Low-gravity Environment Research Articles

Rapid adaptation to microgravity in mammalian macrophage cells

Despite the observed severe effects of microgravity on mammalian cells, many astronauts have completed long term stays in space without suffering from severe health problems. This raises questions about the cellular capacity for adaptation to a new gravitational environment. The International Space Station (ISS) experiment TRIPLE LUX A, performed in the BIOLAB laboratory of the ISS COLUMBUS module, allowed for the first time the direct measurement of a cellular function in real time and on orbit. We measured the oxidative burst reaction in mammalian macrophages (NR8383 rat alveolar macrophages) exposed to a centrifuge regime of internal 0 g and 1 g controls and step-wise increase or decrease of the gravitational force in four independent experiments. Surprisingly, we found that these macrophages adapted to microgravity in an ultra-fast manner within seconds, after an immediate inhibitory effect on the oxidative burst reaction. For the first time, we provided direct evidence of cellular sensitivity to gravity, through real-time on orbit measurements and by using an experimental system, in which all factors except gravity were constant. The surprisingly ultra-fast adaptation to microgravity indicates that mammalian macrophages are equipped with a highly efficient adaptation potential to a low gravity environment. This opens new avenues for the exploration of adaptation of mammalian cells to gravitational changes.

Behavior of blood in a low-gravity environment

Behavior of blood in a low-gravity environment

A Parametric Study for the Design of an Optimized Ultrasonic Percussive Planetary Drill Tool.

Traditional rotary drilling for planetary rock sampling, in situ analysis, and sample return are challenging because the axial force and holding torque requirements are not necessarily compatible with lightweight spacecraft architectures in low-gravity environments. This paper seeks to optimize an ultrasonic percussive drill tool to achieve rock penetration with lower reacted force requirements, with a strategic view toward building an ultrasonic planetary core drill (UPCD) device. The UPCD is a descendant of the ultrasonic/sonic driller/corer technique. In these concepts, a transducer and horn (typically resonant at around 20 kHz) are used to excite a toroidal free mass that oscillates chaotically between the horn tip and drill base at lower frequencies (generally between 10 Hz and 1 kHz). This creates a series of stress pulses that is transferred through the drill bit to the rock surface, and while the stress at the drill-bit tip/rock interface exceeds the compressive strength of the rock, it causes fractures that result in fragmentation of the rock. This facilitates augering and downward progress. In order to ensure that the drill-bit tip delivers the greatest effective impulse (the time integral of the drill-bit tip/rock pressure curve exceeding the strength of the rock), parameters such as the spring rates and the mass of the free mass, the drill bit and transducer have been varied and compared in both computer simulation and practical experiment. The most interesting findings and those of particular relevance to deep drilling indicate that increasing the mass of the drill bit has a limited (or even positive) influence on the rate of effective impulse delivered.

On the interest of microgravity experimentation for studying convective effects during the directional solidification of metal alloys

Under terrestrial conditions, solidification processes are often affected by gravity effects, which can significantly influence the final characteristics of the grown solid. The low-gravity environment of space offers a unique and efficient way to eliminate these effects, providing valuable benchmark data for the validation of models and numerical simulations. Moreover, a comparative study of solidification experiments on earth and in low-gravity conditions can significantly enlighten gravity effects. The aim of this paper is to give a survey of solidification experiments conducted in low-gravity environment on metal alloys, with advanced post-mortem analysis and eventually by in situ and real-time characterization.

Numerical simulations of oscillation-driven regolith motion: Brazil-nut effect

Many if not most small asteroids are rubble piles covered by regolith, and small perturbations may be enough to disturb their surfaces in complex ways due to microgravity. Experiments to study low-gravity regolith dynamics are challenging, and properly validated numerical simulations can provide valuable insights. In this paper, we investigate numerically size segregation among regolith grains, which is likely to occur after repeated shaking events. In particular, we are interested in the so-called Brazil-nut effect (BNE), i.e. the migration of a large intruder towards the top of a vertically shaken granular system. We go a step forward in simulating this effect by implementing horizontal periodic boundary conditions (PBC) in the N-body code pkdgrav, with the aim of making the simulations more representative of the expected asteroid environment. We study the influence of PBC on the BNE in Earth gravity and compare them with a walled case. We also investigate the influence of static and rolling friction on the BNE. With walls, we observe the well-known convection mechanism driving the BNE. However, we find that a different mechanism, consisting of void filling, is responsible for the BNE with PBC, and we discuss its relevance in light of previous studies. By running simulations in 10−4g, we show that this void-filling mechanism remains relevant in a low-gravity environment. However, we find that depending on the gravity level, the void-filling mechanism is differently influenced by the friction properties of particles. We speculate that this is likely due to a change in the granular flow time-scales.

The New Concept of a Sampling Device Driven by Rotary Hammering Actions

Sample return space missions are one of the possible options to extend our knowledge about extraterrestrial materials, processes occurring on surface and subsurface level, as well as interactions between regolith and technology. Collection of surface or subsurface material from such bodies is a key technical process that needs to be performed to achieve the goals of such missions. Although in terrestrial environment the sampling process is relatively easy, smart solutions are needed for zero-gravity, unknown and remotely accessible space environment. In this paper, the concept of a new type of sampling device, called PACKMOON, dedicated for low-gravity bodies space environment, is presented. The principle of operation of the PACKMOON device is based on two key elements: insertion of the spherical jaws (casing) into regolith by rotary hammering actions and minimization of interaction with the lander by taking advantage of doubling mechanical subsystems, which operate in the same angular direction but in opposite sense. Numerical simulations validated by experimental results allow to optimize the device. As a result, the PACKMOON device is a reliable mechatronic system that effectively uses power to sample relatively hard material (up to 5–7 MPa) with minimum interaction with the lander. In addition, both thermal and mechanical interaction with the sample is relatively small, and in that sense, the sample is more valuable for further scientific investigations. This issue is a key driver for planned sample return missions such as ESA Phootprint mission to Phobos.

Comprehensive study of initial diameter effects and other observations on convection-free droplet combustion in the standard atmosphere for n-heptane, n-octane, and n-decane

This paper reports the results of a comprehensive experimental study on the effect of initial droplet diameter (Do) over a very wide range (0.5mm<Do<5mm) on the spherically symmetric droplet burning characteristics in the standard atmosphere of three alkanes – n-heptane, n-octane and n-decane – that are representative of components found in petroleum-based transportation fuels and their surrogates. Spherical symmetry in the burning process was promoted by carrying out the experiments in a reduced convection (stagnant ambience) and buoyancy (low gravity) environment using the facilities of a ground-based drop tower for Do < 0.8mm and a spaced-based platform (the International Space Station) for Do>1.0mm.The results show that for Do greater than about 2mm, K decreases with increasing Do in an early period of burning and with the data being correlated in the form K∼Do−n based on a scale analysis of an energy balance on the flame. For Do larger than approximately 2mm the droplet flames often disappeared indicating an extinction mechanism that was speculated to be due to radiative losses from the flame. Concurrently, measurements of wideband radiation dropped significantly and the burning rate gradually approached pure evaporation.In some instances for n-heptane and n-octane radiative extinction was accompanied by droplet evaporation rates that were significantly higher than evaporation in a hot ambience which persisted for a significant fraction of the burning history before decreasing to evaporation in a cold ambience. An energy balance on the drop related the flame temperature to droplet diameter from which it was predicted that flame temperatures after ignition were greater than 1200K before dropping to under approximately 800K and remaining constant thereafter until eventually reaching near ambient conditions. This intermediate regime of burning was conjectured to be associated with a low temperature combustion process. The transition to this intermediate regime upon radiative extinction was occasionally accompanied by flame oscillations, the origin of which was uncertain but could have been initiated by motion of the droplet owing to the deployment process.

Modeling and Coupling Dynamics of the Spacecraft with Multiple Propellant Tanks

This paper is mainly focused on the modeling and coupling dynamics of the spacecraft with multiple propellant tanks. The dynamic boundary conditions on a curved, liquid, free surface under a low-gravity environment are transformed to general simple differential equations by using a Fourier–Bessel series expansion method, and the state vectors of coupled liquid-sloshing equations are composed by the modal coordinates of a relative potential function and the modal coordinates of the wave height. The overall coupled dynamic equations for the rigid platform motion and liquid fuel sloshing are subsequently obtained by means of Lagrange’s equations in terms of general quasi coordinates. The orbit thruster firing and attitude momentum wheel controller are applied to the coupled system to testify to the mathematical model and analyze the coupling dynamics of a coupled fluid–spacecraft system. MATLAB software is used for symbolic manipulation, coupling dynamics, and control simulations. Numerical simulations via computer are carried out to validate the model derived in this paper.

Numerical investigation of solidification and CET of the transparent alloy NPG-37.5 wt.% DC in microgravity “TRACE” experiment

A solidification experiment “TRACE” of the transparent alloy Neopentylglycol (NPG)-37.5wt.% D-Camphor (DC) was conducted on-board the sounding rocket TEXUS-47 in low-gravity environment to investigate the columnar growth and the columnar-to-equiaxed transition (CET). To improve the fundamental understanding of solidification and CET in microgravity, the current laboratory scale experiment was tried to be numerically reproduced by a recently developed 5-phase volume averaging model. The temperature gradient in the solidification cell is applied to the simulation. In absence of melt flow, the calculated cooling curves, columnar tip position, tip undercooling and velocity, and number density of equiaxed crystals were compared to the results of in-situ real-time observations of the experiment. The CET could be predicted at position close to that of experiment. Simulation reveals the competitive growth between the columnar and equiaxed crystals before CET. Modelling parameters of equiaxed nucleation and columnar tip growth are the key to regulate this competition and to locate the CET. Experimental verification of modelling parameters considering melt flow is intended in the future work.

Post-stroke hip fracture in older people: A narrative review

Background/Aims: A hip fracture is a serious and common complication after stroke. Individuals often experience particular gait problems post-stroke and may have difficulty with everyday activities such as walking. Therefore, the interventions for falls prevention in older patients should be re-examined when applied to the post-stroke population. This study reviews the risk factors for falls and hip fractures that are specific to the post-stroke population and the measures that may be taken to prevent hip fractures and/or falls in this patient group. Method: A narrative review of articles written in English in the scientific literature on the risk factors, natural history and prevention of hip fractures in post-stroke patients. Results: The interventions that were reviewed showed some benefit to post-stroke patients. These included interventions designed to increase physical activity, water-based exercise, general falls prevention programmes, and the use of force platforms and body weight supported treadmills. More solid evidence was found to support strategies such as the symmetrical use of limbs, which provides appropriate support and an environment where an individual can regain more normal movement patterns. This can be achieved by training in a low-gravity environment using water-based exercises or a body-weight supported treadmill. To perform more symmetrical movements, biofeedback (visual feedback) or a force platform can be used in addition to symmetrical exercises. Conclusions: In a post-stroke population, it is better to pay special attention to the prevention of falls and hip fracture than to rehabilitate after a fracture has occurred. Evaluation and management of the risk factors that contribute to falls should be a priority in post-stroke rehabilitation, focusing on as many risk factors as possible in hip fracture prevention programmes. A variety of techniques should be used to facilitate functional recovery, emphasising symmetry and optimal movement patterns.

The microgravity DSC-DCMIX1 mission onboard ISS: Experiment description and results on the measurement of the Soret coefficients for isobutylbenzene, dodecane, tetralin ternary hydrocarbons mixtures

In the energy sector, in particular for hydrocarbon reservoirs, accurate simulation of the various forms of mass flux is important in oil exploration and optimal oil recovery. Since the diffusion and thermodiffusion coefficients of binary hydrocarbon mixtures have been measured and analyzed in detail elsewhere (Urteaga et al., 2012; Jaber et al., 2009; Kianian et al., 2012), here we experimentally analyzed and reported the separation in a ternary hydrocarbon mixture of tetrahydronaphthalene, isobutylbenzene, and dodecane due to thermal gradients, and we determined the Soret coefficients of this mixture for four different compositions. The thermodiffusion experiment was conducted by means of a Mach–Zehnder Interferometer (MZI) using two wavelengths and in a low gravity environment on board the International Space Station (ISS). Thus, we report the chemical concentration variations of the various cases obtained by the recently developed processing technique. In addition we investigated the reliability and the repeatability of the MZI experiment to study thermodiffusion for ternary mixtures. Finally, according to the transient behavior of the separation of the components, the Soret diffusion coefficients for various compositions of this mixture were measured and then compared.

Coupling dynamic analysis of spacecraft with multiple cylindrical tanks and flexible appendages

This paper is mainly concerned with the coupling dynamic analysis of a complex spacecraft consisting of one main rigid platform, multiple liquid-filled cylindrical tanks, and a number of flexible appendages. Firstly, the carrier potential function equations of liquid in the tanks are deduced according to the wall boundary conditions. Through employing the Fourier–Bessel series expansion method, the dynamic boundaries conditions on a curved free-surface under a low-gravity environment are transformed to general simple differential equations and the rigid-liquid coupled sloshing dynamic state equations of liquid in tanks are obtained. The state vectors of rigid-liquid coupled equations are composed with the modal coordinates of the relative potential function and the modal coordinates of wave height. Based on the Bernoulli–Euler beam theory and the D’Alembert’s principle, the rigid-flexible coupled dynamic state equations of flexible appendages are directly derived, and the coordinate transform matrixes of maneuvering flexible appendages are precisely computed as time-varying. Then, the coupling dynamics state equations of the overall system of the spacecraft are modularly built by means of the Lagrange’s equations in terms of quasi-coordinates. Lastly, the coupling dynamic performances of a typical complex spacecraft are studied. The availability and reliability of the presented method are also confirmed.

Constant-force cylinder experiment with low-gravity simulation

Purpose – The purpose of this paper is to describe a technical creation called a constant-force cylinder, which exhibits more advantages in providing constant force in a low-gravity environment than some existing methods. Design/methodology/approach – The authors design the constant-force cylinder with simple ideas and realistic applicability that is easy to achieve. The authors analyze and formulate the cylinder, and explain how the realization of constant force and low gravity are obtained during the experiment by calculations. Force analysis and simple mathematics/statistics are used in the calculation. Findings – The authors prove the effectiveness and accuracy of the constant and low-gravity properties of the new cylinder. In addition, the authors formulate the acceleration value to drive the cylinder which is flexible and easy to be adjusted during the experiment. Practical implications – The constant-force cylinder can be functioning in a low-gravity environment with simple structures and economica...

Using the inertia of spacecraft during landing to penetrate regoliths of the Solar System

The high inertia, i.e. high mass and low speed, of a landing spacecraft has the potential to drive a penetrometer into the subsurface without the need for a dedicated deployment mechanism, e.g., during Huygens landing on Titan. Such a method could complement focused subsurface exploration missions, particularly in the low gravity environments of comets and asteroids, as it is conducive to conducting surveys and to the deployment of sensor networks. We make full-scale laboratory simulations of a landing spacecraft with a penetrometer attached to its base plate. The tip design is based on that used in terrestrial Cone Penetration Testing (CPT) with a large enough shaft diameter to house instruments for analysing pristine subsurface material. Penetrometer measurements are made in a variety of regolith analogue materials and target compaction states. For comparison a copy of the ACC-E penetrometer from the Huygens mission to Titan is used. A test rig at the Open University is used and is operated over a range of speeds from 0.9 to 3ms−1 and under two gravitational accelerations.The penetrometer was found to be sensitive to the target’s compaction state with a high degree of repeatability. The penetrometer measurements also produced unique pressure profile shapes for each material. Measurements in limestone powder produced an exponential increase in pressure with depth possibly due to increasing compaction with depth. Measurements in sand produced an almost linear increase in pressure with depth. Iron powder produced significantly higher pressures than sand presumably due to the rough surface of the grains increasing the grain-grain friction. Impacts into foamglas produced with both ACC-E and the large penetrometer produced an initial increase in pressure followed by a leveling off as expected in a consolidated material. Measurements in sand suggest that the pressure on the tip is not significantly dependent on speed over the range tested, which suggests bearing strength equations could be applied to impact penetrometry in sand-like regoliths.In terms of performance we find the inertia of a landing spacecraft, with a mass of 100kg, is adequate to penetrate regoliths expected on the surface of Solar System bodies. Limestone powder, an analogue for a dusty surface, offered very little resistance allowing full penetration of the target container. Both iron powder, representing a stronger coarse grained regolith, and foamglas, representing a consolidated comet crust, could be penetrated to similar depths of around two to three tip diameters. Speed tests suggest a linear dependence of penetration depth on impact speed.

Isspresso Development and Operations

ABSTRACT The ISSpresso is a small aisle deployed payload developed to demonstrate the capability to brew quality espresso coffee in the environment found on the International Space Station (ISS) as well as in the conditions that would be experienced on possible future human exploration missions beyond Low Earth Orbit (LEO) to the Moon or Mars. A number of design challenges are presented by microgravity and low-gravity environments. In addition, the ISS program has a number of safety and interface requirements that any payload needs to adhere to. For ISSpresso each requirement was fully met as documented by the verifications submitted to NASA, including those required by the Payload Safety Review Panel (PSRP) to demonstrate compliance with ISS safety requirements for transportation, on-orbit operation, and return or disposal NASA Certification was obtained at the end of 2014. ISSpresso is currently onboard ISS having been successfully operated for the first time during Expedition 43.

Benchmark experiments and numerical modelling of the columnar-equiaxed dendritic growth in the transparent alloy Neopentylglycol-(d)Camphor

Solidification benchmark experiments on columnar and equiaxed dendritic growth, as well as the columnar-equiaxed transition have been carried out under diffusion-dominated conditions for heat and mass transfer in a low-gravity environment. The system under investigation is the transparent organic alloy system Neopentylglycol-37.5wt.-%(d)Camphor, processed aboard a TEXUS sounding rocket flight. Solidifications was observed by standard optical methods in addition to measurements of the thermal fields within the sheet like experimental cells of 1 mm thickness. The dendrite tip kinetic, primary dendrite arm spacing, temporal and spatial temperature evolution, columnar tip velocity and the critical parameters at the CET have been analysed. Here we focus on a detailed comparison of the experiment “TRACE” with a 5-phase volume averaging model to validate the numerical model and to give insight into the corresponding physical mechanisms and parameters leading to CET. The results are discussed in terms of sensitivity versus numerical parameters.

A Magna Carta for Mars

Maltman discusses the threats of first humans to reach the Red Planet. Mars One, claims it will send a crewed mission to the Red Planet in 2026. Its well known that the seven-month journey to Mars will expose astronauts to DNA damage from cosmic radiation once they are outside the protective shield of Earth's atmosphere and magnetic field, and their muscle and bone density will deteriorate in the low-gravity environment. What's often overlooked, or diplomatically brushed aside, is the effects on the human psyche of boredom, prolonged close proximity to others and competition for scarce resources. This holds not just for the journey, but also once any space colony is established and growing.

Using natural, stable calcium isotopes of human blood to detect and monitor changes in bone mineral balance

We are exploring variations in the Ca isotope composition of blood and urine as a new tool for early diagnosis and monitoring of changes in bone mineral balance for patients suffering from metabolic bone disease, cancers that originate in or metastasize to bone, and for astronauts who spend time in low gravity environments. Blood samples are often collected instead of, or in addition to, urine in clinical settings, so it is useful to know if variations in the Ca isotope composition of blood carry the same information as variations in urine. We found that the Ca isotope composition of blood shifts in the same direction and to the same magnitude (~2partspertenthousand — pptt) as that of urine in response to skeletal unloading during bed rest. However, the Ca isotope composition of blood is lighter than that of urine by 12±2pptt. This offset between blood and urine may result from Ca isotope fractionation occurring in the kidneys. This is the first study to confirm the suspected offset between the Ca isotope composition of blood and urine in humans, to directly quantify its magnitude, and to establish that either blood or urine can be used to detect and quantify bone loss.

Granular transport in driven granular gas.

We numerically and theoretically investigate the behavior of a granular gas driven by asymmetric plates. The injection of energy in the dissipative system differs from one side to the opposite one. We prove that the dynamical clustering which is expected for such a system is affected by the asymmetry. As a consequence, the cluster position can be fully controlled. This property could lead to various applications in the handling of granular materials in low-gravity environment. Moreover, the dynamical cluster is characterized by natural oscillations which are also captured by a model. These oscillations are mainly related to the cluster size, thus providing an original way to probe the clustering behavior.

A Miniature Surgical Drill Using Ultrasonic/Sonic Frequency Vibration

A study is presented of a miniature ultrasonic surgical drill designed for bone biopsy, based on an ultrasonic/sonic drill which converts high frequency to low frequency vibrations through a freely vibrating mass between an ultrasonic transducer-horn and a drill bit. For conventional surgical drilling using a rotary drill or an ultrasonic drill, considerable power is required to penetrate into bone and the efficiency is low. However, for ultrasonic/sonic drilling, sufficient acoustic energy is accumulated and then released through each impact to achieve precise drilling with a lower power requirement. The ultrasonic/sonic drill was originally invented for rock drilling in low gravity environments. In this study it is incorporated in a miniature ultrasonic surgical drill and the effective impulse delivered to the bone is used to evaluate the drilling performance. To develop a miniature surgical device based on maximising the effective impulse, optimisation of the ultrasonic horn and free-mass is first demonstrated. The shape and dimensions of the ultrasonic horn and free-mass are determined through FEA, which focuses on maximising the post-collision velocity of the free-mass. Then, the entire dynamic stack constituting the surgical drill device is modelled as a mass-spring-damper system to analyse the dynamic behaviour. The numerical model is validated through experiments, using a prototype drill, which record the velocity of the free-mass and the drilling force. The results of the numerical models and experiments indicate this miniature ultrasonic surgical drill can deliver sufficient impulse to penetrate bone and form the basis of an ultrasonically activated bone biopsy device.