Starlink Group 4-16 launches, breaks SpaceX turnaround records

by Alejandro Alcantarilla

SpaceX made its seventeenth launch of the year on Friday to put another batch of Starlink satellites into low Earth orbit. A Falcon 9 rocket carried out the Starlink Group 4-16 mission, lifting off at 5:27:10 pm EDT (21:27 UTC) from Space Launch Complex 40 at the Cape Canaveral Space Force Station in Florida.

Friday’s launch saw SpaceX break several turnaround records with its flight-proven Falcon 9 booster and its launch and recovery infrastructure.

The rocket for this mission conducted its usual 35-minute-long automated countdown sequence from fueling to liftoff before flying northeast from Cape Canaveral to insert the satellites into a planned 304 by 317 kilometer low Earth orbit (LEO) at an inclination of 53.2 degrees. 

The first stage landed about 635km downrange on SpaceX’s Autonomous Spaceport Drone Ship (ASDS) Just Read The Instructions. The fairing halves separated from the upper stage about three minutes into the flight, parachuting down to a splashdown in the Atlantic Ocean around 650km northeast of the launch pad. They will be recovered by SpaceX’s multi-purpose recovery vessel Bob.

After separating from the first stage, Falcon 9’s second stage performed a six-minute-long orbital insertion burn, followed about 30 minutes later by a short two-second burn to circularize the orbit. The separation of the Starlink satellites came about an hour after liftoff.

After spacecraft separation is confirmed, Falcon’s second stage is set to perform a third and final burn to deorbit itself. Re-entry and disposal of the upper stage are expected to occur over the south Indian Ocean.

Over the next few weeks, the satellites will raise themselves into a roughly 350km circular orbit where they will undergo checkout. Those that pass these checks will then be commanded to put themselves into their operational orbit.

Friday’s launch is the 43rd dedicated Starlink mission and put another 53 satellites into shell four of Starlink’s first-generation constellation. This brings the total number of satellites launched to 2,441, of which 241 have already reentered and 1,714 satellites remain in their operational orbits.

Shell #1 Shell #2 Shell #3 Shell #4 Shell #5
Orbit 550km at 53º 570km at 70º 560km at 97.6º 540km at 53.2º 560km at 97.6º
No. of orbital planes 72 36 6 72 4
Satellites per plane (target) 22 20 58 22 43
Satellites launched 1665 51 0 597 0
Satellites in operational orbit 1462 18 0 234 0
Total satellites 1584 720 348 1584 172

(Status of Starlink constellation information from Jonathan McDowell as of April 27)

A record-breaking mission

Friday’s launch breaks four records, all related to turnaround times, making it one of SpaceX’s most record-breaking missions of recent years and illustrating the progress that SpaceX is making towards increasing its launch cadence.

The booster used for this mission is B1062-6. This booster has previously flown five times, with its most recent launch being on the Axiom-1 mission earlier in April. After an on-time liftoff on Friday, the turnaround time was 21 days, 6 hours, and 10 minutes, smashing the previous booster turnaround record by almost a week. 

Booster Time between launches Between flights Missions
B1062 21d 6h 10min 5 and 6 Axiom-1 and Starlink Group 4-16
B1060 27d 4h 4min 4 and 5 Turksat 5A and Starlink v1.0-18
B1058 27d 8h 21min 6 and 7 Starlink v1.0-20 and Starlink v1.0-23
B1060 35d 23h 7min 6 and 7 Starlink v1.0-22 and Starlink v1.0-24
B1052 36d 15h 34min 3 and 4 CSG-2 and Starlink Group 4-10

It is understood that this booster is part of a special refurbishment treatment that SpaceX is experimenting with to increase its launch cadence, especially for Starlink missions. SpaceX aims to compress its booster refurbishment timeline from two or three weeks down to just five to seven days, allowing turnaround times as short as three weeks or perhaps less.

The outcome of Friday’s mission will help to inform the company on whether this accelerated refurbishment timeline will work without compromising Falcon 9’s mission performance or reliability. The rocket’s long streak of successful launches and first stage recoveries has given SpaceX the confidence in its hardware to entertain this kind of experimentation. 

SpaceX’s Space Launch Complex 40 (SLC-40) also set its own turnaround record, with 8 days, 6 hours, and 13 minutes having passed since the previous Starlink launch flew from the same pad. No other SpaceX launch pad has yet been able to support a turnaround this short: LC-39A’s turnaround record stands at around ten days and SLC-4E’s best turnaround to date has been around 23 days. 

Graph of average turnaround time per launch pad and year. Data as of April 28.

Another turnaround record set by Friday’s launch relates to the seaborne recovery of  B1062-6, which was accomplished after the stage has completed its role in boosting the Starlink satellites towards orbit.

The first stage landed aboard SpaceX’s Autonomous Spaceport Drone Ship Just Read The Instructions, which is breaking its own record turnaround time, having arrived at Port Canaveral on April 25 at 1 am EDT with B1060-12 after the Starlink Group 4-14 mission and departed for this mission just 19 hours later at 8 pm EDT that same day. 

It is clear that SpaceX has been making a lot of progress to ready its drone ships for another flight more quickly, with a fast booster unload and quick replenishment of consumables. Missions earlier in the year saw an average turnaround of ten to eleven days achieved with the other east coast drone ship, A Shortfall Of Gravitas. The drone ships would typically have been waiting a day or two in port before being towed out to the landing zone for their next mission, but now this waiting time is being cut from a few days to just a few hours. 

Thanks to all of its record-breaking turnaround times, Friday’s launch broke one more record: it was SpaceX’s sixth launch of the month, the most that the company has conducted in a single calendar month in its history. This marks another milestone in the progress that SpaceX has made to accelerate its launch cadence over the years that Falcon 9 has been in service.

The first time the company made three launches in the same calendar month was in June 2017; the first time they made four launches in the same calendar month was in November 2020, and the first time they made five launches in the same calendar month was in December 2021. This shows not only how SpaceX has been able to accelerate the cadence but also how the company has taken less time to move from five to six launches in the same month compared to the time taken to advance from three to four and four to five. 

B1062 lifts off on its previous mission with Axiom-1 (Credit: Julia Bergeron for NSF)

In the twelve years that it has been in service, Falcon 9 has not only proven to be a success for SpaceX, but it has become a workhorse for the world’s space industries. Friday’s mission marks the 150th orbital launch of the single-core Falcon 9 vehicle.

With the mission completed successfully, Starlink Group 4-16 is the Falcon 9’s 121st consecutive success since the pre-launch testing accident ahead of the Amos 6 mission in September 2016, and the 130th consecutive success since the rocket’s only in-flight failure in June 2015.

SpaceX’s record-breaking launch cadence shows no sign of letting up, with another two Starlink launches planned for next week, while a third is expected to follow by the middle of May.

(Lead image: Falcon 9 lifts off from SLC-40 on the Starlink Group 4-16 mission. Credit: Thomas Burghardt for NSF)

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