Under a clear sunset sky, a SpaceX Falcon 9 rocket streaked into space Monday, boosting a heavy Inmarsat communications satellite into orbit in the California rocket builder's second flight in just two weeks, its sixth so far this year.
Thirty-two minutes after liftoff, the Inmarsat-5 F4 satellite -- the fourth in a global constellation of high-speed Ka-band relay stations serving aircraft, ships at sea and other government and commercial users around the world -- was released into the planned highly elliptical orbit.
Over the next 90 days or so, the bus-size satellite's on-board thrusters will be used to circularize the orbit 22,300 miles above the equator where the relay station will turn in lockstep with Earth and appear stationary in the sky. It is joining three virtually identical Boeing-built satellites in Inmarsat's $1.6 billion Global Xpress constellation.
"It's the first global seamless broadband service specifically designed for mobile applications," Michele Franci, chief technology officer at Inmarsat, told Spaceflight Now. "That is the background of Inmarsat, mobile applications, so this constellation, and the entire network around it, has been designed to be optimized for mobile users."
The mission got underway at 7:21 p.m. EDT (GMT-4) when the Falcon 9's first-stage engines ignited with a rush of fiery exhaust. An instant later, the rocket was released from its firing stand and it smoothly climbed into the early evening sky atop a brilliant jet of flame from its nine Merlin 1D engines.
Arcing away to the east, the rocket climbed out of the thick lower atmosphere and two minutes and 45 seconds after launch, the first stage engines shut down, the stage fell away and the rocket's second stage, powered by a single Merlin engine, continued the climb to space.
The Inmarsat-5 F4 satellite tipped the scales at 13,417 pounds, the heaviest satellite yet launched by SpaceX to a geosynchronous transfer orbit. As a result, the Falcon 9 used virtually all of its first-stage propellants lifting the payload out of the lower atmosphere and it was not possible to fly the booster back to a landing.
Of the six flights launched by SpaceX so far this year, four stages were successfully recovered, two on off-shore drone ships and two back at the Cape Canaveral Air Force Station. Monday's flight was the second this year in which a landing was ruled out by the weight and orbital requirements of the satellite payload.
In any case, the Falcon 9's second stage fired twice to reach a so-called "super synchronous" elliptical orbit and the Inmarsat-5 satellite was safely released to fly on its own.
The Inmarsat-5 satellite originally was built as a spare and is now intended to expand existing service. It originally was scheduled for launch aboard a heavy-lift version of the Falcon, a rocket made up of three Falcon 9 first stage cores and a single upper stage.
The maiden flight of the Falcon Heavy has been repeatedly delayed -- it currently is planned for sometime this summer -- but engine upgrades made it possible to launch the 6.7-ton Inmarsat-5 satellite to a single-core Falcon 9, clearing the way for Monday's flight.
The Inmarsat-5 series satellites are the backbone of the company's Global Xpress system, providing airline passenger connectivity, "so it's wi-fi services for passengers for web browsing, email, video downloads and uploads," said Franci.
"Our biggest market today is in merchant shipping, and there it will provide a combination of operational services and crew welfare," he said. "In maritime, our system is actually integrated. We have L-band and Ka-band that are seamlessly joined up on the ship itself, and our system automatically evaluates the quality of the link.
"We stay in Ka-band as long as we can, and if ever the link would become poor, either because of edge of coverage reasons or very bad weather, we would jump over to L-band. We offer always-on resilience and reliability when it comes down to real needs, and the quality of broadband for most of the time."
This was SpaceX's sixth launch so far this year, its 34th Falcon 9 flight overall and the seventh since a Falcon 9 exploded on its Cape Canaveral Air Force Base launch pad Sept. 1. SpaceX has recovered 10 first stage boosters in 15 attempts over the past two years.
Today's flight was SpaceX's second in just 14 days, demonstrating the rapid-fire pace company officials are counting on to work through a backlog of satellites. If all goes well, SpaceX will launch a space station-bound Dragon cargo ship June 1, a Bulgarian communications satellite on June 15 and an Intelsat relay station around the end of June.
If that blistering pace holds up, SpaceX will have launched nine Falcon 9s in just six months.
A key element in maintaining that rapid launch rate is returning pad 40 at the Cape Canaveral Air Force Station to service. The pad was heavily damaged in the Sept. 1 pre-flight mishap but it is expected to be back on line shortly.
SpaceX operates a launch pad at Vandenberg Air Force Base, California, and two pads in Florida. The company plans to use pad 40 at the Cape Canaveral Air Force Station primarily for commercial payloads and to reserve pad 39A at the Kennedy Space Center for the Falcon Heavy, Dragon space station resupply flights and launches of crew ferry ships being designed to carry astronauts to and from the space station.
Three Dragon cargo flights are planned this year, along with the Heavy's maiden launch. The first unpiloted test flight of SpaceX's Dragon crew ship is expected next March.