Screenshot from SpaceX Webcast of the SES 18-19 launch. Sun’s setting. Time to wake up now
Mission Rundown: SpaceX Falcon 9 - SES 18-19
Written: March 18, 2023
Doubletap with a double shot
SpaceX will launch the SES-18 & SES-19, two C-band satellites, to a Geostationary Transfer Orbit (GTO) on their Falcon 9 Block 5. The rocket will lift off from Space Launch Complex 40 at the Cape Canaveral Space Force Station in Florida, marking the 18th Falcon 9 launch of the SpaceX company this year.
‘It’s me in the corner’ booster supporting the SES 18-19 mission is B1069-6; the nickname implies that the booster has survived and supported five previous flights.
B1069-6 will have made its sixth flight after launching its next mission:
Following stage separation, the Falcon 9 will conduct a reentry burn lasting 20 seconds and a 22 second landing burn. These two burns aim to land the booster softly on SpaceX’s autonomous spaceport drone ship Just Read The Instruction.
NOTAM regarding flight path and recovery area 647 km downrange. Red dot is ASDS are so close
B1069-6 didn’t perform a static fire test after refurbishment while waiting for its next 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 or if external customers wish to save time.
The used fairings, which both have flown two and five times before, will be retrieved by the recovery vessel Bob in the Atlantic Ocean.
The mission payload
The SES-18 & SES-19 are C-band communication satellites owned by SES S.A., a Luxembourgian telecommunication company. The satellites were designed, produced, and tested by Northrop Grumman in Dulles, Virginia.
Each satellite has a mass of 3,500 kg, two solar arrays, a lifespan of 15 years, and is equipped with a high-quality C-band payload. Their main aim is to provide North America with digital broadcasting services.
Together with the other four satellites (SES-20, SES-21, SES-22, and SES-23), the SES-18 & SES-19 satellites will contribute to the effort of clearing the lower portion of the C-band spectrum necessary to deploy 5G services in the United States.
The SES-18 & SES-19 likely make use of a software system called Adaptive Resource Control (ARC). This software already supports the SES-17 satellite launched in October 2021. ARC provides 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.
SES 18 will be parked in geostationary orbit at 103.05o west latitude and SES 19 will be parked a little further over at 134.9o west latitude.
The satellites use a GEOStar-3 satellite platform developed by Northrop Grumman. Compared to the previous generation (GEOStar-2), this platform has better battery capacity and increased solar array power.
Some characteristics of the GEOStar-3 bus can be found here.
The Falcon 9 launch
A typical Starlink mission begins with the liftoff of Falcon 9 from its launchpad. The first stage’s nine Merlin 1D# engines begin their ignition sequence at the T-3 second mark in the countdown, allowing them to achieve maximum thrust and pass final checks before committing to launch.
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 27 seconds of the mission, until the time of main engine cutoff (MECO), at which point all nine engines shut down near-simultaneously.
Stage separation normally occurs four 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.
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 second-stage engine burns will modify or increase the deployment orbit if the mission requires it.
The SES 18-19 satellites are deployed into a transfer orbit; from where the satellites will raise themselves into their geostationary parking orbits, where they will undergo checkouts before heading to their final operational slots in their 24 hour orbit.
After spacecraft separation, the second stage will perform a deorbit burn for proper disposal, ensuring that reentry takes place over the South Pacific Ocean.
The Falcon 9 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. The fairing weighs 2 tons and costs 3 million dollars each.
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.
Disregard these three paragraphs written below.
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.
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