The Falcon 9 rocket and Dragon cargo capsule has blasted off from Cape Canaveral on a mission to the International Space Station.
Powered by nine oxygen and kerosene-burning engines, the 157ft (48m) tall rocket, built by Space Exploration Technologies, lifted off from its seaside launch pad at Cape Canaveral Air Force Station at 8:35pm EDT (0035 GMT Monday).
"This was a critical event for NASA and the nation tonight," said Nasa Administrator Charles Bolden. "Just over a year after the retirement of the space shuttle, we have returned space station cargo-resupply missions to US soil."
The unmanned, privately owned Falcon booster, flying for the fourth time, streaked through balmy, partly cloudy skies as it headed east over the Atlantic Ocean toward the station's orbit, some 250 miles (400km) above Earth.
Despite a problem with one engine during the 10-minute climb to orbit, the capsule was delivered exactly where it was intended to go, company president Gwynne Shotwell said.
"Falcon 9 was designed to lose engines and still make missions, so it did what it was supposed to do," Shotwell said.
"We will learn from our flights and continue to improve the vehicle."
The capsule is scheduled to reach the $100bn space station – a project of 15 nations – on Wednesday.
The company, also known as SpaceX, made a successful practice run to the station in May, clearing the way for it to begin working off a $1.6bn, 12-flight contract to deliver cargo for Nasa.
The Dragon cargo capsule carries about 400kg of food, clothing, science experiments and supplies for the station.
The gear includes a freezer to transport medical samples and a rare treat for the station crew – chocolate vanilla swirl ice cream.
With the retirement of the space shuttles last year, Nasa turned to the private sector to develop and fly freight to the station and is looking to do the same for crew transportation.
"Every time they have a successful mission, that gives the non-believers one more opportunity to get onboard and root for us and help us make this thing happen," Bolden said.
Unlike the Russian, European and Japanese freighters that service the station, Dragon is designed to return to Earth intact, rather than burn up in the atmosphere, so it can bring back research and equipment from the station.
That return capability has been missing since the shuttle's retirement.
Dragon is scheduled to depart the station on 28 October and to splash down into the Pacific Ocean off the coast of California.
SpaceX has a separate Nasa contract to upgrade its Dragon capsule to carry humans as well. Boeing and privately owned Sierra Nevada also have Nasa backing for space taxi design work.
In addition to SpaceX, Nasa has also hired Orbital Sciences to fly cargo to the station.
Orbital's Antares rocket is expected to make a debut flight later this year.