After a nearly week-long delay due to weather and range conflicts, SpaceX successfully launched 10 Iridium NEXT satellites into low-Earth orbit (LEO), marking the Falcon 9’s first flight since the Sept. 1, 2016, AMOS-6 pad incident. As an added bonus, the first stage of the rocket successfully landed downrange on a drone ship – the first time this has been done on the U.S. West Coast.
Hitting the opening of an instantaneous launch window at 9:54 a.m. PST (12:54 p.m. EST / 17:54 GMT), the launch team showed no signs of having endured five months with no active launches. It was the first launch in a seven-launch contract signed in 2010 with Iridium Communications – a deal worth $492 million, the largest single launch deal ever engaged.
“This day has finally come!” said Joy Don Carlos, Iridium NEXT’s launch technical manager, in a statement before launch. “We have worked toward the first launch of the Iridium NEXT satellites for many years, eight for me personally, and I am filled with huge pride and excitement as we launch the first 10 NEXT satellites into the Iridium constellation.”
The countdown proceeded smoothly at Vandenberg Air Force Base’s Space Launch Complex 4E (SLC-4E). It was the third Falcon 9 flight out of this complex since the first in 2013.
The pad originally hosted Atlas rockets starting in 1962. Between then and 2005, the complex saw additional launches from Titan IIID, Titan 34D, and Titan IV rockets before being converted to process and fly Falcon 9 and eventually Falcon Heavy rockets.
For this launch, in a deviation from past Falcon 9 “Full Thrust” launches, propellant loading occurred significantly earlier in the countdown process for this mission when compared to earlier missions.
SpaceX’s previous successful launch of the “Full Thrust” variant of the Falcon 9, the JCSAT-16 mission on Aug. 14, 2016, had both fuel and oxidizer loading underway at T–35 minutes. For the Iridium-1 launch, however, propellant loading was staggered, with the RP-1 fuel loading beginning at T–70 minutes, and the liquid oxygen (LOX) following 25 minutes later at T–45 minutes. It is unclear if this is wholly in response to the AMOS-6 incident, or if it’s a refinement of SpaceX’s launch processes.
The Falcon 9’s nine first stage Merlin 1D engines roared to life shortly before liftoff building up to their combined 1.71 million pounds (7,607 kilonewtons) of sea level thrust. Clearing the strongback shortly after launch, the rocket began its pitch, yaw, and roll maneuvers to assume a southerly heading.
The Falcon 9 continued to accelerate on its “uphill” climb to orbit, with the vehicle experiencing the greatest aerodynamic stresses, also known as max Q, nearly 70 seconds after lifting off from SLC-4E.
With everything progressing nominally, the first stage continued to fire for another 75 seconds, with main engine cutoff occurring just short of two-and-a-half minutes after launch.
After a short coast, the first and second stages separated, followed by ignition of the second stage’s lone Merlin 1D Vacuum engine shortly thereafter.
Although the primary mission was the delivery of the 10 Iridium NEXT satellites to orbit, many interested viewers were focused on what happened with the now-solo first stage.
The second stage – now above a great majority of the atmosphere and no longer needing protection for the Iridium satellites – shed its payload fairing at 3 minutes, 15 seconds into the mission. Although the fairing is necessary for a significant portion of the flight, jettisoning the protective shell once in near-vacuum conditions lightens the overall mass of the second stage, and is necessary to allow for deploying the satellites housed within.
While the second stage, with its payload, continued accelerating to orbit, the first stage began preparations to land on SpaceX’s drone ship, Just Read the Instructions, waiting a few hundred miles off the California coast in the Pacific Ocean.
Flying free from the second stage, the first stage re-oriented itself so that it was flying engines-first, allowing it to perform a couple of trajectory modification burns on its way to an eventual landing on the drone ship.
As the first stage neared the drone ship, it re-ignited the center Merlin 1D engine and brought the booster to a near-bullseye landing. While SpaceX still classifies these landing attempts as “experimental”, it’s clear the rocket’s landing system is very adept at making a difficult task look easy.
This was the first successful landing on Just Read the Instructions and the first successful landing from a West Coast launch.
However, the recovery of the first stage didn’t mark the end of the mission. While the first stage was setting up to land on the drone ship, the second stage continued to climb to orbit, with the first cutoff of the second stage’s engine coming more than nine minutes after liftoff.
Next came a coast phase, lasting nearly 44 minutes, before the Merlin 1D Vacuum was re-ignited for a short three-second burn. Now in the proper orbit, the 10 Iridium-NEXT satellites were deployed over a 15 minute period.
“It’s a clean sweep, 10 for 10,” John Insprucker, SpaceX’s Falcon 9 product manager, said during the company’s launch live stream. “All the bridge wires show open, and that is a conclusion of the primary mission today. A great one [for the] first stage, second stage, and the customer’s satellites deployed into a good orbit.”
This flight was the first of seven that will be conducted over the next year or so to send some 70 Iridium NEXT satellites into orbit to replace Iridium Communication’s aging constellation.
The process of replacing these satellites on-by-one in a constellation of this size – the world’s largest – has never been done before.
“It’s kind of a delicate choreography that we’re doing where each 10 that we launch will go into a parking orbit right below the existing operational satellite where it’s tested for a series of time over weeks,” Diane Hockenberry, director of corporate communications and public relations at Iridium Communications, told SpaceFlight Insider.
The original Iridium constellation was launched during the 1990s and early 2000s. It provides voice and data coverage for some 800,000 subscribers through 66 active satellites.
Hockenberry said once testing is completed and the new satellites are validated, they’ll be moved into a higher orbit beside the older satellites. They will then cross-link and sync together so they can read each other and connect the customer’s information that is going through.
“It’s very delicate when you are moving at 17,000 miles per hour and you don’t want to drop a call,” Hockenberry said. “So, it’ll be seamless to our users and our customers, but there’s a lot that has to go on to be sure that we can do that 66 times, and eventually even more than that, over the coming year.
Hockenberry said the older satellites are going on 19-and-a-half years, are at the end of their life, and will all eventually be de-orbited.
The new satellites are smaller and more capable. Each is 1,874 pounds (850 kilograms). In a $2.1 billion deal, Thales Alenia Space was contracted to build the satellites. A total of 81 were manufactured and 70 will be launched by SpaceX.
Iridium will begin checking out the 10 new additions to its fleet and will move them into production at some future time.
The Iridium-1 mission marked SpaceX’s first launch of 2017, as well as the company’s highly-anticipated return to flight after the AMOS-6 failure.
SpaceX’s next launch, the EchoStar 23 mission, is currently slated for no earlier than Jan. 26, 2017. It will be the first flight out of the famous Launch Complex 39A since the end of the Space Shuttle-era in 2011.
Written by: Curt Godwin
Original source: spaceflightinsider.com