SpaceX finally sent its unmanned Dragon spacecraft to the International Space Station (ISS) for a long-overdue resupply mission.

NASA announced via Twitter the spacecraft lifted off from the Cape Canaveral launch site in Florida. This is the third of 12 resupply missions NASA has contracted SpaceX to perform for $1.6 billion. The space agency has a similar agreement with Orbital Sciences.

According to the Associated Press, the Dragon spacecraft has more than four thousand pounds of cargo on board, including food, equipment for science experiments and more. Also on board are two legs for a humanoid robot and pieces to help ISS crewmembers replace a malfunctioning backup computer.

NASA astronauts Rick Mastracchio and Steve Swanson will perform a spacewalk Tuesday and were prepared to do so even without the new cargo. A series of delays forced SpaceX to delay its launch nearly a month and bad weather almost threatened to push it back further.

This launch has added significance for SpaceX, a commercial space company owned by billionaire Elon Musk. SapceX will try and reuse the Falcon 9 rocket that sent the Dragon spacecraft to the ISS. After the rocket separates and heads back toward Earth, it will deploy four landings legs as is turns on burners to slow itself as it descends on the Atlantic Ocean.

Nicknamed the "grasshopper" rocket, SpaceX will not try to land it back on its landing legs this time, instead putting it gently in the ocean. Previous tests at lower heights have been successful.

"Every mode of transportation we're used to... they're all reusable," Musk told NBC News last year. "If we can't make rockets reusable, the cost is just prohibitive."

If Musk is successful with his reusable rocket, he said he could save NASA 99 percent on resupply missions. Now all SpaceX has to do is iron out all the kinks to limit launch delays such as the ones they have recently experienced.

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