Continuing with their high launch cadence, SpaceX has successfully launched another Falcon 9, this time carrying 49 Starlink satellites to a 339-kilometer orbit, with a 53.22-degree inclination. The launch occurred at 1:13 PM EST (18:13 UTC) on Thursday, February 3, from the historic Launch Complex 39A at NASA’s Kennedy Space Center in Florida.
In addition to reusing a Falcon 9 first stage, both fairing halves were reused from previous missions. One half flew on its sixth mission, setting a new record for SpaceX.
The 45th Weather Squadron at Patrick Space Force Base forecasted an 80% chance of favorable weather for launch with a moderate risk of violating weather criteria in the booster recovery area. If the launch was scrubbed for any reason, a backup launch opportunity existed on Friday, February 4, with a 70% chance of acceptable weather forecasted. This window was not needed, as the launch went on time on Thursday.
This launch marks the sixth mission of the year for SpaceX, having already launched two Starlink missions, Transporter-3, CSG-2, and NROL-87.
As the Falcon 9 lifted off, it headed towards the southeast corridor from Cape Canaveral, hugging the coast of the Bahamas as it performed a dogleg maneuver to avoid flying over populated areas. This maneuver is the reason why SpaceX launched fewer satellites on this mission, compared to other launches from Florida, which launched 53 Starlink satellites.
Stationed 640 kilometers downrange from LC-39A is SpaceX’s newest ASDS (Autonomous Spaceport Drone Ship), ASOG (A Shortfall of Gravitas). Alongside ASOG was SpaceX’s multipurpose vessel named Doug. Named after one of the astronauts who flew on SpaceX’s Demonstration mission-2, Doug provides ASDS support for this mission and recovers fairings as they splash down on the Atlantic Ocean.
The Falcon 9 booster supporting this mission is B1061, which has launched to space six times. Its debut launch was SpaceX and NASA’s first operational commercial crew mission to the International Space Station: Crew-1. It went on to support the Crew-2 mission, the CRS-23 resupply mission to the ISS, the launch of a radio satellite for SiriusXM, and an X-ray space observatory — named IXPE — for NASA.
The record-breaking fairing half making its sixth flight on the Group 4-7 mission supported five previous Starlink missions. The other half, also being reused, previously flew on the Transporter-1 mission as well as two Starlink missions.
Starlink is SpaceX’s Internet Constellation in low Earth orbit that aims to provide satellite internet access coverage to most of Earth, primarily serving areas devoid of a fiber connection.
One of SpaceX’s two most capital-intensive projects, it has been under development for quite a while, with the first regulatory filings dating back to 2014.
Over the years, the plan underwent various changes, but in February 2018, SpaceX’s Tintin A and B satellites, which were experimental precursors to the operational Starlink satellites, were launched as secondary payloads from then Vandenberg Air Force Base.
The constellation consists of five groups of satellites, or “shells,” which will operate at different altitudes and orbital planes. This mission, named Starlink 4-7, launched satellites to the fourth shell. SpaceX is actively scheduling and launching to fill up the fourth shell of the mega-constellation, which when complete, will increase the capacity and reduce the latency for customers located between 52 degrees North and 52 degrees South latitude.
At T-38 minutes, the Launch Director gave a GO for propellant loading. At T-35 minutes, SpaceX began loading sub-cooled RP-1 onto both the first stage and the second stages as well as super-chilled LOX (Liquid Oxygen) onto the first stage.
SpaceX, unlike any other company in the industry, uses RP-1 which is cooled to -7 degrees Celsius and the LOX is cooled to -205 degrees Celsius. Using supercooled propellants increases the performance of Falcon 9 — something that is essential for reuse —since low temperatures increase the density of propellants.
Just before T-20 minutes, the second stage RP-1 load was completed, which was marked by a large vent from the T/E (Transporter Erector). This vent was followed by the purging of the T/E lines ahead of the start of LOX load to the second stage at T-16 minutes.
At T-7 minutes, the Falcon 9 allowed a small amount of liquid oxygen to enter the nine Merlin 1D engines on the first stage. This process cooled the engines slowly so they do not get damaged from the thermal shock when super chilled LOX starts to flow through them at full volume during engine ignition.
At T-1 minute, the Falcon 9 entered start up and began pressurizing its tanks for flight. At this point, Falcon 9’s onboard computers became fully in charge of its countdown, and all technical aborts from this point forward would have been handled autonomously and not by the ground operators.
At T-45 seconds, the Launch Director verified that all positions were go for launch. At T-3 seconds, the F9’s flight computer commanded the ignition of the 9 Merlin 1D engines on the first stage. The ignition happens in pairs within milliseconds of each other to reduce startup transients and loads on the vehicle.
Once the computers ensured all systems are nominal, they command the hydraulic clamps at the base of the vehicle to release, letting the Falcon 9 lift off from the pad.
B1061 burned for approximately two and a half minutes before shutting down — once again in a staggered formation to reduce loads on the vehicle.
The first stage separated from the second stage using pneumatic pushers, followed by ignition of the second stage’s single vacuum optimized Merlin engine seconds later.
After coasting up to its apogee and beginning its descent, B1061 performed two burns to softly touch down on A Shortfall of Gravitas, the Autonomous Spaceport Drone Ship.
The second stage, meanwhile, continued to burn toward orbit. At around three minutes after launch, the vehicle commanded the latches connecting the fairing halves to release.
The fairing halves then used their onboard RCS thrusters to reenter into the Earth’s atmosphere before softly landing on the water. They will then be recovered by SpaceX’s fairing recovery vessel, Doug.
About nine minutes after launch, the second stage shut down its Merlin Vacuum engine. From this point, the vehicle used its RCS thrusters to start rotating around its X-axis.
At T+15 minutes 31 seconds, the vehicle commanded the deployment of the tension rods used to keep the stack of Starlink satellites together, and the satellites slowly drifted away from the second stage.
Shortly after, the second stage performs a deorbit burn and destructively enters Earth’s atmosphere.
(Lead photo: Falcon 9 lifts off from LC-39A with the Starlink Group 4-7 mission. Credit: Stephen Marr for NSF)