The first launch of the Antares rocket, which is intended to fill an important niche in the U.S. space program, took place Sunday at a NASA facility on Virginia’s Atlantic Coast.

Liftoff of the slender, 133-foot long Orbital Sciences rocket from Wallops Island was a key step in a NASA program calling for private companies to deliver supplies to the international space station.

The launch, which had twice been postponed, once as recently as Saturday, was a test of the two-stage rocket and the dummy cargo vessel it carried.

The simulated cargo carrier was to separate from Antares and go into orbit, testing the plan for Orbital Sciences, based in the Dulles area, to resupply the space station as many as eight times. (Still to come is a demonstration in which a cargo vessel will actually go to the space station.)

It appeared that initial expectations were met. First, 750,000 pounds of roaring thrust hurled the rocket upward. About 10 minutes after the 5 p.m. launch, it was reported that the dummy payload had separated from the rocket.

That “lays the groundwork” for the first Antares cargo mission to the space station later this year, said John Holdren, director of the White House Office of Science and Technology Policy.

The program is expected to enhance the image of Wallops and of Virginia as contributors to space exploration.

It was not immediately clear if the launch was seen in Washington, 125 miles away, but social media carried reports from a variety of East Coast spots.

One said, “Saw it from Reedville, Va.” Another, from Delmar, Del., said, “Really good view from our deck.” From Cumberland County, N.J., a poster said, “Saw first stage separation.” A post from relatively near Wallops in Chincoteague, Va., called it “awesome.”