Microgravity Platform Research Articles

Model of a microgravity platform based on the mechanical principle of operation

The paper considers a model of a mechanical microgravity platform. The purpose of the paper is to develop a model of a mechanical microgravity platform. The experience of creating small spacecraft for technological purposes for carrying out gravity-sensitive processes on board is analyzed. The principle of operation of a mechanical microgravity platform is described. The microgravity platform is equipped with an electrodynamic drive to compensate for micro-accelerations. The electrodynamic drive have three identical independent control circuits to compensate for microaccelerations along the three corresponding coordinate axes. The second Kirchhoff rule was used to describe the current strength in the closed circuit of the drive. Dynamic Euler equations were used to develop the control laws. The equations for estimating micro-accelerations inside the protected zone are obtained. The ways of meeting the requirements for microaccelerations for the implementation of gravity-sensitive processes on a spacecraft are shown. Recommendations are given on the use of the platform on board a small spacecraft for technological purposes.

An apparatus to study arc-wire direct energy metal deposition additive manufacturing process in a drop tower microgravity platform.

Understanding the mechanisms and dynamics of molten metal droplet transfer within the plasma of a directed energy deposition arc process in microgravity is critical for optimizing the build process with minimal defects. This paper presents a unique experimental setup designed to investigate the transfer of molten metal droplets in the microgravity environment of a drop tower. The primary design of the apparatus revolves around accommodating, within the confines of the drop tower experimental capsule, essential components, including a high-speed camera with necessary filters for capturing molten metal droplets, a consumable electrode wire-arc setup, batteries, a linear traverse stage for single bead deposition, sensors, data acquisition systems, online communication systems, and the control system. These systems are secured to withstand the high deceleration forces at the end of a free fall in the drop tower. The arrangement has demonstrated consistent deposition outcomes, capturing clear images of droplet transfers using a high-speed camera along with voltage, current, and temperature data during the microgravity state induced by free fall. This apparatus will serve as a foundational element in establishing a viable additive manufacturing capability for space applications, as it provides fundamental insights into the transfer of molten metal droplets.

A Legged Small Celestial Body Landing Mechanism: Landing Simulation and Experimental Test

Landing mechanism tends to rebound and turn over, and the stability time is long when landing on the small celestial body. Its landing performance in different conditions is necessary to be evaluated to guide the landing. Here, landing performance evaluation is realized by simulation. Key factors affecting the landing performance including cardan element damping, foot anchors, retro-rocket thrust, landing slope angle, and landing attitude are analyzed. A microgravity platform is built to test the landing mechanism, and the consistency between the simulation and the experiment is compared. On the basis of simulation and experiment, some landing suggestions are proposed to improve the landing performance.

Bubble coalescence and break-up in confined oscillating two-phase flows under microgravity conditions

Passive two-phase heat transfer systems, such as pulsating heat pipes, are a promising thermal management solution for the rapidly growing space sector. The strong coupling between thermal and hydraulic phenomena complicated the development of reliable off-the-shelf components. This was due to the difficulties in establishing and maintaining the desired slug-plug flow pattern in a wider region sufficiently far from the annular flow, which can lead to evaporator dry-out. In this work, inertial effects on the flow pattern are investigated under adiabatic conditions to define what limits the operability range of a device. The fluid motion characteristics of pulsating heat pipes have been mechanically induced to observe conditions that lead to the break-up or coalescence of bubbles. The authors were granted access to the ESA drop tower microgravity platform to explore surface tension dominant flows and higher hydraulic diameters compared to the ground capillary diameters. A range of fluids (FC-72 and ethanol) and diameters (2.5 mm to 8 mm) has been explored, along with combinations of oscillating fluid flow, analysing high-speed images and estimating velocity and acceleration. Both the Reynolds number, in combination with the modified Bond number, have been investigated, plotting the operating points on a flow map, showing a very clear limit between break-up and coalescence when the velocity and acceleration signs are considered. This new conceptual flow map can be used to further improve existing modelling tools for pulsating heat pipes operating under reduced gravity. Furthermore, images demonstrating the break-up and coalescence may be aid to CFD scientists in verifying their results.

Direct Trajectory Optimization of Free-Floating Space Manipulator for Reducing Spacecraft Variation

This letter investigates the direct trajectory optimization of the free-floating space manipulator (FFSM). The main purpose is to plan the joint space trajectories to reduce the spacecraft motion due to the joint rotation during the FFSM performing tasks. To improve the calculation efficiency, the adaptive Radau pseudospectral method (A-RPM) is applied to discretize the system dynamics and transform the formulated optimal problem into a nonlinear programming problem (NLP). By adaptively subdividing the current segment and assigning collocation points according to the solution error, high-degree interpolation polynomials are avoided. To verify the effectiveness of the proposed method, a ground micro-gravity platform of the FFSM system is designed by using the air-bearing technique, on which experiments are carried out. The results show that the variation of the base spacecraft is dramatically reduced if the joints rotate along the optimized trajectories.

Soft matter dynamics: A versatile microgravity platform to study dynamics in soft matter.

We describe an experiment container with light scattering and imaging diagnostics for experiments on soft matter aboard the International Space Station (ISS). The suite of measurement capabilities can be used to study different materials in exchangeable sample cell units. The currently available sample cell units and future possibilities for foams, granular media, and emulsions are presented in addition to an overview of the designand the diagnostics of the experiment container. First results from measurements performed on ground and during the commissioning aboard the ISS highlight the capabilities of the experiment container to study the different materials.

Simulation Analysis and Experimental Verification of the Locking Torque of the Microgravity Platform of the Chinese Space Station

The Microgravity Platform (MP) of the Chinese Space Station is locked and released by Lock-or-Release (L/R) mechanism on both sides. In order to ensure the safety and reliability of the MP under the vibration environment during the rocket launch, the L/R mechanism must output the appropriate locking torque value. Based on the structural characteristics of the Scientific Experiment Cabinet (SEC), this paper proposes a method of evaluating locking torque by combining theory with experiment, and the relationship between locking force and locking torque of L/R mechanism is proved that the locking force on both sides can reach 2000 N at 25 Nm driving torque. Finally, it is verified by vibration test that the locking torque obtained by this method can effectively guarantee the safety and reliability of the MP under vibration environment.

Experimental Characterization of Weightlessness During Glider Parabolic Flights

Access to earthbound weightlessness is critical to many branches of applied sciences. Besides, several space systems require microgravity testing before their launch. Existing solutions (drop towers, parabolic flights, sounding rockets) offer variable durations and qualities of microgravity environment, but their cost and lead times make them unpractical for small actors such as universities or start-up companies. This leads to a growing interest for alternative microgravity platforms. Here, we study the use of gliders to perform parabolic flights at a lower cost, and we propose a systematic quantification of glider’s 0-g flight capabilities. Results of our flight test campaign show that gliders offer up to 5.5s of weightlessness, with excursions below 0.1g, and a satisfactory level of repeatability. Besides, the recordings do not suffer from the increased level of vibrations generated by piston engines, typical of light-aircraft-based alternatives. Operational considerations associated with glider parabolic flights are also discussed. Finally, we conclude that a microgravity platform based on gliders would be suitable especially for compact experiments and equipment in order to support accelerated design and development, or to produce preliminary experimental results.

Design of experiment-based tolerance synthesis for a lock-or-release mechanism of the Chinese Space Station Microgravity Platform

Abstract. This paper deals with the tolerance synthesis with the application for a typical Lock-or-Release (L/R) mechanism, used for Chinese Space Station Microgravity Platform (SSMP). The L/R mechanism is utilized to lock the SSMP maintaining space position during the launching stage, and to release the SSMP automatically during on-orbit stage. Manufacturing accuracy of L/R mechanism presents direct influence on its kinematic and dynamic behaviors. Tolerance synthesis can provide a reasonable assignment of tolerance, satisfying the critical assembly criteria while lowering manufacturing complexity. In this paper, based on the number-theory method (NTM), a Halton-set based Monte Carlo (MC) simulation is introduced in the accuracy model of the L/R mechanism, aiming at improving analytical precision and efficiency for tolerance synthesis. A design of experiment (DOE) based tolerance synthesis approach is proposed. With initial tolerance determined by capacity, sensitivities of different tolerance factors are generated through the first DOE stage, and then applied to determine feasible tolerance levels. The final tolerance assignments, like points scatted in high-dimensioned space with inherent uniformity, are then produced through uniform DOE in the second stage. Result shows that the majority of feasible tolerance assignments generated have more relaxed tolerance, which can facilitate the manufacturing process.

Accuracy modeling and analysis for a lock-or-release mechanism of the Chinese Space Station Microgravity Platform

With development of Chinese space science and technology, plenty of microgravity experiments will be conducted in the Chinese Space Station to be built, and therefore demand for high-precision electromechanical equipment increases substantially. In this paper, a comprehensive accuracy analysis of a new type of auto lock-or-release (L/R) mechanism, which is applied in the Space Station Microgravity Platform (SSMP), is implemented. Firstly, two models (vector analysis model and vector differential model) are, therefore, proposed to analyze output errors of the mechanism. Due to transmission errors from the transmission chain of the gear mechanism, influence factors on axial errors of lead screws are analyzed using design of experiment (DOE) for factor sensitivities. It shows that manufacturing tolerances of the lead screw is the dominant factor. Then, verification of the two proposed accuracy models is comparatively implemented through Monte Carlo (MC) simulation and DOE. Using the present accuracy model, location errors of the lead screw throughout the mechanism's working stroke are illustrated, where the non-synchronous error of the mechanism is particularly discussed. A linear relation between the variance of the non-synchronous error and that of the structural error is established, followed by analyzing influence factors on the non-synchronous error.

ARION 1 Reusable Sounding Rocket: The New Microgravity Platform in Europe

During Q2 of 2019, the European sounding rocket, ARION 1 will have its maiden flight. ARION 1, a liquid-propelled sounding rocket that is being developed by PLD Space, will lift off from the launch facilities in the South of Spain, concretely in Huelva. PLD Space, a Spanish start-up company established in 2011, has focused during the last years on the development of liquid-propulsion rocket engines that will power their rockets. After having tested successfully the first reusable rocket engine in their facilities at the airport of Teruel, PLD Space is concentrating its efforts on finalizing the entire ARION 1 sounding rocket. ARION 1, the first-ever reusable sounding rocket in Europe, will be able to provide around 4 min of microgravity conditions after reaching an apogee of 150 km in a nominal mission. This sounding rocket will have the capability of carrying up to 100 kg of payload, exposing scientific and technological payloads to low accelerations due to the liquid-propulsion technologies. With this paper, PLD SPACE wants to introduce the ARION 1 reusable sounding rocket, its capabilities as well as the advantages of a liquid-propelled-based sounding rocket with respect to other traditional solid-based sounding rockets. ARION 1 aims to be the sounding rocket reference in Europe, providing an affordable, flexible and simple microgravity platform to industry, space agencies, research centres and academia.

Reachable Relative Motion Design of Space Manipulator Actuated Microgravity Platform

This paper investigates the concept of the space manipulator-based microgravity platform. The system is composed of a spacecraft, a manipulator with an isolating shield as the end effector, and a testbed floating inside the shield. Assuming that the orbit of the spacecraft is circular, this paper focuses on the reachable relative motion design problem. Based on the analytical solution to the Clohessy–Wiltshire equation and the inverse kinematics of the manipulator, the relationship between the initial variables of the manipulator and the relative trajectory is presented. In both the zero-velocity releasing case and the nonzero-velocity releasing case, by investigating the boundaries of the relative motion, the criteria for the reachable relative motion are obtained. In the case in which the initial residual speed is adjustable, the routine solving for the largest elliptical trajectory is developed. Numerical simulations demonstrate the effectiveness of the criteria for the reachable motion in multiple cases.

The 2.5 s Microgravity Drop Tower at National Centre for Combustion Research and Development (NCCRD), Indian Institute of Technology Madras

Space missions involving humans require a better understanding of various phenomena happening in space environments. A number of experiments need to be conducted in microgravity for addressing various issues encompassing safety (primarily fire) and better understanding of fluid and material behaviour. Of the various methods used for obtaining microgravity conditions, drop towers offer ground based microgravity platform. They provide a cost effective platform for doing short duration, repeatable, high quality microgravity experiments. This paper describes key factors that influence the design of a drop tower. The salient features of 2.5 s microgravity tower set up at National Centre for Combustion Research and Development (NCCRD), IIT Madras (IITM) are discussed. Primary features of the three critical elements, namely the drop capsule, the release unit and the decelerator unit are described along with review of these elements in existing drop towers. The IITM drop tower operates in ambient atmospheric conditions to minimise the cost of operation. In order to achieve good quality microgravity levels, a dual capsule configuration is adopted. The shape of the outer capsule is arrived at by detailed transient computational fluid dynamic analysis of the drag shield under free fall condition over the drop height. A pneumatic mechanism is used for capsule release and brought to rest at the end of fall in a carefully designed decelerator unit. The decelerator unit consists of an airbag with controlled air outflow for smooth deceleration.

Miniaturized Lab System for Future Cold Atom Experiments in Microgravity

We present the technical realization of a compact system for performing experiments with cold $^{87}{\text{Rb}}$ and $^{39}{\text{K}}$ atoms in microgravity in the future. The whole system fits into a capsule to be used in the drop tower Bremen. One of the advantages of a microgravity environment is long time evolution of atomic clouds which yields higher sensitivities in atom interferometer measurements. We give a full description of the system containing an experimental chamber with ultra-high vacuum conditions, miniaturized laser systems, a high-power thulium-doped fiber laser, the electronics and the power management. In a two-stage magneto-optical trap atoms should be cooled to the low $\mu$K regime. The thulium-doped fiber laser will create an optical dipole trap which will allow further cooling to sub-$\mu$K temperatures. The presented system fulfills the demanding requirements on size and power management for cold atom experiments on a microgravity platform, especially with respect to the use of an optical dipole trap. A first test in microgravity, including the creation of a cold Rb ensemble, shows the functionality of the system.

Error-correcting codes for reliable communications in microgravity platforms

The PAANDA experiment was conceived to characterise the acceleration ambient of a rocket launched microgravity platform, specially the microgravity phase. The recorded data was transmitted to ground stations, leading to loss of telemetry information sent during the re-entry period. Traditionally, an error-correcting code for this channel consists of a block code with very large block size to protect against long periods of data loss. Instead, we propose the use of digital fountain codes along with conventional Reed-Solomon block codes to protect against long and short burst error periods, respectively. Aiming to use this approach for a second version of PAANDA to prevent data corruption, we propose a model for the communication channel based on information extracted from Cuma II’s telemetry data, and simulate the performance of our proposed error-correcting code under this channel model. Simulation results show that nearly all telemetry data can be recovered, including data from the re-entry period.

The Second Young Engineers' Satellite: Innovative Technology through Education

The second Young Engineers' Satellite,YES2, is the longest manmade structure launched in 2007 and is space piggybacked on the Foton-M3 microgravity platform with the objective of a controlled deployment of a 32km tether. This paper introduces the object and the flight results of YES2 and the performance of the satellite is studied in comparison of the simulations and ground tests with respect to the flight results.

Optimal Design of Hybrid Rocket Motors forMicrogravity Platform

A nested direct/indirect method is used to find the optimal design for a microgravity platform which is based on a hybrid sounding rocket. The direct optimization of the parameters that affect the motor design is coupled with the indirect trajectory optimization to maximize a given mission performance index. A gas-pressure feed system is used, with three different propellant combinations. The feed system exploits a pressurizing gas, namely, helium, when hydrogen peroxide or liquid oxygen is used as an oxidizer. The simplest blowdown design is compared with a more complex pressurizing system, which has an additional gas tank that allows for a phase with constant propellant tank pressure. Only self-pressurization is considered with nitrous oxide; two different models are used to describe the behavior of the tank pressurization. The simplest model assumes liquid/vapor equilibrium. A two-phase model is also proposed: Saturated vapor and superheated liquid are considered and the liquid/vapor mass transfer evaluation is based on the liquid spinodal line. Results show that the different tank-pressurization models yield minimal differences of the optimal motor characteristics. Performance differs slightly due to the different mass of the residual oxidizer. The propellant comparison for the present case shows better performance for hydrogen peroxide/ polyethylene with respect to liquid oxygen/hydroxyl-terminated polybutadiene, while nitrous oxide/hydroxyl-terminated polybutadiene remains attractive for system simplicity and low costs.

Validation of a Front-Tracking Model of the Columnar to Equiaxed Transition using Solidification Results from the Maxus 7 Microgravity Platform

Validation of a Front-Tracking Model of the Columnar to Equiaxed Transition using Solidification Results from the Maxus 7 Microgravity Platform

Preparation and remote control of microgravity experiments

Upon completion in the year 2005, the International Space Station (ISS) will become the largest microgravity platform ever constructed and placed in orbit. The ISS will broaden the current research capabilities in the field of microgravity experimentation, including crystal growth, and material science in general. In planning for the utilization of the ISS, emphasis has been placed on the possibility of controlling experiments in a remote manner (telescience) via an efficiently, pre-determined ground infrastructure, implementing a decentralised approach.

The microgravity environment: its prediction, measurement, and importance to materials processing

One of the primary benefits of conducting scientific research in space is to take advantage of the low acceleration environment. For experimenters conducting space research in the field of materials science the quality of the science return is contingent upon the extremely low frequency acceleration environment (⪡ 1 Hz) aboard the spacecraft. Primary contributors to this low frequency acceleration environment (commonly referred to as the steady-state acceleration environment) include aerodynamic drag, gravity-gradient, and rotational effects. The space shuttle was used on the STS-75 mission as a microgravity platform for conducting a material science experiment in which a lead tin telluride alloy was melted and regrown in the Advanced Automated Directional Solidification Furnace under different steady-state acceleration environment conditions by placing the shuttle in particular fixed orientations during sample processing. The two different shuttle orientations employed during sample processing were a bay to Earth, tail into the velocity vector shuttle orientation and a tail to Earth, belly into the velocity vector shuttle orientation. Scientists have shown, through modeling techniques, the effects of various residual acceleration vector orientations to the micro-buoyant flows during the growth of compound semiconductors. The signatures imposed by these temporally dependent flows are manifested in the axial and radial segregation or composition along the crystal.