Any launch vehicle that flies as often as Russia’s Proton is bound to have its share of mishaps. The venerable heavy-lifter has flown 388 missions since its first in 1965, 45 of which have been deemed total or partial failures.

But the Proton M/Block DM-03 that veered off course and destroyed three Russian Glonass M navigation satellites in a fiery explosion near its Baikonur Cosmodrome launch pad July 2 comes at a particularly vulnerable moment for Russia’s space program, which has suffered a spate of launch vehicle failures in recent years, including five in the past 30 months.

Russia’s apparent nosedive in the quality of its space efforts has so far not affected launch vehicles serving the International Space Station (ISS). However, Proton quality control could have implications for Reston, Va.-based International Launch Services (ILS), which annually launches half of the world’s largest commercial telecommunications satellites atop Proton.

ILS and its majority shareholder, Khrunichev State Research and Production Space Center, have launched 81 commercial Proton missions since 1996 with six failures. But the majority of Proton mishaps have occurred on Russian federal missions, including four out of five failures in the past 30 months, two of which were caused by human error—a December 2010 loss of three Glonass spacecraft due to over-fueling of the rocket’s DM-03 upper stage, and the August 2011 loss of Express-AM4, a telecom satellite left in a too-low orbit due to a faulty parameter entered into its flight software system.

Two subsequent Proton failures—one federal, the other managed by ILS—took place within six months of each other, and were attributed to technical issues associated with the Breeze M upper stage. A manufacturing defect in the Breeze M helium pressurization system led to the loss of Russia’s Express-MD2 and the Indonesian Telkom-3 satellites in August 2012, while an early Breeze M shutdown following the December 2012 launch of the Gazprom Space Systems Yamal 402 commercial telecom satellite left the spacecraft in a useless orbit. A failure review attributed the shortfall to a combination of worst-case factors, including temperature and pressure, that led to damage in an upper-stage turbo-pump bearing.

But last week’s accident, which the Russian government is investigating, appears to have been due to failure of the rocket’s first stage, which powers both Russian federal and commercial Proton missions and has malfunctioned just five times in the course of the rocket’s nearly 50-year history.

According to Russian space agency Roscosmos, the Proton M/Block-DM-03 rocket and its three satellites went wildly off course seconds after liftoff, exploding into a fiery ball before crashing 2.5 km (1.5 mi.) from its Baikonur Cosmodrome launch site in Kazakhstan.

No fatalities were reported, but the Kazakh government is examining the environmental impact of the crash in the area adjacent to the launch site. Talgat Mussabayev, head of the Kazakhstan space agency, said July 2 the simultaneous explosion of rocket fuel and oxygen that took place during the launch likely transformed toxic amyl and heptyl chemicals contained in the first stage into nitric oxide, “which does not represent so big a threat to the life of the population.”

Russia rents the Baikonur Cosmodrome from Kazakhstan for military and commercial satellite launches and for Soyuz missions that ferry astronauts and cosmonauts to and from the ISS. This year, however, the Kazakh government restricted the number of Russia’s commercial satellite missions in a dispute over launch debris, which falls into Kazakh territory.

In the meantime, Russia continues to work on its Angara rocket family, the modular design of which is aimed in part at reducing Moscow’s dependence on Baikonur to launch heavy payloads. The new generation of rockets includes a heavy-lift variant that could replace Proton by the end of the decade and will be able to launch from both the Plesetsk launch site in northern Russia and the new Vostochny space center being developed in the country’s far east.

Khrunichev shipped the first flight model of the lightweight Angara 1.2 rocket to Plesetsk Cosmodrome May 28 in preparation for its inaugural launch next year. Khrunichev says it is also continuing work on the heavy-lift Angara A5, which it expects to ship to Plesetsk in November.

ILS had planned 12 Proton launches in 2013, but it says the launch failure investigation and review of the findings will delay upcoming missions, including the July 20 launch of Astra 2F for commercial fleet operator SES.

See video of the July 2 Proton M launch failure on our OnSpace blog at