Motion Stability Measurements of a Submarine-Towed ELF Receiving Platform.
NAVAL RESEARCH LAB WASHINGTON DC
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The design and ultimate performance of an extremely low frequency ELF superconducting quantum interference device SQUID antenna that is mounted in a submarine-towed buoy depends critically on the motion spectrum of the buoy. Motion spectrum measurements from nearly direct current to 100 Hz were conducted on a hydrodynamically stabilized buoy while being towed in the 650-m towing basin of the David Taylor Naval Ship Research and Development Center, Carderock, Md. The spectra show that the angular motion of the buoy can be held to .000001 rad or less within the ELF receiver bandwidth of 30 to 130 Hz, as long as properly streamlined fairings are used on the hydrofoil trailing edges to prevent oscillations from vortex shedding. Low frequency oscillations of the buoy were .001 rad or less for frequencies down to 0.025 Hz. This performance of the buoy is sufficient to permit it to serve as a towed platform for the NRL prototype SQUID receiver.
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