Sloshsat FLEVO project, flight, and lessons learned
- Paper number
IAC-05-B5.3./B5.5.05
- Author
Mr. J.J.M. (Koos) Prins, National Aerospace Laboratory (NLR), The Netherlands
- Year
2005
- Abstract
Sloshsat FLEVO is a spacecraft for the experimental study of liquid dynamics and liquid management problems in space. It was launched as part of the test payload of Ariane 5 ECA on 12 February 2005. Of the total 129-kg mass of Sloshsat, 33.5 kg is liquid water in a smooth 87-litre tank. The motion of Sloshsat was controlled with a cold-gas reaction control system. The sloshing experiments were performed successfully despite lack of output from the tank instrumentation. Five research institutes are involved with the slosh experiments. The State University Groningen will use Sloshsat data for validation of the existing Computational Fluid Dynamics (CFD) program ComFlo. With a validated program, reliable CFD-predictions for future AOCS designs can be made. Likewise, NLR intends to validate its spacecraft dynamics simulation algorithm for inclusion in (real-time) AOCS simulators. NASA Glenn Research Centre will validate computer programs as well. ESA performed spin axis transfer manoeuvres for operational satellites. The University of Delft investigates how disturbances from liquid motion can be damped effectively. The measurement data indicate that Sloshsat’s accelerometers and gyroscopes -measuring the motions of the satellite- perform very well, allowing good scientific results. Also the rather complicated slosh control whereby the satellite rotates around the mass centre of the liquid in the tank worked well. A setback was the lack of any data on the condition of the water in the tank, which complicated the control of the experiments. As a consequence some experiments will less definite results. In this new situation, the interactive execution of the experiment program proved to be an advantage as the experiment program could be easily adapted during the flight depending on the actual behaviour. Sloshsat FLEVO was originally designed for ejection from a NASA Hitchhiker bridge in the Shuttle cargo bay. Sloshsat is part of the Slosh Test Orbital Facility (STOF), which also includes ESA’s spring-loaded "ESAJECT" ejection mechanism and the Hitchhiker Communication System (HHCS) designed to interface with the Hitchhiker avionics. Since the Shuttle Columbia accident on 1 February 2003, this Shuttle launch opportunity no longer exists. In 2004 the satellite has been adapted and re-qualified for an Ariane 5 ECA launch. The structure required strengthening and the ejection mechanism had to be adapted to Ariane 5. The satellite communication system was designed for communication via the Shuttle at a nominal distance of some 100-km. With the Ariane launch into GEO transfer orbit, the maximum distance has grown to some 36.000-km, now requiring a 15-m tracking antenna on the ground. Sloshsat FLEVO was operated from a dedicated operation control centre installed at the ESOC Diane ground station in Kourou, French Guyana. At this OCC the satellite was monitored and controlled in real-time by NLR’s spacecraft operations team. The telemetry data were also transmitted via Internet to a server at ESA/ESTEC in Noordwijk. After processing a selection of these data, this computer did send graphs and animated images via Internet to the investigators. Using this system (FACT, developed by Atos-Origin and NLR for ESA) all parties were involved in real time and could redirect experiments when necessary. In total, 57 hours of slosh operations were executed during the 8 days following the launch. The operations were terminated with the depletion of all RCS gas, as planned.
- Abstract document
- Manuscript document
IAC-05-B5.3._B5.5.05.pdf (🔒 authorized access only).
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