SpaceX is ready to launch 51 Starlink internet communication satellites into low Earth orbit on its Starlink Group 2-9 mission. Lifting off on May 10, 2023, at 13:09 PDT (20:09 UTC) from Space Launch Complex 4 East (SLC-4E) at the Vandenberg Space Force Base in California, this mission will mark 2023’s 68th orbital launch attempt and SpaceX’s 31st (30th orbital) launch of the year, making up just under 45% of all launch attempts thus far this year.
To help reach SpaceX’s ambitious goal of launching 100 times in 2023, this launch will mark SLC-4E’s third-quickest turnaround time at 12.3 days. While this is substantially longer than Space Launch Complex 40 (SLC-40)’s fastest turnaround (just 5.15 days) and Launch Complex 39A (LC-39A)’s (at 8.96 days), it is clear that cadence is being increased from the west coast to support SpaceX’s busy launch cadence.
The reason why SLC-4E is slower to turn around launches than SpaceX’s other two operational pads is due to its use of SpaceX’s old transporter erector (T/E) design. At T-4 minutes, the T/E falls 13 degrees away from the rocket and does not move further from this position — remaining stationary during liftoff. This is drastically different from the “throwback” T/E style used at SLC-40 and LC-39A, which moves just under two degrees away from the vehicle at roughly T-4 minutes, then falls the remaining distance from the vehicle (~45 degrees) at liftoff. This allows for the T/E to be further out of the vehicle’s exhaust, resulting in less refurbishment needed between flights.
Despite trying to increase Falcon 9’s cadence drastically from the west coast, as apparent by SpaceX’s acquisition of Space Launch Complex 6, the company has no public plans to replace the T/E at SLC-4E.
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The Falcon 9 booster supporting Starlink Group 2-9 is B1075 — one of the newer boosters in the Falcon 9 fleet, having only supported Starlink Group 2-4 and the Space Development Agency’s Tranche 0 Flight 1 mission. Following the launch, the booster will attempt to land on the autonomous spaceport drone ship (ASDS) Of Course I Still Love You, which was tugged ~660 km downrange by Scorpius.
GO Beyond will provide both ASDS support and fairing recovery for this mission. It is thought that this ship is part of SpaceX’s west coast fleet consolidation, replacing both the current fairing recovery ship NRC Quest and ASDS support ship GO Quest.
The 51 Starlink v1.5 satellites atop the Falcon 9 will be placed into an initial 222 by 334 km orbit inclined 70.00 degrees. The satellites will spend the following months further raising their orbits into the second Starlink generation one shell: a 570 km circular orbit at 70 degrees.
Satellite Version
Orbit
(Circular)
Sats Launched
Total in Orbit
Total Working
Operational
Group 1
1.0
550 km 53°
1,665
1,494
1,460
1,426
Group 2
1.5
570 km 70°
305
302
301
101
Group 3
1.5
560 km 97.6°
243
233
233
187
Group 4
1.5
540 km 53.2°
1,637
1,570
1,568
1,513
Group 5
1.5
530 km 43°
386
384
383
200
Group 6
2.0 Mini
530 km 43°
42
40
40
0
(Starlink information from Jonathan McDowell)
Falcon 9’s launch countdown sequence will start at T-38 minutes where the launch director will verify that all systems are go for propellant load. When given the go, both the first stage and second stage will begin being fueled with rocket propellant-1 at T-35 minutes. Also at this time, the first stage will begin being filled with liquid oxygen (LOX).
At T-20 minutes, fueling on the second stage will complete, and the T/E will begin purging its lines, ensuring the lines are not contaminated and are thermally ready for LOX flow, which starts at T-16 minutes. This purging is what causes the iconic Falcon 9 T-20 minute vent.
One minute before launch, the Falcon 9 will enter start-up, which is when the vehicle takes command of the count. At T-3 seconds the booster’s flight computer will command all nine Merlin 1D engines to ignite, which will then be checked by the on-board flight computer. If the flight computer detects no off-nominal systems, it will command the hydraulic launch clamps to be released, allowing Falcon 9 to lift off.
December’s Falcon 9 launch with the first pair of O3b mPOWER satellites. (Credit: Stephen Marr for NSF)
B1075-3 will burn for two minutes and 26 seconds before shutting down and separating from the second stage. Stage two will burn until T+8:40; meanwhile, the booster will complete its entry and landing burns. If all goes to plan, B1075 will land atop OCISLY, becoming B1075-4 and marking SpaceX’s 190th successful landing to date. During this time, the two fairing halves will be deployed at T+2:41, which will then utilize cold gas thrusters and parafoils to softly land in water for recovery.
The second stage will then coast for approximately 10 minutes, during which the stage will start to rotate end-over-end. The four tension rods will then be deployed at T+17:21, allowing all 51 Starlink satellites to deploy at once.
This launch is SpaceX’s first Starlink launch of the week, with Starlink Group 5-9 scheduled to lift off later in the week. Later this month, SpaceX is scheduled to launch the Axiom Mission 2, Arabsat 7B, Iridium-9 and OneWeb flight 19, and several more Starlink missions.
(Lead image: B1075 on SLC-4E ahead of the Tranche 0 Flight 1 mission. Credit: Jack Beyer for NSF)
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