SpaceX Completes Iridium NEXT Constellation, Kicks Off Ambitious 2019

A reused SpaceX Falcon 9 rocket taking flight with the final set of 10 Iridium NEXT satellites from Vandenberg AFB, CA on Jan 11, 2019. Photo: Brian Sandoval / AmericaSpace.com

Two years to the week since it began its Iridium NEXT journey, SpaceX has successfully lofted the eighth and final batch of global mobile communications satellites into low polar orbit. Liftoff of the Upgraded Falcon 9—which previously saw service to carry the powerful Telstar 18V communications satellite on its uphill climb to Geostationary Transfer Orbit (GTO) last September—occurred during an “instantaneous” window at 7:31 a.m. PST Friday, 11 January, from Space Launch Complex (SLC)-4E at Vandenberg Air Force Base, Calif. This mission represented the 18th occasion since March 2017 that Falcon 9 hardware has been reused and wrapped up the delivery of 75 Iridium NEXT birds under the terms of the largest single commercial launch-services contract ever signed.

The nine Merlin 1D+ engines power the final batch of Iridium NEXT satellites to orbit. Photo: Brian Sandoval / AmericaSpace.com

The completion of the constellation after two years of launches and two decades of work was likened by Iridium CEO Matt Desch to a transformation “from caterpillar to butterfly”.

In many ways, Iridium NEXT’s journey has paralleled SpaceX’s own. When the mammoth $492 million contract was signed in June 2010, the smoke had only barely settled a few days earlier from the Falcon 9 booster’s maiden flight. And by the time the first batch of ten Iridium NEXT satellites rode to orbit on 14 January 2017, the capabilities of SpaceX’s Falcon 9 fleet had been significantly upgraded to boast a string of first-stage oceanic touchdowns on the Autonomous Spaceport Drone Ship (ASDS) and on land at Landing Zone (LZ)-1 at the Cape. The first four batches of ten Iridiums apiece flew in 2017—in January, June, October and December—of which one saw the first use of titanium grid-fins for improved first-stage descent controllability and another saw a reused Upgraded Falcon 9 first stage. Last year, in March, May and July, a further three batches rose to orbit, with 25 Iridium NEXT birds delivered in all. Two of these missions launched atop reused boosters, whilst one accomplished a safe first-stage ASDS landing in the worst offshore weather conditions ever experienced by SpaceX.

The contracts between McLean, Va.-based Iridium Corp. and SpaceX were inked back in June 2010 and, at the time, represented the largest single deal of their kind. It was expected that Iridium NEXT would completely replace Iridium’s aging constellation of first-generation satellites, whose earliest members were launched two decades ago. Iridium NEXT is overseen by prime contractor Thales Alenia Space, with subcontractor Orbital ATK—now part of Northrop Grumman Innovation Systems (NGIS)—selected to fabricate the operational satellites, together with a cadre of on-orbit and ground-based spares. Each satellite is based upon the Extended LifeTime Bus (EliTeBus)-1000, which weighs around 1,760 pounds (800 kg) and is powered by twin solar arrays.

Each Iridium NEXT operates at a mean altitude of 485 miles (780 km), inclined 86.4 degrees to the equator and capable of a decade-long lifetime. When fully unfurled, Iridium NEXT’s solar arrays span 31 feet (9.4 meters) and generate two kilowatts of electricity, a 50-percent uplift on the power-producing potential of earlier Iridiums. The EliTeBus-1000 previously saw service for the low-orbiting GlobalStar mobile voice/data communications satellites, 24 of which were launched atop Soyuz-Fregat boosters from Baikonur between 2010-2013. Under the June 2010 contract, SpaceX was tasked with delivering 70 Iridium NEXT satellites into orbit over seven missions, but in January 2017 it was announced that it would benefit from a “rideshare” arrangement, flying an additional five “spares” on an eighth Upgraded Falcon 9. That rideshare took place in May 2018, flying alongside NASA’s Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) payload.

Today’s launch begins an ambitious 2019 manifest for SpaceX, which is also expected to see the first unpiloted and piloted missions by the Crew Dragon. Photo: Brian Sandoval / AmericaSpace.com

Last week, the 230-foot-tall (70-meter) Upgraded Falcon 9 rolled out of its horizontal integration facility to SLC-4E and on 6 January completed a customary static fire test of the nine Merlin 1D+ first-stage engines. It was then returned to the hangar for the 8 January installation of its bullet-like payload fairing, which encapsulated the ten Iridium NEXT satellites and their dispenser mechanism. The decision to install the payload after the static fire dates back to SpaceX’s on-the-pad loss of the Amos-6 mission in September 2016. Late on 8 January, SpaceX declared that it had received Western Range approval to launch at 7:31 a.m. PST Friday, 11 January, with a 60-percent likelihood of acceptable weather conditions at T-0. “Weather in the morning doesn’t look too bad right now,” tweeted Iridium CEO Matt Desch, “and the rocket should be ready.”

Loading of the booster with liquid oxygen and a highly refined form of rocket-grade kerosene, known as “RP-1”, commenced about 35 minutes before Friday’s opening launch attempt. Passing T-10 minutes in the countdown, the terminal autosequencer was initiated and the first-stage engines were chilled down, ahead of the ignition sequence. At T-2 minutes, the Air Force Range Safety Officer verified that all ground-side assets were “Go for Launch” and the vehicle transitioned to Internal Power and assumed primary command of all critical functions, entering “Startup” at T-1 minute. At this point, the Niagara deluge system began flooding the surface of SLC-4E with 30,000 gallons (113,500 liters) of water, per minute, to suppress the acoustic energy at liftoff.

Iridium NEXT-8 mission artwork. Image: Iridium Corp.

At T-3 seconds, the nine Merlins thundered to life. Liftoff occurred precisely on time and the vehicle followed a perfect ascent trajectory, its first stage providing the muscle for the first 2.5 minutes, before separating. Meanwhile, the second stage picked up the baton with a six-minute “burn” to deliver its ten-strong payload of satellites to orbit. Shutdown of the second stage’s Merlin 1D+ Vacuum engine occurred at 8.5 minutes, after which the stack coasted for three-quarters of an hour, ahead of a final burn to establish positioning for deployment. Over a 15-minute period, departing at a rate of one every 90 seconds, the last ten Iridium NEXT satellites were successfully deployed from their dispenser.

Meanwhile, the Upgraded Falcon 9’s first stage began a six-minute descent back to Earth, guided by its hypersonic grid-fins and engine burns, to alight smoothly onto the deck of the ASDS “Just Read the Instructions”, a little over seven minutes after leaving Vandenberg. It was the sixth uccessful ASDS touchdown on the West Coast-based JRTI since January 2017 and the 21st overall drone ship landing—also counting the East Coast-based “Of Course I Still Love You”—since April 2016.

The triumphant completion of SpaceX’s Iridium NEXT contract sets the organization on track for an ambitious 2019. Attempts by AmericaSpace to gain clarification from SpaceX about the number of launches planned for this year have been unsuccessful, but a flight rate closely approximating 2018’s 21-mission accomplishment is not unreasonable. Three Dragon cargo missions to the International Space Station (ISS)—CRS-17 in March, CRS-18 in May and CRS-19 in October—will deliver equipment and supplies, including a second International Docking Adapter (IDA) for Commercial Crew use. As many as two flights of the Falcon Heavy may occur, delivering a technology demonstration payload for the Air Force’s Space Test Program (STP) and Saudi Arabia’s heavyweight Arabsat-6A communications satellite. Other customers include Indonesia’s PSN-6 communications satellite, Israel’s Beresheet lunar lander, Canada’s Radarsat and a second Global Positioning System (GPS) Block IIIA satellite. Also provisionally targeted to fly during 2019 are Israel’s Amos-17 communications satellite, the Audi-built ALINA lunar lander, Argentina’s SAOCOM-1B radar-imaging platform.

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