Roundup: Orbital ATK resumes U.S. cargo missions to ISS months after rocket explosions

A private U.S. cargo spaceship was launched toward the International Space Station (ISS) on Sunday afternoon, months after two U.S. commercial shipments were destroyed in launch explosions.

A live broadcast by NASA TV showed Orbital ATK's Cygnus blasted off atop a United Launch Alliance (ULA) Atlas V rocket as planned at 4:44 p.m. EST (2144 GMT) from Cape Canaveral Air Force Station in Florida.

Following a 21-minute ascent, the spacecraft was successfully deployed into its intended orbit about 232 km above the Earth, flying free to begin its pursuit of the ISS.

"We are very proud to be back in space again," Frank Culbertson, president of Orbital ATK's Space Systems Group, told reporters at a post-launch press conference.

"We have some more work in front of us of course, but we're optimistic that's going to go as planned. Everything was about as it could get," said Culbertson.

The launch of the Cygnus spacecraft was delayed three times this week due to bad weather, including thick clouds and high winds, but Sunday's launch went smoothly.

"We launched (this mission) OA-4 on our fourth attempt at 4:44 p.m. local time, so I guess all the numbers lined up today," said Vernon Thorp, ULA's program manager for NASA missions, who also took part in the briefing.

This marked Orbital ATK's fourth operational mission to the ISS for the U.S. space agency NASA under the Commercial Resupply Services (CRS) contract as well as the debut of the enhanced Cygnus, which has about 3,500 kg of cargo on board.

The earlier version of the spaceship could carry only about 2,000 kg of cargo.

Virginia-based Orbital ATK is one of the two commercial companies hired by NASA to fly cargo to the ISS after the space shuttles were retired. Its third CRS mission using the company's own Antares rocket was destroyed in a launch explosion in October last year.

The other company, SpaceX, is recovering from a similar launch explosion in June this year as well.

At a pre-launch news conference earlier this week, Kirk Shireman, NASA's ISS program manager, called the explosions "growing pains" in what he said was "a transition period."

"Commercial space is going to happen," Shireman said. "It is inevitable. It is occurring right now. It is our future."

The NASA official put 2015 as "a difficult year" for the ISS as a result of the two U.S. cargo delivery failures as well as the loss of a Russian cargo spacecraft in April, revealing that the orbiting lab has basically toilet supplies through February next year and that food supplies would also run out on April 12.

"So we're looking forward to having those supplies being replenished" by Orbital ATK's latest cargo resupply mission, he said.

Shireman stressed that NASA wanted to "have a regular cadence of resupply flights" over the next year as both Cygnus and SpaceX's Dragon resumed cargo missions to the ISS.

If all go as planned, Cygnus will arrive at the ISS on Wednesday for an expected two-month visit.

Orbital ATK has three CRS missions scheduled in 2016 to support ISS cargo needs.

A second Cygnus launch using the Atlas V rocket will take place next spring from Florida, followed by the return to operations at NASA's Wallops Flight Facility in Virginia in mid-2016 where the company will continue CRS missions atop the upgraded Antares rocket.

NASA Deputy Administrator Dava Newman congratulated Orbital ATK on Sunday's successful launch.

"We look forward to the next milestones of our other commercial partners, including commercial crew launches from American soil in the near future," Newman said in a statement.

"All these missions are critical to our journey to Mars," said Newman. Endi