Screenshot from SpaceX Webcast of the 03b mPower 3 & 4 launch
Mission Rundown: SpaceX F9 - 03b mPower 3 & 4
Written: April 28, 2023
It’s twin satellites again
SpaceX has launched the first of a pair of Falcon 9 missions approximately 4 hours apart from the company’s two Florida launch pads.
The first mission carried the first two satellites for a new constellation known as O3b mPOWER to orbit on Friday, April 28, with liftoff coming 60-minute into the launch window at 18:12 EDT (22:12 UTC) from Space Launch Complex 40 (SCL-40) at the Cape Canaveral Space Force Station (CCSFS).
It landed on the drone ship Just Read The Instruction, 688 km due east of the launch site, roughly eight and half minutes after liftoff.
Notam: JRTI is waiting on the Atlantic Ocean downrange. Fairing landing site was undisclosed
Both fairing recovery ships, Bob and Doug, were called on to support the double mission and recover the payload fairing halves which protect the payloads during ascent through Earth’s atmosphere. They also supported one of the two droneships.
Bob supported O3b mPOWER’s fairing retrieval with JRTI while Doug supported Falcon Heavy 6 with retrieval of the fairings.
B1078-2 will have made its second flight after launching its next mission:
B1078-2 didn’t perform a static fire test after refurbishment while waiting for an east coast launch out of Cape Canaveral. SpaceX has 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. Other commercial missions have chosen to omit the static fire test.
The fairings are a refurbished old pair from 2 and 3 previous missions 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.
The Payload
SES is a Luxembourg-based satellite telecommunications network with 67 currently operational satellites (before the O3b mPOWER launch) under its control in both geostationary orbit (GEO) and medium Earth orbit (MEO). Five of those are part of a group called O3b, also referred to as O3b MEO.
The O3b mPower is a successor of the O3b constellation operating in MEO by SES S.A. It will consist of 11 next-generation high-throughput satellites that will also work in MEO around 8,000 km above the Earth. From MEO, the constellation will cover 96% of the globe.
The satellites are built and tested by Boeing and are based on its flight-proven 702 platform. Moreover, the O3b mPower 1 & 2 feature an all-electric propulsion system, custom solar arrays manufactured by Spectrolab, and the 702X software-defined payload with more than 5,000 steerable and fully-shapeable beams per satellite.
The O3b mPower 1 & 2 satellites make use of a software system called Adaptive Resource Control (ARC). ARC will provide dynamic management of service requests and available resources in orbit and on the ground. SES has been working on ARC with Kythera Space Solutions since September 2019, when they jointly announced the development.
The O3b mPower satellite system aims to provide high-performance connectivity services to multiple sectors, including government, energy, and cruise sectors, as well as telecom companies and mobile network operators.
Apart from the 11 satellites in orbit, the constellation will comprise eight ground stations worldwide and dozens of software service providers. The O3b mPower’s start-of-service date is scheduled for Q3 2023 with six satellites in orbit.
The O3b mPOWER network’s 11 satellites will be launched on five different SpaceX Falcon 9 rockets, including the two on this mission. The satellites are designed to be stacked and launched in batches of two or three.
SES says the plan is to launch four more satellites on two different launches during the first quarter of 2023. That is expected to be followed by two more satellites launched later in 2023. A final three satellites are expected to launch in 2024, completing the network.
The company expects it to take approximately six months after launch for each satellite to reach its designated orbit 8,000 km above Earth and to be commissioned. The service is expected to begin rolling out to customers at the start of Q3 in 2023.
The Falcon 9 launch
A typical Starlink mission begins with the countdown that has a traditional 35-minute long propellant load sequence which begins with RP-1 (a refined form of kerosene) loading on both stages and liquid oxygen (LOX) loading on the first stage only.
Loading of RP-1 on the second stage wraps up first at the T-20 minute mark followed by the usual “T-20 minute vent” as the oxygen purging begins on the pipelines of the Falcon 9 Transporter/Erector (T/E) that supplies fluids and power to the vehicle. LOX load on the second stage begins about four minutes after that at T-16 minutes.
Engine chill commences at the T-7 minute mark with a small flow of LOX going into the turbopumps on all nine Merlin engines on the first stage. RP-1 loading on the booster then wraps up about a minute later at the T-6 minute mark.
LOX load on the first and second stages ends at around the T-3 minute and T-2 minute mark respectively, and the rocket takes control of the countdown at the T-1 minute mark.
Engine ignition is commanded at T-3 seconds allowing them to achieve maximum thrust and pass final checks before committing to launch and if engine checks look correct, the ground clamps release the rocket for liftoff at the expected T0 time.
After liftoff, Falcon 9 climbs away from the launch site, pitching downrange as it maneuvers along its pre-programmed trajectory. Approximately 72 seconds into the flight, the vehicle passes through Max-Q — the point of maximum dynamic pressure, where mechanical stresses on the rocket are the greatest.
The nine first-stage engines continue to power Falcon 9 for the first two minutes and 30 seconds of the mission, until the time of main engine cutoff (MECO), at which point all nine engines shut down nearly simultaneously.
Stage separation normally occurs 3-4 seconds later, with the ignition of the second stage’s Merlin Vacuum engine coming about seven seconds after staging.
While the second stage continues onward to orbit with its payload, the first stage coasts upward to apogee — the highest point of its trajectory — before beginning its trip back to Earth. The booster refines its course toward the landing zone before attempting to softly touch down on the deck of one of SpaceX’s three drone ships.
Two or three burns are required to secure the safe return and landing of a Falcon 9 booster depending on the chosen landing site. A boost back burn nullifies the horizontal speed from about 7000 km/h plus to a 1000 km/h negative if a return to launch site is chosen.
Normally a free fall trajectory is chosen which requires a re-entry burn designed to break the speed into the denser atmosphere. The Merlin 1D# engines start in a 1-3-1 sequence with the center engine 9 starting 4 seconds before lighting up engine 1 and 5 in a burn lasting 14-16 seconds ending with a 2 second center engine solo burn.
The re-entry burn last 20-22 seconds and the booster is now falling and steering through the denser atmosphere with the 6x8 feet grid fins. A last landing burn performed by the Merlin 1D# center engine is timed to the last millisecond securing the aiming and breaking of the boosters speed. The booster landing has now been performed 187 times.
Using a drone ship for booster recovery allows SpaceX to launch more mass in a payload on Falcon 9 than it would be able to launch on a return-to-launch-site mission.
In the meantime, the second stage carries on with the primary mission. After stage separation and Merlin Vacuum engine ignition, the payload fairing halves are jettisoned, thereby exposing the satellites to space.
Much akin to the Falcon 9 first stage, the fairing halves can be recovered and reused, using a system of thrusters and parachutes to make a controlled descent into the ocean where they will be picked up by a recovery vessel.
Second-stage engine cutoff (SECO-1) takes place just over eight and a half minutes into the flight. Other engine burns to modify or increase the deployment orbit will follow if the mission requires it. This mission used a second transfer burn and a third circulation burn before deploying the two 03b mPower 3 & 4 satellites into a medium orbit.
After spacecraft separation, the second stage will perform a deorbit burn for proper disposal, ensuring that reentry takes place in the south Pacific-Indian Ocean.
The Falcon 9 rocket vehicle
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 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 and launch the TEA-TEB is provided by the ground service equipment. However, as 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 Falcon 9 can put some or many payloads in different orbits on missions with many burns and/or long coasts between burns, the second stage is able to be equipped with a mission extension package.
When the second stage has this mission extension package it has a gray strip, which helps keep the RP-1 warm in sunlight, an increased number of composite-overwrapped pressure vessels (COPVs) for pressurization control, and additional TEA-TEB.
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.
The Falcon 9’s fairing consists of two dissimilar reusable halves. The first half (the half that faces away from the transport erector) is called the active half, and houses the pneumatics for the separation system. The other fairing half is called the passive half.
Comparison of Type 1 and 2 with measurements based on pixels - Type 2 are 5-6 inches thicker
As the name implies, this half plays a purely passive role in the fairing separation process, as it relies on the pneumatics from the active half.
SpaceX used boats with giant suspended nets to attempt to catch the fairing halves, however, at the end of 2020 this program was canceled due to safety risks and a low success rate. On this mission, SpaceX will attempt to recover the fairing halves from the ocean with their recovery vessels Bob and Doug.
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.
In 2021, SpaceX started flying a new “upgraded” version of the Falcon 9 fairing. The 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.
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.
