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Inquiry Finds Cable Clip to Blame For Telstar 14R Deployment Failure
PONTE VEDRA, Fla. — The May 21 solar array deployment failure on the Telstar 14R/Estrela do Sul 2 telecommunications satellite was caused when a small clip holding the array’s graphite cabling in place came loose, allowing the cable to swing wildly and snag on a piece of metal used to hold the array in folded position against the satellite’s body during launch, an independent board of inquiry has determined.
The stress on the cabling from the deployment energy built up and eventually forced the cable to snap, and also caused a piece of the solar panel to break off, the inquiry board concluded.
As a result, the north solar array will be almost useless, causing satellite owner Telesat of Canada to rely exclusively on the south array, which deployed normally, to operate Telstar 14R/Estrela do Sul 2.
Solar array performance degrades over time, and the absence of 50 percent of the satellite’s intended solar power will limit the satellite’s operational life to about 12 years and reduce the number of transponders it can use to serve customers.
An insurance claim in excess of $200 million is likely to be filed in the coming weeks, industry officials said.
The failure review board, which acted independently of satellite builder Space Systems/Loral, was able to replicate the failure sequence on the ground but otherwise found no design flaw in the solar array deployment mechanism.
Space Systems/Loral President John Celli said the board likewise came across no evidence of a workmanship lapse in the construction or testing of the satellite.
“What happened? I would not say it was a workmanship error. We really found nothing indicating that as we went through the records,” Celli said in an Aug. 18 interview. “Maybe this little clip was weakened by multiple tests, or perhaps something touched it during integration of the satellite with the launch vehicle.
“The clip is a nylon hook. It attaches to the panel with a screw. Did the screw come off? Was the nylon bracket damaged? We went through tests and examined all the paperwork. The [failure review board] looked at all the designs and the qualification margins and safety factors and documentation relating to this. They couldn’t find a thing. The design was solid and there were no red flags on the workmanship.”
Something nonetheless went wrong, and Space Systems/Loral is adding tests and verifications for future satellite deliveries, as well as making minor modifications to make the cable clip more resistant to shock. Adding another screw to keep it in place is one measure that has already been taken for the next satellites Loral is delivering, the QuetzSat-1 satellite owned by SES of Luxembourg, and the ViaSat-1 satellite owned by ViaSat Inc. of Carlsbad, Calif.
Loral and the failure review board have briefed insurance underwriters on their findings, and insurers have agreed with Loral’s assessment that it is ready to lift the suspension of satellite deliveries.
The failure review board had the assistance of the U.S. Air Force, which provided a few images of the satellite taken while it was in geostationary transfer orbit. Celli confirmed that a few authorized Space Systems/Loral employees had access to the classified images, but he said they were inconclusive. He declined to identify the Air Force sensor that was used to take the images.
The seven-week inquiry, plus the loss of revenue from future incentive payments from Telesat, have cost Loral Space and Communications of New York, which owns Space Systems/Loral, about $13 million, Loral Chief Executive Michael B. Targoff said in an Aug. 10 conference call with investors.
Celli said that at the peak of the seven-week investigation into the failure, Space Systems/Loral had some 275 of its engineers working on the issue. He said they and the board of inquiry initially selected nine scenarios that might have caused the problem before settling on what they agreed was the most probable chain of events.
The inquiry was able to replicate the failure on the ground by placing a simulated satellite in a shaker and then detaching one of the cable fasteners. The cable swung in a way that would have enabled it to clear a small fencing component that is designed to prevent the cabling from getting caught on one of the fasteners, called hold-downs, that keep the arrays in a folded position against the satellite during launch.
One early focus of the inquiry was the eerie similarity between the May 21 failure and a similar solar array deployment failure on the original Telstar 14/Estrela do Sul satellite, launched in January 2004.
Since that 2004 incident, Loral has had no similar problems. Celli said the satellite launched May 21 carries the same solar array and deployment configuration as 14 previous satellites, all launched without incident. And the second array on the same satellite deployed without a hitch.
“Twenty-eight previous successes, with no problems,” he said. “Then we have this happen on the 29th. The 30th was deployed also without a problem.”
An investigation into the 2004 failure was unable to pinpoint what happened, but in addition to the fact that the arrays of the two satellites are not the same, “the signatures of the two events were completely different,” Celli said.
“The 2004 event occurred during launch, before the satellite was separated from the vehicle,” Celli said, referring to the Sea Launch rocket that carried the original Telstar 14/Estrela do Sul satellite.
“There was an event that occurred during max-Q,” he said, meaning the period of maximum stress on the rocket as it traverses the atmosphere. “The sensors picked up a kind of explosion. The sound and pressure were recorded. The solar wing was broken by the time the satellite was released from the rocket.”
Using U.S. Air Force imagery of the satellite plus the telemetry available on the satellite’s condition, “we determined that breakage of this magnitude would have required the equivalent of three metric tons of pressure. We looked at possible sources including heat pipes, and the fairing, and data provided by Sea Launch, and we never were able to identify the cause,” Celli said.
In its written conclusions, the failure review board concurred that “there is no relationship between the two” failures.
The Telstar 14R/Estrela do Sul 2 satellite is now flying in a configuration in which the south solar array is fully extended while the broken north array has one panel still snugly against the body of the satellite, and the three other panels are deployed but at an angle resembling a bird with a broken wing.