Update at 7:55 PM ET: After launching right on time, the Inmarsat spacecraft reached low Earth orbit, and after two consecutive burns from the Falcon 9 second stage, the satellite was successfully deployed into geosynchronous orbit. This means that SpaceX has now completed six successful missions in 2017, all in the past four months.
Original message: Tonight SpaceX will attempt to launch its sixth Falcon 9 rocket of 2017. If successful, this launch would put SpaceX on track to launch more than a dozen missions this year and possibly as many as eighteen. The 49-minute launch window begins Monday at 7:21pm ET (Tuesday 12:21am UK) and the rocket will carry an Inmarsat-5 F4 communications satellite to geostationary orbit. The weather is near ideal for a launch tonight from the Kennedy Space Center, with a 90 percent chance of favorable conditions.
Because the satellite is so heavy — over six tons — and heading to a higher orbit, the Falcon 9 rocket won’t have enough fuel to make a reentry attempt, even at sea. The company has not disclosed whether it will make another experimental attempt to restore the rocket’s fairing.
A successful mission tonight by SpaceX would allow the company to demonstrate that it is making good progress toward its long-promised goal of flying the Falcon 9 regularly and clearing a backlog of about 70 missions. Since SpaceX returned to flight on January 17 this year, five Falcon 9 rockets have been launched. A seventh launch could come after tonight, just two weeks later in early June, a cargo resupply mission to the International Space Station.
Even with a static fire accident that destroyed a rocket and its payload on Sept. 1, 2016 was the company’s most successful year in terms of overall launches with its workhorse Falcon 9 booster. Prior to the accident, SpaceX had made eight flights of the Falcon 9 rocket, a cadence of one launch per month.
The SpaceX webcast for tonight’s launch should start about 20 minutes before the window opens. The first and second stages will separate at 2 minutes and 49 seconds into flight, and the second stage will burn until 8 minutes and 38 seconds after launch. The satellite is deployed after 31 minutes and 48 seconds.