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A NASA report on the loss of a Utah State University-designed space experiment concludes that the tethered satellite delivered significant scientific data before the tether broke.

In addition, concluded the 358-page report released Tuesday, the tether was well-engineered. The break happened when damage to the cable's insulation allowed electricity to arc and burn wires and their superstrong Kevlar wrappings.The experiment used a small satellite connected to the space shuttle Columbia by a tether nearly 13 miles long and as thin as a shoelace. As the cable and satellite swung through the Earth's magnetic fields at 17,500 mph, the system generated electricity.

The experiment was working well and electrical data were recorded, as the tether was reeled out during the Feb. 25 experiment. But when the tether was nearly fully extended, it broke.

"It was within a kilometer (six-tenths of a mile) of full deployment," USU physics department chairman John Raitt told the Deseret News Wednesday. About 12.2 miles of tether sailed into space behind the small satellite.

A NASA investigative board released its findings on Tuesday: "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 arcing happened either because some debris penetrated the cable or because defects in the tether itself caused a breach in the layer of insulation surrounding the conductor, according to the report. If the cause was external material, it was not orbital debris or micrometeorites, it adds.

The failure of the insulation provided a path for electrical current to arc from the copper wire inside the tether to a nearby electrical ground. Once most of the insulation was burned away, the pulling force exerted by the satellite was enough to break the tether entirely.

The satellite was not recovered and was believed to have burned up upon entering the atmosphere shortly afterward.

"The tether itself was a remarkable engineering achievement," said Ken Szalai, chairman of the NASA investigation. It "produced some startling scientific discoveries."

According to NASA, theories about space physics are being revised or overturned because of the data returned.

During the short period that the satellite was connected to Columbia, the system generated 3,500 volts of direct current and up to 0.5 amps of current. The current was three times higher than theoretical models had predicted before the flight.

The amount of current generated was "the big surprise" of the experiment, Raitt said. Current is the flow of electrons through material.

"The very practical good results from this is we're able to generate current . . . that was significantly higher than expected."

Raitt said power generated by Earth's own magnetic field through such a system will be available at higher levels than anticipated.

He called the results very promising, "particularly in the era coming up with the space station." Although nobody expects tethered satellites to replace the solar cells that the station will use for power, such a system could give an extra boost of energy if needed for some high-powered experiment.

Debris and contamination discovered in the mechanism used to deploy the tether, and in the tether itself, could have pushed into the insulation layer when the cable was on the reel, the report says.

According to NASA's Michael Braukus, the investigation found evidence of damage to the copper wire inside the remaining part of the tether. It also established that natural forces on the tether while it was in the reel could push a single copper strand or a piece of foreign debris through the insulation.

Rigorous tests showed that an undamaged tether would not arc, even with much higher voltages.

"I'm glad it's nothing to do with the system or any of our experiments," Raitt said.