The Falcon 9 rocket lifted off Tuesday at 3:44 a.m. from Cape Canaveral, Fla. It's carrying a capsule packed with 1,200 pounds of food and supplies for the space station crew. The rocket was built by SpaceX, a Southern California-based company.
Previously, trips to the space station were only carried out by major government space programs.
"It's just indescribable. It's just all the hard work we did all this time. Just to see the results and everybody else's, it's just unbelievable," said SpaceX engineer Mariam Safaryan.
Tuesday's launch was the second attempt. The launch was aborted just a half second before liftoff on Saturday because of a bad engine valve, which has since been replaced.
The real test comes on Thursday when the SpaceX capsule reaches the vicinity of the space station. It will begin practice maneuvers to dock. If all goes well, docking occurs on Friday. The capsule is supposed to remain there for a week, and then return with equipment and experiments.
NASA and SpaceX officials stress that this is a test flight, so if something goes wrong, there is a lot to learn from it. The eventual goal is to get American astronauts blasting off from U.S. soil again. American astronauts are currently riding Russian rockets to orbit until SpaceX or one of its competitors takes over the job.