Starlink Group 4-4 | Falcon 9 Block 5

Lift Off Time
December 18, 2021 – 12:41 UTC | 04:41 PST
Mission Name
Starlink Group 4-4: the third launch to Starlink shell 4
Launch Provider
(What rocket company launched it?)
SpaceX
Customer
(Who paid for this?)
SpaceX
Rocket
Falcon 9 Block 5 B1051-11; 223 day turn around
Launch Location
Space Launch Complex 4 East (SLC-4E), Vandenberg Space Force Base, California, USA
Payload mass
~15,000 kg (33,000 lb)
Where did the satellites go?
Starlink Shell 4; 540 km circular 53.2° low-Earth Orbit (LEO)
Did they attempt to recover the first stage?
Yes
Where did the first stage land?
B1051-11 successfully landed 638 km downrange on Of Course I Still Love You

Tug: Scorpius; Support: Adele Elise
Did they attempt to recover the fairings?
Fairing recovery was attempted ~688 km downrange by NRC Quest; outcome TBD
Were these fairings new?
No, one fairing half flew two previous times and the other flew three previous times
This was the:
First 11th flight of a Falcon 9 booster
– 132nd Falcon 9 launch
– 73rd Falcon 9 flight with a flight proven booster
– 77th re-flight of a booster
– 28th re-flight of a booster in 2021
– 98th booster landing
– 29th launch for SpaceX in 2021 (a record)
– 19th SpaceX launch from SLC-4E
– 134th orbital launch attempt of 2021
(125th successful)
Where to watch
Official replay

How Did It Go?

SpaceX’s Starlink Group 4-4 mission successfully launched 52 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 4-4 marked the 32nd operational Starlink mission, boosting the total number of Starlink satellites launched to 1,944, of which ~1,807 are still in orbit. This mission marked the third launch of the fourth 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 operational, allowing anyone in approved regions to order or preorder. After 28 launches SpaceX achieved near-global coverage, but the constellation will not be complete until ~42,000 satellites are in orbit. 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, satellite dispenser.
A stack of 60 Starlink V1.0 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 295 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 payload capacity of the Falcon 9 to LEO, around 16 tonnes. 

As small as 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. 

Each Starlink V1.5 satellite is also equipped with an inter-satellite laser communication system. This allows each satellite to communicate directly with other satellites, not having to go through ground stations. This reduces the number of ground stations needed, allowing coverage of the entire Earth’s surface, including the poles.

The Starlink satellites are also equipped with an autonomous collision avoidance system, which utilizes the US Department of Defense (DOD) debris tracking database to autonomously avoid collisions with other spacecraft and space junk. 

To decrease costs, each satellite 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 for both ensuring the correct orbital position, as well as 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 270.0570720
Shell 397.6560348
Shell 453.25401,584
Shell 597.6560172

Shell 1

The first orbital shell of Starlink satellites consists of 1,584 satellites in a 53.0° 550 km low-Earth orbit. Shell one consists of 72 orbital planes, with 22 satellites in each plane. This shell is currently near complete, with occasional satellites being replaced. The first shell provides coverage between roughly 52° and -52° latitude (~80% of the Earth’s surface), and will not feature laser links until replacement satellites launch after this year.

Shell 2

Starlink’s second 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 coverage around 94% of the globe. SpaceX will put 20 satellites in each of the 36 planes in the second shell. This shell is currently being filled, along with shell four.

Shell 3

Shell three 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. SpaceX launched an additional three satellites to this shell on the Transporter-2 mission. On April 6, 2021 Gwynne Shotwell said that SpaceX will conduct regular polar Starlink launches in the summer, but this shell is now the lowest priority, and is expected to be the last filled. All satellites that will be deployed into this orbit will have inter-satellite laser link communication. Shell three will have six orbital planes with 58 satellites in each plane.

Shell 4

The fourth 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. This shell is currently being filled alongside shell two.

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 five will also consist purely of satellites with laser communication links; however unlike shell four it will consist of four 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 complete half of Phase 1 and must fully complete Phase 1 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 its 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 still be able to successfully place the payload into orbit.

The Merlin engines are ignited by triethylaluminum and triethylboron, 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 4-4 is B1051, which had flown ten previous times. As Starlink Group 4-4 marked the booster’s 11th flight, it changed its designation to B1051-11. This marked the first eleventh flight of a booster, surpassing SpaceX’s goal to fly a Falcon 9 10 times.

B1051’s missionsLaunch Date (UTC)Turnaround Time (Days)
SpaceX Demonstration Mission-1March 2, 2019N/A
RADARSAT ConstellationJune 12, 2019102
Starlink V1.0 L3January 29, 2020231
Starlink V1.0 L6April 22, 202084
Starlink V1.0 L9August 7, 2020107
Starlink V1.0 L13October 18, 202072
SXM-7December 13, 202056
Starlink V1.0 L16January 20, 202138
Starlink V1.0 L21March 14, 202153
Starlink V1.0 L27May 9, 202156
Starlink Group 4-4December 18, 2021223

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

SpaceX, booster, landing
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 4-4, SpaceX attempted to recover both fairing halves from the water with their recovery vessel GO Quest.

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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