A United Launch Alliance Atlas 5 rocket boosted a high-power military communications satellite into space Thursday, the sixth and final relay station in a jam-resistant, blast-hardened constellation valued at more than $11 billion.

The flight was the first national security space launch under authority of the newly established U.S. Space Force, carried out amid extensive precautions at the Cape Canaveral launch site to slow the spread of the deadly coronavirus.

The Air Force and ULA reduced the number of on-site personnel by 20-25% respectively while implementing social distancing and other safety protocols for those who remained.

A United Launch Alliance Atlas 5 rocket climbs away from the Cape Canaveral Air Force Station Thursday afternoon, carrying a $1.2 billion military communications satellites. William Harwood/CBS News

"Obviously (personnel) can't necessarily telework on a launch, but ... we're limiting the crew to just the necessary folks that need to be there," said Brigadier General Douglas Schiess, commander of the 45th Space Wing and director of the Eastern Range at Patrick Air Force Base.

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"We are cleaning all of our [operation] centers ... and telling our folks that are on crew that this is not the time to be out and about. If you're working a mission, make sure that you're keeping yourself at home and being prepared for mission operations. We're doing everything we can."

In the meantime, he said, launch operations will proceed, but "obviously, if the situation changes, then we would adjust. But we're going to continue operations at this time."

Running an hour and 21 minutes late because of trouble with ground equipment, the Atlas 5's Russian-built RD-180 first stage engine fired up at 4:18 p.m. EDT, followed a moment later by ignition of five solid-propellant strap-on boosters.

Generating 2.6 million pounds of thrust, the 20-story-tall rocket quickly climbed away from pad 41 at the Cape Canaveral Air Force Station, arced over to the east and disappeared from view high above the Atlantic Ocean.

The strap-on boosters burned out and fell away as planned, followed by first stage engine shutdown and separation about four-and-a-half minutes after liftoff. The hydrogen-powered Centaur second stage engine then took over with the first of three planned burns.

Between the second and third Centaur firings, a small satellite known as TDO-2, built by the Georgia Institute of Technology for the Air Force Research Laboratory, was released from the bottom of the upper stage to serve as a target for space sensor development.

But the primary goal of the flight was to put the Advanced Extremely High Frequency communications satellite into an optimized "high-energy" elliptical orbit designed to minimize the fuel and time needed to reach its operational station.

Built by Lockheed Martin, the AEHF-6 satellite was bound for a circular orbit 22,300 miles above the equator. At that altitude, satellites take 24 hours to complete one orbit and thus appear stationary in the sky, allowing the use of fixed antennas on the ground.

The three Centaur firings were designed to put AEHF-6 into an elliptical "transfer" orbit with a high point of about 21,900 miles and a predicted low point of 6,760 miles. On board thrusters will be used to circularize the orbit at and to maneuver the satellite into its final operational location.

The six AEHF satellites are designed to provide a globe-spanning network of encrypted, jam-proof communications for strategic command and control and for tactical missions around the world. The satellites are shared by the U.S., Canada, the U.K. and the Netherlands.

"This is the nation's only strategic and tactical protected comm satellite network," Mike Cacheiro, Lockheed Martin AEHF program manager, said before an earlier launch. "It's also the only system that survives through a near nuclear burst and can provide communications through environments that other comm systems could not.

"So on a really bad day, you really want to have this system in place," he said.

The AEHF satellites can handle 10 times more data than the older Milstar relay stations they are replacing, feature advanced encryption technology and are designed to give "senior leadership a survivable line of communications to military forces in all levels of conflict, including nuclear war," ULA said in a brochure describing the spacecraft.

The first two satellites in the system, launched in 2010 and 2012, cost about $5.8 billion, including ground systems and terminals. The third satellite in the series, launched in 2013, cost some $900 million while the fourth satellite, featuring a variety of modifications, had a price tag of $1.8 billion, officials said before launch in 2018.

The final two satellites, AEHF-5 and 6, cost a combined $2.15 billion.