IAC-02-J.3.07 Flight on MASER 9 - European Space Agencyeea.spaceflight.esa.int/attachments/soundingrockets/ID456d531f2c608.pdf · evaporation could drive Marangoni convection and

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IAC-02-J.3.07ITEL Experiment Module and itsFlight on MASER 9

K. Löth, B. Larsson, H. Schneider, O. Jansson, Y. HoultzSwedish Space Corporation

P. Colinet, C. IorioUniversité Libre de Bruxelles, Microgravity Research centre,

L. Joannes, O. DupontLambda-X

53rd International Astronautical CongressThe World Space Congress – 2002

10-19 Oct 2002/Houston, Texas

Copyright© 2002 by Kenneth Löth, Swedish Space Corporation. 1Published by the American Institute of Aeronautics and Astronautics,Inc., with permission. Released to IAF/IAA/AIAA to publish in all forms.

ITEL EXPERIMENT MODULE AND ITS FLIGHT ON MASER 9

Kenneth Löth, Bengt Larsson, Heike Schneider, Olle Jansson, Ylva HoultzSpace Systems Division, Swedish Space Corporation

P.O.Box 4207, S-171 04, Solna, Sweden (e-mail: [email protected])

Pierre Colinet, Carlo IorioUniversité Libre de Bruxelles, Microgravity Research centre,Av. Fr. Roosevelt, 50 CP 165/62, B-1050 Bruxelles, Belgium

Luc Joannes, Olivier DupontLambda-X, Rue de Marcassins, 10 Everzwijntjestraat, B-1170 Bruxelles, Belgium

ABSTRACT

The Interfacial Turbulence in EvaporatingLiquids (ITEL) experiment module flew inmicrogravity during 6 minutes and 9 seconds onthe Sounding Rocket MASER 9 on March 162002. Swedish Space Corporation and Lambda-X, Belgium developed the ITEL module undercontract from the European Space Agency(ESA).The objective of the experiment of Dr PierreColinet from Université Libre de Bruxelles(ULB) is to observe cellular convection(Marangoni-Bénard instability) in an evaporatinghighly volative liquid with a free surface.The experiment module contains one experimentcell. An interferometric optical tomograph, withsix viewing directions, measures the 3-dimensional distribution of temperature in theevaporating liquid and a Schlieren systemvisualizes the temperature gradients inside theliquid together with the liquid surface.During the flight when microgravity is achievedthe liquid is injected into the cell and a freeliquid surface is established and kept flat. Theevaporation rate of the free surface is to becontrolled by regulating the gas pressure and gasflow. The two optical systems worked properlyduring flight and the interferometric opticaltomograph was validated. The scientific resultsare under evaluation but it was verified thatevaporation could drive Marangoni convectionand chaotic patterns.

1. INTRODUCTION

This project included development and flight of anew complex experiment module for theSounding Rocket program MASER. TheInterfacial Turbulence in Evaporating Liquids(ITEL) was built under contract from theEuropean Space Agency (ESA) and flew on the9th MASER rocket on March 16, 2002.

Figure 1. ITEL experiment module without outerstructure.


In order to perform the experiment several newsystems had to be developed, such as:- An experiment cell with a free liquid surface

including thermal control, gas flow system,liquid injection system and surface flatnessregulation.

- An interferometric optical tomograph, withsix viewing directions parallel to the liquidsurface, in order to measure the 3-dimensional temperature distribution in theliquid. This system is to our knowledge thefirst interferometric tomograph to be onboarda space system.

- A Schlieren optical system to visualize theconvective motions.

One technical objective was to validate theoptical tomography system, which was built forgeneral utilisation in fluid physics experiments inmicrogravity.The Swedish Space Corporation (SSC)conducted the project together with Lambda-X asa subcontractor responsible for the opticalsystems.The experiment in ITEL on Maser 9 is apreliminary step in the preparation of the CIMEX(Convection and Interfacial Mass Exchange)program, which will make use of theInternational Space Station.

2. EXPERIMENT DESCRIPTION

2.1 Experiment

In this module an experiment of Dr PierreColinet, Université Libre de Bruxelles (ULB)Belgium, called “Interfacial Turbulence inEvaporating Liquids” (ITEL) was performed.The objective of the experiment was to analysethe fluid dynamics of an evaporating liquid inmicrogravity. A highly volatile liquid layer wasevaporated and the convection phenomenongenerated in this process was observed. Indeeddue to the cooling by latent heat consumption atthe level of the evaporating free surface, atemperature gradient is induced perpendicularlyto it. Due to the surface tension variation withtemperature, thermocapillary instability istriggered which leads to cellular convection(Marangoni-Bénard). The main scientific goal

was to show that, in microgravity, evaporationcould drive Marangoni convection and chaoticpattern.

2.2 Experiment Set-Up

The idea was to keep the experiment cell atconstant and uniform temperature. Inject liquidinto cell at microgravity and to control theevaporation rate of the free surface by regulatingthe gas pressure and gas flow.The liquid-gas interface had to be kept flatduring the experiment imposing injection ofliquid to compensate for evaporation.

Figure 2. Simplified sketch of experiment cell.

2.2.1 Experiment sequence during flight

Liquid is injected into the cell and whenisothermal situation and equilibrium is obtainedthe flow/pressure sequence will be started. 14experiment points are to be used during themicrogravity phase in order to observe theinterfacial motions. The pressure is changed insteps of 1000, 900, 800, 700, 600 and 500mbars.The duration of the steps is set to 15 or29seconds and the flow is to be changed from 0-600ml/min.


Figure 3. ITEL module layout

3. EXPERIMENT MODULE

3.1 General Description

The module has a length of 750mm and a massof 63.5kg. The mechanical system consists of anouter structure of Al-alloy (� 17”), to which theexperiment deck is attached via dampers. Theouter structure is insulated with glass fibreinsulation and equipped with lids. The injectionunit can be taken out from the module via a lateaccess hatch.

The ITEL module comprises:-Experiment cell including reference volume-Gas flow and liquid injection system-Schlieren Optical system-Tomography Optical system-Image capture and storage system-Electronic control system-Software-Thermal system including cooling loop


3.2 Overall design

Due to the limited diameter of the Soundingrocket the optical systems are splitted in threelevels, as described further in paragraph 3.5,requiring two optical decks and one experimentdeck.The two optical decks contain the cameras andlenses for the tomographical interferometers aswell as for the Schlieren system. On the upperside of the lower optical deck the experiment cellwith its correction lenses and thermocouples aswell as tubing for gas are positioned. Below thelower deck the laser source for the tomographysystem is placed. On the experiment deck the twooptical decks are mounted as well as the memoryunits, heat exchanger, thermocouple amplifier,pressure valve and flow meter. The electronics aswell as the batteries, the laser driver, the Peltiercontrol, three DV recorders and the gas vesselare located under the experiment deck.

3.3 Thermal system

The module incorporates a thermal systemconsisting of two liquid loops connected beforelaunch via liquid umbilicals to two thermal baths.One loop is used for controlling the initialtemperature in the injection unit and theexperiment cell. The other loop transportsexcessive heat from the electronics and consistsof a heat exchanger with fan placed on theexperiment deck.

3.4 Experiment system

3.4.1 Experiment cell

The cell is designed in three levels (top, mid,bottom) with experiment volume and referencevolume in-between. The experiment liquidvolume is 12 ml, active area Ø15 mm, and depth5 mm.The free liquid surface is defined by a stainlesssteel thinfoil. Water loops for pre-launchthermalisation are included in all three levels.Cylindrical correction lenses are mounted to thetop plateThe interior design and material properties havebeen chosen according to the results of cell

filling tests performed on a parabolic flight. Thecell is pressure tight and has a gas inlet/outletand liquid inlet.

Figure 4. Cross-section of experiment cell

The top part of the cell is designed for a laminarflow of Nitrogen across the free surface. The cellbottom is polished to serve as mirror for theSchlieren system.

3.4.2 Liquid injection unit

The liquid injection unit is assigned for initialfilling of the experiment cell at microgravity aswell as for dispensing small volumes tocompensate for evaporation and for surfaceregulation during flight. It consists of 2 syringeswith driving mechanisms and DC-motors, 2 zero-volume inert solenoid valves, one manual valveand Teflon tubing.The Injection unit could be taken out from themodule via a late access hatch.

Figure 5. Injection unit


Figure 6. ITEL Gas flow system

3.4.3 Gas flow system

The evaporation rate was controlled by a gasflow system consisting of a pressure controlsystem and a gas injection system.During flight, the pressure regulation in the cellwas controlled via an electronic adjustablepressure valve on the outlet and a pressure sensorin the cell. A software controlled PI(D) regulatorregistered the actual pressure in the cell andadjusted the pressure valve according to the setpoint.The N2 injection system comprised a pressurevessel, primary and secondary pressure sensors,pressure reducer and a relief valve on the inlet tothe cell. The mass flow controller regulated theflow into the cell and a mass flow metermeasured the outlet flow. The gas on the outletwas symmetrically distributed through outletdiffusers in order not to disturb the microgravitylevels.

3.5 Optical systems

The optical systems developed by Lambda-X aredivided around two optical decks. The Schlierensystem is located on the lower side of the upperdeck. The tomography optical system is split inthree levels (see figure 7). The first one from thebottom (Tomo-Source level) is the level wherethe laser beam coming from a single red laserdiode is split into six identical collimated beams.The second one (Tomo-Interferometers level)includes the interferometers and the experimentalcell. The third one (Tomo-Imaging level) is theimaging level. Afocal systems image the centreof the experimental cell onto CCD cameras andviews are combined (three on each CCD).

Figure 7. Layout of optical systems


3.5.1 Schlieren optical system

The tasks of the Schlieren system is to:- Visualize liquid-gas interface deformation

and refractive index gradients in the liquid- Localization of convection cells to be used

for tomographic reconstruction- Interface flatness controlThe Schlieren system uses a LED source and isused in transmission mode with a mirror at thebottom of the cell. It has a variable sensitivity bya variable iris diaphragm/modulation of LEDintensity.

3.5.2 Tomographic system

Interferometric tomography is a technique thatallows measuring the 3 dimensional (relative)refractive index distribution in a typical volume.Multiple interferometer paths are crossing in thevolume at different angles and each measures theintegrated refractive index distribution in theexperimental volume. The views are lying in aplane and the central part, called ‘CommonVolume’, crossed by all the views is the volumein which the refractive index distribution can beretrieved. The arrangement design for the 6views in ITEL can be seen in Fig.8.

Figure 8. Organisation of views.The central part is the liquid.

Beam generationIn the tomo-source level the single laser diodegenerates 6 beams with the help of a modifiedbeam splitter and holographic gratings.

Figure 9 Tomo-source level

InterferometersThe interferometers are of Mach-Zehnder type.This configuration is very robust since any smalldisplacement or rotation of these prisms will notcompromise the performance of the system (noadditional fringes will be induced).

Experiment cellFor thermo-hydrodynamic reasons anexperimental cell with circular geometry is toprefer. Thus to ensure that the laser beams arecollimated in the liquid, some compensationcylindrical lenses have been introduced.Note that the compensation is only valid at thedesign temperature since the refractive index ofthe liquid is strongly depending with thetemperature. Since a reference cell filled with thesame liquid is positioned in the reference pathsof the interferometers, the system is operatingcorrectly even if the ambient temperature differsfrom the design temperature up to ±5°.

Beam combinationThe last level has two functions: the image of thecell is produced onto the CCD sensor, and threeviews are combined in each camera.

Phase shiftThe tomographic reconstruction requires themeasurement of the optical phase. Thus a phaseshift system has been implemented. Its principleis to record a set of images of the same fluid statewith a controlled modulation of the phase shift.The fringe phase is then calculated from theseimages.


3.6 Interface flatness control

One of the difficulties with an evaporating freesurface is how to automatically detect andregulate the flatness to compensate for theevaporated liquid. The interface flatness controlsystem in the ITEL module used the image fromthe Schlieren system and was verified during theflight.A curved interface produces a not uniform imagein the Schlieren system and it is easy todiscriminate between an overfilled or underfilledliquid surface. This image from the Schlierencamera was fed to a framegrabber in the PC/104control system in order to make a real-timeanalysis in the onboard software. In the case thatthe surface is not uniform, the injection unit willinject or retract liquid to achieve a flat surface.

3.7 Video system

The two cameras for the tomographic system aswell as the camera for the Schlieren system werein progressive scan mode and were synchronisedwith the 25Hz phase-shift of the tomographylaser source.

Each of the three cameras was connected to anearlier flight proven video recorder of miniDVtype.

During the flight on MASER 9 two video signalswere transmitted to ground by analog TV-transmitters for real-time control of theexperiment. A third video signal was alsotransmitted to ground thanks to the successfultest-flight of the Digital Video System (DVS).

3.8 Electronic system and software

The experiment is controlled by a PC/104system developed by SSC that incorporates areal-time operating system software. The PC/104system controls the experiment automaticallyduring flight but the sequence can be overriddenby tele-command. All data is saved onboard at25Hz during the active phase of the experiment.The data saving is synchronised with the video

signal so all data is saved at the same time aseach video frame is captured.

The main parts in the PC/104 system are:- CPU including flash disc- I/O cassettes, analogue and digital input/output- Motor cards, for inj. unit and Schlieren aperture- Video framegrabber, grabbing Schlieren images- TM/TC interface- Housekeeping unit- Pressure and valve control unit- Thermocouple amplifier- LANC I/F to control the DV recorders- Video switch unit- Batteries and DC/DC converters

3.9 Ground Support Equipment

The module was operated and monitored duringtests and flight by ground support equipment(GSE) including power control andmodule/experiment checkout computers.

4. MASER 9, CAMPAIGN AND FLIGHT

4.1 Preparation

The campaign took place at ESRANGE, Kirunaon March 4-16 2002. It included preparation onmodule level as well as tests on payload levelboth in the integration hall and in the launchtower. The main tasks are listed below:- Preparation of Experiment module including

optical alignment, Schlieren image check andaperture motor alignment

- Scientific flight simulation tests- Bench test with MASER Service Module

(MASM) TV module+DVS- Experiment module check on launcher- Payload Assembly, and Payload Test, EMI

test- Induced vibration test- Launcher and Blockhouse Preparations- Payload Test, Payload in tower- Test Countdown, and Launch Readiness

Review


4.2 Hot Countdown

The final hot countdown started on March 162002. The preparations for the flight startedalready before start of countdown by degassingthe experiment liquid, ethyl alcohol, and fillingof the injection unit as well as starting thetemperature control of the experiment cell.The injection unit was installed in the ITELmodule about 6 hours before lift-off.Two module checkouts were performed duringthe countdown.

Figure 10. Schlieren image from the flightshowing the free surface from above and typicalthermal ripples generated by evaporation.

4.3 Flight

The lift-off of MASER 9 took place on March16, 2002.Before flight the temperature control of theexperiment cell and the injection unit had beensuccessful and the temperature differencebetween the experiment cell and injection unitwas nominal.After motor burnout, the experiment waspowered up and the initial filling of theexperiment cell started after microgravity wasachieved. The automatic filling of the experimentcell was remarkably smooth, and showedsimilarities with the experiments performed inparabolic flights May 2000.After the filling, the temperature was stable andthe initial tomographic images were good.Thanks to the Schlieren system and the automaticsurface regulation a flat interface was observedduring all the flight, with an accuracy of about 50microns. The flow/pressure sequence was startedon timeout but the pressure regulation did notwork properly.The behaviour of the module during flight wasnormal except for the off nominal pressurecontrol. During flight several commands weresent in order to regulate the pressure manually.Although there were abnormal changes inpressure, the surface regulation worked properly.Good quality of transmitted images from thethree cameras.

Figure 11. Set of tomo images from one camera (three views on each camera) showing the filling ofthe experiment cell in microgravity. The free surface is upwards and the sequence starts from the left.In the first image there is liquid visible only on the left side but in next image the liquid has spreadaround the cylindrical glass and continues to fill the cell.


4.3 Result of the flight

The following results were observed directlyafter flight:- Good thermal control of the cell during

countdown and therefore at the moment offluid injection. This is extremely importantfor tomography, as a good reference image isneeded.

- No disturbances were noticed from pumps orcentrifuges in the other modules.

- The initial injection of the fluid in the cellwas perfect

- A flat interface was observed during allflight due to the good quality of the Schlierenimage and the automatic flatness controlalgorithm.

- The main scientific objective, to show thatevaporation can drive Marangoni convectionand chaotic patterns, was observed. Howevera full flight scenario with 14 observationpoints could not be executed due to thepressure regulation problem.

- The interferometric tomography systemworked perfect and is hereby validated.

- Images and data recorded onboard withnominal function

5. CONCLUSION

All complex systems of the ITEL module such asliquid filling, surface regulation, interferometrictomography and Schlieren system workedsuccessfully during flight apart from ananomalous pressure control.The automatic pressure control did not workbecause a software parameter was unexplainablychanged before flight. Tomographicreconstruction from the flight is underway atLambda-X but already the first preliminaryreconstruction validates the tomography system.The scientific evaluation is performed by the PIand will be reported separately.

6. ACKNOWLEDGEMENTS

The authors would like to take the opportunity tothank:- ESA/ESTEC for their support, especially

W. Herfs and W. Riesselmann.- The mission scientific advisor:

Prof. Dr G. Frohberg, University of Berlin,for his valuable advice.

Figure 12. ITEL team before launch

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IAC-02-J.3.07 Flight on MASER 9 - European Space Agencyeea.spaceflight.esa.int/attachments/soundingrockets/ID456d531f2c608.pdf · evaporation could drive Marangoni convection and