SpaceX is ready to launch another batch of 60 Starlink satellites on the Starlink v.0 L21 mission from historic Launch Complex 39A, Kennedy Space Center. Liftoff is targeted for March 14 at 6:01 AM EDT (10:01 UTC). The flight is the 21st operational and the 22nd overall Starlink mission.
This will mark the eighth Falcon 9 flight of the year, and the third in March, as SpaceX pursues their rapid launch cadence goals for 2021. The mission will also mark the first time a booster has flown nine missions. 
Booster Reuse and Launch Preparations
The Starlink v1.0 L21 mission will use a flight-proven Falcon 9 Block 5 booster, B1051-9. The 9 signifies that this mission is the stage’s ninth flight. This is the first time a booster has been 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 mission, B1051 had a turnaround time of 38 days, which was the fastest at that time. 
For its ninth flight, B1051 will have a turnaround of 53 days. While not the fastest turnaround overall, it will be B1051s second-fastest turnaround. 
For this Starlink v1.0 L21 mission, B1051 will launch from LC-39A and land on SpaceXs autonomous spaceport drone ship Of Course I Still Love You (OCISLY). This will mark B1051s sixth time launching from LC-39A as well as it’s sixth landing on OCISLY. 
OCISLY left Port Canaveral on March 11. It will be stationed ~633 kilometers downrange. 
It will also be the fastest pad turnaround at LC-39A.  Just ten 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.
The Falcon 9 will also be using a set of flight-proven payload fairings. Both fairing halves first supported the Transporter-1 mission in January 2021. This will also mark the fastest fairing turnaround at 49 days. 
The fairings will separate from the Falcon 9 at three minutes and 10 seconds into the flight. Once separated, they will fall for about 45 minutes until splashdown, where they will be picked out of the ocean by GO Searcher and GO Navigator.
B1051-8 launches the Starlink v1.0 L16 mission – via Stephen Marr for NSF/L2
Once the Falcon 9 was fully assembled and its payload of 60 Starlink satellites was encapsulated, the integrated vehicle was rolled out to the pad just a couple of days before launch.
No static fire test was conducted prior to this launch. 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.
Once Falcon 9 was raised vertical at LC-39A, the launch team began final launch preparations. 
Launch
At T-38 minutes, a final go/no-go poll is conducted to begin propellant loading. Once the final go is given, the Falcon 9 begins liquid oxygen fueling in the first stage and RP-1 kerosene fueling in the first and second stages at T-35 minutes.
Liquid oxygen loading into the second stage begins at T-16 minutes.
At T-7 minutes, the Falcon 9 will begin engine chill to ensure there are no thermal shocks to the engines at ignition. At T-4 minutes, the transporter/erector retracts to 88.2 degrees for launch. 
Two minutes before launch, the propellant loading onto the rocket is complete. At T-1 minute, the Falcon 9 begins to pressurize its tanks and enters startup, which is when the Falcon 9 computers take over the countdown. At T-45 seconds, the SpaceX Launch Director gives the final go for launch. 
Three seconds before liftoff, the engine controller commands the Falcon 9 to ignite its nine first-stage engines.
Once its engines are at full thrust, the hydraulic hold-down clamps release the Falcon 9, and the T/E retracts to 45 degrees as the vehicle lifts off. 
B1051-8 launches the Starlink V1.0 L16 mission – via SpaceX
A few seconds later, the Falcon 9 begins to pitch downrange, flying northeast from Kennedy Space Center towards a 53 degree inclined orbit. At T+1 minute and 12 seconds, the Falcon 9 reaches Max-Q, where the aerodynamic forces are at their highest.
Two minutes and 33 seconds after launch, the nine first-stage engines will shut down. Following that, the second stage will separate and ignite its single Merlin Vacuum engine. The first stage will then deploy its grid fins and begin a flip maneuver to prepare for re-entry. 
After six minutes into the flight, the first stage will reignite three of its engines to decelerate and protect itself from re-entry heating. The burn will last about 20 seconds. 
A couple minutes later, the first stage will reignite one of its engines to land on OCISLY. If successful, it will mark the 77th Falcon 9 recovery. It will then be taken back to Port Canaveral and begin inspection and refurbishments for its historic tenth flight.
B1051-1 lands on OCISLY after supporting the Demo-1 mission – via SpaceX
At eight minutes 50 seconds after liftoff, the second stage engine will shutdown. It will then begin a coast phase which will last about 45 minutes before restarting the Merlin Vacuum engine. This burn will last about one second. Once the burn is complete, the upper stage and payload will begin another 15 minute coast. 
After the coast is complete, the upper stage will begin to slowly spin in preparation for Starlink deployment. The 60 Starlink satellites will then deploy from the second stage, completing the launch phase and beginning the satellites’ journey to their operational orbits.
Starlink
Starlink is SpaceXs low Earth orbit satellite internet constellation. Starlink aims to deliver fast, affordable, and low latency service to where internet is currently either unavailable or expensive.
Starlink is currently in a Better Than Nothing Beta, 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 Earths 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. Starlink v1.0 L22 will launch 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 mission 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)