In recent years, the Russian space program has had a series of problems with its flagship rockets, the heavy-lift Proton booster and the smaller Soyuz rocket used to launch crews and cargo to the International Space Station. The Proton rocket has been grounded since last summer, and the Soyuz has not flown since December, when its third stage engine failed and a Progress cargo spacecraft was lost.

Most of these problems have been traced to engines that power the second and third stages of the Proton and Soyuz rockets. The majority of these engines are built at the Voronezh Manufacturing Plant in southwestern Russia, near the Ukrainian border. Russian Space Web reports that Ivan Koptev, director general of the engine manufacturing facility, has resigned.

According to the news reports, the final straw may have come after recent tests of engines to be used by future second and third stages of the Proton rocket that resulted in more failures. "The failure of the engine was reportedly traced to illegal replacement of precious heat-resistant alloys within the engine's components with less expensive but failure-prone materials," Zak writes. The Russian space agency, Roscosmos, has already recalled some of the engines to be used in the upper stage of its Soyuz rockets, and now it is also recalling dozens of Proton upper stage engines. The next Proton launch could be delayed into this summer.

It is not clear what implications this will have for NASA, which relies on the Soyuz rocket to launch its astronauts to the International Space Station. NASA's head of human spaceflight, William Gerstenmaier, is in Russia this week to meet with Roscosmos officials to discuss the failure of the December 1 launch of the uncrewed Progress cargo vehicle. Although cargo and crew launches take place on different variants of the Soyuz rocket, the two rockets share a common third stage, which is where the December failure occurred.

For now, Russia's next Progress launch is scheduled for a launch no earlier than March 1, according to Russian officials. That will have to occur before the next crew launch, of cosmonaut Fyodor Yurchikhin and NASA's Jack Fischer, which may well slip past March. A source told Ars the launch date for Yurchikhin and Fischer should be firmed up in the "next week or two."

It's also worth noting that the Voronezh manufacturing facility is distinct from the NPO Energomash, which manufactures the more powerful first-stage engines for many of Russia's rockets. This facility also builds the RD-180 engines used by the Atlas V rocket, the workhorse for the United Launch Alliance. There is no indication of problems with these engines.