SpaceX CEO Elon Musk welcomed the launching of Space Force, the newest US military service, with a "Star Trek"-themed tweet: "Starfleet begins."

On Friday, President Donald Trump signed the National Defence Authorization Act (NDAA) a US$738 billion bipartisan defence spending bill.

Part of the NDAA authorizes the Space Force as a military service under the Department of the Air Force. It is the first military service introduced since the US Air Force spun off from the US Army in 1947.

Trump first floated a Space Force initiative in March 2018 speech. (A similar bipartisan proposal for a Space Corps was introduced in the House in 2017 was cut from a previous NDAA.)

Musk (whose SpaceX has contracts with NASA and has worked with the US Air Force) has shown support for Space Force. In 2018, he told Recode's Kara Swisher that "Space Force is a sensible thing to do."

"Well, this may be a little controversial, but I actually like the idea," he said in the interview. "I think it's cool. You know, like, when the Air Force was formed, there was a lot of like pooh-poohing, and like, 'Oh, how silly to have an Air Force!' You know, because the aircraft in World War II were managed by the Army."

The overall mission as defined by Space Force includes "developing military space professionals, acquiring military space systems, maturing the military doctrine for space power, and organising space forces to present to our Combatant Commands."

But it will not be a large force. "Air Force Space Command was immediately redesignated the Space Force, and 16,000 active duty and civilian personnel from AFSPC will now be assigned to the Space Force," Defence News explains.

The personnel will still technically be part of the Air Force, unless they request to transfer permanently into Space Force. (That number is expected to be somewhere between 5,000 and 6,000, according to CNN.)

"The Space Force won't be measured by the number of people unlike for instance the Marine Corps, which is really a labour-intensive service," Air Force Secretary Barbara Barrett said, CNN reported. "Space Force is much more measured by the technology and the capabilities."

This article was originally published by Business Insider.

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