Elon Musk's SpaceX continues to win approval from NASA. On Thursday, NASA awarded SpaceX, along with Orbital ATK (NYSE:OA) and Sierra Nevada, contracts to resupply the international space station, or ISS, with cargo. The missions will begin in 2019 and end in 2024, but funding begins immediately. The move adds to SpaceX's excellent track record of contracts with NASA.

A used Falcon 9 rocket. Image source: SpaceX.

The contract
Ahead of NASA's decision on Thursday, it wasn't clear how many of the active proposals from the space companies vying for the important program NASA would approve. After denying Lockheed Martin and Boeing's proposals in 2015, there were only three company's left to compete for the contracts -- and all three won. These cargo resupply contracts follow the last round of contracts, which were awarded in 2008 to SpaceX and Orbital.

The contract will provide the three space companies with considerable resources as they prepare and execute. The "maximum potential value of all contracts is $14 billion from 2016 through 2024," NASA said in a press release. 

"The second generation of commercial cargo services to low-Earth orbit begins today," said ISS Program manager Kirk Shireman. "By engaging American companies for cargo transportation, we can focus our attention on using this one-of-a-kind laboratory in the sky to continue advancing scientific knowledge for the benefit of all humanity."

SpaceX is the only company that will certainly use an entirely American-developed rocket. Sierra Nevada plans to use its own Dream Chaser for cargo on top of the United Launch Alliance's Atlas V rocket, which has a first stage powered by the Russian-built RD-180 engine.

Orbital plans to use its Cygnus cargo craft on either its Antares rocket, which should soon be completed, or the Atlas V rocket. SpaceX will use its Dragon cargo capsule, and its reusable Falcon 9 rocket.

Sierra's Dream Chaser Cargo System is built to land on a runway after returning from space. Image source: Sierra Nevada.

The contracts guarantee at least six cargo resupply missions for each company.

Good news for SpaceX
With SpaceX's successful Falcon 9 rocket landing now in the rearview mirror, it's easy to think the Hawthorne, CA-based company had the contract in the bag. But before the December mission, the company was on shaky ground.

Following 20 successes in a row, SpaceX's Falcon 9 blew up during flight in the summer of 2015, leading to a six-month hiatus. If SpaceX hadn't successfully returned to flight in December, the company could have easily been out of the running. Sure, a successful landing of the Falcon 9 may not have been necessary during the December mission, but there was definitely immense pressure for everything else to go as planned.

Orbital, too, experienced a major setback recently, when its Antares rocket exploded on the launch pad in 2014. But, like SpaceX, the company had a successful return to flight.

NASA's decision to include SpaceX in its next resupply mission to the ISS adds to SpaceX's previous ISS resupply contract, which has resulted in the transportation of 35,000 pounds of cargo together with Orbital. And it adds to SpaceX's contract with NASA to ferry astronauts back and forth from the ISS as part of the Commercial Crew Program -- a program that also awarded Boeing with a contract.

SpaceX has yet to put a press release on its website to acknowledge the contract. Perhaps that's because employees are hard at work prepping for the company's upcoming flight

If all goes according to plan, and NASA is currently saying the mission is a go, SpaceX will be put to the test this weekend. On Sunday, SpaceX aims to deploy a NASA Jason-3 satellite into lower earth orbit, and land its Falcon 9 in a barge in the Pacific Ocean.

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