Fluid Physics

RX32 – DROPSTAR (Study of Oil Droplet Coalescence in Emulsions in Microgravity)

Aristotle University of Thessaloniki

Launch Date: March 2024

Our experiment aims to study the oil droplet coalescence phenomena that take place in an emulsion, under microgravity conditions. The emulsion will be produced using a novel emulsification device, originally designed by the Laboratory of Chemical and Environmental Technology in the Department of Chemistry of Aristotle University of Thessaloniki, and perfected to suit the needs of the REXUS rocket by our team. The emulsification will take place during the rocket’s flight and will come to a stop before the low gravity phase. The studying of the emulsion will be done in situ by two diagnostics. First, a video camera aimed at the back of the cell that will be recording during the entire flight. Secondly, the I-VED technique will be measuring the conductivity of the emulsion.

After the flight, we plan to analyze the given data by plotting conductivity – time diagrams, closely studying the video, analyzing a number of frames in BubblesEdit to extract the size distribution of the droplets and comparing the measurements of the two diagnostics

With our experiment we expect to contribute to the existing data regarding coalescence phenomena and expand their study in microgravity conditions.

RX31 – FerrAS (Ferrofluid Application Study)

Universität Stuttgart

Launch Date: March 2024

The Ferrofluid Application Study (FerrAS) is a project of the small satellite student association of the University of Stuttgart, KSat e.V., and the successor of PAPELL, an experiment conducted on the ISS to investigate the behaviour of ferrofluids in microgravity. The PAPELL experiment demonstrated succesfully that the manipulation of ferrofluids in microgravity is possible. FerrAS will test two ferrofluid-based pumping mechanisms: a Displacement Pump for demonstrating an efficient pumping mechanism and a Linear Pump to be used in a fluid-based attitude control system (ACS).

The objective of the Displacement Pump experiment is to develop a ferrofluid-based pumping system. The displacement body is replaced by a neodymium magnet encapsulated in a ferrofluid layer. This layer acts as both a seal and a bearing and guidance for the displacement body (i.e. piston), thus replacing two crucial components. The neodymium magnet is driven by an external coil, eliminating the necessity for an engine drive with its moving parts. Current designs are capable of pumping 40 ml/min at 5 W. The application goal of the Linear Pump experiment is the attitude control system (ACS) of small satellites. For this purpose, electromagnets are used to move a small volume of ferrofluid in order to generate an angular momentum. The resulting pumping movement can be visualised using tracer balls in a pipe system. The process is evaluated by utilising a camera. By using ferrofluids, mechanical-moving parts can be minimised or fully removed, whereby losses and wear due to friction are supposed to be avoided. This is particularly important in space applications, where maintenance or replacement of parts is only possible in exceptional cases (i.e. presence of astronauts) and is associated with high costs.

RX27 – FLORENCE (FLOw boiling REgime iN microgravity Conditions Experiment)

KU Leuven, Belgium

Launch Date: 5 November 2022

Boiling is an efficient heat transfer process and is largely used for thermal energy conversions, transport systems, heating or cooling of components. Two types of boiling are commonly distinguished: pool boiling, for steady reservoirs and flow boiling, typical of channel flows. Boiling studies are performed since decades, nevertheless, many questions are still open regarding the physical mechanisms of the boiling process, mainly due to the complexity of the phenomena and the number of parameters involved, such as liquid subcooling, surface roughness or hysteresis. The purpose of this experiment is to simulate the flow through rocket engine cooling channels. Therefore an experimental set-up is constructed for observing flow boiling in microgravity conditions and reproduce the working conditions of these engines as accurately as possible.
During the experiment the goal is to observe different flow boiling regimes in microgravity. FLORENCE stands for FLOw boiling REgime iN microgravity Conditions Experiment. The experimental set-up consists of a flow loop in which the fluid HFE is circulated, the different flow boiling regimes will be observed by a high speed camera.

RX22 – U-PHOS (Upgraded Pulsating Heat-pipe Only for Space)

University of Pisa, Italy

Launch Date: 16 March 2017

U-PHOS Project aims to analyse and characterise the behaviour of a large diameter Pulsating Heat Pipe (PHP) on board of REXUS 22 sounding rocket. A PHP is a passive thermal control device consisting in a serpentine capillary tube, evacuated, partially filled with a working fluid and finally sealed. In this configuration, the liquid and vapour phases are randomly distributed in the form of liquid slugs and vapour plugs. The heat is efficiently transported by means of the self-sustained oscillatory fluid motion driven by the phase change phenomena. On ground conditions, a small critical diameter is required in order to obtain the desired liquid slug/vapour plug flow regime. In milli-gravity conditions, buoyancy forces become less intense and the critical diameter of the PHP can be increased. Thus, the PHP’s heat power capability in that condition may increase. U-PHOS intends to characterise the thermal response of a large diameter PHP under milli-g condition.

Student Experiment Documentation v5-0

RX20 – BOILUS (Boiling management by means of ultrasounds in microgravity conditions)

Universitat Politècnica de Catalunya, Spain

Launch Date: 15 March 2016

In order to carry out long-term space exploration missions it is required to control and maximize the propellant. During long term missions, even if multi-layer insulators (MLI) are used to protect propellant tank from radiation, its deterioration is unavoidable. As a result, for cryogenic propellants (CP) which need to be stored at very low temperatures (e.g. LH2 is stored at 20K) heat leaks in the tank walls cause localized boiling, leading to bubble formation. Vapour bubbles under reduced g-forces cannot rise the ullage as in terrestrial conditions and its accumulation can be hazardous for tank chill down, engine restart, propellant loading and space propellant management. Since the nineties, no microgravity experiment have been reported involving boiling and ultrasounds. The aim of the proposed project is to fill this lack investigating the efficiency of using a low power acoustic actuator (piezoelectric transducer, PZT) to enhance boiling heat transfer from a flat surface by removing vapour bubbles from the surface. Our experiment will be mounted on a REXUS 19 sounding rocket in order to reach high altitudes and simulate in this way the absence/reduction of gravity. The experimental set-up will consist in a test cell which will have assembled a heater to produce boiling in the fluid and a PZT to generate ultrasounds. We expect to store information about the dependence of heat transfer on the frequency and amplitude of the US, as well as to obtain relevant information about the relation between the US and the primary bubble’s detachment, its size and as well as on the behaviour of the secondary bubbles.

In general, from this study we aim to obtain a reliable basis to achieve a better knowledge that will be useful in the development of future applications to control boiling in microgravity conditions.

RX18 – PHOS (Pulsating Heat pipe Only for Space)

University of Pisa, Italy

Launch Date: 18 March 2015

Passive systems such as heat pipes are becoming the most popular choice for high heat power dissipation in electronics. The main aim of the PHOS experiment is to characterize the start-up and the stationary operations of a large diameter aluminium PHP (Pulsating Heat Pipe) operating in milli-g environment, by analysing the temporal trend of the local fluid pressure and temperature, and the external wall temperature in several locations. The team wishes to understand firstly if the PHP is successfully operating with a larger diameter in space condition, secondly to compare this experiment results with several experiments made on the same PHP on ground and the PHP162 mounted on the same module, for detecting the flow regimes inside the PHP. Both the experiments will be compared to ones done on ground.

RX16 – CWIS (Chemical Wavesin Soret effect)

University libre de Bruxelles, Belgium, University Naples “Federico II”

Launch Date: 28 May 2014

The purpose of the experiment is to visualize with a Fizeau interferometer, the chemical wave produced thanks to the Soret effect in a binary mixture. The chemical wave is the result of a strong variation of the concentration of the species at the very beginning  f the Soret effect, or thermodiffusion.

Thermodiffusion has several applications in industry and the applied sciences, such as fabrication of semiconductor devices in molten metal and semiconductor mixtures, separation of species such as polymers, manipulation of macromolecules such as DNA, and the study of its initial phase will help to optimize all those processes. Moreover, thermodiffusion is of interest as a basic science phenomenon that is not very well understood.

Since on ground this effect is masked by buoyancy, there is the need to perform the experiment in a reduced gravity environment. The REXUS milli-gravity conditions are suitable for our purposes, and the suborbital flight is consistent with our focus on the initial transient component of the phenomenon. The driving force for thermodiffusion will be a temperature gradient, that will be applied to the liquid cell using a resistive heating element

CWIS Conference Paper 1

CWIS Conference Paper 2

RX11 – CaRu (Capillarity under milligravity shown on Runge pictures)

TU Dresden, Germany

Launch Date: 16 November 2012

The objective of the CaRu experiment is to examine the effects of microgravity on capillarity, and to compare it with existing theoretical models. In this context, the formation of so called Runge pictures on Earth under normal gravity, and in-orbit microgravity conditions will be studied. Runge pictures are formed by the combined effects of chemical reactions and the capillary effect. To simulate this process, a drop of chemical fluid will be applied to filter paper, which will be impregnated with reactive chemicals. This leads to a reaction that can be monitored by observing irregular circles which form on the surface of the paper, and can be differentiated by their colours. The fluid will be applied onto the paper with the help of a syringe, actuated by a spring operated piston. The release of the spring is achieved through the melting of a Nichrome filament. The start of the experiment will be triggered by the REXUS electrical interface immediately after shutdown of the engines, which will then switch on the data acquisition system interfaced to the micro-controller, which returns telemetry via the REXUS interface. Independently, a fully integrated camera will start to record the experiment. The recorded video will be recovered from the experiment module after re-entry for analysis.

RX05 – VIB-BIP (VIBration effects on BIPhasic fluids)

Technical University of Catalonia, Spain

Launch Date: 13 March 2009

The aim of the VIB-BIP experiment was to characterise the behaviour of two-phase fluids (liquid and gas), under controlled harmonic vibrations in micro-gravity conditions. The experiment consisted of a test cell containing cylindrical cavities filled with liquid (water or silicon oil) and air in different proportions. The test cell was attached to a commercial shaker, which vibrated the system as a whole, at varying frequencies and amplitudes during the micro-gravity phase of the REXUS flight. The formation and behaviour of the bubbles inside the cavities was recorded using a high-speed camera and LED arrays. This data was then compared against previous ground derived studies, and has helped to provide an insight into the influence that varying frequency and amplitude vibrations have in the distribution of bubbles in cavities.