SpaceX flies historic 10th mission of a Falcon 9 as Starlink constellation expands

SpaceX conducted the historic 10th flight of a Falcon 9 rocket booster on the Starlink V1.0 L27 mission Sunday. The mission launched from SLC-40 at Cape Canaveral Space Force Station on 9 May at 02:42 EDT / 06:42 UTC with an 80% positive launch weather and a “low risk” for recovery weather.

This mission marked SpaceX’s 14th orbital launch in 2021, the 11th Starlink flight this year, and SpaceX’s second orbital launch and third flight overall in less than five days this month.

Starlink is SpaceX’s global internet constellation which aims to deliver fast, low latency, and inexpensive internet to locations where ground based internet is either unreliable or completely unavailable.

Starlink Constellation Progress 

SpaceX is currently filling the first shell of Starlink located in a 550 km circular orbit with an inclination of 53 degrees. Once complete, the first shell will consist of 1,584 operational satellites across 72 orbital planes with 22 satellites per plane. Prior to this mission, the shell contained approximately 1,456 operational working satellites, of which about 882 are in their final orbit, meaning this is the third-to-last Starlink launch before all Starlinks for the the first shell are in space. 

However, it will take a few months for all of the first shell satellites to reach their operational orbits; once that occurs, Starlink will cover approximately ~80% of Earth’s surface. 

Once all the satellites in the first shell are in orbit, SpaceX will begin building out additional orbital shells that will increase bandwidth and achieve 100% global coverage thanks to some satellites in polar orbits.

Overall, the first phase of the Starlink constellation will consist of approximately 4,408 satellites, in the following shells:

Inclination (°) Orbital Altitude (km) Number of Satellites
Shell 1 53.0 550 1,584
Shell 2 53.2 540 1,584
Shell 3 70.0 570 720
Shell 4 97.6 560 348
Shell 5 97.6 560 172
The two polar shells will both reside at the same inclination and the same altitude but will have a different number of planes for the Starlinks to reside in. Shell 4 will have six orbital planes with 58 satellites per plane while Shell 5 will consist of four orbital planes with 43 satellites in each.

According to Gwynne Shotwell, SpaceX will begin conducting regular Starlink launches into the polar shells beginning in July. These missions are expected to launch from SLC-4 East at Vandenberg Air Force Base, California. It is understood that these missions will coincide with the continued launch of Starlink satellites from Florida to lower inclinations.

History of Reuse

For this mission, SpaceX used the Falcon 9 booster B1051-10 with the “-10” signifying the booster’s 10th flight.

Booster B1051 is the second oldest operational first stage booster in the Falcon 9 fleet, debuting in prominence with the uncrewed Demo-1 flight of Crew Dragon to the International Space Station on 2 March 2019. During its life, it has flown the following missions:

B1051’s missions Launch Date (UTC) Turnaround Time (Days)
SpaceX Demonstration Mission-1 2 March 2019 N/A
RADARSAT Constellation 12 June 2019 102
Starlink V1.0 L3 29 January 2020 231
Starlink V1.0 L6 22 April 2020 84
Starlink V1.0 L9 7 August 2020 107
Starlink V1.0 L13 18 October 2020 72
SXM-7 13 December 2020 56
Starlink V1.0 L16 20 January 2021 38
Starlink V1.0 L21 14 March 2021 53
Starlink V1.0 L27 9 May 2021 56

This was the first time an orbital class rocket booster flew 10 missions and marked a critical reuse milestone for SpaceX.

On 30 March 2017, SpaceX reused a Falcon 9 booster for the first time when SES-10 launched from LC-39A at the Kennedy Space Center under the power of core B1021, which a year prior became the first booster to land on SpaceX’s floating platform Of Course I Still Love You.

B1021 on Of Course I Still Love You after landing (Credit: SpaceX)

In May 2018, SpaceX debuted an upgraded Block 5 variant of the Falcon 9. This new version was to be capable of carrying crewed missions and take lessons learned from previous blocks to decrease turnaround and refurbishment time; the company set the ambitious goal of reusing a booster 10 times with minimal refurbishment between each flight.

Since the first flight of Falcon 9 Block 5, SpaceX has transitioned from simply manufacturing Falcon 9 first stages to operating a fleet of reusable rockets. Although the company still manufactures new boosters, they are becoming increasingly rare to see on the launch pad; in fact, not a single new first stage has launched so far in 2021.

With less demand for first stage boosters, SpaceX’s Hawthorne, California factory now focuses more on producing a large number of second stages to support an ever-increasing launch cadence.

Over the years, customers have become more and more comfortable flying on reused rockets. The United States Space Force recently allowed key national security missions to fly on used hardware, and even NASA has accepted flown boosters on crewed missions, the first of which launched several weeks ago on the Crew-2 mission.

In December 2020, Sirius-XM became the first paying customer to use a “high-flight number” booster when the SXM-7 satellite successfully launched on the seventh flight of booster B1051.

Thanks to their homegrown internet constellation, SpaceX has been able to expand the envelope of recovering and reusing hardware. With an abundance of internal payloads to launch, the company has been able to reduce turnaround times and launch individual boosters more and more without risking paying customers’ payloads.

This is evident in the number of times a booster has flown before each launch:

Flight 1 Flight 2 Flight 3 Flight 4 Flight 5 Flight 6 Flight 7 Flight 8 Flight 9 Flight 10
2017 13 5 0 0 0 0 0 0 0 0
2018 10 12 1 0 0 0 0 0 0 0
2019 7 5 4 1 0 0 0 0 0 0
2020 5 3 4 6 4 2 2 0 0 0
2021 0 1 0 1 2 3 2 2 2 1

SpaceX has also drastically reduced the turnaround times in 2021. Before this year, the fastest turnaround of a Falcon 9 was 51 days, between Starlink L11 and Starlink L14 — itself a global record.

In 2021, SpaceX has so far beaten this record six times, with two turnaround times at just 27 days. The average turnaround time has also decreased by approximately 48% since 2020:

Year Average Turnaround Time (Days)
2017 225.2
2018 224.5
2019 139.8
2020 113.8
2021 59.5

SpaceX has several more missions in the coming weeks. First is the Starlink V1.0 L26 mission on 15 May at 18:58 EDT / 22:58 UTC. That mission will use B1058-8 and launch from LC-39A. The mission may include two rideshare payloads: the Capella 5 and 6 satellites.

Next is SiriusXM’s SXM-8 on 1 June at 00:25 EDT / 04:25 UTC from SLC-40. Two day later, SpaceX will launch the CRS-22 mission on 3 June using booster B1067-1 (the first new core to enter the fleet in 2021) launching from LC-39A.

The final confirmed upcoming SpaceX mission is GPS-III SV05 on 17 June; it will use B1062-2 and launch from SLC-40.

The Launch

Prior to launch, no static fire test was conducted, continuing a trend among SpaceX’s internal Starlink missions to skip the static fire and proceed to launch.

Since Starlink V1.0 L8, 14 Falcon 9 flights have not required a static fire test due to both the reliability of flight-proven first stage boosters and the majority of those missions being internal Starlink flights.

For external missions, paying customers can request a static fire before launch.

Pre-launch countdown:

T- time to launch Event
T-38 mins Launch Director confirms “go” for propellant loading
T-35 mins Fueling begins with RP-1 kerosene to both stages & liquid oxygen to Stage 1 only
T-17 mins RP-1 kerosene load to Stage 2 complete
T-16 mins Liquid oxygen load into Stage 2 begins
T-7 mins First stage Merlin engine chilldown begins
T-2 mins 30 secs Fueling of the Falcon 9 for launch complete
T-1min Falcon 9 takes control of countdown & pressurizes its propellant tanks for launch
T-45 secs Launch Director verifies “go” for launch
T-3 secs Merlin 1D engine ignition command sent
T0 Liftoff

After lifting off, the vehicle performed a pitch and roll maneuver to place itself onto the correct heading and into the proper orientation to achieve a 53 degree orbit of the Earth. Falcon 9 achieved MaxQ 1 minute 12 seconds into flight, followed by staging at T+2 minutes 36 seconds.

The second stage then ignited as the first stage oriented itself for its 10th reentry and landing.

Over six minutes into flight, the first stage reignited its center engine, E9, shortly followed by two outer engines, E1 and E5. These three engines contain TEA-TEB canisters, allowing them to be relit in flight, which is different from how the engines are ignited on the ground before liftoff. On the ground, the TEA-TEB is provided by the launch pad’s ground service equipment.

Shortly after, the first stage then lit E9 again to land on the Just Read the Instructions droneship approximately 615 km downrange.

This marked the 83rd landing of a Falcon 9 booster and the 21st landing attempt on Just Read the Instructions. The droneship will now take the booster back to Port Canaveral to begin a series of inspections ahead of rejoining the fleet.

Meanwhile, the second stage continued to haul the Starlink stack into its initial parking orbit.  The payload fairings separated 3 minutes 04 seconds into flight and parachuted into the Atlantic where the Shelia Bordelon was standing by to recover them from the water approximately 680 km downrange of the launch site. 

As with the first stage, the payload fairing halves on this flight were reused. Both fairing halves previously flew together on the GPS III SV04 mission 185 days ago.

The second stage and Starlink payload reached their initial parking orbit 8 minutes 47 seconds after launch. The second stage then began to coast for about 37 minutes before settling its propellant and reigniting its Mvac engine for one second. Once the second burn was complete, the Falcon 9 was in a 260 x 280 km orbit. 

Afterward, the second stage began to spin in preparation for Starlink deployment. The 60 satellites will then deploy from the second stage and drifted apart due to the difference in angular momentum imparted by the spinning rocket stage.

The 60 satellites will now begin to maneuver to reach their 550 km operational orbits. 

(Lead image credit: B1051-10 on its 10th launch. Credit: Stephen Marr)

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