WASHINGTON The midair explosion of a workhorse Russian cargo rocket on July 5 could have been averted by a simple filter, the head of the rockets design bureau told the newspaper Isvestia. The rocket, carrying a military communications satellite, exploded when one of its second stage rocket engines caught fire and disintegrated, destroying the entire rocket and its satellite payload. According to Anatoli Kiselev, Director General of the Khrunichev State Research and Production Center, the engine failed because a particle of aluminum entered its turbo pump. "A fire started in the number three engine of the second stage, " Kiselev is reported to have said. "The fire was started by a stray aluminum particle in a seam between the cover and the apparatus as a result in a defect in a weld," he explained.

The particles can enter the pumps through either "neglect" in welding or other means. Such pumps send the fuel and oxidizer into the engines thrust chamber for ignition and combustion. That results in thrust that lifts the rocket. "Particles as small as 0.2 grams can cause a fire to start," Kiselev said, "if the welds are as little as 25 percent below the norm". He also said that the designers expected to lose four rockets out of every batch of 100, or a 96 percent flight success rate. "In reality, we are losing even less," he said.

Kiselev told Isvestia that return of the Proton to flight status and the lifting of a Kazakhstan-imposed ban on its launches from the Baikonur spaceport was anticipated shortly. "We expect to launch another four western spacecraft before the end of the year," he predicted. Return of the Proton rockets to commercial and operational service is crucial to the International Launch Services consortium, which has a backlog of satellite payloads for the large booster. The Russian military and civil space agencies use the vehicle to launch satellites, and the rocket is also needed to launch components to the International Space Station. Proton competes with the Boeing Sea Launch Zenit 3SL, European Ariane 5, Lockheed Martin Atlas III, and Chinese Long March 2E and 3B commercial launchers. Lockheed Martin is also a partner in the ILS consortium.