"The silvery stretched pumpkin seed shape ... is a "polecap". ... The polecap is used during calibration of the main pylon. The shape of the pylon is so stealthy, that only the very tip of the pylon ends up being a significant source of signal return. To minimize this, a precisely shaped polecap is placed on the tip of the pylon to eliminate any radar returns from this spot. Then, once the very small return from the pylon is accurately determined and the system calibrated, the polecap is removed and a model put in its place. Perhaps surprisingly, the polecap was fabricated for Lockheed by a boat-building firm, Goetz Boats in Bristol, Rhode Island. It consists of aluminum honeycomb and carbon fiber, and the band along the outside edge is made of Kevlar, and the whole thing coated with RAM. After fabrication, it was shipped across country on a flatbed truck, looking to the world like the hull of a racing yacht."
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"The silvery stretched pumpkin seed shape ... is a "polecap". ... The polecap is used during calibration of the main pylon. The shape of the pylon is so stealthy, that only the very tip of the pylon ends up being a significant source of signal return. To minimize this, a precisely shaped polecap is placed on the tip of the pylon to eliminate any radar returns from this spot. Then, once the very small return from the pylon is accurately determined and the system calibrated, the polecap is removed and a model put in its place. Perhaps surprisingly, the polecap was fabricated for Lockheed by a boat-building firm, Goetz Boats in Bristol, Rhode Island. It consists of aluminum honeycomb and carbon fiber, and the band along the outside edge is made of Kevlar, and the whole thing coated with RAM. After fabrication, it was shipped across country on a flatbed truck, looking to the world like the hull of a racing yacht."
Picture here:
http://www.thehowlandcompany.com/radar_stealth/Bluefire_Helendale.htm