SpaceX Iridium Next
Photo shows the empty upper stage of the SpaceX Falcon 9 mission that carried 10 Iridium Next satellites to low Earth orbit on Dec. 22. Credit: SpaceX

WASHINGTON — SpaceX closed out its most successful year to date Dec. 22 with the launch of 10 satellites for mobile satellite services operator Iridium, notching a personal best of 18 launches in a single year.

The Falcon 9 mission, which took off from Vandenberg Air Force Base in California at 8:27 p.m. Eastern in an instantaneous launch window, was the fourth of eight missions for Iridium, carrying the McLean, Virginia-based operator’s second generation satellites, called Iridium Next.

In what now is considered a rarity, SpaceX opted not to recover the rocket’s first stage, instead letting the booster fall into the Pacific Ocean. SpaceX has recovered 20 out of 42 first stage Falcon 9 boosters to date, with the first success following the launch of 11 Orbcomm satellites to low Earth orbit (LEO) in December 2015. Today’s launch was SpaceX’s fifth with a previously flown Falcon 9, using a first stage that had launched the second batch of 10 Iridium Next satellites back in June.

After two years that each had a rocket failure stunting launch rates, SpaceX’s 2017 cadence far exceeded the eight missions of 2016 and the six missions of 2015. Gwynne Shotwell, SpaceX president and COO, told SpaceNews last month that the company will shoot for 30 to 40 missions next year, not including SpaceX’s own LEO satellites, and anticipates leveling out at that rate in years to come.

Iridium has the largest launch contract with SpaceX of any commercial satellite operator, launching 75 LEO satellites to replace the company’s aging 20 year old fleet that has nearly tripled its design life. Of the 75, nine will be spares and 66 will be active, providing higher throughput services for Iridium customers. The satellites also carry hosted payloads for Aireon’s flight tracking service and Harris Corp and exactEarth’s ship-tracking business.

Iridium originally planned to launch 70 satellites with SpaceX, but increased the number after Kosmotras, operator of the Russian-Ukrainian Dnepr rocket, was unable to secure Russian approval for the mission. That increase involved ordering an eighth mission, which will carry five Iridium Next satellites and two NASA-Germany science satellites that also rebooked from a Dnepr. The joint mission is sixth in Iridium’s launch order.

When Iridium first booked its Falcon 9 missions, the satellite operator contracted new rockets, but in October the company switched missions four and five to pre-flown boosters to avoid schedule slippage. Shotwell said in March that SpaceX hoped to launch as many as six pre-flown boosters this year, and would use them to ease the pressure on manufacturing new rockets fast enough to keep pace with a backlog of customers that had grown increasingly crowded because of both good business and substantial delays. Even with SpaceX’s 2017 record pace, more than half a dozen missions planned for this year — including the Falcon Heavy debut — now fall into 2018. 

The Falcon 9 used for batch two and now batch four of Iridium Next was a “Block 3” version of the rocket, which Shotwell said in June could only fly two or three times before being retired. SpaceX is fielding an improved version called the Block 4 now, and expects to fly the Block 5, capable of 10 or more missions, next year.

Caleb Henry is a former SpaceNews staff writer covering satellites, telecom and launch. He previously worked for Via Satellite and NewSpace Global.He earned a bachelor’s degree in political science along with a minor in astronomy from...