Live coverage: Falcon 9 launch scrubbed

Live coverage of the countdown and launch of a SpaceX Falcon 9 rocket from Cape Canaveral with the Thaicom 8 communications satellite. Text updates will appear automatically below; there is no need to reload the page. Follow us on Twitter

19:56

SpaceX chief executive Elon Musk says the issue being analyzed during this evening's countdown was with the Falcon 9's second stage Merlin engine

"There was a tiny glitch in the motion of an upper stage engine actuator. Probably not a flight risk, but still worth investigating," Musk tweeted

19:41 SCRUB

SpaceX has called off tonight's launch attempt and reset liftoff for no earlier than Friday at approximately 5:40 p.m. EDT (2140 GMT).

19:36 T-minus 60 minutes

One hour away from launch. SpaceX has not provided any more update on the nature of the issue that caused the delay from the opening of tonight's window, or if the data review is complete and satisfactory.

Chilldown of the pad's liquid oxygen system has started.

19:02

The SpaceX launch team just adjusted the target launch time four minutes earlier to 7:36 p.m. EDT (2336 GMT).

18:59 New launch time

SpaceX has reset tonight's Falcon 9 launch for 7:40 p.m. EDT (2340 GMT), at the end of tonight's window, assuming the issues that caused the earlier delay are resolved.

18:51

SpaceX has not yet set a new launch time this evening. The countdown remains in a hold at this moment.

18:23

SpaceX says the countdown clock is holding because the "launch team (is) finalizing review of vehicle data and check outs."

18:19

DELAY. The Falcon 9 rocket will not lift off as scheduled at 5:40 p.m. EDT (2140 GMT). The countdown is holding, but officials have not disclosed the reason for the pause.

This evening's launch window extends to 7:40 p.m. EDT (2340 GMT).

18:17

Fueling of the Falcon 9 rocket should have started more than 10 minutes ago, but SpaceX has not confirmed the milestone.

18:17

Fueling of the Falcon 9 rocket should have started more than 10 minutes ago, but SpaceX has not confirmed the milestone yet.

17:59 Falcon 9 targets "supersynchronous" orbit

SpaceX's Falcon 9 rocket will aim for an elongated "supersynchronous transfer orbit" on today's mission.

The Thaicom 8 satellite has a relatively light launch mass of 6,669 pounds (3,025 kilograms), according to its Bangkok-based owner.

The heavy-lifting capacity of the Falcon 9 allows the rocket to place it in an orbit with an apogee, or high point, of approximately 90,000 kilometers (nearly 56,000 miles) and a perigee, or low point, of 250 kilometers (124 miles), Thaicom tells Spaceflight Now.

17:52

T-minus 48 minutes. 

Coming up on several major milestones in the countdown, beginning with a poll of the launch team at T-minus 38 minutes and the start of propellant loading at T-minus 35 minutes.

17:38

SpaceX will attempt to land the 156-foot-tall first stage of the Falcon 9 rocket downrange aboard a recovery vessel, extending the company's experiments with rocket re-entry and reusability.

The drone ship, christened "Of Course I Still Love You," is positioned about 420 miles (680 kilometers) east of Cape Canaveral in the Atlantic Ocean.

SpaceX says a successful landing is challenging on this mission because of the higher speed the rocket needs to reach with the Thaicom 8 communications satellite, which is heading toward an orbit with a high point thousands of miles above Earth.

"Following stage separation, the first stage of Falcon 9 will attempt an experimental landing on the 'Of Course I Still Love You' droneship," SpaceX said in a statement. "As with other missions going to geostationary orbits, the first-stage will be subject to extreme velocities and re-entry heating, making a successful landing challenging."

SpaceX successfully landed a rocket on the drone ship for the first time April 8 after a launch from Cape Canaveral with a Dragon supply ship. That mission went into low Earth orbit on the way to the International Space Station.

The Falcon 9's last launch May 6 ended with another successful landing at sea, with the booster surviving a scorching atmospheric re-entry after launching the JCSAT 14 communications satellite. That was the first Falcon 9 intact recovery on a geostationary mission.

The above photo of the drone ship was taken before a previous launch

17:17

The U.S. Air Force Eastern Range has finished hold-fire checks with the Falcon 9 rocket

The Falcon 9 countdown is significantly changed with the upgraded version of the rocket

While radio checks and flight termination system tests complete, fueling of the rocket with its propellant mixture of RP-1 rocket-grade kerosene and liquid oxygen will not begin until about a half-hour before the launch, instead of at about T-minus 3 hours on earlier Falcon 9s.

The upgraded Falcon 9 consumes a chilled propellant mix that allows engineers to load additional fuel into the rocket. The cryogenic liquid oxygen is chilled closer to its freezing point, from minus 298 degrees Fahrenheit to minus 340 degrees, while the RP-1 fuel is cooled from a more standard room temperature of about 70 degrees Fahrenheit to 20 degrees, according to SpaceX founder Elon Musk.

The change essentially permits the volume of the Falcon 9 fuel tanks, which are also slightly enlarged on this launch, to hold more mass of propellant, giving the rocket more performance.

The Merlin engines on the first and second stages will also produce more thrust. At liftoff, the nine-engine first stage will generate 1.5 million pounds of thrust, up from 1.3 million force-pounds on the Falcon 9's previous version.

The second stage engine is also modified with a bigger nozzle, and the stage separation system includes a new pusher device to help guide the first stage as it is jettisoned, ensuring no recontact.

Taken together, the modifications allow the Falcon 9 to carry heavier satellites into orbit and still attempt booster landings on the coast or on an ocean-going barge. This afternoon's launch will target a landing on a barge 420 miles (680 kilometers) offshore in the Atlantic Ocean.

17:05

The SpaceX launch team reports they have completed checks of the Falcon 9 rocket's flight termination system, which would be used to destroy the rocket if it flew off course.

16:41

A check of all SpaceX launch team stations at T-minus 2 hours indicates all is ready to proceed with tonight's flight.

Checks of the rocket's propulsion system are in work, and there are no open issues being tracked at this point in the countdown. The launch pad has also been cleared for this afternoon's liftoff.

16:05

SpaceX's launch crew is evacuating the pad at Cape Canaveral as the countdown ticks toward liftoff at 5:40 p.m. EDT (2140 GMT).

The launch window extends for two hours.

The launch team is on console at the launch control center this evening to run the Falcon 9 through prelaunch tests at the Complex 40 launch pad, then begin fueling the two-stage booster with super-chilled kerosene and liquid oxygen propellants about 35 minutes before liftoff.

Forecasters predict favorable weather during this evening's launch window, with a 90 percent chance conditions will be acceptable for liftoff.

Mostly sunny are in the forecast. Winds will be from the east-northeast at 17 to 22 mph, and the temperature at launch time is forecast to be 78 degrees Fahrenheit.

16:00 Processing photos

Thai communications satellite is fastened to the top of SpaceX’s 229-foot-tall Falcon 9 rocket for launch at 5:40 p.m. EDT (2140 GMT) Thursday.

See photos of the Falcon 9 rocket and Thaicom 8 satellite prepared for launch.

04:25 Launch timeline

The Falcon 9 rocket’s fifth flight of the year will take off from Cape Canaveral on Thursday, heaving the Thaicom 8 communications satellite into orbit on an easterly trajectory from Florida’s Space Coast.

It will take about 32 minutes to inject the approximately 6,800-pound (3,100-kilogram) spacecraft into a highly elliptical geostationary transfer orbit on the way to the satellite’s final perch 22,300 miles (35,700 kilometers) at 78.5 degrees east longitude over the equator.

See more details in this launch timeline.

03:48

SpaceX is counting down to the 25th launch of a Falcon 9 rocket Thursday at 5:40 p.m. EDT (2140 GMT). The commercial booster will haul up the Thaicom 8 television broadcasting satellite from Cape Canaveral and attempt another landing on SpaceX's recovery platform in the Atlantic Ocean.

The 229-foot-tall (70-meter) rocket will be making its fifth flight of the year, and second launch for Thaicom, a Bangkok-based satellite operator providing television broadcast and data services over the Asia-Pacific.

Thursday evening's liftoff is also the second Falcon 9 flight this month for SpaceX.

The weather outlook issued Wednesday by the U.S. Air Force's 45th Weather Squadron indicates a 90 percent chance of acceptable conditions during the two-hour launch window.

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