Just three days after launching a heavyweight communications satellite from Cape Canaveral, SpaceX fired off another Falcon 9 rocket from California early Wednesday carrying 10 Iridium NEXT satellites, the latest additions to a nearly complete $3 billion network of satellite telephone relay stations.
The rocket's first stage, meanwhile, the third enhanced "block 5" version of the booster, flew itself to a landing on a SpaceX droneship "Just Read The Instructions," a company spokesman said, chalking up the California rocket builder's 15th successful recovery and 27th overall.
There was no immediate word on whether the company was successful recovering the rocket's nose cone fairing. Both recovery attempts were carried out in the roughest weather ever for a Falcon 9 landing try.
But rocket recoveries, while dramatic, are a strictly secondary objective. The primary goal of the mission was to launch another 10 Iridium NEXT satellites, boosting the company's constellation of next-generation relay stations to 65 with another 10-satellite SpaceX launch expected later this year.
Sixty-six of the 1,896-pound satellites operating in six orbital planes will provide global coverage, allowing customers to make calls from anywhere in the world. Another 15 satellites will be stored in orbit as spares with six more held on the ground in reserve for launch as needed.
The new satellites are replacing older, less-capable spacecraft that are being driven into the atmosphere to ensure they do not pose a threat to other satellites in low-Earth orbit.
While the new constellation is not yet complete, "our customers will be serviced by our NEXT satellites, on average, well over 80 percent of the time since we are biasing our NEXT satellite beams to carry more of the traffic, particularly in the Northern Hemisphere," Iridium CEO Matt Desch said before the sixth launch in May.
"The NEXT satellites are faster, voice calls sound better, and we want our customers to get service through them as soon as possible."
The NEXT-series satellites also carry equipment to track ships at sea on a minute-by-minute basis and another system, provided by a multi-agency consortium known as Aireon, that eventually will track aircraft anywhere in the world.
Iridium also offers an "internet of things" service to transmit data between connected devices anywhere in the world.
"Iridium Next is more than just a new constellation for our company," Desch said. "It's completion represents a level of financial maturity that we've been seeking, but never before obtained. ... it's been a long journey."
The latest mission got underway at 4:39 a.m. PDT (GMT-7) when the Falcon 9s nine first stage engines ignited with a thundering roar, throttled up to full thrust and climbed away from fog-shrouded pad 4E at Vandenberg Air Force Base, Calif., northwest of Los Angeles.
The slender 229-foot tall rocket quickly accelerated as it consumed its load of first stage propellants, arcing away to the south over the Pacific Ocean atop a sky-lighting jet of flame.
Two minutes and 24 seconds later, the engines shut down, the first stage fell away and the flight continued on the power of a single Merlin engine powering the rocket's second stage.
The first stage, meanwhile, re-started three of its engines to reverse course and then fired them a second time to slow down just before plunging back into the thick lower atmosphere.
Falling tail first and using titanium "grid fins" to control its orientation, the booster homed in on the droneship "Just Read The Instructions," restarted a single engine and deployed four landing legs.
Long-range video was difficult to make out, but SpaceX tweeted later that the rocket landed on the droneship as planned.
A little more than a minute after touchdown, the second stage engine shut down, putting the payload into the planned preliminary orbit. A short nine-second firing was planned about 43 minutes later to put the Iridium NEXT satellites into the desired orbit around Earth's poles.
The 10 Iridium NEXT satellites were expected to be released two at a time over 15 minutes to complete the mission.