Screenshot from SpaceX Webcast of the launch of OneWeb 16. It’s not too late to deliver gifts
Mission Rundown: SpaceX Falcon 9 - OneWeb 16
Written: January 13, 2023
Santa forgot a lot of boxes
SpaceX and its workhorse Falcon 9 rocket have launched the second of three OneWeb missions from Space Launch Complex 40 (SLC-40) at the Cape Canaveral Space Force Station (CCSFS) in Florida.
The OneWeb Flight #16 mission saw Falcon 9 carry 40 OneWeb high-speed internet satellites into a polar low Earth orbit. Liftoff occurred on January 9, 2023 at 11:50 PM EST - equivalent to 04:50 UTC on January 10.
The first stage booster B1076-2 will land on LZ-1 almost nine minutes after liftoff.
After boosting the second stage along with its payload towards orbit, the first stage will do a direct boost back burn before it performs a 30 second re-entry burn meant to slow the vehicle down before the atmospheric reentry. The booster will then perform a 27 second landing burn and softly land on Landing Zone 1 at CCSFS, Florida.
B1076-2 will have made its second flight after launching its next mission:
B1076-2 didn’t perform a static fire test after refurbishment while waiting for a west coast launch out of Vandenberg. 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 Atlantic Ocean with the recovery vessel Doug, named after Demo-2 Astronaut Dough Hurley.
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.
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. It’s not clear whether or not the cold gas nitrogen thrusters are capable of doing a boost back ‘push’ so the fairings stop their forward momentum mid flight.
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.
Comparison of Type 1 and 2 with measurements based on pixels - Type 2 are 5-6 inches thicker
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 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.
The fairings are an old pair flying on their seventh and sixth mission 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 OneWeb Payload
OneWeb Flight #16 was the second of three missions for OneWeb by SpaceX and marked OneWeb’s first mission in 2023. Additionally, this launch marked the third rocket type OneWeb has flown on.
36 OneWeb satellites mounted on five ESPA rings on a Soyuz Fregat rocket from Roscosmos. link
SpaceX has room for four more satellites within its fairing. The OneWeb 40 satellite tower weighs in at 5,880 kg - 12,963 lb. The payload adaptor fitting ring tower weighs?
The Sun-Synchronous Polar Orbit chosen by OneWeb is however straining the mission profile of Falcon 9 to its limits and the Return To Launch Site mission profile is straining it even more. Plus the 1st stage dogleg maneuver to avoid the populated coastal areas of Florida so it's stretched as thin it can be.
Airbus built the first set of satellites at their factory in France before the satellites’ primary production moved to Florida. OneWeb satellites are small, ~148 kg, and use electric propulsion to raise and keep their 1,200 km orbits. Twin solar panels power the spacecraft and its Ku-band antennas. With 40 satellites on Launch #15 – the most OneWeb satellites launched at once – the total mass on Falcon 9 is ~6,000 kg.
The first operational launch with 34 satellites took place a year after OneWeb Launch #1, on Feb. 6, 2020. OneWeb and Arianespace completed 12 more launches until Feb. 10, 2022, when the final launch with a Soyuz took place.
Launches on Soyuz halted and were abandoned shortly after the Russian invasion of Ukraine, when, shortly after, OneWeb signed launch contracts with SpaceX and India to launch its remaining satellites.
India launched the first of its two missions in October 2022 with 36 satellites. SpaceX will launch three missions, with its second scheduled for January 2023. Following Launch #16, OneWeb will have one more launch before its initial constellation is complete.
The OneWeb 16 Launch
Final launch preparations began at T-38 minutes, with an electronic go/no-go poll for propellant loading. Launch control started the auto sequence, allowing propellant loading to begin, at T-35 minutes with the first and second stages beginning RP-1 loading while LOX loading simultaneously started on the first stage.
Thirteen minutes later, stage two RP-1 loading was complete, with a purge of the T/E at T-20 minutes. At T-16 minutes, LOX loading began on stage two. At T-7 minutes, the Falcon 9 first stage chilled its engines with liquid oxygen to ensure there were no thermal shocks to the engines at ignition. The T/E retracted to the launch position at T-4 minutes 30 seconds.
Propellant loading was completed at T-2 minutes. Two significant events occurred simultaneously a minute later: the flight computer entered “startup,” and the propellant tanks pressurized to flight levels. The launch director gave the final “go” for launch 45 seconds before liftoff.
At T-3 seconds, the engine controller commanded the nine first-stage Merlin 1D engines to ignite. A second later, the engines ignited and began a final health check. Once the engines were verified healthy and producing full thrust, the hydraulic hold-down clamps and the T/E retracted, allowing the vehicle to lift off.
Shortly after liftoff, Falcon 9 pitched to follow the proper flight path to reach an 87.4o degree orbit. Initially, Falcon 9 pitched south-southeast and then completed a “dogleg” maneuver to the south to reach the proper azimuth for the desired orbit.
The dogleg maneuver is needed to avoid overflight of populated areas on the Florida coast south of the space center.
After one minute and 12 seconds of flight, Falcon 9 reached maximum aerodynamic pressure (Max-Q).
After burning for two minutes and 17 seconds, the nine first-stage engines shut down. A few seconds later, the two stages separated. Second Engine Start (SES)-1 began just after stage separation. At the same time, the first stage began a flip maneuver to head back to LZ-1. After a near 180-degree rotation, the first stage ignited engines one, five, and nine for a 48-second burn back to LZ-1.
Six minutes and four seconds into the flight, the same three engines reignited for the entry burn, which lasted 17 seconds. The entry burn helped protect the stage from the forces caused by reentering Earth’s atmosphere.
Once the entry burn was complete, the first stage descended before reigniting engine nine one last time for the landing burn. The nearly 30-second burn allowed for a gentle landing on LZ-1. B1076-2 was redesignated B1076-3 after a successful landing.
SpaceX will now move B1076 of LZ-1 to refurbish the booster for a future mission.
While B1076-2 returned to LZ-1, the second stage continued to orbit. The payload fairing separated just over three minutes into the flight, exposing the 40 OneWeb satellites to space. The fairings were recovered ~604 km downrange by Doug.
Stage two burned until reaching an initial low Earth parking orbit. The second stage then coasted to apogee for a short and final four-second burn. In this final orbit, the OneWeb satellites separated from the payload adaptor in three sets over a span of just 32 minutes.
With this batch of satellites in orbit, the total number of OneWeb satellites in space stands at 544 of its initial 648 satellite target.
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