From SpaceX Webcast of the Starlink Grp 5-7 launch. No sleeping in Vandenberg and Hawthorne
Mission: SpaceX Falcon 9 - Starlink Group 5-7
Written: June 22, 2023
Just keep turning southeast
SpaceX’s Starlink Group 5-7 mission successfully launched 47 Starlink satellites atop a Falcon 9 rocket. B1075-4 lifted off from Space Launch Complex 4E (SLC-4E) on Thursday, June 22, 2023 at 00:19:00 PDT from the Vandenberg Space Force Base, California.
Starlink Group 5-7 marked the 85th operational Starlink mission and is thought to be a test mission for the evolution of this constellation’s spacecraft: Starlink gen 2.
Because of this, and despite the name, the satellites were not put into the previously filled Starlink Shell 5 — a polar low-Earth circular orbit at 560 km. Instead, the satellites were inserted into a 43-degree orbit at 530 km.
As mentioned, Starlink Group 5-7 is testing new hardware, involving technologies from SpaceX’s recently acquired internet of things (IoT) company SWARM. It is unknown how these technologies are being tested. In addition to this, the Starlink v1.5 satellites are thought to have been altered with equipment from v2 satellites, no details are known.
These test satellites will pave the way for SpaceX to begin proper Starlink V2 launches, which are scheduled to start in early 2023 on Starlink Group 6-1. Until SpaceX’s Starship launch vehicle is operational, these missions will utilize the Starlink v2 mini satellites.
Starlink Group 5-7 boosted the total number of Starlink satellites launched to 4,642, of which ~4,312 were still in orbit around Earth once launched. Starlink Group 5-7 marked the tenth launch of Group 5 satellites.
The fifth shell of phase 1 of Starlink was supposed to host 172 satellites in another 97.6° inclination in a 560 km low-Earth polar orbit. Shell 5 will consist of four orbital planes with 43 satellites in each plane. This shell doesn't host any regular Starlink V1.5 satellites.
This fifth shell of the now identified phase 2 has now received 542 enhanced Starlink v1.5 satellites in a 43.0° inclination in a 530 km low-Earth orbit.
NGA Falcon 9 flies southeast and performs a 10o dogleg maneuver bending across Baja California
The booster launched is B1075-4. It landed on the drone ship Of Course I Still Love You, some 660 km southeast of SLC-4E, roughly eight and half minutes after liftoff.
After boosting the second stage along with its payload towards orbit, the first stage will freefall in a parabolic curve before it performs a 26 second re-entry burn meant to slow the vehicle down before the atmospheric reentry. The booster will then perform a 21 second landing burn and softly land aboard SpaceX’s autonomous spaceport drone ship.
B1075-4 will have made its fourth flight after launching its next mission:
B1075-4 didn’t perform a static fire test the day before after refurbishment while waiting for its east coast launch out of Cape Canaveral. SpaceX has since Starlink L08 omitted this safety precaution many times so far. It isn’t required to perform a static fire test on inhouse missions like Starlink as to save time.
SpaceX will also recover both fairing halves in the Pacific Ocean with the newest recovery vessel GO Beyond stationed in Long Beach harbor.
The Starlink Grp. 5-7 Payload
In August 2021, SpaceX presented plans to the Federal Communications Commission (FCC) to either use Falcon 9 or Starship to deploy satellites into Starlink Gen 2. But then, in January 2022, the company announced they would use only Starship as they thought it was going to be ready for launches as soon as March of this year.
However, technical delays in readying Starship for its first orbital flight meant that the company had to revisit its plans and in August 2022 it announced to the FCC that they would now launch into Starlink Gen 2 using both Starship and Falcon 9.
The document detailed that “while SpaceX will use technically identical satellites on both rockets, the physical structures will be tailored to meet the physical dimensions of the rockets on which they will be launched.”
This indicated that SpaceX intended to use downsized satellites that would be able to fit inside Falcon 9’s payload fairing. It was then confirmed by Elon Musk during an event with T-Mobile later that month.
The CEO of the company referred to these as Starlink v2 “Mini” but unlike the document, where it doesn’t specify any conditions to launching Starlink v2 satellites on Falcon 9, he said this would only be in the event Starship were to be delayed even further.
Indications that this launch in particular was related to Starlink Gen 2 came in late October 2022 when SpaceX filed a permit with the FCC requesting authorization to communicate with the Falcon 9 rocket during launch and landing for this mission.
These permits normally include the landing location of the Falcon 9 booster, whether it is a drone ship or otherwise.
The landing coordinates on the permits for this and subsequent Group 5 missions indicated not only that they intended to use a southeast launch trajectory again just like they did earlier this year, but also that the Group 5 launches wouldn’t be to polar orbit as previously thought.
Starlink’s Gen 1 constellation consists of five orbital shells at four different inclinations. The initial Gen 1 launch campaign to fill the 53.2-degree shell used mission numbers of the form LNN, up to the L28 launch in May of 2021.
In September 2021, SpaceX started using the Group X-Y designation for their Starlink missions. It was understood at that time that the first number, X, would be the shell to which the satellites are being deployed while the second one, Y, indicated the mission number (but not necessarily the order of launch). So far SpaceX has launched missions to three of those shells using “Group X-Y” mission designations.
It was easy then to think that Group 5 launches would be going into the remaining orbital shell which is one with Sun-synchronous orbits – a type of polar orbit.
However, based on the landing coordinates on the FCC permits, it was clear that the Group 5 missions wouldn’t be going into that orbital shell and therefore it had to be related to something new. In particular, these landing coordinates indicated that Group 5 launches were going into a mid-inclination orbit.
The number of satellites flying on Starlink Group 5-7 suggests this mission is flying the F9 satellite configuration which would allow them to use hardware and processes similar to launching Starlink v1.5 satellites under the Gen 1 constellation.
SpaceX has already applied for more Group 5 launches in the next couple of months and sources indicate they’ll start launching Group 6 missions as early as February, also headed to Starlink’s Gen 2 constellation.
The Falcon 9 Launch
The Falcon 9 countdown for Sunday’s launch followed the 35-minute-long automated propellant load sequence. At T-3 seconds the engine controller sent the ignition command to all nine Merlin 1D engines on the first stage ramped up to full power in 2.8 seconds.
The rocket was then released at T0 by the launch clamps and began its climb into orbit. The first stage for this mission, B1075, flew for the 4th time.
The booster fired its engines for the two-and-a-half minute ascent into near space, after which B1075-4 shut down its engines and separated from the second stage. After separation, it made a landing on SpaceX’s Autonomous Spaceport Drone OCISLY which was located 624 km downrange a little west of Baja California.
For this mission, the Falcon 9 launch trajectory went southeast and performed a dogleg maneuver around Baja California. SpaceX used this launch trajectory to avoid flying over populated areas in Mexico before reaching orbital velocity.
After stage separation, the second stage ignited its single Merlin 1D Vacuum (MVacD) engine for approximately six minutes to inject the satellites into LEO.
The fairing halves separated shortly after MVacD ignition and performed a parachute assisted splashdown in the Pacific Ocean. They will be retrieved from the water by SpaceX’s multi-purpose recovery vessel Go Beyond.
The target insertion orbit for this mission was 229 by 339 km at 43 degrees inclination. The second stage used a single burn of its MVacD engine to put the satellites into the target orbit. Deployment occurred at around the T+19 minute mark.
Less than one hour after deployment the second stage performs another burn to deorbit itself in order to safely burn up in the north Pacific Ocean.
This mission launched 47 Starlink satellites for the 530 km altitude, 43-degree inclination shell of Starlink’s Gen 2 constellation. This is the tenth time SpaceX launched a payload to this new constellation using the Falcon 9 rocket.
The Falcon 9 rocket
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 17x34 feet 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 tests and the actual launch the TEA-TEB is provided by the ground service equipment.
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 ignitions - burns, allowing the Falcon 9 to put payloads in several different orbits.
A second type of the MVacD engine with a shorter engine nozzle has been introduced; this MVacD engine only produces 893 kN of thrust and an ISP of 348 seconds. The shorter bell reduces the expensive alloy used to make the engine nozzle by 75%. The fifth launch of this type is expected to be performed with the Starlink Group 5-7 mission.
For missions with many burns and/or long coasts between burns, the second stage is able to be equipped with a mission extension package. This package consists of a gray paint strip, which helps keep the RP-1 tank warm, and extra composite overwrapped pressure vessels (COPVs) for pressurization control, and additional TEA-TEB.
Comparison of Type 1 and 2 with measurements based on pixels - Type 2 are 5-6 inches thicker
SpaceX is the first entity ever that recovers and reflies its fairings. After being jettisoned, the two fairing halves will use cold gas thrusters to orientate themselves as they descend through the atmosphere. Once at a lower altitude, they will deploy drogue chutes and parafoils to help them glide down to a soft landing for recovery.
There are three known types of 34 x 17 foot fairings used by SpaceX to protect payload during ascent through the atmosphere. The first type had 10 evenly spaced ventilation ports in a circle on the bottom part of the fairings. This type was not aerodynamic enough to carry a parachute and ACS - Attitude Control System.
The aerodynamic balance during descent must have made them prone to stalling, or they burned up too easily. ACS gas tanks, flight orientation computers and ACS thrusters must have helped with these problems during development of type 2 fairings.
The second type is a slightly thicker fairing with only 8 evenly spaced ventilation ports in a circle on the bottom part of the fairings. The ventilation ports release the pressurized Nitrox gas during ascent, but let seawater in which makes it harder to refurbish the fairings after recovery from the ocean.
The new third type has 8 ventilation ports in pair’s near the edge of the fairings. Some old type 2 fairings have been rebuilt and reused in Starlink launches. That have been a test program to develop the type 3 fairings to prevent saltwater from the ocean from flooding and sinking the fairing, and makes refurbishment toward the next flight easier.
Falcon fairings halfs have been recovered and reused more than 100 times since 2019. Improved design changes and overall refurbishment procedures have decreased the effects of water landings and led to an increased recovery rate of fairings.
Lately it’s apparent that the fairings are actively being aiming for the droneship in order to speed up the recovery process and cut corners of the time table. The fairing is actively breaking its speed and turning back before deploying its parachute at the last moment.
Another solution is a ‘vertical’ boost lifting the fairings apogee so the ballistic trajectory is changed aiming for a landing nearer the droneship. It’s equivalent to raising the angle on a water hose giving the water stream an higher arc but giving it a shorter reach.
It’s not clear whether or not the cold gas nitrogen thrusters alone are capable of doing a ‘boost back’ or a ‘push up’ so the fairings can alter their forward momentum mid-flight.
The fairings are a used pair both on its - third - flight with no known joint mission. Both fairings are expected to survive the landing. Active fairings are equipped with four pushrods to separate the two fairing halfs.
