Experiment

Experiment file

STOF.html

Experiment

in-orbit fluid/spacecraft dynamics interaction

Primary investigator

Vreeburg, J.P.B.

co-investigators

An International Investigators Working Group (IWG) controls the design and execution of the experiments. Parties interested in participation in the IWG are expected to contribute to the industrial realization of the experiment.

Contact point

J.J.M. Prins at National Aerospace Laboratory NLR, The Netherlands

Experiment Category

Fluid Sciences

Main research area

Liquid dynamics in micro-g

Abstract

Wet Satellite Model launched from sounding rocket as a precursor

Sloshsat FLEVO is a precursor to small satellite development. Its experimental purpose is to provide experience on the prediction and accurate control of the dynamics of satellites with large amounts of liquids on-board.

Sloshing liquid, e.g. in fuel tanks, influences the behaviour of such satellites, however there is also an increasing demand for having liquids (fuel) on-board: e.g. it extends the operational life time of the satellite. Hence, knowledge and insight in the prediction and control of the dynamic behaviour of "liquid filled" satellites is of growing importance.

In order to contribute to the solution of this problem, the National Aerospace Laboratory NLR has in the past already conducted several 'micro-gravity' fluid-spacecraft interaction experiments. These experiments involved parabolic flights, Spacelab (Spacelab 1 and D-1) missions and Sounding Rockets (WSM experiment). As an outcome of these experiments, the need grew for a more advanced flight experiment. It should feature longer experiment duration, a 3-D tank, a choice of 3-D excitation possibilities, much enhanced tank instrumentation and multiple experiment runs, controllable by the experimenters. To implement this, the Slosh Test Orbital Facility (STOF) has been defined, of which Sloshsat FLEVO is the main component. NLR is responsible for the development of Sloshsat FLEVO. For the development of Sloshsat FLEVO a phase A and phase B study has been performed. Phase C/D is currently in progress.

3-D experiment tank integrated in the satellite

First prototype coated tank

the satellite will be controlled via the Shuttle

In addition to Sloshsat FLEVO, the STOF project involves the development of two more elements:

• an ejection system, ESAJECT, to eject Sloshsat FLEVO from the Space Shuttle,
• a HitchHicker communication system, to facilitate data communication between the free flying Sloshsat FLEVO and the Space Shuttle.

Ejection takes place from a Shuttle Hitchhiker-C system. The ejection system and Hitchhiker communication system are developed under separate ESA contracts.

The free flying mini-spacecraft has been named Sloshsat Flevo. The satellite is currently under development at NLR with Fokker Space and Systems (FSS), Rafael, Verhaert and NEWTEC as subcontractors.

The payload of the satellite consists of an experiment tank with elaborate instrumentation. The tank shape is a circular cylinder with hemispherical ends and no internal structures. The volume of the tank is 87 litres. The tank will be partially filled with 33.5 litres of water. With a sensor system, the liquid height at the tank wall will be measured at 270 locations. Additional sensors are provided at a few locations to measure liquid height with a better resolution, liquid velocity at the wall, pressures and temperatures. The mass of the dry satellite is approximately 70 kg. The fluid/rigid mass ratio is about 0.5.

Objectives

The objectives of the experiment are to:

• develop and perform the Sloshsat Flevo flight experiment
• obtain experiment data to verify/validate existing fluid dynamics models
• develop and qualify a low-cost small spacecraft(S/C)-Bus.

The detailed objectives of the SLoshat Flevo experiment are to:

• Obtain flight data to verify the adequacy of existing analytical fluid dynamics models, and indicate where improvement is needed
• Obtain flight data to verify adequacy of existing computational fluid dynamics software numerical models, and indicate where improvement is needed.
• Characterise the dynamic interaction between liquid motions and spacecraft
• Provide understanding of the motions of liquid with a free surface in a low gravity environment
• Generate phenomenological information on less well organised flow patterns as a basis for further mathematical modelling
• Provide relevant information for the design of liquid management techniques in micro-gravity
• Obtain data on diagnostic instruments performances.

The detailed objectives of the S/C-Bus development are to:

• Develop a mini satellite bus (S/C-Bus) with manoevring capability (i.e. with thrusters and motion diagnostics) capable of supporting a variety of dynamics test payloads, of which the design can be re-used in the future
• Qualify the S/C-Bus performance with the flight results
• Keep development cost as low as possible, establish/prove a cost efficient method/management for such a development programme.

Funding agency

The project is part of the Technology Demonstration Program (TDP-2) of the European Space Agency (ESA). The project is sponsored by the Netherlands Agency for Aerospace Programs (NIVR). The S/C-Bus related objectives are the main Sloshat Flevo objectives for the Dutch Funding Agency NIVR. Cooperation with NASA has been established. The satellite will be launched from a Shuttle/Hitchhiker.

Launcher

Space Shuttle

Duration

The free-flying mini-satellite will be designed for a total of at least 24 hours of fluid/spacecraft interaction experiments, executed in several experiment blocks during the duration of the Shuttle flight of approximately 2 weeks.

Equipment

Overall block diagram of SLoshsat

A complete mini-satellite will be developed, including all the usual satellite subsystems, notably:

• a 12 thruster reaction control subsystem (RCS) for motion initialisation and excitation, operating with compressed nitrogen gas,
• a motion sensing subsystem for measurement of the fluid/spacecraft interactive motion, consisting of three gyroscopes and 6 linear accelerometers,
• an on-board data handling subsystem (DHS) for autonomous experiment control, measurement control, data acquisition, telemetry functions, etc.
• a power subsystem with batteries and solar cells,
• a radio frequency subsystem (RFS),
• a thermal control subsystem,
• a structure subsystem, and
• a ground support subsystem for experiment programming, "on-line" control and data reception and storage.

The satellite will allow telecommanding from GSFC. Telemetry will be distributed to allow various sites to participate in remote operations.

General
Related experiments are:

On Spacelab-1

On Spacelab D-1

On Maser-5

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