A privately-owned, unmanned Falcon 9 rocket and Dragon cargo capsule successfully blasted off from Cape Canaveral for the International Space Station.
The mission is to restore a US supply line to the ISS following the retirement of the space shuttle programme.
The 48m-tall rocket, built by Space Exploration Technologies, is powered by nine oxygen and kerosene-burning engines.
It lifted off from its seaside launch pad at Cape Canaveral Air Force Station in Florida at 8.35pm (1.35am Irish time).
The Falcon booster headed east over the Atlantic Ocean toward the station's orbit, 400km above Earth.
If all goes as planned, the capsule will reach the $100bn (€77bn) space station on Wednesday.
With the retirement of the space shuttles last year, NASA turned to the private sector to develop and fly station freight and is looking to do the same for crew transportation.
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 (€1.2bn), 12-flight contract to deliver cargo for NASA.
The Dragon cargo capsule is bringing 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 of chocolate vanilla swirl ice cream.
Shortly before the launch, NASA Deputy Administrator Lori Garver said: "We're thrilled that we are again launching to the space station from Florida."
Unlike the Russian, European and Japanese freighters that service the station, Dragon is designed to return to Earth intact.
As a result, it can bring back research and equipment from the station.
The capability to bring back research and equipment 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 Corp also have NASA backing for space taxi design work.
In addition to SpaceX, NASA has also hired Orbital Sciences Corp to fly cargo to the station.
Orbital's Antares rocket is expected to make a debut flight later this year.