Trump-Musk split exposes how reliant NASA has become on SpaceX

• Musk eventually walked back the threat Thursday, but it demonstrates how critical SpaceX is to the American space program.

Catch up quick: The feud between the president and world's richest man exploded into public view Thursday after Musk criticized Trump's flagship spending bill.

• Trump subsequently threatened to cut all of Musk's government contracts, and Musk retaliated by threatening to mothball SpaceX's Dragon.
• It's an acrimonious ending to Musk's tenure in the White House.

State of play: The Dragon spacecraft can carry up to seven passengers into orbit, according to the SpaceX website.

• "It is the only spacecraft currently flying that is capable of returning significant amounts of cargo to Earth, and is the first private spacecraft to take humans to the space station," the website said.
• Between 2011 when the space shuttle program ended and 2020 when the Dragon entered service, American astronauts relied on other countries to reach space, particularly Russia.
• The Dragon has completed 51 missions and 46 visits to the ISS, per SpaceX.

Russia's Soyuz capsules are the only other way for crews to reach the space station, per AP.

• Each Soyuz launch carries two Russians and one NASA astronaut. Every SpaceX launch carries one Russian.

Flashback: NASA in 2014 awarded contracts to SpaceX and Boeing to transport crews to the ISS.

• Boeing's Starliner, though, experienced significant setbacks and left astronauts stranded on its first crewed test flight.

Zoom out: While NASA relies on SpaceX for its astronauts, other companies including Northrop Grumman and the United Launch Alliance successfully transport cargo to the ISS and launch satellites.

Go deeper:

• Musk calls for Trump's impeachment
• Trump-Musk feud shows signs of thawing