) ethics and partnerships (ethics and consent issues and how they relate to partnerships and relationships). In identifying some key areas that need to be incorporated in future planning of clinical trials for interplanetary missions, we also identified areas that are relevant to engaging patients in clinical trials on Earth. We will suggest using the same methodology to facilitate more in-depth discussions on specific aspects of clinical trials in aerospace medicine. The methodology can be more widely used in other areas to open new inclusive conversations around innovating research methodology.

A study of the microstructure modification of a space crawling robot adhesive feet based on discrete element method

According to the on-orbit maintenance mission requirements of a proposed space cooperative spacecraft, a new type of space crawling robot, which can be mounted on a grasping manipulator, is proposed. After the active spacecraft and the faulty target form a connection, the crawling robot can move to the spot on the faulty target that requires maintenance to be performed using fine operations. In this paper, the adhesion technology of space crawling robots was studied, and an adhesive microarray structure, which imitates gecko setae, was proposed. The simulation model was established using the discrete element software EDEM. The effects of the structural parameters, such as the contact area, length–diameter ratio, length, diameter, and density, on the adhesion characteristics of the microarrays in zero-gravity space environment were analysed using simulation. Based on the simulation results, a plasma deep etching process was used to process the microarray specimens. The desorption process was tested in the ground environment using the water droplet method, and the tangential desorption force was tested. The experimental data show that the tangential adhesion decreases with an increase in the spacing and the length–diameter ratio. The experimental results are very consistent with the simulation results, which further demonstrated the correctness of the discrete element simulation with respect to the desorption process and the rationality of the optimal design of the microarray structure.

Bubble population balance modelling for stationary and rotating columns under zero-gravity environment: Numerical study

Two axisymmetric dimensional Eulerian/Eulerian simulation of two-phase (gas/liquid) transient flow was performed for both stationary and rotating columns under zero gravity. Multiphase flow simulation is modelled using flow algorithm based on the finite-volume method to simulate bubble population balance modelling. Two coalescence kernels, one for laminar flow and the other for laminar shear flow, are experimented under zero gravity using special user defined functions. Effects of rotation speed are investigated at angular velocities of 0, 0.25, 0.5, 0.75 and 1 rad/s, and effects of air inlet velocity are conducted at 1, 2, 3 and 4 cm/s. The numerical results show that the centrifugal force is pulling the bubbles towards the axis of rotation and shifts them away from the wall. Also, rotation could accelerate the moving bubbles throughout the column under zero-gravity conditions. Increasing the inlet air velocity accelerates the coalescence rate with a decrease in the inlet bubble diameter. Under zero gravity, the bubbles are formed with limited size distribution and may not be represented by an equivalent phase with Sauter mean diameter. Coalescence and break-up phenomena must be considered under normal gravity and coalescence phenomenon only under zero gravity.

CFD investigation on thermodynamic characteristics in liquid hydrogen tank during successive varied-gravity conditions

In the present paper, a computational fluid dynamics (CFD) model is developed to simulate the successive varied-gravity operations for a liquid hydrogen (LH2) tank, and pressure evolution, physical field distributions and phase change amounts are obtained and analyzed. The results show that owing to the existence of helium accumulation in ullage, excessive pressure decline could be restrained, and instead a relatively stable pressure is maintained during the most time of the mission. The diffusion process of helium towards liquid surface is probably beneficial to the occurrence of mass transfer from liquid to vapor. However, the H2-He diffusion is nearly terminated within a relatively short time, so that a uniform H2-He mixture could be assumed in the researches on propellant performance in space. Moreover, acceleration level plays the dominant role in liquid-gas distribution. When an acceleration change from 3g0 to 10−3g0 occurs, no apparent interface deformation is observed. The liquid-gas interface maintains approximately horizontal distribution and only a slight liquid bending upwards is observed in near-wall region. When a zero-gravity environment is encountered, however, a complete coverage of ullage by liquid phase could be reached. Specially, it should be noted that a superheated ullage could exist in the tank center region for a long time even after its coverage by liquid phase. To meet secondary ignition requirement, orbit control thrust engines, producing axial acceleration of 10−3g0 and lasting over 100 s, could realize reliable liquid-gas separation. In addition, along with pressure reduction in the beginning stage of launching, a remarkable vapor condensation occurs. Coverage of ullage by liquid phase also yields a significant vapor condensation, while under space thrust effect, liquid evaporation mostly happens. Generally, the present study gives clear exhibitions on the pressure evolution and thermodynamic behaviors of cryogenic propellant tank, which is beneficial for the design and optimization of fuel tank system.

The underwater transformer: Ex-NASA engineers built a robot sub that transforms into a skilled humanoid

I'm drifting weightlessly, in a silence broken only by my own breathing and the occasional update from Mission Control in my headset. But this isn't the dark void of space. I'm in Houston, scuba diving in a massive swimming pool that NASA uses to train astronauts for zero-gravity environments. And though it's a thrill to watch the space-suited figures at work, I didn't come to see them. I'm here for a peek at Aquanaut, the bright orange robot that we're sharing the pool with.

Dynamics and control of a 7-DOF hybrid manipulator for capturing a non-cooperative target in space

This paper proposes a 7-DOF hybrid serial-parallel manipulator for capturing a non-cooperative target in space and discusses its dynamics and control. The hybrid manipulator is connected in a series by a 3-DOF parallel part with 1-PU&2-PUS configurations and a 4-DOF serial part with a 4R configuration. First, the UP-RRRR equivalent serial mechanism is presented for the kinematic analysis of the hybrid manipulator. Utilizing the Newton-Euler method, the dynamic model of the equivalent serial mechanism is derived in a recursive form. Then the dynamic equations of the parallel part in recursive form are also developed using the Newton-Euler method. Based on the complete dynamic model, we propose a control scheme for a hybrid robot to capture a non-cooperative target in a zero-gravity environment, including three modules: admittance control, motion estimation of the target satellite, and feedforward of the reaction forces. Finally, experimental results of full physical experiments based on air-bearing testbeds confirm the validity of the proposed control scheme for the hybrid robot to capture a non-cooperative target in space.

Electrochemical Peroxide Generation for in Situ Disinfection

Novel technologies with limited earth support are required to enable energy-efficient maintenance of closed air, water, and waste systems in microgravity spacecraft habitats such as International space station (ISS). One area of need for the interstellar travel community is cleaning/sanitizing supplies to meet personal hygiene requirements, which is currently accomplished through the use of pre-packaged, disposable, wetted wipes, or ion exchange cartridges. These items represent an appreciable carry-along mass and disposal/replacement burden requiring earth based support. Therefore, if a system could be developed to use onboard utilities to create cleaning and disinfecting solutions it would reduce the astronaut’s dependence on earth based supplies. We are addressing this challenge by demonstrating a technology that will use utilities on-board the spacecraft habitat to create sanitizing solutions and eliminate the need for regular delivery of disinfecting wipes. This concept is founded on the electrochemical reduction of oxygen to hydrogen peroxide using readily available on-board supplies of O2 and water. Peroxide is well-established disinfectant with non-toxic decomposition products (viz., O2 and H2O), that is safe enough for human contact to be sold commercially as a 3% w/w solution. Thus, it is an ideal disinfecting solution for closed space environments. The electrochemical reduction of oxygen to hydrogen peroxide occurs by two electron transfer reactions which proceeds as [O2 + 2H+ + 2e- → H2O2 or O2 + 2H2O + 2e- → H2O2 + 2OH-][1]. We designed and constructed an electrochemical reactor for generating peroxide that is compatible with the available low conductivity water stream based on a patented concept of one of our commercialization partners (De Nora Technology, Inc. U.S. patent number 6,254,762). The peroxide generation unit (PGU) system consists of oxygen chamber, catholyte chamber (with catalyzed GDE cathode[2]), whose volume can be modified as desired by changing the catholyte plate (width/length) and size/density of the NAFION bead packing material, and anolyte chamber with commercially-available mixed-metal oxide anode pressed against a cation exchange membrane, as shown in the conceptual schematic (Figure - left) and the modified PGU (Figure - right). Initial trials confirmed that the PGU can generate peroxide utilizing high conductivity sodium sulfate as catholyte. Further, the PGU was used to demonstrate the potential of generating peroxide in very low conductivity electrolytes such as distilled water (DI) and reverse osmosis water (RO) by enabling transfer conductivity through the use of NAFION ionomer “beads”. These results are promising and an early indication that the PGU will be able to generate peroxide with high performance efficiency. Faraday is continuing the technology development efforts by: (1) demonstrating the potential of the device design by testing under zero gravity; (2) optimizing the gas diffusion electrode (GDE) catalytic structure, and wettability, (3) demonstrating the potential to use onboard International Space Station (ISS) water utilities, (4) developing an electrochemical peroxide detector, and (5) designing and building an α-scale reactor to produce 1 L/day of 2 w/w% H2O2. Some of the results aimed at evaluating the system in zero-gravity environments will be presented at the conference. In addition to being an integral component of long term life support on NASA manned space missions; this technology has the potential to be an alternative method for synthesis of commercial hydrogen peroxide for on-demand onsite disinfection of process waste streams and/or field remediation systems. Acknowledgements: The financial support of NASA Contract No. NNX16CA43P and NNX17CJ12C is acknowledged. We would also like to thank Dr. Jeffrey J. Sweterlitsch from NASA Johnson Space Center (Houston, TX), who provided insight and expertise that greatly assisted the research

Electrochemical Peroxide Generation

Among the numerous technological advances sought in order to facilitate human space travel, solutions are needed for technology that supports energy-efficient maintenance of closed air, water, and waste systems in microgravity spacecraft habitats, like Mars. In particular, a technique for the in-situ generation of cleaning/sanitizing solutions is needed to reduce the demand of earth based materials like cleaning supplies to meet personal hygiene requirement during space missions. Therefore, if a system could be developed to use onboard utilities to create cleaning and disinfecting solutions it would reduce the astronaut’s dependence on earth based supplies. In Faraday’s current program we are addressing this challenge by developing a system that uses on-board resources for efficient electrochemical generation of hydrogen peroxide (H2O2) for surface sanitation applications. This concept is founded on the electrochemical reduction of oxygen to H2O2 using readily available on-board supplies of O2 and water. Peroxide is an ideal disinfecting solution for closed space environments because it has non-toxic decomposition products (viz., O2 and H2O), is safe for direct skin contact at functionally active concentrations (~1-5% w/w), and has a demonstrated disinfection capability. The goal of our initial feasibility study was to demonstrate a proof-of-concept electrochemical reactor, based on conventional fuel cell structures, that can efficiently produce H2O2 using gas diffusion electrodes (GDE)[1],[2],[3]. Specifically, the primary goals were to control product distribution (viz., exclusive production of H2O2 at the expense of H2O or H2), minimization of the energy input (by maximizing current efficiency), and maximization of the generation rate of the peroxide product. Therefore, we designed an in-situ peroxide generation system utilizing gas diffusion electrode (GDE) based electrochemical cell as illustrated in Figure 1. The cell consists of catalyzed GDE cathode[4], commercially-available mixed-metal oxide anode[5], and a cation exchange membrane separating the two electrodes. The process occurs by electrochemical reduction of oxygen to hydrogen peroxide by two electron transfer reactions which proceeds as [O2 + 2H+ + 2e- → H2O2 or O2 + 2H2O + 2e- → H2O2 + 2OH-] [6] . Within this study we have: 1) evaluated various GDE structures, catalyst, and electrolytes in order to understand the effects of system parameters on performance, 2) demonstrated the potential to efficiently produce up to 3 w/w% H2O2 concentrations, 3) demonstrated H2O2 concentrations as low as 1% are sufficient for a complete kill of E. Coli bacteria, and 4) investigate the potential of an alpha-scale peroxide generation system that is compatible with available ISS architectures, systems, and utilities. In conclusion, this study indicated a process to efficient reduction of O2 to peroxide for surface cleaning and sets the stage for scale-up and evaluation in zero-gravity environments. These results will be presented at the conference. Acknowledgements: The financial support of NASA Contract No. NNX16CA43P is acknowledged.

Research Gaps and Opportunities in Sensor-Based Medical Exploration Capabilities in Extravehicular Astronaut Suits

NASA’s Human Research Program has identified the need to improve their capability to predict estimated medical risks during exploration missions, as well as the need to provide computed medical decision support while minimizing medical resource utilization. From May 2017 through October 2017, a research team with the University of Mississippi Electrical Engineering Department conducted interviews with a dozen NASA personnel from the Human Research Program, Life Support Systems Technology Development, Game Changing Development Program, the Wyle Science, Technology and Engineering Group, and MEI Technologies. This report outlines the challenges and gaps identified as a result of these interviews in the Human Research Roadmap towards implementing a sensor-based medical monitoring system in EVA suits, as well as the opportunities in pursuing solutions towards these challenges. We describe the knowledge gaps in determining a clear definition for which measurable EVA suit environment and astronaut medical conditions are mission critical. We detail the current principle and special challenges of monitoring mission critical measurables in micro-gravity and zero-gravity environments with respect to their sensing ability. We then propose a three-stage research framework for meeting these objectives that is robust in scope, yet partitioned such that innovations or setbacks in one stage will not unduly harm progress. First, identifying a set mission critical measurable will enable innovations in sensor networks in EVA suits. We discuss proposed approaches to monitoring astronaut health and environments and relevant gaps. The second stage is using data from the sensor network as inputs to algorithms for determining when mission-critical parameters have been violated, as well as priorities for reporting that information. The third research area focuses on secure and reliable delivery of sensor information to the IV crewmembers, along with rendering of mission-critical information in a Heads-Up Display (HUD) worn by the astronaut. We discuss the current status of HUD technology in EVA suits and the challenges towards advancing that technology for mission deployment. We also discuss challenges in how the astronaut and IV crewmembers will utilize logged health and tracking information operationally. Finally, the status of the work already conducted under the proposed research framework is discussed.

Skeleton growth under uniformly distributed force conditions: producing spherical sea urchins

AbstractSea urchin skeletons, or tests, comprise rigid calcareous plates, interlocked and sutured together with collagen fibres. The tests are malleable due to mutability in the collagen fibres that loosen during active feeding, yielding interplate gaps. We designed an extraterrestrial simulation experiment wherein we subjected actively growing sea urchins toone factorassociated with zero-gravity environments, by growing them under conditions in which reactionary gravitational forces were balanced, and observed how their tests responded. Preventing tests from adhering to surfaces during active growth produced more-spherical bodies, realized as increased height-to-diameter ratios. Sea urchin tests constitute ideal systems for obtaining data that could be useful in extraterrestrial biology research, particularly in how skeletons grow under altered-gravity conditions.

Thermocapillary Flow and Coalescences of Heterogeneous Bubble Size Diameter in a Rotating Cylinder: 3D Study

Two dimensional axisymmetric and three-dimensional VOF simulations of gas/liquid transient flow were performed using a multiphase flow algorithm based on the finite-volume method. The results for motion of a multiple bubbles of a heterogeneous sizes aligned horizontally and perpendicular to a hot surface incorporating thermocapillary forces in a rotating liquid in a zero-gravity environment have been presented for the first time. No bubbles broke in any of the cases observed. The results also show that collision and agglomeration of bubbles of unequal sizes diameter are different from those of similar size diameters presented from earlier research work of Alhendal et al. Acta Astronaut. 117, 484–496 (2015). Different flow patterns such as thermocapillary bubble migration, collision, and stream function were observed and presented for the 2-D and 3-D models.

Hardware-in-the-loop simulation for the contact dynamic process of flying objects in space

In the one-gravity environment on the ground, the simulation of the contact process of two flying objects in the zero-gravity environment of space has been a challenging issue since humans first explored space by flying objects. Hardware-in-the-loop (HIL) simulation is an important and effective method to test the usability, reliability, and safety of real docking mechanisms in space. There are four main issues for HIL simulation systems: Design of simulators capable of high frequency response, high motion precision, high velocity, and rapid acceleration; compensation for simulation distortion; design of a control model for the HIL simulation process; and experimental verification. Here, we propose a novel HIL simulator system with a 6-DOF 3-3 perpendicular parallel mechanism and a 3-DOF 3-PRS parallel mechanism; discover the principle of simulation distortion; present distortion compensation models for the force measurement system, dynamic response, and structural dynamics of the simulator; and provide a control model for the HIL simulation process. Two kinds of experiments were performed on the passive-undamped elastic rod and the docking mechanisms to test their performances and to verify the effectiveness and usability of the HIL simulator. The HIL simulation system proposed in this paper is useful for developing space docking, berthing, refueling, repairing, upgrading, transporting, and rescuing technologies.

Spatially-selective cooling by liquid jet impinging orthogonally on a wettability-patterned surface

Jet impingement finds application in high-rate cooling because of its numerous merits, which, however, do not include selective directionality. The present study introduces a new configuration employing a wettability-patterning approach to divert an orthogonally-impinging laminar water jet onto a pre-determined portion of the target surface. Diverging wettable tracks on a superhydrophobic background provide the means to re-direct the impinging jet and enable spatially-selective cooling on the heated surface. An open-surface heat exchanger is constructed using this approach, and its heat transfer performance is characterized. Sensible heat transfer is quantified in terms of the extracted cooling flux and the heat transfer coefficient. Since this approach facilitates prolonged liquid contact with the underlying heated surface through thin-film spreading, evaporative cooling is also promoted. Thus, phase-change heat transfer is also facilitated, and results in the extraction of 12.4W/cm2 at water flow rate of ∼1.5mL/min. By comparing with other jet-impingement cooling approaches, the present method provides roughly four times more efficient cooling by using less amount of coolant. The reduced coolant use, combined with the gravity-independent character of this technique, offer a new paradigm for compact heat transfer devices designed to operate in reduced- or zero-gravity environments. Multiple hot spot cooling is also demonstrated using a single jet to feed two different tracks by minimally displacing or splitting the impinging jet.

Thermocapillary bubble flow and coalescence in a rotating cylinder: A 3D study

The process of thermocapillary bubbles rising in a rotating 3D cylinder in zero gravity was analysed and presented numerically with the aid of computational fluid dynamics (CFD) by means of the volume of fluid (VOF) method. Calculations were carried out to investigate in detail the effect of the rotational speed of the hosted liquid on the trajectory of both single and group bubbles driven by the Marangoni force in zero-gravity conditions. For rotational speeds from 0.25 to 2rad/s, bubble displacement with angular motion was found to be directed between the hotter surface and the rotational axis. This is contrary to the conventional bubble flow from areas of high pressure to low pressure, radial direction, or from cold to hot regions, axial direction. The results demonstrate that for the ratio of rotational speeds to the thermocapillary bubble velocity larger than unity, the surface tension gradient is the dominant force and the bubble motion towards the hotter. On the other hand, for ratio less than 1, the bubble motion is dominated and is significantly affected by centrifugal force. As rotation speed increases, the amount of deflection increases and the Marangoni effect vanishes. The current study is novel in the sense that single- and multi-bubble motion incorporating thermocapillary forces in a rotating liquid in a zero-gravity environment has never been numerically investigated.

Gravitational dispersion in a torsional wave machine

We demonstrate that mechanical waves traveling in a torsional, mechanical wave machine exhibit dispersion due to gravity and the discreteness of the medium. We also show that although the dispersion due to discreteness is negligible, the dispersion due to gravity can be easily measured and can be shown to disappear in a zero-gravity environment.

Magnetic Convection Heat Transfer in an Open Ended Enclosure Filled with Paramagnetic Fluids

Numerical simulations of thermomagnetic convection of paramagnetic fluids placed in a micro-gravity condition (g ≈ 0) and under a uniform vertical gradient magnetic field in an open ended square enclosure with ramp heating temperature condition applied on a vertical wall is investigated in this study. In presence of the strong magnetic gradient field thermal convection of the paramagnetic fluid might take place even in a zero-gravity environment as a direct consequence of temperature differences occurring within the fluid. The thermal boundary layer develops adjacent to the hot wall as soon as the ramp temperature condition is applied on it. There are two scenario that can be observed based on the ramp heating time. The steady state of the thermal boundary layer can be reached before the ramp time is finished or vice versa. If the ramp time is larger than the quasi-steady time then the thermal boundary layer is in a quasi-steady mode with convection balancing conduction after the quasi-steady time. Further increase of the heat input simply accelerates the flow to maintain the proper thermal balance. Finally, the boundary layer becomes completely steady state when the ramp time is finished. Effects of magnetic Rayleigh number, Prandtl number and paramagnetic fluid parameter on the flow pattern and heat transfer are presented.

Gravity-dependent estimates of object mass underlie the generation of motor commands for horizontal limb movements.

Moving requires handling gravitational and inertial constraints pulling on our body and on the objects that we manipulate. Although previous work emphasized that the brain uses internal models of each type of mechanical load, little is known about their interaction during motor planning and execution. In this report, we examine visually guided reaching movements in the horizontal plane performed by naive participants exposed to changes in gravity during parabolic flight. This approach allowed us to isolate the effect of gravity because the environmental dynamics along the horizontal axis remained unchanged. We show that gravity has a direct effect on movement kinematics, with faster movements observed after transitions from normal gravity to hypergravity (1.8g), followed by significant movement slowing after the transition from hypergravity to zero gravity. We recorded finger forces applied on an object held in precision grip and found that the coupling between grip force and inertial loads displayed a similar effect, with an increase in grip force modulation gain under hypergravity followed by a reduction of modulation gain after entering the zero-gravity environment. We present a computational model to illustrate that these effects are compatible with the hypothesis that participants partially attribute changes in weight to changes in mass and scale incorrectly their motor commands with changes in gravity. These results highlight a rather direct internal mapping between the force generated during stationary holding against gravity and the estimation of inertial loads that limb and hand motor commands must overcome.

A Miniaturized Analyzer Capable of White-Blood-Cell and Differential Analyses During Spaceflight

Spaceflight has adverse effects on the human body that pose health risks to astronauts spending extended time in space missions. For clinical monitoring of astronauts and for in-flight biomedical research, laboratory instruments must be available in the spaceflight environment. Currently, no instrument has been shown to be capable of generating a white blood cell (WBC) count and differential during spaceflight to our knowledge, although this is a medical requirement of the National Aeronautics and Space Administration (NASA). We evaluated a compact hematology analyzer for compatibility with a zero-gravity environment. We performed analyses in reduced-gravity during parabolic flight. Herein, we describe our engineering evaluation and report the reduced-gravity validation data we collected. The hematology analyzer we tested met the basic requirements for use in spaceflight and should be capable of accurately measuring WBC parameters aboard the International Space Station.

Investigation on zero-gravity behavior of particle dampers

The simulation study of particle damping in microgravity or zero-gravity environments is carried out using the Discrete Element Method in this paper. The results show that the damping particles in zero-gravity environments have a reasonable damping performance only when the particle container is almost fully filled with particles and at large displacement amplitude. The damper will have little effect because the particles will come together and form a floating cluster in the middle of the container, if the vibration amplitude is less than half of the gap between the particle bed and the ends of the container. To break that floating cluster, a cross-shaped spoiler is introduced and fitted inside the container, which greatly raises the damping performance in zero-gravity environments.

Numerical Study on High Prandtl Number Liquid Bridge

The overall numerical analysis of liquid bridge for high Pr number fluid and flow field of ambient air under the zero-gravity environment was carried out in the present paper. The paper used level set method of mass conservation to capture two phase interfaces. Not only the free surface deformation was considered, but also the effect of ambient gas was taken into account. Simultaneously, results of stream function in liquid bridge and ambient gas-phase were given.