SpaceX launched its first Falcon 9 rocket on June 4, 2010, nearly a dozen years ago. During those first years, the company grappled with a whole host of challenges, from things as seemingly simple as trying to transport the rocket over land instead of by sea or air to more demanding tasks such as producing enough Merlin engines.

The company’s first 50 flights took nearly eight years to complete, and in that time SpaceX engineers and technicians learned much about building large rockets, testing and transporting them, and then flying them. From 2010 to early 2018 SpaceX would make three major “block” upgrades to the rocket, as well as debuting the Falcon Heavy variant of the booster.

During this learning period of activity, SpaceX managed to launch a Falcon 9 rocket only every 56.6 days. As it started to experiment with reusing the first stage, of its first 50 launches, seven of those were on reused rockets. Also during this learning period, SpaceX had one launch failure, CRS-7 in 2015, and one failure during pre-launch activities, the Amos-6 accident in 2016.

The company has not had a Falcon 9 launch failure since then, and earlier this year this rocket set the record for the most consecutive successes by any orbital rocket, ever.

Second 50 days

The company profited from these lessons. SpaceX launched its 51st rocket on March 30, 2018, and flew its 100th on November 25, 2020. During this period the company began to fly the rocket more frequently, averaging a launch every 19.4 days. And of these 50 launches, 35 were reused.

Probably the most significant milestone during this timeframe was the company’s 54th launch—of a Bangladeshi commercial satellite. This mission saw the debut of the “Block 5” version of the Falcon 9 rocket, which incorporated several improvements to optimize the rocket for reuse.

The Block 5 version, for example, included modifications such as improved thermal shielding around the Merlin engines, unpainted components to save mass, and changes to the octaweb structure that holds the engines so they can be inspected, refurbished, and tested more quickly.

“For those that know rockets, this is a ridiculously hard thing,” SpaceX founder Elon Musk said in 2018, upon the Block 5’s debut. “It has taken us since, man, since 2002. Sixteen years of extreme effort and many, many iterations, and thousands of small but important development changes to get to where we think this is even possible.”

Third 50 days

SpaceX launched its 101st mission on December 6, 2020, to supply cargo to the International Space Station. It flew its 150th on Wednesday, launching the Crew-4 mission for the US space agency, carrying four astronauts to the International Space Station.

During this period SpaceX has flown the Block 5 version of the Falcon 9 rocket exclusively, launching a booster on average every 10.1 days. Remarkably, of the company’s last 50 rocket launches, 47 have used a previously flown first stage booster.

In recent years SpaceX has made relatively few technical iterations on its Falcon 9 work horse, but the company has continued to learn about the optimal refurbishment of boosters. For example, it has now flown two different first stages a dozen times apiece and will likely continue to push these “fleet leaders” further to find the limits of reuse.

SpaceX has also learned how to rapidly turn around the vehicle. Two days after its 150th launch, the company will make its 151st as early as today, Friday, April 29. This Starlink launch will feature a booster that has flown five previous times, including most recently launching the Axiom-1 mission into orbit. That crew flight took place just 21 days ago, so SpaceX has managed to cut its refurbishment period to just three weeks.

https://arstechnica.com/?p=1850762