Panel Blames W3B Failure on Misaligned Propellant Tube
WASHINGTON — A four-month investigation into the Eutelsat W3B Declared Total Loss; Plans Under Way To Deorbit Craft”>loss of Eutelsat’s W3B telecommunications satellite less than 24 hours after launch last October has concluded that the failure was caused by a sudden, catastrophic leak in a single propellant tube connected to one of the satellite’s 16 thruster motors, industry officials said.
Conclusions about what happened on a satellite that cannot be recovered are never 100 percent certain, especially in a case like W3B, which represented one of the more mysterious losses in recent years.
“I’ve never seen anything like it,” Eutelsat Chief Technical Officer David Bair said during a March 16 briefing here during the Satellite 2011 conference.
Bair said Eutelsat is nonetheless satisfied that the board of inquiry looking into what happened to W3B has solved the mystery and that the satellite manufacturers in question — in this case, Thales Alenia Space as prime contractor and Astrium Satellites as propulsion-system provider — have taken the needed steps to prevent a recurrence.
Eutelsat Chief Executive Michel de Rosen said the contractors have agreed to tighten some of their oversight procedures in the future, and notably to verify that the W3C satellite, a W3B twin now planned for launch this summer aboard a Chinese Long March rocket, has no similar issues.
The tube’s rupture was due to a faulty alignment with the thruster assembly, which the board of inquiry said was a result of poor workmanship during the satellite’s assembly.
The board further concluded that the assembly glitch was at least indirectly caused by the decision of prime contractor Thales Alenia Space to replace a so-called ITAR-free thruster with a standard unit.
Officials familiar with the investigation said the misalignment probably would have occurred even if the change-out had not related to ITAR, or the International Traffic in Arms Regulations that govern the export of U.S.-built satellite parts.
W3B was originally intended for launch aboard a Chinese Long March rocket. Because the U.S. government forbids U.S. satellite components from being exported to China, satellites launched there must use non-U.S. hardware in order to be beyond the reach of ITAR.
But when Thales Alenia Space ran short of spare ITAR-free components it wanted to take to China for the launch preparations, Eutelsat opted to switch to a European Ariane 5 rocket rather than risk a delay in the launch.
Once that decision was made, the need for the more expensive ITAR-free components disappeared and Thales Alenia Space thought it prudent to replace some ITAR-free hardware and save it for future use.
W3B was launched together with Japan’s Bsat-3b telecommunications satellite aboard a European Ariane 5 rocket. The Evry, France-based launch operator reported that flight conditions, meaning the vibration effects that every satellite suffers as the rocket traverses the atmosphere, were within specification.
But almost from the moment the satellite separated from the vehicle, ground teams began seeing telemetry data suggesting a severe leak in an oxidizer feed line.
The leak was so bad that ground controllers soon realized that not only was the W3B a total loss, but that the satellite could not be raised into a graveyard orbit or sent into a controlled atmospheric re-entry to burn up over the Pacific Ocean.
W3B, which weighed 5,370 kilograms at launch, will now spend 20 years or more as another piece of space garbage in an orbit of 250 kilometers by 35,900 kilometers. Thales Alenia Space officials said they succeeded in rendering passive the satellite’s electronics to reduce the risk of explosion in orbit.
The satellite was insured for about 245 million euros ($325 million).
The board of inquiry included the prime and propulsion contractors, plus the French space agency, CNES; Eutelsat; and Arianespace as an observer.
One official familiar with the investigation said that the investigation was able to identify the volume of the leaked propellant and deduce the size of the leak, as well as its location.
The board noted a slightly off-nominal separation of the rocket’s payload shroud, or fairing, but soon concluded that this could not have caused the fuel-line rupture given the location of the fuel line.
“There is no evidence that the launch vehicle was involved in this,” one official said. “The fact is that there was a need to change the thruster fairly late in the program from ITAR-free to non-ITAR-free and that the execution of this maneuver proved to be faulty.”
The misalignment had the effect of causing the fuel line to rupture under a lower level of stress than designed. One official said there had been an indication during the satellite’s ground testing that the stress tolerance of this tubing may not be sufficient, but this was simply noted in the satellite preparation documents and not given any special attention.
The tube was manufactured by Astrium from technical specifications given by Thales Alenia Space.
Eutelsat has received a portion of its insurance claim and expects to give a final briefing to underwriters in early April.