With the return-to-flight of its Proton rocket scheduled for next week, International Launch Services (ILS) is planning to launch seven missions between now and the end of August, including one for the Russian government.

Reston, Va.-based ILS, which markets commercial launches of Proton for Moscow-based Khrunichev, will loft the Satmex 8 commercial communications satellite on March 26, the first Proton mission since a Dec. 8 mishap left the Gazprom Space Systems Yamal 402 Ku-band commercial telecom satellite in a low orbit after the rocket’s Breeze M upper stage shut down 4 min. early.

“Customer confidence is returning,” ILS President Phil Slack told reporters on the sidelines of the Satellite 2013 conference here March 18. “Obviously we need to have a good string of successes to really win back full customer confidence, but we’re certain we’ll be able to do that.”

Failure review

Slack said a failure review investigation found the shortfall was caused by a combination of worst-case factors, including temperature and pressure, that led to damage in a turbopump bearing in the upper stage.

“This last failure wasn’t where there was something manufactured wrong or a procedure wasn’t followed,” he said. “This was a buildup of tolerances where the combination of these ended up creating a condition that caused a failure.”

The December launch mishap followed a spate of failures that have plagued Proton over the past three years, including the December 2010 loss of three Russian Glonass navigation satellites due to over fueling of the rocket’s Breeze upper stage, followed by an August 2011 failure that cost Russia its Express-AM4 telecommunications spacecraft due to a programming error in the rocket’s guidance system. On Aug. 6, 2012, an out-of-specification component in a Breeze M fuel line led to loss of the Russian Express-MD2 and Indonesian Telkom-3 telecommunications satellites.

Slack says Proton manufacturer Khrunichev is in the process of implementing a quality management system audit and is planning to conduct a reliability improvement study of the rocket’s Breeze M upper stage over the next year. “Khrunichev will look at the whole system, on a subsystem-by-subsystem basis, to try to get the demonstrated reliability up to where the theoretical reliability is,” Slack said. “That study will take a year or so to complete, and from that there will be a number of recommendations that will be implemented going forward.”