Magnetic Gearboxes for Aerospace Applications Jose Luis Perez-Diaz*, Efren Diez-Jimenez*, Marco Antonio Alvarez-Valenzuela*  Juan Sanchez-García-Casarrubios**, Christian Cristache***and Ignacio Valiente-Blanco*** Abstract Magnetic gearboxes are contactless mechanisms for torque-speed conversion. They present no wear, no  friction and no fatigue. They need no lubricant and can be customized for other mechanical properties as  stiffness or damping. Additionally, they can protect structures and mechanisms against overloads, limitting the transmitted torque. In this work, spur, planetary and “magdrive” or “harmonic drive”  configurations are compared considering their use in aerospace applications. The most recent test data  are summarized to provide some useful help for the design engineer.  Introduction Magnetic gears were proposed almost a hundred years ago. The absence of contact and wear between  teeth seemed a worthy feature to prompt their development, but low efficiency, difficulties with  manufacturing techniques, and cost were strong handicaps. It was at the beginning of this century that  attention has been paid to their development, using new magnetic materials with higher magnetization or  permeability, new precise manufacturing techniques, and advanced magnetomechanical modeling tools.  The number of papers devoted to magnetic gears has increased exponentially in the last two years and  the technology has overcome many of the first difficulties. The specific development of magnetic gears for aerospace has been the objective of several projects  carried out in Universidad Carlos III and MAG SOAR SL, some of them funded by the European  Community's SPACE and CLEAN SKY Programs ([FP7/2007-2013]) under grant agreements n° 263014  and nº 323423. Specific aerospace design techniques have been developed to increase their TRL [1-7]. The main advantages of magnetic gears are a consequence of the absence of contact between teeth. There is no wear. No lubricant is needed. They can be operated at a broad range of temperatures ranging  from -270ºC up to 350ºC. They present intrinsic anti-jamming properties and there is a clutching effect if  the applied torque exceeds a limit therefore protecting the output from overloads. This effect is completely reversible. No damage or wear is produced while operating. The motion direction is also reversible with highly reduced backlash. Input and output axles can also be  exchanged so that the same device can be used as a reducer or a multiplier. An additional advantage is that they are suitable for through-wall transmission requiring no joints or sealing. Magnetic gears are also compatible with the presence of dust, sand or non-magnetic particles. As there is a gap between the moving parts, sand can flow not producing significant scratches, wear or stalling.  *Dto. Ingeniería Mecánica, Universidad Carlos III de Madrid, Leganés, Spain **MAG SOAR S.L., Valdemoro, Spain ***Instituto Pedro Juan de Lastanosa, Universidad Carlos III de Madrid, Leganés, Spain /g51/g85/g82/g70/g72/g72/g71/g76/g81/g74/g86/g3/g82/g73/g3/g87/g75/g72/g3/g23/g21/g81/g71/g3/g36/g72/g85/g82/g86/g83/g68/g70/g72/g3/g48/g72/g70/g75/g68/g81/g76/g86/g80/g86/g3/g54/g92/g80/g83/g82/g86/g76/g88/g80/g15/g3/g49/g36/g54/g36/g3/g42/g82/g71/g71/g68/g85 /g71/g3/g54/g83/g68/g70/g72/g3/g41/g79/g76/g74/g75/g87/g3/g38/g72/g81/g87/g72/g85/g15/g3/g48/g68/g92/g3/g20/g23/g16/g20/g25/g15/g3/g21/g19/g20/g23 365