SpaceX resumes parallel pad operations with Starlink v1.0 L25 mission

Both of SpaceX’s Florida launch pads are back into Starlink launch flow as the company continues to deploy the satellite internet constellation with the Starlink v1.0 L25 mission lifting off from LC-39A at the Kennedy Space Center at 15:01 EDT / 19:01 UTC on Tuesday, 4 May.

Following a relatively quiet stretch at 39A surrounding the crucial Crew-2 mission, another wave of Starlink satellite batches will now launch from both 39A and SLC-40 at the Cape Canaveral Space Force Station over the next month.  This rapid launch cadence will soon complete the initial shell of the constellation and provide opportunities for new Falcon 9 reuse milestones.

The 45th Weather Squadron predicted an 80% chance of favorable weather for Tuesday’s launch attempt, as well as a moderate booster recovery weather risk. 

The recovery weather, which was being monitored, surrounded the Stage 1 landing zone about 633 kilometers to the northeast of the launch site, where the Autonomous Spaceport Drone Ship (ASDS) Of Course I Still Love You is stationed.  Fairing recovery vessel Shelia Bordelon was positioned further downrange, about 730 kilometers from the launch site, to recover both fairing halves after splashdown.

The first stage supporting the v1.0 L25 mission was B1049-9.  This booster made its debut on the Telstar-18V mission in September 2018 before making the trip to Vandenberg Air Force Base, California, to support the Iridium-8 mission in January 2019.  B1049 was then returned to Florida and has now launched seven Starlink missions.

First stage B1049 has also now become the second Falcon 9 stage to launch a ninth mission, after booster B1051.  While this ties the record for flights of a Falcon 9 booster, the record will be short lived as B1051 is slated to launch its 10th mission as early as Sunday, 9 May from SLC-40.

In addition to the first stage of Falcon 9, one of the fairing halves supporting Starlink v1.0 L25 was re-flown.  This half previously supported two Starlink missions.

Booster and fairing reuse have proven critical to supporting the rapid deployment of SpaceX’s Starlink satellite constellation, with new milestones being reached regularly by the Falcon 9 fleet.  This also brings new risk with each launch, as the company continues to push the reuse limits of each vehicle.

Elon Musk has previously set 10 flights for a single booster without major refurbishment as a goal. While this is not the flight limit for Falcon 9, as Elon has also said each booster is designed for up to 100 re-flights, Gwynne Shotwell has cast doubt on whether the flight rate for Falcon 9 will reach a point to permit a Falcon 9 to fly 100 times given Starship’s development.

The ultimate number of times a booster will be reused will depend on post-flight inspections of each Falcon 9 and the effects of corrosion from the salty ocean environment the boosters are exposed to after drone ship landings.

A booster that pushes the reusability limit — aka “Life Leader” — is reserved for in-house Starlink missions so SpaceX can both monitor the booster’s performance on a mission that is not carrying a paying customer’s satellite as well as mitigate any fall out that might result from an in-flight mishap.

To date, the reuse issues that have been found in flight have only affected landing and recovery operations — with the primary mission continuing on to orbit successfully.

Also crucial to continuing Starlink deployment has been the parallel use of both SpaceX launch pads in Florida.  LC-39A must be reserved at times to support high priority missions to the International Space Station, including Commercial Crew and cargo flights, and will also return to supporting Falcon Heavy operations later this year.  

But between these missions, the historic pad supplements the workhorse SLC-40 pad.

Starlink V1.0 L25 marked the 13th Falcon 9 launch of the year and the 13th flight out of the Cape, too, this year as no other rocket has yet launched from Florida in 2021.  Later this year, SpaceX’s third Falcon 9 launch site in California may also begin supporting the Starlink constellation with the first dedicated launches to polar orbits.

Time since launch (T+) Event
T+1 min 12 secs MaxQ
T+2 mins 32 secs First stage shutdown
T+2 mins 35 secs Stage separation
T+2 mins 43 secs 2nd stage ignition
T+3mins 03 secs Fairing deployment
T+6 mins 57 secs First stage Entry Burn complete
T+8 mins 39 secs First stage landing on Of Course I Still Love You
T+8 mins 46 secs Second stage engine cutoff; parking orbit achieved
T+45 mins 32 secs Second stage re-ignition
T+45 mins 33 secs Second stage cutoff
T+1hr 03 mins 49 secs Stalink deployment

The pair of SpaceX drone ships, Of Course I Still Love You and Just Read the Instructions, have been returning landed boosters to Port Canaveral just in time to almost immediately return to sea for another mission.  A third drone ship, A Shortfall of Gravitas, remains planned to join the recovery fleet later this year.

The v1.0 L25 launch utilized two Stage 2 burns. Following stage separation, the second stage of Falcon 9 conducted the first burn to reach a preliminary parking orbit, while the first stage descended towards Of Course I Still Love You for its landing.

After 8 minutes and 46 seconds of flight, the Merlin Vacuum engine on the second stage shut down, followed 37 minutes later byu a 1-second re-ignition that finalized the orbit and precipitated deployment of all 60 Starlinks 1 hour 1 minute after launch.

In the days following launch, the satellites will deploy their solar arrays and begin maneuvering to their operational orbits using their onboard krypton fueled Hall-effect thrusters. Depending on the health of the satellites launched to date and the occasionally changing plans for the constellation, the initial shell of satellites may finish being delivered to low Earth orbit in mid-2021.

Looking ahead in the Falcon 9 manifest, additional Starlink missions are planned for May, before early June sees a salvo of customer flights.

Falcon 9 soars into the skies over Florida as she departs on a previous Starlink mission. (Credit: Stephen Marr for NSF/L2)

The first is currently scheduled to be SXM-8, launching from SLC-40 no earlier than 1 June at 00:25 EDT / 04:35 UTC.  This is set to be closely followed by the CRS-22 cargo mission from LC-39A to the International Space Station no earlier than 3 June at approximately 13:00 EDT / 17:00 EDT.

Moving back to SLC-40, the next mission thereafter is currently that of the GPS III SV05 satellite for the US Space Force.  That mission is currently targeted for no earlier than 17 June in an 18:00-21:00 EDT / 22:00 – 01:00 UTC window.

For non-SpaceX launches, May will also see the return of the Atlas V following an unplanned stand down due to a lack of payload readiness since November 2020.  Atlas V’s mission will loft the SBIRS GEO-5 satellite for the US Space Force on 17 May in a window that is yet to be defined publicly.

(Lead photo: Falcon 9 launches on the Starlink v1.0 L25 mission – via Stephen Marr for NSF)

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