SpaceX launches Starlink 4-15 mission, expands booster fleet

SpaceX launches its twentieth Falcon 9 rocket of the year with a batch of Starlink satellites into low Earth orbit (LEO) as part of the Starlink Group 4-15 mission. Liftoff took place Saturday, May 14 at 4:40:50 p.m. EDT (20:40:50 UTC) from Space Launch Complex 40 (SLC-40) at Cape Canaveral Space Force Station (CCSFS ) in Florida.

The Falcon 9 for this mission was of particular interest because it uses a new booster, the B1073-1, something never before seen on a Starlink mission.

The Falcon 9 rocket performed its traditional 35-minute automated launch countdown sequence before liftoff. Main engine cut-out – or MECO – occurred approximately two and a half minutes into the flight, with stage separation and MVac ignition occurring shortly thereafter. Fairing halves separated approximately 5 seconds after MVac ignition.

The first leg of this mission then made its usual return to Earth via a series of entry and landing burns. It landed softly on SpaceX’s Spaceport Autonomous Drone Craft (ASDS) “Just Read The Instructions” stationed about 626 km downriver in the North Atlantic Ocean.

The fairing halves are also returned to Earth via a set of thrusters that steer them for reentry and a parachute that slows them down to a gentle splash in the ocean. Recovery from the ocean will be carried out by SpaceX’s multipurpose recovery vessel Bob.

The first second stage burn, the orbital insertion burn, lasted about 6 minutes, after which the second stage and Starlink satellites were in low elliptical Earth orbit (LEO). About 30 minutes later, the second stage performed a second burn to inject the satellites into the 305 by 318 kilometer 53.2° inclination target orbit. The satellites will then separate about an hour after launch.

The second stage will perform a third and final burn for deorbit and disposal over the Indian Ocean west of Australia. The Starlink satellites will then raise their orbit to a circular orbit of approximately 350 km for checks and phasing. Those who pass the checks will then raise their orbit to the operational altitude of 540 km.

This mission was the 46th dedicated Starlink mission by SpaceX and it launches 53 Starlink satellites into shell four of Starlink’s first-generation constellation. This will represent a total of 2600 satellites launched in LEO by SpaceX. Of these, 248 of them have returned and 1749 are in their operational orbit.

Shell #1 Shell #2 Shell #3 Shell #4 Shell #5
Orbit 550km circular at 53º 570km circular at 70º Circular of 560 km at 97.6º 540km circular at 53.2º Circular of 560 km at 97.6º
# of orbital aircraft 72 36 6 72 4
Satellites by plane (target) 22 20 58 22 43
Satellites launched 1665 51 0 756 0
Satellites in operational orbit 1459 18 0 272 0
Total number of satellites (target) 1584 720 348 1584 172

(Starlink Constellation Information Status of Jonathan McDowell to May 13)

The booster fleet is growing, SpaceX is upgrading launch pads and improving rocket performance.

Saturday’s mission included a new Falcon 9 booster, something never seen before for a Starlink mission. The only other Starlink mission that saw a booster this early in its flight history was Starlink v1.0-28 launched in May 2021 when booster B1063-2 lifted off from SLC-40 with 60 Starlink satellites aimed at one of the constellation.

It is understood that this new booster, B1073-1, debuted on this mission to expand SpaceX’s Falcon 9 booster fleet. The company aims to launch up to 60 times this year and plans to expend or temporarily retire some of the older boosters in the fleet, meaning it will need to have new boosters on hand to keep up with demand. increased theft both internal and from customers. .

(Chart of active Block 5 boosters by flight number and year)

For example, booster B1049 is now ready to be used for the Nilesat 301 mission, with O3b mPOWER missions having been rescheduled so that the first stage does not have to be used to meet customer requirements.

On the other hand, booster B1060 is expected to be temporarily retired once it reaches 15 flights later this year; it is an in-depth review of its systems and components to better understand how to refurbish and reuse boosters for up to 20 flights.

Apparently, this isn’t a complete overhaul, but rather a study of what it takes to efficiently and cost-effectively refurbish and continue to use Falcon 9 boosters beyond the mark. 15 flights. After that, the booster will return to the fleet with the goal of flying it to the 20-flight mark by next year.

With boosters out of service and unprecedented demand at SpaceX to launch their own Starlink satellites and new customers like One Web, it was necessary to introduce another booster into the fleet to meet schedules. Although it could have been done on a customer mission, apparently SpaceX had already assigned boosters to customer missions well into the year, so the only possibility was to introduce the booster into one of their own assignments.

Another particular rarity of this booster is the lack of the usual F9 logo, and the SpaceX logo is only on one side of its fuselage, leading observers to initially believe it was intended to be a side booster. Falcon Heavy. While its first flight will be as a Falcon 9 booster, it is indeed true that currently this booster is targeted for flight as a Falcon Heavy side booster on its seventh flight.

SpaceX’s drive to stay on schedule includes not only expanding the fleet or, as noted earlier, experimenting with faster turnaround times, but also upgrading ground systems. It is understood that SpaceX’s two launch pads in Florida are seeing incremental upgrades between launches to reduce the work needed between flights, making it cheaper and faster to prepare ground systems for the next launch.

However, problems with ground systems still occur to this day. Sources say SpaceX had to repair the SLC-40 launch pad after the previous launch with reports of cracks and fatigue shown in the Transporter/Erector reaction frame. While this could be considered a deal breaker, ground crews were able to quickly repair and bring the launch pad to full functionality in record time, supporting another flight just two weeks after the previous one.

Part of the increase in internal demand on Starlink missions stems from SpaceX’s desire to deploy the constellation as soon as possible. The company plans to not only do this by increasing the rate, but also the performance of the rocket. We’ve seen them recently launch 53 satellites into trajectories and orbits where on previous occasions the rocket could only launch 46 or 47 satellites.

William Gerstenmaier, SpaceX’s vice president of construction and flight reliability, has previously asserted at the Flight Readiness Review Conference for Axiom-1 that thrust profile optimizations for flights Starlink had been implemented to improve the performance of the rocket.

It is understood that SpaceX is also improving the performance of the rocket by modifying certain timings during the flight, such as turning on the MVac engine a few seconds earlier than on other missions or separating the fairing closer to the separation of the stages to lose weight. dead weight earlier in the flight.

Additionally, SpaceX is loading propellants onto the rocket at slightly lower than normal temperatures in order to pack more into the tanks and increase the amount of Starlink satellites the Falcon 9 can launch into orbit.

All of these Falcon 9 performance improvements were made possible by the rocket’s flight history and the enormous amounts of data the company can collect with each Starlink flight and confidence in its reliability.

Two more SpaceX missions are set to launch this month with another Starlink mission and a Transporter mission both scheduled for the second half of May.

(Main photo: A Falcon 9 sits at SLC-40 before launching the GPS-III-SV05 mission in June 2021. Credit: Julia Bergeron for NSF)

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