What is Block 5 of Falcon 9? Why'd SpaceX throw non Block 5's away?
Video from the channel Everyday Astronaut about Falcon 9, linked on its Above Ten Thousand entry. Duration: 17:30. Language: English. Video type: Documentary.
What it's about
Explainer piece that traces the evolution of the Falcon 9 up to the Block 5 version to clarify what a block change means at SpaceX. It explains the block as an iteration incorporated into the production line, within an incremental development approach that trades more prototypes and more changes for a more capable vehicle. It also explains why SpaceX was discarding first stages built before Block 5.
Historical context
The first version flew on June 4, 2010 from SLC-40 at Cape Canaveral. It measured 47.8 m, produced 4,940 kN with nine Merlin 1C engines in a square layout, and flew five times, the last on March 1, 2013 (CRS-2). The v1.1 debuted on September 29, 2013 at Vandenberg (SLC-4E): it grew to 68.4 m, kept the 3.66 m diameter, reached 5,880 kN with the Merlin 1D and introduced the octaweb. Landing legs appeared on CRS-3 (April 18, 2014) and grid fins on CRS-5 (January 10, 2015). After the CRS-7 failure on June 28, 2015, the Full Thrust version arrived. Its first flight, on December 21, 2015 (OG2), achieved the first landing of an orbital first stage.
Key figures
The Full Thrust measures 70 m and produces 7,600 kN, mainly thanks to subcooled oxygen. Block 5 doesn't grow in size, but raises thrust by around 7%, to 8,130 kN. It also brings titanium grid fins, retractable legs, thermal protection, reinforced turbines and a new COPV tank. NASA requires seven flights without changes before carrying astronauts. The goal is ten flights without refurbishment and around a hundred total. Older stages were discarded because recovering them was costly and because it allowed testing extreme reentry profiles.