WASHINGTON — International Launch Services, the commercial arm of Proton rocket manufacturer Khrunichev, says it still expects to complete all three launches planned for 2017 once Proton returns to flight.

Russian Deputy Prime Minister Dmitry Rogozin said last month via Twitter that engines from Voronezh Mechanical Plant, used in the upper stages of the Proton and Soyuz launch vehicles, would be replaced, resulting in the dismantling of three Proton-M rockets and a three and a half month hiatus from launches.

In an interview with SpaceNews, ILS president Kirk Pysher said the company had three missions planned with Proton for this year, including EchoStar 21, which slipped from 2016 to this year when the engine issues surfaced. AsiaSat-9 and Hispasat’s Amazonas-5 are the other two missions.

“We are still working to conduct our full manifest for the year and continue the development of the Proton variants,” Pysher said.

Pysher said the engine troubles traced to Voronezh do not have any impact on the Proton Medium and Light configurations of the rocket first announced last year. Russian officials also intend to launch all previously planned non-ILS missions — of which there are four — bringing Proton’s manifest for the year to seven, he said.

Tracing the cause

Pysher said engine testing at the Voronezh plant revealed that some of engine parts were bonded using a solder with a higher melting point than the solder the plant was supposed to use.

“The way they build this joint is they basically build up the component and have cold solder in the buildup process,” Pysher explained. “Then they put that component in an oven and they bake it. During that baking process the solder melts, flows and wicks into the various components to create a bond. When they cut up that component they discovered that bonding process was less than expected.”

Pysher said Russia’s testing procedure for Proton’s third stage engines involves producing six engines even though the rocket only needs four, and selecting two for a “destructive inspection,” where they are sliced apart and analyzed. That routine inspection process revealed that a substitute had been used for the normal solder, prompting the Russian space agency, Roscosmos, to launch an investigation.

“What happened was, during the baking process, because [the solder] had a higher melt point, it didn’t flow as easily and wick into all the areas that they expected it to. They were able to isolate that and make a determination that there were a number of engines built by the manufacturer that used this higher melt point solder. So even though the engine survived this periodic test, they made the decision to recall all those engines that had been suspect to using the higher melt point solder,” Pysher said.

Voronezh builds the second and third stage engines for Proton.

Getting Proton back on track

The current timeline calls for Proton’s return in April or May. Pysher said ILS anticipates EchoStar-21 will very likely remain the return to flight mission, though ILS is “still working to understand the overall schedule and impact.”

Rogozin, in last month’s tweets about Proton, said “All those responsible for the substitution of technologies and documentation will be severely punished.” Pysher declined to comment on the deputy prime minister’s statement, saying only that the investigation in which Roscosmos and Khrunichev are involved is still ongoing.

“I would expect that there are going to be a number of corrective actions implemented over the course of the next few months. We won’t know those until that investigation is completely resolved,” he said.

Russia is doubling down on Proton to avert a loss of confidence in the wake of several anomalies. Proton has experienced an average of one anomaly a year for the past five years. The most recent, a premature second-stage engine shut down during the June 10, 2016 mission for Intelsat 31, didn’t impact the satellite but still resulted in a stand down and an in-depth investigation.

Pysher said the engines tested with the substitute solder passed hot firing tests of twice the normal mission duration and at a higher thrust level without issue, but there was no easy way to guarantee that all the recalled engines would perform as expected. Russia has tested Proton’s engines the same way for more than 50 years, he said, and convincing customers to fly with engines that had an unrequested change would have been difficult.

“What we are seeing is this is a renewed dedication to 100-percent mission success,” Pysher said.

He added that Khrunichev is implementing additional quality initiatives beyond the engine recall to further ensure Proton’s reliability.