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Space satellite mechanism testing
Space satellite mechanism testing A large programme of mechanism testing in support of the INMARSAT 2 communication satellite has begun in NCT's European Space Tribology Laboratory (ESTL). INMARSAT is an international co-operative organisation which provides mobile communications for aircraft, shipping, the offshore industry and other applications. To meet future needs, INMARSAT are buying, from British Aerospace, up to nine INMARSAT 2 geostationary satellites, the first of which is scheduled to be launched by the French rocket ARIANE in 1988. ESTL is responsible for the lubrication, assembly, testing and qualification of the mechanisms used to rotate the solar panels, the solar array drive mechanisms (SADM). These are the mechanisms at the junction between the solar panels and the spacecraft body. A new design of SADM has been evolved for INMARSAT 2. This uses thin-section angular contact ball bearings and these are sized to withstand the launch vibration without any protective off-loading mechanism. The shaft of the SADM is rotated by a mini-step motor and two-stage spur gearbox. With the proximity of
electrical slip-rings, NCT advised the use of ion-plated lead as a solid lubricant for both bearings and gears, using the 'space qualified' process developed in ESTL. This is the first use of ion-plated lead in a thin-section bearing and required the special manufacture of lead-bronze cages. The life and performance of the lead lubricant for both gears and bearings has been proved in accelerated testing in ESTL. This testing highlighted the importance of cage circularity and guiding when used in a thin-section bearing. ESTL has also been awarded a contract for the part assembly of the SADM's, the principal task of which is the fitting of the bearings onto beryllium housings and their running-in. ESTL is further contracted to perform a qualification and accelerated life test of the preflight (qualification) model SADM for INMARSAT 2. This test, under simulated space conditions, will take place in a one-metre diameter vacuum chamber. As well as thermal control, this test involves complex torque measurements to assess any disturbance transmitted to the satellite body from the SADM and slip-ring measurements. Both require high speed data
acquisition and analysis in real time. National Centre of Tribology, UKAE, Risley, Warrington, Cheshire WA3 6AT, UK
Interface dynamics at the 14th Leeds-Lyon Symposium on Tribology Whether in lubricated or in dry friction, a lot of attention has been devoted lately to the study of the role, composition, and properties of transfer, of interfacial films and/or third bodies. The 14th Leeds-Lyon Symposium will attempt to bring together what is known on this subject in both lubrication and friction. Emphasis will be put on recent work on third body generation, composition, theology and flow, load-carrying concepts and surface protection and destruction, boundary conditions, modeling, and on information concerning the dynamics inside the contact. Approximately thirty papers will be presented. With the obvious exception of oils in hydrodynamic lubrication, third bodies are either created or modified within the contact. Tire Symposium will discuss the mechanics and physics of the generation in situ of transfer fihns, chemical films and debris beds. Particle detachment by fatigue processes or rupture will be given priority. Composition alone has been studied extensively in recent years. The Symposium will attempt to relate composition to other themes: rheology and boundary conditions for example but will not discuss chemical analysis techniques. New developments in oil and grease rheology, new information on relations between oil composition and rheology, and new models will be discussed. Papers on powder theology under the high stress and high strain-rates found in contacts will be prominent along with attempts at modeling this behaviour. Third-body rheometry and theology under representative running conditions will be high-lighted.
Artist's impression o f lNMARSA T 2
160
Like oil films, third bodies can protect
June 1987 Vol 20 No 3
electrical slip-rings, NCT advised the use of ion-plated lead as a solid lubricant for both bearings and gears, using the 'space qualified' process developed in ESTL. This is the first use of ion-plated lead in a thin-section bearing and required the special manufacture of lead-bronze cages. The life and performance of the lead lubricant for both gears and bearings has been proved in accelerated testing in ESTL. This testing highlighted the importance of cage circularity and guiding when used in a thin-section bearing. ESTL has also been awarded a contract for the part assembly of the SADM's, the principal task of which is the fitting of the bearings onto beryllium housings and their running-in. ESTL is further contracted to perform a qualification and accelerated life test of the preflight (qualification) model SADM for INMARSAT 2. This test, under simulated space conditions, will take place in a one-metre diameter vacuum chamber. As well as thermal control, this test involves complex torque measurements to assess any disturbance transmitted to the satellite body from the SADM and slip-ring measurements. Both require high speed data
acquisition and analysis in real time. National Centre of Tribology, UKAE, Risley, Warrington, Cheshire WA3 6AT, UK
Interface dynamics at the 14th Leeds-Lyon Symposium on Tribology Whether in lubricated or in dry friction, a lot of attention has been devoted lately to the study of the role, composition, and properties of transfer, of interfacial films and/or third bodies. The 14th Leeds-Lyon Symposium will attempt to bring together what is known on this subject in both lubrication and friction. Emphasis will be put on recent work on third body generation, composition, theology and flow, load-carrying concepts and surface protection and destruction, boundary conditions, modeling, and on information concerning the dynamics inside the contact. Approximately thirty papers will be presented. With the obvious exception of oils in hydrodynamic lubrication, third bodies are either created or modified within the contact. Tire Symposium will discuss the mechanics and physics of the generation in situ of transfer fihns, chemical films and debris beds. Particle detachment by fatigue processes or rupture will be given priority. Composition alone has been studied extensively in recent years. The Symposium will attempt to relate composition to other themes: rheology and boundary conditions for example but will not discuss chemical analysis techniques. New developments in oil and grease rheology, new information on relations between oil composition and rheology, and new models will be discussed. Papers on powder theology under the high stress and high strain-rates found in contacts will be prominent along with attempts at modeling this behaviour. Third-body rheometry and theology under representative running conditions will be high-lighted.
Artist's impression o f lNMARSA T 2
160
Like oil films, third bodies can protect
June 1987 Vol 20 No 3