An unmanned Falcon 9 rocket blasted off from Cape Canaveral in Florida on Friday. It will deliver a cargo capsule to the International Space Station for NASA.
The Dragon capsule is packed with equipment, experiments and supplies.
It should reach the orbital outpost on Sunday.
SpaceX, or Space Exploration Technologies, was supposed to fly last month, but delayed the mission to check a potential issue with its rocket.
When that was resolved, an Air Force radar system became damaged, further delaying the mission.
This is the third cargo run by Space X since NASA shuttles were retired in 2011.
Friday’s launch was planned to test new technology to recover and reuse rockets.
The company considers the test has less than a 40 percent chance of success.
There was no immediate word on whether the test was successful.
Eventually, Space X hopes to fly its Falcon rockets back to land for refurbishment and reuse.