An unmanned Antares rocket exploded seconds after liftoff from a commercial launchpad on Tuesday in the first accident since NASA turned to private operators to deliver cargo to the International Space Station.

The 14-story rocket, built and launched by Orbital Sciences Corp, blasted off at the Wallops Flight Facility on Virginia's eastern seaboard at 6:22 pm, carrying a Cygnus cargo ship bound for the space station. It burst into flames moments later, then plunged to the ground in a huge ball of fire and smoke. The authorities said no one was hurt.

The six crew members in orbit aboard the space station - two NASA astronauts, one from the European Space Agency and three Russian cosmonauts - watched the launch via a TV feed, said Mike Suffredini, the space station program manager.

"They were disappointed. Of course they are well aware that they have plenty of resources in orbit," Suffredini said.

With a Russian cargo ship due to reach the space station just 14 hours after the explosion, the loss of the Cygnus supply vessel poses no immediate problem for the orbiting team.

Russia on Wednesday offered to help the US with deliveries to the station. "If a request is made for the urgent delivery of any American supplies to the ISS with the help of our vessels then we will fulfill the request," Russian space agency official Alexei Krasnov said, adding that NASA had not yet asked for assistance.

NASA Associate Administrator William Gerstenmaier said: "There was no cargo that was absolutely critical to us that was lost on that flight. The crew is in no danger."

Suffredini, the program manager, added that the crew has enough food and other supplies aboard to last four to six months.

Frank Culbertson, executive vice-president of Orbital Sciences, said the cause of the mishap is under investigation.

Footage showed flames engulfing the rocket from the bottom to the top 11 seconds after liftoff, and it sank back downward in a conflagration.

Ronda Miller, manager of the Ocean Deli in Wallops Island, Virginia, said that she felt the force of the blast from the eatery, nearly 8 kilometers from the launchpad.

"We were standing outside waiting for it to launch and we saw bright red, and then we saw a big black cloud, and it shook the whole building where we work," Miller said. "I came back in to work and saw fire trucks going every which way."

Reuters - AP - AFP

(China Daily 10/30/2014 page12)