SpaceX to attempt 150th Falcon recovery on Starlink Group 3-4

SpaceX is set to launch another batch of Starlink satellites into orbit on their Starlink Group 3-4 mission. Launching from Space Launch Complex 4 East (SLC-4E) at the Vandenberg Space Force Base in California, the Falcon 9 Block 5 is scheduled to lift off at 10:40 PM PDT on Tuesday, August 30 (05:40 UTC on Wednesday, August 31). This mission will mark SpaceX’s 39th mission of 2022–a mission every 6.13 days.

Starlink Group 3-4 is expected to mark the 110th orbital launch of 2022, making SpaceX account for over a third of all orbital launches this year. Overall, this will be Falcon 9’s 174th mission (173rd launch) and 111th launch with a flight-proven booster.

The Starlink Group 3-4 mission will utilize SpaceX’s booster B1063-7. The -7 signifies that this is the seventh flight of this specific booster, having previously supported Sentinel-6A, the Double Asteroid Redirection Test (DART), and four Starlink missions. The booster last supported the Starlink Group 3-1 mission, which flew just 51 days ago.

Following stage separation the booster will attempt a landing 640 km downrange on SpaceX’s Autonomous Spaceport Drone Ship (ASDS) Of Course I Still Love You (OCISLY). This will be SpaceX’s 150th Falcon recovery attempt and, if successful, will mark SpaceX’s 65th consecutive landing (a record) and 139th booster landing.

Inside Falcon 9’s 5.2-meter diameter payload fairing will be 46 Starlink v1.5 satellites. These satellites will be into a 321 x 307 km low-Earth polar orbit at 97.66º. The satellites will then spend months raising their orbit to the operational 560 km circular orbit at 97.6º, also known as Starlink shell 3.

This shell consists of six orbital planes with 58 satellites in each plane, for a total of 348 satellites. Because of the small size of this shell, it is expected that it will be filled in as many as 10 Falcon 9 launches, and could be completed by the end of 2022.

The Starlink v1.5 satellites have a compact flat-panel design, allowing for SpaceX to launch many at once. Each satellite has a mass of ~305 kg and is equipped with an inter-satellite laser communication system, allowing for the satellites to communicate directly with one another, rather than going through ground stations. This is required for the satellites in the polar shells due to the inability to build ground stations in those regions. The also allows for Starlink Maritime — which is essentially Starlink for boats.

On August 25, 2022, SpaceX CEO Elon Musk and T-Mobile CEO Mike Sievert announced that the next generation Starlink satellites (called Starlink v2, and will launch on SpaceX’s Starship launch vehicle) will be able to act as cell towers and communicate directly with most modern cellular devices.

Musk noted that each satellite will have 2-4 megabits per second of throughput per region, allowing each satellite to handle 1,000-2,000 calls at any one time, or send millions of SMS text messages per second. While this will not enable global data connection on phones, it will allow communication with emergency services and family members from anywhere in the world.

During this same press conference, Musk also noted that due to delays in the Starship program, SpaceX is looking into making “mini Starlink v2” satellites that would launch on the Falcon 9. It is unknown if the aforementioned cell phone connectivity would also be on the mini version of these satellites, but it is unlikely due to the large antennas needed for a satellite to “hear” the low-power signals from cell phones.

Starlink V1 satellites inside a Falcon 9 fairing. (Credit: SpaceX)

Falcon 9’s launch sequence will start at T-38 minutes when the launch director will verify that teams are GO for propellant loading. Three minutes later, both stages will begin to be filled with chilled RP-1 (a refined form of kerosene) and the first stage will begin being filled with super chilled Liquid Oxygen (LOX).

Fueling on the second stage will be wrapped up at T-20 minutes when SpaceX will then purge the Transporter / Erector (T/E) lines to prepare for second stage LOX filling. This will start at T-16 minutes.

At T- seven minutes, the first stage will flow a small amount of LOx through the turbo pump of the Merlin 1D engines to cool it ahead of full propellant flow at engine ignition.

At T- one minute, the vehicle will enter “startup,” which means that the automated launch sequence is handed over from the ground computers to the vehicle’s onboard computer.

Three seconds before liftoff, the vehicle will command ignition of all nine Merlin 1D engines at the base of the first stage. By T-0.2 seconds the engines will be at full power, and the vehicle will check the health of all the engines. If all engines and the vehicle are nominal, it will command the hydraulic launch clamps to release, allowing the vehicle to lift off from the pad.

The first stage will burn for approximately two and a half minutes before separating from the second stage. At this point, the first stage will perform two burns to attempt to land on OCISLY (the entry burn and landing burn). Shortly after stage separation, the fairings will be departing from the Falcon 9 second stage. The fairings will later be recovered downrange by SpaceX’s West coast recovery ship NRC Quest after re-entering Earth’s atmosphere.

Stage two will burn for just under six minutes before cutting off. At this point, the stage will coast for ~45 minutes, before igniting again for less than two seconds. After engine cutoff, the stage will begin to rotate end-over-end.

At T+ one hour, two minutes, and 57 seconds, the tension rods will deploy from the Starlink stack. Due to the stage’s, the satellites will slowly rotate away from the vehicle and spread out. The satellites will spend the following hours deploying their solar arrays and communication dishes.

This will be SpaceX’s final launch in August; However, SpaceX has several launches scheduled for September, including Starlink Group 4-20 (which will also carry the Sherpa-LTC2 spacecraft), Starlink Group 4-2 (which will carry BlueWalker 3), and Transport and Tracking Layer (TTL).

(Lead image: Falcon 9 on the pad at SLC-4E at Vandenberg SFB. Credit: Pauline Acalin for NSF)

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