The Russian maker of the engine used in the unmanned US supply rocket that exploded after liftoff in Virginia denied on Wednesday that its product was at fault for the catastrophe.

The launch phase of the Orbital Sciences Corporation’s Antares rocket relied on two AJ-26 engines that were originally produced in the 1970s for a failed Soviet moon programme and later modernised for US space flights. Speculation quickly centred on the Soviet-based engines, which have failed in tests, when the rocket exploded in a giant fireball after takeoff on Tuesday night.

But the Kuznetsov company in the Russian city of Samara suggested the blame lay not with its NK-33 engines, which formed the basis for the AJ-26 engines, but rather with their later modification in the United States, the Russian news agency Itar-Tass reported.

“Due to certain specifics, it’s not possible to talk about the construction details of the rocket itself and the interaction of its systems during launch, since this is the field of American specialists,” Kuznetsov’s press service said. “However, it’s important to note that during yesterday’s launch, the AJ-26 first-stage engines, which are a modification of the NK-33, were functioning normally.”

Investigators from Nasa were scouring the site of the failed launch in Virginia by helicopter on Wednesday as they attempted to assess the extent of damage to the Wallops Flight Facility, which is owned by the agency. Engineers working for Orbital Science were trying to work out what caused the failure of the company’s $200m rocket, which forced the cargo mission resupplying the International Space Station to be aborted seconds after launch.

No injuries were reported from the explosion, but the incident sent ripples though the space industry on Wednesday and forced Orbital to convene a conference call with its investors after its shares fell more than 15% in early trading.

Lasting damage to the launchpad could delay other flights from Wallops, although the successful launch of manned Russian mission early on Wednesday morning means the space station crew will continue to be supplied.

Nasa also drew some comfort in the hours after the incident from the fact that some pressure sensors at the Wallops launchpad were still functioning after the crash, suggesting parts of facility may have been successfully shielded from falling debris.

No injuries were reported from the explosion. Guardian

The launch was the first time the Antares rocket had been launched at night from Wallops, and the fireball caused by its explosion could be seen from miles around.

The accident is likely to intensify scrutiny over Nasa’s deal to subcontract resupply missions to private space operators following the end of its shuttle programme.

Orbital is under particular pressure to explain whether its use of ageing Russian rocket engines to power the first stage of the Antares rocket was a factor.

Kuznetsov argued that its NK-33 engines had undergone significant modernisation in the United States, including the addition of new components to direct the rocket’s thrust vector. “The development and certification of all new systems were done by the American side without Kuznetsov specialists. In essence, the AJ-26 engine is undergoing flight tests,” it said.

The NK-33 engines were first developed for the Soviet Union’s N-1 moon rocket, but many of them wound up in storage when that programme was cancelled after several launch failures. The US company Aerojet Rocketdyne reportedly bought about 40 of the Soviet engines in the 1990s and began modifying them for use in US rockets. The resulting AJ-26 engine has suffered some failures during tests: one caught fire in 2011, and another being tested in May before use in an Antares flight burned up.

Orbital Sciences revealed plans on Wednesday to end its use of the ageing Russian rockets for future launches, a transition that could take up to a year to complete and delay its next scheduled launch in April.

“The AJ-26 rocket engines used in [the Antares first stage main propulsion system] have presented us with some serious technical and supply challenges in the past,” said the chairman, David Thompson, in a hastily convened conference call with investors.



“So Orbital has been reviewing alternatives since the middle of last year and recently selected a different main propulsion system for future use by Antares. It is possible we may decide to accelerate this change if the AJ-26 turns out to be implicated in the failure.”

Thompson played down the cost of the accident, insisting damage to Nasa’s launch site was minimal and fully covered by insurance.

“Based on the preliminary inspection carried out this morning, it appears the launch pad sustained no major damage,” he said.

But a spokesman for Nasa said it was too early to get close to the launchpad for a definitive answer.

“The damage assessment team on Wallops Island began their task this morning at sunrise,” agency spokesman Keith Koehler told the Guardian. “They have taken aerial photos of the launchpad area but they have not been able to go into the area to do a close-up visual assessment.”

An accident investigation board led by Nasa and the national transportation safety board has been convened to study the exact causes of the rocket failure.

People who came to watch the launch walk away after the explosion in Virginia. Photograph: Steve Alexander/AFP/Getty Images

Since the end of its space shuttle programme in 2011, the United States has had to rely on Russian engines and entire rocket systems to deliver astronauts and supplies to the International Space Station.

But rising political tensions between the two countries have complicated their space cooperation. Following US sanctions against Russia over its role in the Ukraine crisis, Dmitry Rogozin, the deputy PM in charge of the space and defence industries, barred the export of Russian engines used to launch US military satellites into orbit and threatened to end US participation in the ISS beyond 2020.

Although Nasa has begun using US private contractors like Orbital Sciences Corp to lift payloads into orbit, the loss of Tuesday’s launch carrying a Cygnus cargo ship to the station highlights these firms’ dependence on Russian engines.

On Wednesday, the newspaper Kommersant reported that the state oil company Rosneft was seeking new retaliatory measures over sanctions against Russia, including limiting western astronauts’ use of Russian modules of the ISS. In response, Rosneft and Vladimir Putin’s spokesman both denied such measures were being prepared, and the oil company said it would sue the newspaper.

An unmanned Russian Progress spacecraft successfully launched from Kazakhstan’s Baikonur Cosmodrome just hours after the US rocket crash with three tons of food, fuel and supplies for the ISS. But confidence in the Russian space industry in general has been shaken by several recent fiascos, prompting Moscow to promise £30bn ($48bn) in state investment until 2020. Shortly after the announcement in the spring, a Proton rocket exploded after liftoff.

This summer, the televised maiden launch of the next-generation Angara rocket had to be cancelled and delayed by a month.

But although suspicions in the west have surrounded the Russian-made components of the Antares, space industry insiders in Moscow have predicted that the crash will force the United States to rely even more on Russian rockets. A space industry source told the news agency Interfax that the crash had likely damaged the launch complex in Virginia and that the United States would likely be forced to ask Russia to use one of its Progress rockets to launch supplies for the US section of the space station.

Defence and space industry analyst Pavel Felgenhauer said the United States would likely be forced to use Russian rockets despite the “Russian gloating” over the Antares crash, and the country’s “new anti-American front in space”. But he also said it was premature to accuse the Russian engine manufacturer for Tuesday’s explosion.

“It’s really too early to talk about placing blame, although both sides are trying to push away responsibility,” Felgenhauer said. “There will be an investigation into what was at fault. Such mass explosions in the early part of the space era were often caused by the second-stage engine prematurely going off, so even if it was an engine, we still need to find out what exactly went wrong.”