December 6, 2015

— The S.S. Deke Slayton II is now on its way to the International Space Station.

The Orbital ATK Cygnus cargo spacecraft, named in honor of the late Mercury astronaut and commercial spaceflight pioneer, lifted off on a United Launch Alliance (ULA) Atlas V rocket from Launch Complex 41 at the Cape Canaveral Air Force Station in Florida at 4:44 p.m. EST (2144 GMT) on Sunday (Dec. 6).

After a 21 minute ascent, the Deke Slayton II was released into orbit from the Atlas V's Centaur second stage to begin its rendezvous with the space station.

The launch marked the return to flight for the Cygnus after Orbital ATK's first "Slayton" was lost in a rocket explosion in October 2014. Sunday's liftoff was the first time Cygnus flew on board a ULA Atlas V from the Cape, as Orbital ATK continues work to resume use of its own Antares booster from the Wallops Flight Facility in Virginia next year.

Enlarge and view the video in a new pop-up window. (NASA TV)

"It's been a challenge to get back to this point," said Frank Culbertson, a former astronaut and the president of Orbital ATK's Space Systems Group. "But return to flight became the company's very, very sharp focus."

"With the help of our friends at ULA, who stepped forward and offered us a ride, in a very short period of time we've reached this point and we're very excited about it," he said. "That's quite an accomplishment for a commercial space industry in my opinion, and I think it says a lot about what we can do to support NASA and all of exploration."

The Deke Slayton II's mission, dubbed OA-4, is delivering some 7,700 pounds (3,500 kg) of science experiments and supplies when it arrives at the station on Wednesday. As the Cygnus pulls up to the orbiting laboratory, NASA flight engineer Kjell Lindgren will use the space station's laptop computers to monitor the ship's status while controlling the station's Canadarm2 robotic arm to grapple and berth the Deke Slayton II to the Earth-facing side of the Unity node.

"This is the first berthing to the Node 1 nadir in quite some years," said Kirk Shireman, NASA's space station program manager, noting the relocation of a pressurized module in May, which freed up use of the port.

Artist's concept of Orbital ATK's Cygnus in orbit. (Orbital ATK)

The OA-4 mission is setting a few other firsts, including the maiden use of Orbital ATK's Ultraflex solar arrays and the inaugural flight of the enhanced Cygnus with a pressurized cargo module that is a third longer than the prior launched ships.

"Cygnus is bringing up a tremendous amount of cargo, in fact the most cargo ever brought up on a Cygnus vehicle," Shireman said.

The additional capacity is coming at a time when it is most needed. After the loss of the Orb-3 Deke Slayton in 2014, the space station program suffered two more supply craft losses, leaving the orbiting laboratory running low on basic needs.

If the Cygnus were to again fail at reaching the outpost and if no other vehicles were able to be launched, then the station's crew members would begin consuming their food reserves in February and would ultimately run out of meals on April 12. Similarly, without the Cygnus and subsequent deliveries, the station's residents would cross the redline of toilet supplies in about two months time.

Orbital ATK's OA-4 Cygnus mission patch. (Orbital ATK)

"2015 has been a difficult year for [the] ISS," Shireman told reporters prior to the launch. "So we are looking forward to having those supplies replenished on board Cygnus."

In addition to the logistics, the S.S. Deke Slayton II is also carrying spacesuit components for the station's astronauts to use on spacewalks, two pressurized tanks to replenish the station's air supply, and spare equipment for the water recycling system.

Research flying on OA-4 includes a life science facility to support studies on cell cultures, bacteria and other micro-organisms; the first microsatellite to be deployed from the space station; experiments to study the behavior of gases and liquids and to test the properties of molten steel; and evaluations of flame-resistant textiles. A CubeSat, the first ever to be designed and built by an elementary school, is also on board.

The Deke Slayton II is expected to remain berthed to the station through early February, while the crew unpacks its contents and then refills the module with refuse and spent equipment. It will then be released and directed to reenter the Earth's atmosphere to be destroyed.

Orbital ATK plans to launch one more Cygnus using ULA's Atlas in March, followed by a return to flight for its Antares rocket in May.

Sunday's Cygnus launch marked the 60th flight of a United Launch Alliance Atlas V (the 30th in the 401 configuration).