SpaceX postpones SES-9 launch

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Updated 7:30 p.m. Eastern.

WASHINGTON — SpaceX postponed the launch of an SES communications satellite on an upgraded Falcon 9 by 24 hours Feb. 24.

SpaceX postponed the launch a little more than a half-hour before the launch window opened at 6:46 p.m. Eastern, shortly before propellant loading was scheduled to begin. “Out of an abundance of caution, the team opted to hold launch for today to ensure liquid oxygen temperatures are as cold as possible in an effort to maximize performance of the vehicle,” the company said in a statement.

The upgraded version of the Falcon 9, which is making its second launch on this mission, uses liquid oxygen cooled to near its freezing point to increase its density. The use of “densified” propellants is one of several changes to the vehicle to improve its performance and increase its payload capacity.

SpaceX has tentatively rescheduled the launch for 6:46 p.m. Eastern Feb. 25. Weather conditions, which were improving as the launch time approached, are expected to be better in 24 hours, with forecasts calling for an 80 percent chance of acceptable weather at the new launch time. The company added that the launch vehicle and spacecraft itself remain healthy.

The launch attracted considerable attention because it marks the latest attempt by SpaceX to recover the Falcon 9’s first stage by landing it on a ship several hundred kilometers downrange from the launch site. However, the company had deemphasized that in the days leading up to launch, saying that a successful landing was not likely because of the “mission’s unique GTO [geostationary transfer orbit] profile.”

The launch is noteworthy regardless of any landing attempt as the SES-9 satellite, weighing about 5,300 kilograms, is the heaviest geostationary orbit satellite to be launched by SpaceX and requires this new, upgraded version of the Falcon 9. The upgraded version of the Falcon 9 has flown once before, launching 11 ORBCOMM satellites in December.

The Boeing-built SES-9 will operate at 108.2 degrees east in GEO. The spacecraft’s 81 Ku-band transponders will provide communications services for parts of Asia, Australia and the Middle East.