Preliminary Aerodynamic Measurements from a Magnetic Suspension and Balance System in a Low-Speed Wind Tunnel

Abstract

An existing Magnetic Suspension and Balance System (MSBS) has been restored to operation in a small (octagonal test section, 6-inches across flats) low-speed wind tunnel as the first phase of a project to develop new dynamic test capabilities for planetary entry capsules at supersonic speeds. The MSBS and associated wind tunnel were originally designed and built at MIT and were subsequently relocated to NASA Langley Research Center. NASA ceased operations of the system in the late 1990s and it was transferred to Old Dominion University where it had been mothballed until the present work started in 2015. All-new position sensor electronics, electromagnet power supplies, digital controller, and other hardware have been developed, leading to more efficient and reliable operation. Important features of the new hardware will be briefly described. Wind tunnel testing has commenced, focusing first on static aerodynamics of re-entry capsule shapes. Some preliminary results will be reviewed, including comparison to reference data. The proposed extension to dynamic stability testing, using a variety of free-to-pitch approaches will be described. Finally, the preliminary design of the all-new Phase II (supersonic) system will be briefly outlined. NomenclatureBx,y,z Magnetic flux density in the x, y and z directions (Tesla) Bxx Gradient of flux density in the axial (tunnel flow) direction d Capsule diameter CD Drag coefficient, Fx/(qs) Fx Force in the x direction ""⃗ Magnetization vector (A/m) Mx,y,z Components of the magnetization vector along the x, y and z axes q Dynamic pressure Red Reynolds number based on model diameter: density*velocity*diameter/(kinematic viscosity) S Reference area (area of circle with diameter of wind tunnel model) "⃗ Torque vector Tx,y,z Torque components about the x, y and z axes x,y,z Tunnel axes: +x = upstream, +y = right when looking upstream, +z = down

The Oxford Magnetic Suspension and Balance System: a Brief History & Development Status

“…Calibration of the drag coils related the required current in the coils to a known load applied to a suspended model. Although typical for MSBSs [22][23][24], this relation is in contrast with the method used on the first generation balance whereby the magnetic flux gradient was independently measured and calibrated [4]. It is unclear which method is superior.…”