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Broken tether lost in space
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NASA

Tethered satellite investigation report
News story originally written on June 4, 1996

NASA and the Italian Space Agency (ASI) have released the report of the investigative board appointed to determine factors which resulted in the Feburary 25 tether break and loss of the Tethered Satellite during the STS-75 Space Shuttle mission.

"The tether failed as a result of arcing and burning of the tether, leading to a tensile failure after a significant portion of the tether had burned away," the report concludes. The arcing occurred because either external foreign object penetration (but not orbital debris or micrometeoroids) or a defect in the tether caused a breach in the layer of insulation surrounding the tether conductor. The insulation breach provided a path for the current to jump, or arc, from the copper wire in the tether to a nearby electrical ground.

The board found that the arcing burned away most of the tether material at that location, leading to separation of the tether from tensile or pulling force. The break occurred when approximately 12.2 miles (19.7 km) of tether was unreeled, in a period when the tether was experiencing normal stresses of approximately 15 pounds (65 newtons).


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