Update (Sunday, 7:35 p.m. ET): Launch is officially scrubbed for tonight. SpaceX does not yet have another launch date scheduled. Its engineering team will examine the rocket before another launch attempt, the company said.
Update (Sunday, 7:23 p.m. ET): SpaceX aborted the launch just as the engines fired. "The Falcon 9 is safe," a SpaceX spokesperson said. They have not determined the cause, but likely related to some aspect of the startup sequence. The launch is not yet officially scrubbed for the evening.
Update (Sunday, 6:55 p.m. ET): The launch is on hold for a few minutes as SpaceX tries to figure out an undetermined issue going at the launch site, unrelated to the Falcon 9.
Update (Sunday, 12:21 a.m. ET): SpaceX has set a new launch window starting at 6:46 p.m. ET Sunday.
Update (Thursday, 6:49 p.m. ET): SpaceX scrubbed the launch with 1:41 remaining on the countdown. The company has not yet set a new launch date.
Today at 6:47 p.m. EST, SpaceX will make its fifth attempt to launch, and then land, its Falcon 9 rocket on an at-sea platform.
The launch will take place at Cape Canaveral Air Force Station, Florida. One of the big goals of the mission, as with several previous tries, is to land the rocket's first stage at sea on a so-called "drone ship," which SpaceX has named "Of Course I Still Love You."
Each of the company’s four previous planned attempts to land the rocket at sea have failed, some in spectacular explosions, some in oh-so-close misses, and one in which the rocket exploded before it could be brought back for landing. Last month, the first stage made it back to the drone ship, but exploded after one of its legs broke on impact.
In December, for the first time, SpaceX successfully landed the Falcon 9 first stage after launch, returning it to terra firma. But the company wants to be able to complete a landing both on land and at sea, which would give it maximum flexibility in the future.
About 10 minutes after liftoff from Cape Canaveral, the first stage will attempt to land itself upright on the deck of a 100-foot-by-300-foot, unmanned floating platform off the coast of Florida. The rocket is meant to guide itself to the barge using GPS.
However, in a mission description (PDF) published ahead of time, SpaceX said that because of the launch’s specific profile, " a successful landing is not expected."
Still, for Elon Musk’s company, successfully reusing a rocket—and demonstrating that last month’s performance wasn’t a fluke—is a key element of a future of affordable launches.
"SpaceX believes a fully and rapidly reusable rocket is the pivotal breakthrough needed to substantially reduce the cost of space access," the company says on its website. "The majority of the launch cost comes from building the rocket, which flies only once. Compare that to a commercial airliner—each new plane costs about the same as Falcon 9, but can fly multiple times per day, and conduct tens of thousands of flights over its lifetime. Following the commercial model, a rapidly reusable space launch vehicle could reduce the cost of traveling to space by a hundredfold."
Today's mission, of course, also has a scientific purpose beyond returning the rocket home. The launch is meant to deliver the SES-9 commercial communications satellite for SES, a global satellite company, to a geostationary transfer orbit (GTO). SES clients, who receive satellite-based communications from the company, include Internet service providers, broadcasters, business and governmental organizations, and mobile and fixed network operators. The company has a fleet of more than 50 geostationary satellites.
"SES-9 is the largest satellite dedicated to serving the Asia-Pacific region for SES," SpaceX wrote in the mission description. "With its payload of 81 high-powered Ku-band transponder equivalents, SES-9 will be the 7th SES satellite providing unparalleled coverage to over 20 countries in the region."
The new satellite will be co-located with SES-7.
Watch a live stream of the satellite launch above. We will update this article with news of the ocean landing attempt.