SpaceX launched another batch of 56 Starlink internet communication satellites into low Earth orbit (LEO) on Sunday, May 14, at 01:03 EDT (05:03 UTC). Launching from Space Launch Complex 40 (SLC-40) at the Cape Canaveral Space Force Station, in Florida, the Starlink Group 5-9 mission marks SpaceX’s fourth launch in May.
Starlink Group 5-9 was 2023’s 69th orbital launch attempt; with four missions failing to reach orbit, SpaceX currently makes up just under 50% of all successful orbital launches this year.
On May 11 the Space Launch Delta 45’s weather squadron released a launch mission execution forecast for this mission, giving the weather a 95% chance of supporting the launch. The only concern was the cumulus cloud rule, which stated that a launch cannot happen within 18.5 km of cumulus clouds with tops that extend into freezing temperatures.
The weather proved to be no issue for this opening attempt.
The booster supporting this mission was B1067-11, which has previously supported CRS-22, Crew-3, Turksat-5B, Crew-4, CRS-25, Hotbird-13G, O3b mPOWER 1&2, and three Starlink missions. After stage separation, B1067 landed atop Just Read the Instructions (JRTI), stationed ~660 km downrange in the Atlantic Ocean.
The autonomous spaceport drone ship was tugged downrange by Crosby Skipper. SpaceX’s multi-purpose recovery vessel Bob will be providing support to the drone ship and will recover the fairings from the water.
Overall, this mission marked SpaceX’s 125th from SLC-40 (including Amos-6’s failure), 223rd Falcon 9 launch, 165th reflight of a booster, 191st booster landing, and 117th consecutive booster landing. The last booster landing failure was on Starlink v1.0 L19 on Feb. 16, 2021, when a hole in the engine boot led to engine shutdown during descent, leading to the booster crashing in the Atlantic Ocean.
Atop the Falcon 9 in its payload fairing was 56 Starlink v1.5 communication satellites. These satellites were placed into an initial LEO of 298 by 340 km at 43.00 degrees. The satellites will then spend the coming months raising this orbit into a Starlink generation two shell: a 530 km circular shell inclined at 43 degrees.
The familiar launch sequence of the Falcon 9 started at T-38 minutes when the launch director verified that teams were go for propellant load. Three minutes later, both stages began being fueled with chilled RP-1 (a refined form of kerosine) and the first stage began being filled with super-chilled liquid oxygen (LOX).
Departure! Just Read the Instructions droneship is outbound to support the Starlink 5-9 mission. Tug Crosby Skipper is towing.
— Gav Cornwell (@SpaceOffshore) May 10, 2023
Fueling on the second stage wrapped up at T-20 minutes when SpaceX purged the lines of the transporter erector to prepare for second stage LOX filling. This started at T-16 minutes.
At T-7 minutes, the first stage flowed a small amount of LOX through the turbo pump of the Merlin 1D engines to cool it down ahead of full propellant flow at engine ignition. Doing so ensures that once full propellant flow starts at engine ignition, the propellants will not boil instantly, creating a gas bubble that can damage the engine’s turbines; in extreme cases, this can result in an engine exploding.
At T-1 minute, the vehicle entered startup. At this time, control of the countdown was handed over to the vehicle. Humans are able to call aborts up until T-10 seconds, after which all aborts must be handled by the vehicle itself.
Three seconds before liftoff, the vehicle commanded ignition of all nine M1D engines. By T-0.2 seconds the engines were at full power, and the vehicle checked the health of all the engines. With all engines and the vehicle nominal, the hydraulic launch clamps released, letting the vehicle lift off.
The first stage burned for two minutes and 28 seconds before shutting down and separating from the second stage. At this point, the first stage performed its entry and landing burns, landing on JRTI. Shortly after stage separation, the payload fairings were deployed from the Falcon 9 second stage, which using cold gas thrusters and parachutes to softly splash down in the Atlantic Ocean for recovery.
Fairing reentry on the ViaSat-3 mission was the hottest and fastest we've ever attempted. The fairings re-entered the atmosphere greater than 15x the speed of sound, creating a large trail of plasma in its wake pic.twitter.com/VgdlH6r3yR
— SpaceX (@SpaceX) May 2, 2023
For this mission, stage two burns for just under six minutes before cutting off at T+8:36. At this point the stage coasts for ~45 minutes, before igniting again for less than two seconds. After the second engine cutoff, the stage begins to rotate end-over-end before deploying the four tension rods at T+1:04:53.
The second stage coasted for a while longer, before igniting for a deorbit burn, causing the stage to reenter just south of Cape Town, in South Africa.
SpaceX has a number of other launches planned for the rest of this month, including Starlink Group 6-3, Iridium-9 & OneWeb flight 19, Axiom Mission 2, and Arabsat 7B next week. The week after that, SpaceX is expected to conduct several more Starlink flights.
(Lead image: B1069 on SLC-40 ahead of the Hotbird-13F mission. Credit: Thomas Burghardt for NSF)