SpaceX postpones the latest Starlink Group 3 launch

SpaceX’s 27th launch of the year is set for Tuesday, April 25, 2023, as it lifts another batch of 46 Starlink satellites into low Earth orbit. However, the liftoff, scheduled for 6:40 a.m. PST (13:40 UTC) from Space Launch Complex 4 East (SLC-4E) at Vandenberg Space Force Base in California, was delayed before the load could be set. prop.

The mission, Starlink Group 3-5, marks the resumption of Starlink Group 3 flights to heliosynchronous orbit, which began in the summer of 2022 and were paused after just four flights. This crust provides coverage for the polar regions. This launch also marks SpaceX’s 40th flight of the SLC-4E.

The B1061 will fly its thirteenth time, becoming the fifth booster aircraft to fly multiple times. It is scheduled to land on the unmanned deck of SpaceX’s Autonomous Spaceport Ship Of course I still love you (OCISLY), which will be stationed at a depth of 634 km in the Pacific Ocean.

Falcon 9 will begin the pre-launch propellant load sequence at the T-35 minute mark when the automated launch countdown sequence begins.

Automatic launch equalization is responsible for starting the load of RP-1 – a refined form of kerosene – in both stages, as well as starting the load of liquid oxygen (LOX) to the first stage.

RP-1’s second-stage load will end in about T-20 minutes, after which Earth systems will begin purging and cooling the liquid oxygen lines that connect to the second stage.

This is performed in order to properly cool the lines to the appropriate temperatures before liquid oxygen flows through them at the rates necessary to fill the LOX tank in the upper stage. This creates the now famous “20-minute T-vent.” This vent will stop after about four minutes, indicating that LOX loading has begun in the second stage.

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Seven minutes before liftoff, ground systems will begin cooling the Merlin 1D’s nine first-stage engines. Just like ground line cooling, this is also done for thermal conditioning of the oxygen turbo pump before liquid oxygen flows at high rates during ignition.

After about a minute, the RP-1 will finish loading in the first stage and the tanks will press for a powerful back pull. The strong buttress is the vertical support structure of the carrier system (T/E) that provides fluids and power to the second stage and clears the interface and fairing of the Falcon 9.

On the SLC-4E, this hull retracts about 20 degrees away from vertical and stays that way during liftoff, instead of retracting 1.8 degrees and performing the maneuver to “bounce” to 45 degrees on takeoff – a procedure performed at the Falcon 9 launch pads in Florida. This is a carryover of the old Falcon 9 launch pad design that was in use from 2010 to 2017 but is still in use at Vandenberg to this day.

The liquid oxygen load in the first and second stages will end at about T-3 and T-2, respectively. One minute before liftoff, the Falcon 9’s onboard computers will take over the automated launch countdown and begin pre-flight checks.

Three seconds before takeoff, the engine computers begin the engine ignition sequence for all nine M1D engines in the first stage. This ignition sequence oscillates and takes about two seconds to complete with the last second in the count used to perform engine health checks before take off.

After liftoff, Falcon 9 will descend to the southwest of SLC-4E and should approach supersonic speeds about 50 seconds into flight.

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The two-and-a-half minute initial ascent will take the rocket and satellite to an altitude of about 65 km and a speed of 2.3 km/s before turning off the engines and separating the first and second stages.

After separation, the first stage will orient itself to the engines first stand for re-entry into the atmosphere. It will perform a three-engine entry burn to protect the missile and engines from entry heat. And then – near the ground – it will trigger a single-engine landing burn.

Once separated from the first stage, the second stage will ignite its single Merlin 1D Vacuum Engine (MVacD) for about six minutes to usher Starlink satellites into a low-parking orbit. About 10 seconds after the MVacD ignites, the two fairing halves will separate for a parachute-assisted splash into the Pacific Ocean. It will then be recovered by SpaceX’s west coast salvage recovery vessel NRC Quest.

About 45 minutes after orbital insertion, the torch’s MVacD engine will return to orbit and prepare for satellite deployment. The upper stage will spin from end to end and then release four tension rods that hold the Starlink satellites together during launch.

By inertia, the satellites will fly away at launch, while the second stage will stop its rotation. The stage will then perform a third and final burn of its MVacD engine to de-orbit and dispose of it over the southwestern Pacific Ocean.

This launch will carry 46 Starlink v1.5 satellites in the cluster 3 envelope of the Starlink first generation constellation. The satellites in this shell operate in an almost circular orbit with an altitude of 560 km and an orbital inclination of 97.6 degrees.

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Starlink Gen 1 Starlink Gen 2
missions Version 1.0 Group 2 Group 3 Group 4 Group 5 Group 6
orbit 550 km at 53 degrees 570 km at 70 degrees 560 km at 97.6 degrees 540 km at 53.2 degrees 530 km at 43 degrees
Satellite launch 1665 305 197 1637 330 42
Satellite re-entry 169 3 10 67 2 2
satellites in operational orbit 1426 82 187 1474 183

(State of the Starlink constellation of doctor. Jonathan McDowell data As of April 24, 2023)

This batch of satellites will bring the total number of Starlink satellites launched to 4,284, of which 3,352 are in operational orbits and 325 are reentrants. Of these, 3,912 were launched in support of the first-generation Starlink constellation and 372 were launched in support of the second-generation Starlink constellation.

Starlink Group 3-5 will be SpaceX’s eighth launch of 2023 from the SLC-4E, keeping it on track to launch about 25 times this year, five times short of SpaceX’s goal of 30 launches from the Vandenberg launch site.

If launched on time, it would break the record for the fastest turnaround among launches from an SLC-4E by just over one day. The record is currently 11 days, 16 hours between Starlink Group 3-1 and Starlink Group 3-2.

SpaceX is preparing for a doubleheader later this week from Florida, which includes the launch of a Falcon Heavy VI rocket that puts the Americas’ VisaSat 3 satellite into near geostationary orbit. Another launch of the twin-header will include a Falcon 9 rocket flying two SES internet satellites for the O3b mPOWER constellation.

(TOP PHOTO: Falcon 9 in SLC-4E prior to the SDA Tranche 0 Flight 1 mission. Credit: Jack Beyer for NSF)

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