LOS ANGELES - NASA has secured the area around the Wallops Flight Facility in Virginia as the investigation begins into why an Orbital Sciences Antares rocket blew up just seconds after liftoff on its way to deliver a Cygnus cargo spacecraft to the International Space Station (ISS).

The vehicle, the first stage of which is powered by two refurbished AJ-26 rocket engines, suffered a “catastrophic anomaly shortly after liftoff,” the agency says. The mission was to have been the third Orbital resupply flight to the ISS, carrying 5,000 lb. of NASA cargo, and had been delayed from a previous attempt on Oct. 27 because of a boat straying into the range safety zone southwest of the launch pad.

“The ascent stopped. There was some disassembly of the first stage, it looked like, and then it fell to earth. We don’t have any early indications of what exactly might have failed,” Orbital Executive Vice President Frank Culbertson said at a press conference shortly after the mishap. Although investigators are keeping their options open, a prime suspect is expected to be a potential failure mechanism involving the AJ-26, a liquid oxygen/kerosene-powered engine originally developed for the Russian space program as the NK-33. An AJ-26 slated to power an Antares on a mission to the ISS in 2015 experienced a failure during a hot-fire test at NASA’s Stennis Space Center in Mississippi on May 22.  

“We didn’t see any anomalies or anything that would indicate there were problems with the engine," Culbertson said. "We don’t know whether the engine was involved at all or not. These were extensively tested, are very robust and rugged, and go through extensive testing at Stennis before they are installed on the rocket. These went through normal acceptance and pressure testing.”  Orbital announced earlier this month it had selected a new main engine for the Antares, but has not yet revealed the supplier or the engine itself.

The failure visibly occurred around 10 sec. after liftoff at 6:22 pm EDT, and range safety officials triggered the vehicle’s flight termination system about 20 sec. after liftoff as the rocket was descending. The resulting explosions took place very close to, and partially above, the launch facility. Images of the site show burning debris littering the pad area and the adjacent beach on the Atlantic coast. NASA says the range confirms launch officials are continuing to secure the area, and adds that all personnel are accounted for and there have been no injuries.