SpaceX’s two-vessel drone ship fleet has successfully returned two boosters from sea to port in the space of just ~40 hours, an impressive feat that simultaneously shed light on a new kind of bottleneck for Falcon launches.

Completed on January 20th and 24th and originally planned as few as 25 hours apart, SpaceX’s back-to-back Starlink-16 and Transporter-1 launches made it clear that drone ship availability could quickly become a constraint as the company eyes increasingly ambitious launch cadence targets. CEO Elon Musk has stated that SpaceX is targeting up to 48 launches in 2021, translating to an average of one launch every 7.5 days.

As it turns out, measured from port departure to port arrival, that target is practically the same as the average amount of time it takes one of SpaceX’s two drone ship landing platforms to complete a booster recovery. Both existing drone ships must be slowly towed to and from the booster landing area, generally involving a minimum round trip of 800 miles (~1300 km) and some five days in transit.

In other words, even given a perfectly optimized schedule in which SpaceX launches missions requiring at-sea recovery every ~180 hours throughout 2021, each mission would have just a handful of days worth of margin before one launch delay would inherently delay another launch. Fundamentally, with a fleet of two drone ships requiring an average of five days of transit time per recovery, SpaceX could theoretically support as many as ~70 booster recoveries annually assuming zero downtime, no launch delays, and mere hours spent at the landing zone before turning around and heading back to port.

To be clear, recovery ship availability is an excellent problem to have, as it implies that SpaceX is fast approaching a rate of launch (and routine rocket landings) unprecedented in the history of commercial spaceflight. Thankfully, SpaceX also has an exceptional track-record of solving hard problems and there remains a great deal of ‘slack’ to be optimized out of its fleet of recovery ships.

That is all to say that removing the fundamental bottlenecks posed by SpaceX’s existing fleet will absolutely require at least one or two new drone ships on top of at least two major oil rig conversion projects in work for Starship. Whether in the form of one or more new converted barges or some kind of faster, self-propelled vessel, it’s safe to say that new ships are virtually guaranteed and likely close at hand unless SpaceX has decided to accept a semi-arbitrary ceiling on annual East Coast launches.

Just one month into 2021, SpaceX’s two drone ships are already being stretched to their operational limits to the point of launch delays. Delayed from January 17th to January 20th, Starlink-16 held up drone ship Just Read The Instruction for several days, resulting in the vessel returning to port on the 24th, just ~60 hours prior to Starlink-17’s original January 27th launch target. With drone ship Of Course I Still Love You (OCISLY) already indisposed at sea to support SpaceX’s January 24th Transporter-1 launch, SpaceX had to move Starlink-17 to January 30th.

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After a few days in port for booster processing and maintenance, drone ship JRTI ultimately departed Port Canaveral for Starlink-17 on the evening of the 27th, most likely delaying the launch to Sunday, January 31st. For now, though, Falcon 9 booster B1049 is scheduled to launch for eighth time no earlier than (NET) 7:24 am EST (12:24 UTC), January 30th. Simultaneously, drone ship Of Course I Still Love You will likely need to depart Port Canaveral later this weekend to support Starlink-18, scheduled to launch as soon as 1:19 am EST, February 4th.