Elon Musk’s SpaceX has launched the US Air Force’s most powerful GPS satellite ever built.

A SpaceX rocket carrying a US military navigation satellite has blasted off from Florida’s Cape Canaveral, marking the space transportation company’s first national security space mission for the US.

The Falcon 9 rocket carrying a roughly $A711 million GPS satellite built by Lockheed Martin lifted off from Cape Canaveral at 8.51am local time on Sunday.

Four previous scheduled launches in the past week, including one on Saturday, were cancelled because of weather and technical issues.

The successful launch is a significant victory for billionaire Elon Musk’s privately held rocket company, which has spent years trying to break into the lucrative market for military space launches dominated by Lockheed and Boeing.

Heather Wilson, secretary of the Air Force, says this next-generation GPS satellite is three times more accurate than previous versions and eight times better at anti-jamming.

It’s the first in a series and nicknamed Vespucci after the 15th-century Italian explorer who calculated Earth’s circumference to within 80 kilometres.

SpaceX sued the US Air Force in 2014 over the military’s award of a multibillion-dollar, non-compete contract for 36 rocket launches to United Launch Alliance, a partnership of Boeing and Lockheed. It dropped the lawsuit in 2015 after the Air Force agreed to open up competition.

The next year, SpaceX won an $US83 million Air Force contract to launch the GPS III satellite, which will have a lifespan of 15 years.

The satellite is the first to launch out of 32 in production by Lockheed under contracts worth a combined $US12.6 billion for the Air Force GPS III program, according to Lockheed spokesman Chip Eschenfelder.

The launch was originally scheduled for 2014 but has been hobbled by production delays, the Air Force said.

The next GPS III satellite is due to launch in mid-2019, Eschenfelder said, while subsequent satellites undergo testing in the company’s Colorado processing facility.

ELON MUSK’S TUNNEL OF THE FUTURE
Elon Musk unveiled his underground transportation tunnel on Tuesday, allowing reporters and invited guests to take some of the first rides in the revolutionary albeit bumpy subterranean tube — the tech entrepreneur’s answer to what he calls “soul-destroying traffic.”

Guests boarded Musk’s Tesla Model S and rode along Los Angeles-area surface streets about a mile away to what’s known as O’Leary Station.

The station, smack dab in the middle of a residential neighbourhood — “basically in someone’s backyard,” Musk says — consists of a wall-less elevator that slowly took the car down a wide shaft, roughly nine metres below the surface.

The sky slowly fell away and the surprisingly narrow tunnel emerged.

“We’re clear,” said the driver, who sped up and zipped into the tunnel when a red track light turned green, making the tube look like something from space or a dance club.

The car jostled significantly during the ride, which was bumpy enough to give one reporter motion sickness while another yelled, “Woo!” Musk described his first ride as “epic.”

“For me it was a eureka moment,” he told a room full of reporters.

“I was like, ‘This thing is going to damn well work.”’

He said the rides are bumpy now because “we kind of ran out of time” and there were some problems with the speed of his paving machine.

“It’ll be smooth as glass,” he said of future systems.

“This is just a prototype. That’s why it’s a little rough around the edges.”

Later in the day, Musk emerged from the tunnel himself inside one of his cars.

He high-fived guests and pumped his fists in the air before delivering a speech in the green glow of the tunnel about the technology and why it makes sense.

“Traffic is soul-destroying. It’s like acid on the soul,” he said to guests who snacked on marshmallow treats and hot dogs and hoped for a turn in the tunnel.

On Tuesday, he explained for the first time in detail how the system, which he simply calls “loop,” could work on a larger scale beneath cities across the globe.

Autonomous, electric vehicles could be lowered into the system on wall- less elevators, which could be placed almost anywhere cars can go.

The cars would have to be fitted with specially designed side wheels that pop out perpendicular to the car’s regular tires and run along the tunnel’s track.

The cost for such wheels would be about $200 or $300 a car, Musk said.

A number of autonomous cars would remain inside the tunnel system just for pedestrians and bicyclists.

Once on the main arteries of the system, every car could run at top speed except when entering and exiting.

“It’s much more like an underground highway than it is a subway,” Musk said.

The cars would have to be autonomous to work in the system but not Teslas specifically, and they would have to be electric because of the fumes from gas, Musk said.