By Andrew Osborn and Maria Kiselyova
MOSCOW (Reuters) - Two astronauts who survived the mid-air failure of a Russian rocket will fly again and are provisionally set to travel to the International Space Station (ISS) in spring of next year, the head of Russia's space agency said on Friday.
Dmitry Rogozin, the head of Russian space agency Roscosmos, was speaking a day after Russian cosmonaut Alexei Ovchinin and American Nick Hague made a dramatic emergency landing in Kazakhstan after the failure of the Soyuz rocket carrying them to the orbital ISS.
Thursday's accident was the first serious launch problem experienced by a manned Soyuz space mission since 1983, when a crew narrowly escaped before a launch pad explosion.
Russia is now under pressure to prove its space program is safe and received a boost on Friday when NASA administrator Jim Bridenstine said he had full confidence in Russian-made Soyuz rockets and expected U.S. astronauts to fly on them again.
Bridenstine, speaking to reporters in Moscow, also said he was confident that a planned Soyuz launch in December, which is due to transport three people, including one American, to the $100 billion orbital research laboratory, would happen.
Still, Moscow has suspended all manned space launches until it confirms exactly what went wrong and why, and Rogozin has ordered a state commission to investigate. Russian investigators have also opened a criminal investigation.
Sergei Krikalev, a senior Roscosmos official, said on Friday that Russia may also delay a planned unmanned cargo shipment by a Progress spacecraft to the ISS. Unmanned cargo launches carry food and other supplies to the ISS and use the same rocket system as the Soyuz. Russia says there is enough food on board to last until April.
Three people are now aboard the space station: a German, a Russian and an American. They were due to return to Earth in December, but may now be stuck there longer.
Roscosmos chief Rogozin on Friday posted a picture on Twitter of himself seated next to the two astronauts involved in Thursday's accident, saying they had arrived in Moscow. Both men escaped unscathed and feel fine, Roscosmos and NASA have said.
Rogozin said both would fly into space again, probably in the spring. NASA's Bridenstine said Hague, the U.S. astronaut, had told him he wanted to fly again and that NASA had huge confidence in him but that he didn't know when he might fly.
Thursday's mishap occurred as the first and second stages of the Russian rocket separated shortly after the launch from Kazakhstan's Soviet-era Baikonur cosmodrome.
The Interfax news agency on Friday cited a source familiar with the Russian investigation as saying that an important valve had failed to open due to a faulty firing cartridge. That in turn had hindered the separation of the first stage of the rocket from its second stage.
NASA has relied on Russian rockets to ferry astronauts to the space station since the United States retired its Space Shuttle program in 2011. The agency is waiting for the tests early next year of two commercial rockets, by SpaceX and Boeing.
"I think that by the middle of next year we'll be flying crews on those rockets," said Bridenstine.
NASA's top official said it was unlikely the Russian rocket failure would speed up development of those rockets because work on them was already flat out, but said it underlined the need for the world to have more than one way of getting to the ISS.
"I think this demonstrates how important it is ... not be dependent on one system or another system. This is an inflection point," he said.
Space is an area of cooperation between the United States and Russia at a time of fraught relations. Bridenstine told reporters he didn't expect political differences to impinge.
"To keep space separate from the political environment has been our tradition and we want to keep that," said Bridenstine.
For a graphic of the Soyuz spacecraft, see - https://tmsnrt.rs/2Oi1tDM
(Writing by Andrew Osborn; Editing by Christian Lowe, Peter Graff and Toby Chopra)