The SpaceX Falcon 9 rocket ran out of fuel as it tried to land.

SpaceX founder Elon Musk tweeted Thursday that he believed he knew what happened to the rocket.

The rocket launched Wednesday morning. The first stage of the rocket crashed on the landing attempt on an ocean faring barge.

SpaceX launched two communications satellites into orbit Wednesday, servicing Latin America, Africa, Russia, South Asia and Southeast Asia.

The next Falcon 9 rocket will head to the International Space Station next month.

Meanwhile, United Launch Alliance will launch an Atlas V rocket carrying a military satellite next week on Friday, June 24.