Featured image credit: SpaceX
Lift Off Time
|February 17, 2023 – 19:12 UTC | 11:12 PST|
|Starlink Group 2-5; the 4th launch to Starlink Shell 2|
|Falcon 9 Block 5, B1063-9; 112.75-day turnaround|
|Space Launch Complex 4 East (SLC-4E), Vandenberg Space Force Base, California, USA; |
17 days, 02 hours, 57 minutes turnaround
|~15,600 kg (~34,300 lb) (51 x ~307 kg, plus dispenser)|
Where did the satellites go?
|Starlink Shell 2; 570 km circular 70° low-Earth Orbit (LEO), initial orbit 222 x 330 km orbit at 70.00º|
Did they attempt to recover the first stage?
Where did the first stage land?
|~664 km downrange on Of Course I Still Love You|
Tug: Scorpius; Support: GO Quest
Did they attempt to recover the fairings?
|The fairing halves were recovered from the water ~664 km downrange by NRC Quest|
Were these fairings new?
|No, both fairing halves were flight proven|
This was the:
|– 204th Falcon 9 launch|
– 139th Falcon 9 flight with a flight-proven booster
– 145th re-flight of a booster
– 11th re-flight of a booster in 2023
– 172nd booster landing
– 98th consecutive landing (a record)
– 11th launch for SpaceX in 2023
– 35th SpaceX launch from SLC-4E
– 23rd orbital launch attempt of 2023
Where to watch
How Did It Go?
SpaceX’s Starlink Group 2-5 mission successfully launched 51 Starlink 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 2-5 marked the 72nd operational Starlink mission, boosting the total number of Starlink satellites launched to 3,981, of which ~3,684 are still in orbit around the Earth. Starlink Group 2-5 marked the fourth launch to the second Starlink shell.
What Is Starlink?
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 one 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.
What Is The Starlink Satellite?
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 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.
Starlink v2 and v2 Mini
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. The specs of these satellites are currently unknown.
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.
What Is The Starlink Satellite Constellation?
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.
Starlink Phase 1 Orbital Shells:
|Inclination (°)||Orbital Altitude (km)||Number of Satellites|
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.
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 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.
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.
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 is still going to be filled; previous group 5 launches have gone to a 43° orbit.
Starlink Generation 2 Orbital Shells:
The Starlink Gen 2 constellation consists of nine orbital shells. It is currently unclear how these shells will be named.
|Inclination (°)||Altitude (km)||Orbital Planes||Satellites per Plane||Number Of Satellites|
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.
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 triethylaluminum and triethylborane (TEA-TEB), which instantaneously 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.
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 composite-overwrapped pressure vessels (COPVs) for pressurization control, and additional TEA-TEB.
Falcon 9 Booster
The booster that supported the Starlink Group 2-5 mission was B1063-9; as the name implies, the booster had supported eight previous flights. Upon successful landing, its designation changed to B1063-10.
|B1063’s missions||Launch Date (UTC)||Turnaround Time (Days)|
|Sentinel-6||November 21, 2020 17:17||N/A|
|Starlink V1.0 L28||May 26, 2021 18:59||186.07|
|DART||November 24, 2021 06:21||181.47|
|Starlink Group 4-11||February 25, 2022 17:12||62.45|
|Starlink Group 4-13||May 13, 2022 22:07||108.20|
|Starlink Group 3-1||July 11, 2022 01:39||58.15|
|Starlink Group 3-4||August 31, 2022 05:40||51.17|
|Starlink Group 4-31||October 28, 2022 01:14||57.82|
|Starlink Group 2-5||February 17, 2023 19:12||112.75|
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 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 2-5, SpaceX attempted to recover the fairing halves from the water with their recovery vessel NRC Quest.
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.
Starlink Group 2-5 Countdown
All times are approximate
|00:38:00||SpaceX Launch Director verifies go for propellant load|
|00:35:00||RP-1 (rocket grade kerosene) loading underway|
|00:35:00||1st stage LOX (liquid oxygen) loading underway|
|00:16:00||2nd stage LOX loading underway|
|00:07:00||Falcon 9 begins engine chill prior to launch|
|00:01:00||Command flight computer to begin final prelaunch checks|
|00:01:00||Propellant tank pressurization to flight pressure begins|
|00:00:45||SpaceX Launch Director verifies go for launch|
|00:00:03||Engine controller commands engine ignition sequence to start|
|00:00:00||Falcon 9 liftoff|