Starlink Group 2-1 | Falcon 9 Block 5

Lift Off Time
September 14, 2021 – 03:55 UTC
September 13, 2021 – 20:55 PDT
Mission Name
Starlink Group 2-1: the 30th Starlink mission
Launch Provider
(What rocket company launched it?)
SpaceX
Customer
(Who paid for this?)
SpaceX
Rocket
Falcon 9 Block 5 B1049-10; 133 day turn around
Launch Location
Space Launch Complex 4 East (SLC-4E), Vandenberg Space Force Base, California, USA
Payload mass
~13,260 kg (29,200 lb)
Where did the satellites go?
Starlink Shell 3; 570 km circular 70° low-Earth Orbit (LEO), initial orbit of 343 km x 213 km at 70.01°
Did they attempt to recover the first stage?
Yes
Where did the first stage land?
B1049-10 successfully landed 640 km downrange on Of Course I Still Love You

Tug: Scorpius; Support: Adele Elise
Did they attempt to recover the fairings?
Yes, they attempted recovery from the water ~688 km downrange by NRC Quest; outcome TBD
Were these fairings new?
No, the active half had flown one previous time and the passive half had flown two previous times; 269 and 249 day turn around time, respectively
This was the:
– 100th successful Falcon mission in a row
– 1st launch of the third Starlink shell
125th Falcon 9 launch
66th Falcon 9 flight with a flight proven booster
70th re-flight of a booster
– 21st re-flight of a booster in 2021
– 91st booster landing
– 22nd launch for SpaceX in 2021
17th SpaceX launch from SLC-4E
– 88th orbital launch attempt of 2021
(82nd successful)
Where to watch
Official replay

How did it go?

SpaceX’s Starlink Group 2-1 mission successfully launched 51 Starlink satellites atop its Falcon 9 rocket. The Falcon 9 lifted off from Space Launch Complex 4E (SLC-4E), at the Vandenberg Space Force Base, in California, United States. Starlink Group 2-1 marked the 29th operational Starlink mission, boosting the total number of Starlink satellites launched to 1,788. This mission also marked the first launch of the third Starlink shell.

Starlink is SpaceX’s internet communication satellite constellation. The Low-Earth orbit constellation will deliver fast, low-latency internet service to locations where ground-based internet is unreliable, unavailable, or expensive. The first phase of the constellation consists of 5 orbital shells.

Starlink is currently in the “Better Than Nothing Beta,” allowing anyone in approved regions to order or preorder. However, for now, only higher latitudes are fully covered, so people of lower latitudes are currently only able to pre-order Starlink. After 28 launches SpaceX will achieve global coverage, but the constellation will not be complete until ~42,000 satellites are in orbit. Given SpaceX’s current Starlink production and launch rate, Starlink will have global coverage, excluding the poles, by the middle of 2021.

Once Starlink is complete, the venture is expected to profit $30-50 billion annually. This profit will largely finance SpaceX’s ambitious Starship program, as well as Mars Base Alpha.

Starlink satellites and dispenser.
A stack of 60 Starlink satellites prior to be encapsulated into Falcon 9’s payload fairing. (Credit: SpaceX)

Each Starlink V1.5 satellite has a compact design and a mass of 260 kg. SpaceX developed a flat-panel design, allowing them to fit as many satellites as possible into the Falcon 9’s 5.2 meter wide payload fairing. Due to this flat design, SpaceX is able to fit up to 60 Starlink satellites and the payload dispenser into the second stage, while still being able to recover the first stage. This is near the recoverable Falcon 9’s payload capacity to LEO, at around 17 tonnes. 

For how small each Starlink satellite is, each one is packed with high-tech communication and cost-saving technology. Each Starlink satellite is equipped with 4 phased array antennas, for high bandwidth and low-latency communication, and two parabolic antennas. The satellites also include a star tracker, which provides the satellite with attitude data, ensuring precision in broadband communication. 

The Starlink satellites are also equipped with an autonomous collision avoidance system, which utilizes the DOD’s debris tracking database to autonomously avoid collisions with other spacecraft and space junk. 

The Starlink satellites being launched are equipped with an inter-satellite laser communication system. This allows the satellites to communicate directly with each other, eliminating the need for costly ground stations.

To decrease costs, each satellite only has a single solar panel, which simplifies the manufacturing process. To further cut costs, Starlink’s propulsion system, an ion thruster, uses krypton as fuel, instead of xenon. While the specific impulse (ISP) of krypton is significantly lower than xenon’s, it is far cheaper, which further decreases the satellite’s manufacturing cost.

Ion Power

Each Starlink satellite is equipped with the first Hall-effect krypton powered ion thruster. This thruster is used not only for ensuring the correct orbital position, but also for orbit raising and orbit lowering. At the end of the satellite’s life, this thruster is used to deorbit the satellite.

A satellite constellation is a group of satellites that work in conjunction for a common purpose. Currently, SpaceX plans to form a network of 11,716 satellites; however, in 2019 SpaceX filed an application with the Federal Communication Commission (FCC) for permission to launch and operate an additional 30,000 satellites as part of phase 2 of Starlink. To put this number of satellites into perspective, this is roughly 20 times more satellites than were launched before 2019. 

Of the initial ~12,000 satellites, ~4,400 would operate on the Ku and Ka bands, with the other ~7,600 operating on the V-Band. 

Due to the vast number of Starlink satellites, many astronomers are concerned about their effect on the night sky. However, SpaceX is working with the astronomy community and implementing changes to the satellites to make them harder to see from the ground and less obtrusive to the night sky. SpaceX has changed how the satellites raise their orbits and, starting on Starlink V1.0 L9, added a sunshade to reduce light reflectivity. These changes have already significantly decreased the effect of Starlink on the night sky.

Phase 1 Orbital Shells:

Inclination (°)Orbital Altitude (km)Number of Satellites
Shell 153.05501,584
Shell 253.25401,584
Shell 370.0570720
Shell 497.6560348
Shell 597.6560172
Orbital Shells

Shell 1

The first orbital shell of Starlink satellites will consist of 1,584 satellites in a 53° 550 km low-Earth orbit. Shell 1 consists of 72 orbital planes, with 22 satellites in each plane. This was the first shell that SpaceX completed, and all of the satellites should be in their final orbit by the end of 2021. Once the satellites are in the shell, the first shell will provide coverage between roughly 52° and -52° latitude (~80% of the Earth’s surface), and will not feature laser links until replacement satellites will launch after 2021.

Shell 2

The second shell will consist of 1,584 satellites in a 540 km 53.2° LEO. This updated orbital configuration will slightly increase coverage area and will drastically increase the bandwidth of the constellation. This shell will also consist of 72 orbital planes with 22 satellites in each plane.

Shell 3

Starlink’s third shell will host 720 satellites in a 70° 570 km orbit. These satellites will significantly increase the coverage area, which will make the Starlink constellation cover around 94% of the globe. SpaceX will put 20 satellites in each of the 36 planes in the third shell. This is the shell that SpaceX is currently filling.

Shell 4

Shell 4 will consist of 348 satellites in a 97.6° 560 km orbit. SpaceX deployed 10 laser link test satellites into this orbit on their Transporter-1 mission to test satellites in a polar orbit. All satellites that will be deployed into this orbit will have intersatellite laser link communication. Shell 4 will have 6 orbital planes with 58 satellites in each plane.

Shell 5

The final shell of phase 1 of Starlink will host 172 satellites in another 97.6° 560 km low-Earth polar orbit. Shell 5 will also consist purely of satellites with laser communication links, however unlike shell 4 it will consist of 4 orbital planes with 43 satellites in each plane.

Phase 2 Orbital Shells:

Shell 6

The sixth orbital shell of Starlink satellites is permitted to consist of 2,493 satellites in a 42° 335.9 km LEO. This large number of satellites will decrease latency and increase bandwidth for lower latitudes.

Shell 7

The seventh Starlink shell permits SpaceX to deploy 2,478 satellites into a 48° 340.8 km low-Earth orbit. These satellites will further decrease latency and increase bandwidth for lower latitudes.

Shell 8

The final shell of Starlink phase 2 allows SpaceX to deploy 2,547 satellites in a 53° 345.6 km orbit.

SpaceX has until March of 2024 to be half complete with phase 1, and phase 1 must be complete by March of 2027. Phase 2 must be half complete by November of 2024, and be finished by November of 2027. Failure to do so could result in SpaceX losing their dedicated frequency band.

What is Falcon 9 Block 5?

The Falcon 9 Block 5 is SpaceX’s partially reusable two-stage medium-lift launch vehicle. The vehicle consists of a reusable first stage, an expendable second stage, and, when in payload configuration, a pair of reusable fairing halves.

First Stage

The Falcon 9 first stage contains 9 Merlin 1D+ sea level engines. Each engine uses an open gas generator cycle and runs on RP-1 and liquid oxygen (LOx). Each engine produces 845 kN of thrust at sea level, with a specific impulse (ISP) of 285 seconds, and 934 kN in a vacuum with an ISP of 313 seconds. Due to the powerful nature of the engine, and the large amount of them, the Falcon 9 first stage is able to lose an engine right off the pad, or up to two later in flight, and be able to successfully place the payload into orbit.

The Merlin engines are ignited by TEA-TEB. During static fire and launch the TEA-TEB is provided by the ground service equipment. However, as the Falcon 9 first stage is able to propulsively land three of the Merlin engines (E1, E5, and E9) contain TEA-TEB canisters to relight for the boost back, reentry, and landing burns.

Second Stage

The Falcon 9 second stage is the only expendable part of the Falcon 9. It contains a singular MVacD engine that produces 992 kN of thrust and an ISP of 348 seconds. The second stage is capable of doing several burns, allowing the Falcon 9 to put payloads in several different orbits.

For missions with many burns and/or long coasts between burns, the second stage is able to be equipped with a mission extension package. When the second stage has this package it has a grey strip, which helps keep the RP-1 warm, an increased number of COPVs for pressurization control, and additional TEA-TEB.

Falcon 9 Block 5 launching on the Starlink V1.0 L27 mission (Credit: SpaceX)

The booster that supported Starlink Group 2-1 was B1049, which had flown nine previous times. As Starlink Group 2-1 marked the booster’s 10th flight, it changed its designation to B1049-10.

B1049’s missionsLaunch Date (UTC)Turn Around Time (Days)
Telstar 18VSeptember 10, 2018N/A
Iridium NEXT-8January 11, 2019123
Starlink V0.9 L1May 24, 2019133
Starlink V1.0 L2January 7, 2020228
Starlink V1.0 L7June 4, 2020149
Starlink V1.0 L10August 18, 202075
Starlink V1.0 L15November 25, 202099
Starlink V1.0 L17March 4, 202199
Starlink V1.0 L25May 4, 202161
Starlink Group 2-1September 13, 2021133

Following stage separation, the Falcon 9 conducted 2 burns. These burns softly touched down the booster on SpaceX’s autonomous spaceport drone ship Of Course I Still Love You.

Falcon 9 landing on Of Course I Still Love You after launching Bob and Doug (Credit: SpaceX)

Falcon 9 Fairings

The Falcon 9’s fairing consists of two dissimilar reusable halves. The first half (the half that faces away from the transport erector) is called the active half, and houses the pneumatics for the separation system. The other fairing half is called the passive half. As the name implies, this half plays a purely passive role in the fairing separation process, as it relies on the pneumatics from the active half.

Both fairing halves are equipped with cold gas thrusters and a parafoil which are used to softly touch down the fairing half in the ocean. SpaceX used to attempt to catch the fairing halves in nets on GO Ms. Tree and GO Ms. Chief. However, at the end of 2020 this program was cancelled due to safety risks and a low success rate. On Starlink Group 2-1, SpaceX attempted to recover one of the fairing halves from the water with their recovery vessel GO Searcher.

SpaceX is currently flying two slightly different versions of the Falcon 9 fairing. The new “upgraded” version has vents only at the top of each fairing half, by the gap between the halves, whereas the old version had vents placed spread equidistantly around the base of the fairing. Moving the vents decreases the chance of water getting into the fairing, making the chance of a successful scoop significantly higher.

All Times Approximate

HR/MIN/SECEVENT
00:38:00SpaceX Launch Director verifies go for propellant load
00:35:00RP-1 (rocket grade kerosene) loading underway
00:35:001st stage LOX (liquid oxygen) loading underway
00:16:002nd stage LOX loading underway
00:07:00Falcon 9 begins engine chill prior to launch
00:01:00Command flight computer to begin final prelaunch checks
00:01:00Propellant tank pressurization to flight pressure begins
00:00:45SpaceX Launch Director verifies go for launch
00:00:03Engine controller commands engine ignition sequence to start
00:00:00Falcon 9 liftoff

All Times Approximate

HR/MIN/SECEVENT
00:01:12Max Q (moment of peak mechanical stress on the rocket)
00:02:321st stage main engine cutoff (MECO)
00:02:351st and 2nd stages separate
00:02:432nd stage engine starts
00:02:59Fairing deployment
00:06:461st stage entry burn start
00:07:071st stage entry burn complete
00:08:241st stage landing burn start
00:08:461st stage landing burn complete
00:08:512nd stage engine cutoff (SECO-1)
00:15:32Starlink satellites deploy

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