SpaceX launches 5 Iridium NEXT, 2 GRACE-FO satellites on Falcon 9 ride-share mission
LOMPOC, Calif. — Sending the quintuple-satellite Iridium-6 mission into space for Iridium Communications along with NASA’s twin Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) spacecraft as part of a ride-share agreement, SpaceX launched its ninth Falcon 9 of 2018.
Liftoff of the Falcon 9, which sported a previously-flown Block 4 first stage (the one that launched Zuma earlier in the year), took place at 12:47 p.m. PDT (3:47 p.m. EDT / 19:47 GMT) May 22, 2018, from Space Launch Complex 4E at Vandenberg Air Force Base. Weather did not pose any problems during the countdown as the 30th Space Wing at Vandenberg predicted a 90 percent chance of favorable conditions.
As such, the quiet countdown proceeded nominally with the loading of rocket grade kerosene proceeding some 70 minutes before the planned liftoff time. About 35 minutes later, this was followed by the loading of liquid oxygen into the vehicle.
Seven minutes before launch, the 229-foot (70-meter) tall Falcon 9’s nine first stage Merlin 1D engines began chilling to condition themselves for launch.
One minute before rising skyward, the flight computer began its final pre-launch checks to verify the vehicle was healthy. At this time, the Falcon 9’s propellant tanks began pressurizing to flight pressures. Fifteen seconds later, the launch director verified the vehicle was “go” for launch.
Three seconds before liftoff, the nine Merlin 1D engines at the base of the rocket ignited and began to spool up to full power before finally rising off the pad and into the early-afternoon California skies.
Over the course of the next minute, the Falcon 9 began to rise faster and faster, pitching over toward the south over the Pacific Ocean. Around a minute after launch, it reached the speed of sound and the moment of peak mechanical stress.
Two minutes 46 seconds into the flight, the first stage, having finished its job in the ascent, separated from the second stage. Seconds later, the second stage’s lone Merlin Vacuum engine ignited to continue propelling the five Iridium-6 and two GRACE-FO satellites spaceward.
Three minutes, 12 seconds after launch, with the vehicle high enough out of Earth’s atmosphere, the protective payload fairing—the rocket’s nose cone—fell away from the vehicle as it was no longer needed.
Burning for just over seven minutes, the second stage propelled the stack into an initial orbit some 305 miles (490 kilometers) in altitude.
There, while coasting around Earth toward the second stage’s next burn point, the twin GRACE-FO spacecraft separated and drifted away. This occurred at about 11.5 minutes after leaving California. The spacecraft are expected to operate in this orbit for about five years to perform its mission, fly in tandem some 137 miles (220 kilometers) apart to measure the ever-so-slight distance that areas of higher and lower mass changes their separation distance.
“GRACE-FO will provide unique insights into how our complex planet operates,” Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate at NASA Headquarters, said in a press release. “Just as important, because the mission monitors many key aspects of the Earth’s water cycle, GRACE-FO data will be used throughout the world to improve people’s lives – from better predictions of drought impacts to higher quality information on use and management of water from underground aquifers.”
Once the GRACE-FO satellites are at a safe distance, the second stage began positioning itself for its second and final burn to place the five Iridium NEXT satellites into their target orbit.
At a mission elapsed time of about 57 minutes, the second stage reignited for a brief eight seconds. About eight minutes after that, the five spacecraft began deploying. This was completed at around one hour, 12 minutes after launch.
Over the coming weeks and months, Iridium Communications will send each of these next-generations satellites to replace a legacy satellite in its Iridium satellite constellation.
“With every successful launch, we are one step closer to Iridium NEXT being fully operational, which officially starts a new age of satellite connectivity,” said Iridium Communications CEO Matt Desch in a company statement. “When it comes to safety communications, especially for those operating in the skies or out at sea, having built-in network redundancy and resiliency enabled by our satellite’s crosslinks is paramount, especially during times of distress. We recognize this and feel that as the only network covering the entire planet, we have an inherent responsibility to constantly innovate for this critical arena.”
Since January 2017, Iridium has been methodically replacing these legacy satellites—some of which launched as early as 1997—with the Iridium NEXT satellites. The $3 billion dollar upgrade is expected to be completed by the end of the third quarter of 2018, some 30 days after the conclusion of the Iridium-8 mission.
In total, the constellation will have 75 satellites in orbit. Only 66 of those are required for the operational constellation. Nine will serve as on-orbit spares. Furthermore, an additional six will remain on the ground as spares to be launched as needed bringing the total number built to 81.
The next flight for Iridium is slated to be the Iridium-7 mission atop a Block 5 Falcon 9 sometime in July.
While this particular Falcon 9 first stage was not going to be recovered, SpaceX did attempt to catch one of the two fairing halves on it’s “catchers mitt”-like recovery vessel named “Mr. Steven,” which was deployed downrange in the Pacific Ocean.
SpaceX said the payload fairing halves both deployed their parachutes successfully, but they landed in the Ocean.
“The fairing recovery ship Mr. Steven came very close, but not quite,” said John Insprucker, a SpaceX principal integration engineer, during the company’s launch webcast.
SpaceX has been trying to catch Falcon 9 fairings, which cost about $6 million per flight, since at least the beginning of 2018. While it has been able retrieve fairing halves from the ocean on several occasions, they are not likely to be reused because of the corrosiveness of the salt water, which would likely make refurbishment more expensive.
The May 22 flight was the 10th SpaceX mission in 2018, the ninth for a Falcon 9. Including the three-core Falcon Heavy, the company has launched 12 first stages—seven of them were flown on previous missions.
Since its debut in 2010, SpaceX has now launched 55 Falcon 9 missions. Before 2018 concludes, the company could fly 10 or more, including one dedicated to the first unpiloted test flight of the Crew Dragon for NASA’s Commercial Crew Program.
Video courtesy of NASA
Derek Richardson has a degree in mass media, with an emphasis in contemporary journalism, from Washburn University in Topeka, Kansas. While at Washburn, he was the managing editor of the student run newspaper, the Washburn Review. He also has a website about human spaceflight called Orbital Velocity. You can find him on twitter @TheSpaceWriter.