Screenshot from SpaceX Webcast of the OneWeb 17 launch. To get there just keep turning south
Mission Rundown: SpaceX Falcon 9 - OneWeb 17
Written: March 9, 2023
More boxes marching on
SpaceX and its workhorse Falcon 9 rocket have launched the third of three OneWeb missions from Space Launch Complex 40 (SLC-40) at the Cape Canaveral Space Force Station (CCSFS) in Florida.
The OneWeb Flight #17 mission saw Falcon 9 carry 40 OneWeb high-speed internet satellites into a polar low Earth orbit. Liftoff occurred on March 9, 2023 at 14:13 PM EST - equivalent to 19:13 UTC on January 9.
Notam on the flightpath and debris fields used by Falcon 9 with OneWeb #17. Top red one is the disaster area on launch failure. Second is the ‘Boost Back’ maneuver failure debris field. Third area is a possible ASDS location and the fourth most southern area is Bob's fairing recovery area.
The first stage booster B1062-13 will land on LZ-1 almost seven 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.
SpaceX will also recover both fairing halves in the Atlantic Ocean with the recovery vessel Bob, named after Demo-2 Astronaut Bob Behnken.
The fairings are an old pair both flying on their 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.
B1062-13 will have made its thirteenth flight after launching its next mission:
B1062-13 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.
The OneWeb Payload
OneWeb Flight #17 was the third of three missions for OneWeb by SpaceX and marked OneWeb’s second mission in 2023. Additionally, this launch marked the third rocket type OneWeb has flown on.
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 kilos?
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 each on Launch #15, #16 and #17 – 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.
36 OneWeb satellites mounted on five ESPA rings on a Soyuz Fregat rocket from Roscosmos. link
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 third launch scheduled for March 2023. After Launch #17 OneWeb will have a few more launches before its initial constellation is completed.
The OneWeb 17 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. B1062-13 was redesignated B1062-14 after a successful landing.
SpaceX will now move B1062 of LZ-1 to refurbish the booster for its fourteenth mission.
While B1062-13 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 ~602 km downrange by Recovery Ship Bob.
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 584 of its initial 648 satellite target.
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 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.
This mission was going to be the first mission of SpaceX’s upcoming second stage Merlin vacuum nozzle redesign, which will be used on lower-performance missions. This shorter nozzle will decrease the number of return to launch site (RTLS) missions that SpaceX is able to launch; for this reason, it is likely that future missions in this 6 ton payload class will land on one of SpaceX’s drone ships.
After 1 1/2 orbit the second stage will deorbit itself at T+2:20 ish.. over the Indian Ocean.
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.
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.
Comparison of Type 1 and 2 with measurements based on pixels - Type 2 are 5-6 inches thicker
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.
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.
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