What Happened?

On February 15 at 10:59 EST, a Falcon 9 Block 5 launched from Launch Complex 40 (SLC-40) in Cape Canaveral for the Starlink L-19 mission.

As always with these missions, the vehicle was carrying 60 Starlink satellites to low-Earth orbit, increasing the constellation. Booster 1059 (B1059) was assigned to this mission, earning its sixth flight.

The plan was to stage separate, with B1059 landing back on the Autonomous Spaceport Drone Ship (ASDS) ‘Of Course I Still Love You’ – something which many of us have become accustomed to.

The vehicle successfully lifted off the pad, and followed an expected and nominal flight profile. Stage separation occurred, with the second stage igniting toward an orbital insertion.

The first stage completed its reorientation maneuver, to face aft-first into its trajectory. With ASDS recoveries, the booster performs two key burns: the re-entry burn and the landing burn.

The re-entry burn occurs at approximately 50km in altitude, whereby three of the nine Merlin 1D engines reignite to slow the stage down, so much so, that it remains structurally integral as it passes through the thick portion of atmosphere.

Once complete, the sheer size of the stage and increasing air density slows the vehicle further by atmospheric drag, with control provided by the four titanium grid fins and Reaction Control System (RCS) thrusters.

Once nearing the landing site, the landing burn is initiated whereby just one Merlin engine is reignited to perform a ‘hoverslam’ – in essence, igniting the engine at the precise moment that the vehicle’s velocity reaches zero when it touches the ground.

Back to Starlink L-19; B1059 did perform a re-entry burn.

But, this was slightly shorter and less velocity scrubbed than typically expected. More significantly, a trail of exhaust could be seen after the re-entry burn shutdown.

Interesting views at the call out for booster re-entry bur conclusion. pic.twitter.com/tb6qJs7kXg

— Chris B – NSF (@NASASpaceflight) February 16, 2021

Telemetry of the booster was lost shortly after the off-nominal re-entry burn. Likely due to the build-up of plasma engulfing the vehicle, caused by a combination of velocity and atmosphere – a normal phenomenon for camera loss, but not at the intensity that telemetry connection is lost.

It was not clear whether the fate of the booster had been sealed at this point, as the camera patiently waited on the droneship.

But then we could visibly see an orange glow in the distance reflected by the clouds and sea, before then vanishing to darkness in an instant, accompanied by scared birds.

They’ve lost the booster. Note: They did expect to lose a small percentage of boosters for drone ship landings. We’ve just got so used to them coming back all the time.

Also, several seagulls get to live another day. pic.twitter.com/CCjrhgwPp6

— Chris B – NSF (@NASASpaceflight) February 16, 2021

A landing burn was never enunciated.

It’s not clear what exactly happened here; the glow may have been a landing burn attempt or the residual plume we saw in the re-entry burn.

The rapid loss of color and back to darkness was likely the booster hitting the sea at high velocity creating a bang, explaining the scared birds.

However, the second stage continued to follow a nominal mission, and the 60 Starlink satellites were deployed into orbit – after all, this was the primary objective.

Deployment of 60 Starlink satellites confirmed pic.twitter.com/apZ7oTOvNk

— SpaceX (@SpaceX) February 16, 2021

What does this mean for SpaceX?

SpaceX has not suffered a booster recovery failure since March 18 2020 on Starlink L-5.

Since then, the Falcon 9 has enjoyed the longest recovery streak ever, recovering the booster on 24 missions.

Unfortunately, Starlink L-19 ends this streak.

SpaceX will now be hard at work diagnosing and resolving the anomaly which led to the loss of B1059.

Starlink L-17 was scheduled to launch on Wednesday February 17, but this will no longer happen as teams troubleshoot.

More significantly, Crew-2 is set to launch in April 2021 to the International Space Station. NASA will likely want to be in close contact with SpaceX throughout this investigation.

This does not mean that Crew-2 will be delayed, but it’s likely that NASA will want to see the Falcon 9 perform at least a couple successful missions before Crew-2, to verify the investigation outcome. The launch manifest can easily allow this to happen.

SpaceX have had to overcome many, many hurdles in their time, and this is definitely not the highest they’ve had to jump.

Undoubtedly, we’ll be seeing boosters back on the droneships and landing pads very soon, and the streak can be built up once again.