Starlink Group 6-20 | Falcon 9 Block 5

Lift Off Time
August 08, 2023 – 03:57 UTC
August 07, 2023 – 20:57 PDT
Mission Name
Starlink Group 6-20; a launch of v2 Mini Starlink satellites
Launch Provider
(What rocket company launched it?)
SpaceX
Customer
(Who paid for this?)
SpaceX
Rocket
Falcon 9 Block 5, B1075-5; 46.86-day turnaround
Launch Location
Space Launch Complex 4 East (SLC-4E), Vandenberg Space Force Base, California, USA
Payload mass
~12,000 kg (~26,500 lb) (15 x ~800 kg, plus dispenser) (estimated)
Where did the satellites go?
530 km circular low-Earth orbit (LEO) at 43°; initial orbit 285 x 315 km at 43.00º
Did they attempt to recover the first stage?
Yes
Where did the first stage land?
~660 km downrange on Of Course I Still Love You

Tug: Scorpius; Support: GO Beyond
Did they attempt to recover the fairings?
The fairing halves were recovered from the water ~660 km downrange by GO Beyond
Were these fairings new?
No, both fairing halves flew for their 6th time
This was the:
– 245th Falcon 9 launch
– 178th Falcon 9 flight with a flight-proven booster
– 186th re-flight of a booster
– 52nd re-flight of a booster in 2023
– 215th booster landing
– 141st consecutive landing (a record)
– 55th launch for SpaceX in 2023
– 48th SpaceX launch from 
SLC-4E
– 120th orbital launch attempt of 2023
Where to watch
Official Replay

How Did It Go?

SpaceX’s Starlink Group 6-20 mission successfully launched 15 Starlink v2 satellites atop a Falcon 9 rocket. The Falcon 9 lifted off from Space Launch Complex 4 East (SLC-4E), at the Vandenberg Space Force Base, in California, United States. Starlink Group 6-20 marked the 96th operational Starlink mission, boosting the total number of Starlink satellites launched to 4,918, of which 4,577 are still in orbit around the Earth.

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

Starlink is currently available in certain regions, allowing anyone in approved regions to order or preorder. After 28 launches SpaceX achieved near-global coverage, but version 1 of the constellation will not be complete until all five shells are filled. Once Starlink generations 1 and 2 are 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 307 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 v1.0 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 four 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.

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.

SpaceX’s Starlink v2 satellites are larger, more powerful satellites meant to be launched on SpaceX’s Starship launch vehicle. While little is known about these satellites thus far, it is known that they mass roughly 1,200 kg and feature a twin-solar array design, to increase power delivered to the satellite. On top of this, according to SpaceX CEO and CTO Elon Musk, the satellites will have an order of magnitude more bandwidth, higher speeds, and be roughly 10x better in every way.

In the future, Starlink v2 satellites will act as cell towers, providing worldwide cell phone coverage to T-Mobile customers. Musk has stated that each of these satellites will have roughly 2-4 Mb/s of bandwidth per cell phone zone, which will allow for tens of thousands of SMS text messages per second or many users placing phone calls. While this technology is primarily meant for contacting emergency services worldwide (similar to Apple’s connect to satellite feature on the iPhone 14 series), it will also be able to be used for sending non-emergency-related messages.

Due to delays in the Starship launch vehicle, SpaceX is preparing (and has filed for permission) to launch Starlink v2 “Mini” satellites that will launch on the Falcon 9 rocket. These satellites have a more powerful phased array antenna and utilize the E-band for backhaul. This allows each satellite to provide 4x more capacity than Starlink v1.0 and v1.5.

The Starlink v2 Mini satellites are equipped with a new argon Hall thruster for on-orbit maneuvering. These generate 2.4 times as much thrust as the thrusters on v1.5 satellites and have 1.5 times the specific impulse. Starlink v2 Mini satellites will be the first satellites to use an argon thruster on-orbit.

Starlink v2 Mini satellites
21 Starlink v2 Mini satellites prepared for encapsulation in Falcon 9’s fairing (Credit: SpaceX)be

A satellite constellation is a group of satellites that work in conjunction for a common purpose. SpaceX’s Starlink constellation consists of two generations: the first (which is largely complete) is filled with Starlink v1/1.5 satellites and the second is to be filled with Starlink v2 and v2 Mini satellites.

Starlink generation one consists of five orbital shells and has a total of 4,408 satellite slots. These satellites will entirely be launched on Falcon 9, and it is expected for these launches to finish in 2023.

Generation two consists of 29,988 satellites–this is roughly 20 times more satellites than were ever launched before the start of Starlink in 2019. These satellites will primarily be launched by Starship; however, as previously mentioned, Falcon 9 will launch some of these satellites while Starship is not operational.

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.

Inclination (°)Orbital Altitude (km)Number of Satellites
Shell 153.05501,584
Shell 270.0570720
Shell 397.6560348
Shell 453.25401,584
Shell 597.6560172
Generation 1 Orbital Shells

Shell 1

The first orbital shell of Starlink satellites consists of 1,584 satellites in a 53.0° 550 km low-Earth orbit. Shell 1 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 replaced.

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 cover around 94% of the globe. SpaceX will put 20 satellites in each of the 36 planes in the third shell. This shell is currently being filled, along with Shell 4.

Shell 3

Shell 3 will consist of 348 satellites in a 97.6° 560 km orbit. SpaceX deployed 10 laser link test satellites into this orbit on its 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 3 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 2.

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 3, it will consist of four orbital planes with 43 satellites in each plane.

However, it is unclear if this shell will still be filled; previous Group 5 launches have gone to a 43° orbit.

The Starlink gen 2 constellation consists of nine orbital shells. It is currently unclear how these shells will be named.

Inclination (°)Altitude (km)Orbital PlanesSatellites per PlaneNumber Of Satellites
53.0340481105,280
46.0345481105,280
38.0350481105,280
96.9360301203,600
53.0525281203,360
43.0530281203,360
33.0535281203,360
148.06041212144
115.76141818324
Generation 2 Orbital Shells

SpaceX has until March of 2024 to complete half of Generation 1 and must fully complete Generation 1 by March of 2027. In the highly unlikely case that SpaceX fails this goal, 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 nine 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 the flight, and be able to successfully place the payload into orbit.

The Merlin engines are ignited by triethylaluminum and triethylborane (TEA-TEB), which instantly burst into flames when mixed in the presence of oxygen. 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.

SpaceX is currently flying two different versions of the MVacD engine’s nozzle. The standard nozzle design is used on high-performance missions. The other nozzle is a significantly shorter version of the standard, decreasing both performance and material usage; with this nozzle, the MVacD engine produces 10% less thrust in space. This nozzle is only used on lower-performance missions, as it decreases the amount of material needed by 75%. This means that SpaceX can launch over three times as many missions with the same amount of Niobium as with the longer design.

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 composite-overwrapped pressure vessels (COPVs) for pressurization control, and additional TEA-TEB.

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

Falcon 9 Booster

The booster that supported the Starlink Group 6-20 mission was B1075-5; as the name implies, the booster had supported four previous flights. Upon successful landing, its designation changed to B1075-6.

B1075’s previous missionsLaunch Date (UTC)Turnaround Time (Days)
Starlink Group 2-4January 19, 2023, 15:43N/A
Transport & Tracking Layers 0-1April 2, 2023 14:2972.95
Starlink Group 2-9May 10, 2023 20:0938.24
Starlink Group 5-7June 2, 2023 07:1942.47
Starlink Group 6-20August 8, 2023 03:5746.86

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

falcon 9 booster, landing, drone ship
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, however, at the end of 2020 this program was canceled due to safety risks and a low success rate. On Starlink Group 6-20, SpaceX attempted to recover the fairing halves from the water with its recovery vessel GO Beyond.

In 2021, SpaceX started flying a new version 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 are 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

Starlink Group 6-20 Launch, Landing, And Deployment

All Times Approximate

HR/MIN/SECEVENT
00:01:12Max Q (Moment of peak mechanical stress on the rocket)
00:02:251st stage main engine cutoff (MECO)
00:02:291st and 2nd stages separate
00:02:342nd stage engine starts (SES-1)
00:02:40Fairing deployment
00:07:361st stage entry burn begins
00:08:001st stage entry burn ends
00:08:432nd stage engine cutoff (SECO-1)
00:09:091st stage landing burn begins
00:09:331st stage landing
00:14:36Starlink satellites deploy

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