SpaceX has launched another batch of 60 Starlink satellites on the Starlink v.0 L21 mission from historic Launch Complex 39A at the Kennedy Space Center. Liftoff took place on March 14 at 6:01 am EDT (10:01 UTC) and was the 21st operational and the 22nd overall Starlink mission.
This also marked the first time a Falcon 9 first stage flew nine times, the eighth Falcon 9 flight of the year, and the third in March as SpaceX pursues their rapid launch cadence goals for 2021.
Booster Reuse and Launch Preparations
The Starlink v1.0 L21 mission used a flight-proven Falcon 9 Block 5 booster, B1051-9 — with the “-9” signifying the stage’s ninth flight. This was the first time a booster was used on nine launches, making B1051 the “fleet-leader” of SpaceX’s active Falcon cores. With this milestone, SpaceX will be nearing its goal of launching and landing a booster at least 10 times.
B1051 is the second oldest active booster in the fleet. It made its debut on the uncrewed SpaceX Demo-1 mission from KSC in March 2019. It then supported the RADARSAT Constellation mission from Vandenberg, California, in June 2019.
B1051 later returned to Florida and supported the Starlink v1.0 L3 mission in January 2020, the Starlink v1.0 L6 mission in April 2020, the Starlink v1.0 L9 rideshare mission in August 2020, and the Starlink v1.0 L13 mission in October 2020. It then supported the SXM-7 mission in December 2020, the first time a seven times flown booster launched a commercial mission.
B1051-7 launches the SXM-7 satellite – via SpaceX
It most recently supported the Starlink v1.0 L16 mission in January 2021. This was the first time a booster flew on an eighth mission, making it the fleet leader at the time. On this prior mission, B1051 had a turnaround time of 38 days, which was the fastest at that time.
For its ninth flight, B1051 was turned around in 53 days. While not the fastest overall, it was this booster’s second-fastest turnaround.
For this Starlink v1.0 L21 mission, B1051 launched for the sixth time from LC-39A and landed for the sixth time on SpaceX’s autonomous spaceport drone ship Of Course I Still Love You (OCISLY), which left Port Canaveral on March 11 and was stationed ~633 kilometers downrange.
This was also the fastest pad turnaround at LC-39A. Just 10 days after the Starlink v1.0 L17 mission, this turnaround beats the previous record of 12 days between the Starlink v1.0 L12 and Starlink v1.0 L13 missions.
This mission also used a completely flight-proven payload fairing, with each half having previously supported the Transporter-1 mission in January 2021 — making this the fastest fairing turnaround at 49 days.
B1051-8 launches the Starlink v1.0 L16 mission – via Stephen Marr for NSF/L2
Prior to launch, no static fire test was conducted. Since Starlink v1.0 L8 with B1059-3, several missions have not required a static fire test before flight due to the reliability of using flight-proven first-stage boosters. For external missions, launch customers can request a static fire test before a launch carrying their payload, even if SpaceX does not require one.
Launch
At T-38 minutes, a final go/no-go poll was conducted to begin propellant loading, and Falcon 9 began liquid oxygen and RP-1 kerosene fueling of the first stage, while only RP-1 kerosene flowed into the second stage, at T-35 minutes
Liquid oxygen loading into the second stage began at T-16 minutes after RP-1 kerosene load was complete.
At T-7 minutes, the Falcon 9 began engine chilldown to ensure there were no thermal shocks to the engines at ignition. At T-4 minutes, the transporter/erector retracted to 88.2 degrees for launch.
Just two minutes before liftoff, propellant loading onto the rocket was completed. At T-1 minute, the Falcon 9 pressurized its tanks and entered “startup”, which marked the moment Falcon 9’s computers took control of the countdown.
Three seconds before liftoff, the engine controllers commanded the Falcon 9 to ignite its nine first stage engines.
Once its engines were at full thrust, the hydraulic hold-down clamps released the Falcon 9, and the transporter/erector retracted to 45 degrees as the vehicle lifted off.
B1051-8 launches the Starlink V1.0 L16 mission – via SpaceX
A few seconds later, the Falcon 9 began to pitch downrange, flying northeast from Kennedy towards a 53 degree inclined orbit. At T+1 minute 12 seconds, the Falcon 9 reached Max-Q, where the aerodynamic forces were at their highest.
T+2 minutes 33 seconds after launch, the nine first-stage engines shut down followed by second stage separation and ignition of its single Merlin Vacuum engine. The first stage then deployed its grid fins and began a flip maneuver to prepare for re-entry.
After 6 minutes of flight, the first stage reignited three of its engines to decelerate and protect itself from reentry heating.
A couple minutes later, the first stage again ignited one of its engines to land on OCISLY for the 77th Falcon 9 recovery. It will now be taken back to Port Canaveral and begin inspection and refurbishment for its historic 10th flight.
B1051-1 lands on OCISLY after supporting the Demo-1 mission – via SpaceX
While the booster was landing, the second stage continued on to its initial parking orbit, after which it coasted for about 45 minutes before restarting its Merlin Vacuum engine for just one second. Once that second burn was complete, Falcon 9 was in its proper 260 x 280 km orbit.
Afterward, the upper stage began to slowly spin in preparation for Starlink deployment. The 60 satellites then deployed from the second stage, completing the launch phase and beginning the satellites’ journey to their operational orbits.
Starlink
Starlink is SpaceX’s low Earth orbit satellite internet constellation that aims to deliver fast, affordable, and low latency service where internet is currently either unavailable or expensive.
Starlink is currently in a “Better Than Nothing Beta” test campaign, allowing certain regions of the world to order Starlink. So far, Starlink has provided people with ~120 megabits per second download speeds, ~40 megabits per second upload speeds, and with ~40 milliseconds of latency. SpaceX wants to increase the download speed to ~300 megabits per second and ~20 milliseconds of latency by the end of the year.
Speed will double to ~300Mb/s & latency will drop to ~20ms later this year
— Elon Musk (@elonmusk) February 22, 2021
The Starlink constellation will consist of five orbital shells. The Starlink satellites launched on Starlink v1.0 L21 will continue to build the first shell, which will consist of 1,584 total satellites in a 53 degree inclination, 550 kilometer altitude orbit. Once the first shell of Starlink is complete, Starlink will provide coverage to over 80% of the Earth’s surface.
Each satellite is 260 kilograms and has a compact design, allowing SpaceX to fit 60 of them in the fairing of Falcon 9. The satellites are equipped with a Hall-effect krypton powered ion thruster, which is used to maneuver the satellites into their operational orbit, automatically avoid space debris, and at the end of their life, deorbit the satellites.
SpaceX is set to launch another batch of 60 satellites on March 21 at 1:37 am EDT (05:37 UTC) from SLC-40. This is expected to be followed by another two Starlink missions which will launch in April.
After those missions take place, the SpaceX Crew-2 flight will launch on April 22 using Falcon 9 booster B1061-2. It will launch the four-person crew on Crew Dragon Endeavour to the International Space Station for a six-month stay.
(Lead photo: B1051 on LC-39A ahead of the Starlink v1.0 L6 mission – via Stephen Marr for NSF)