SpaceX wants 10 flights with a bare minimum of refurbishment and 100 or more launches with intermittent maintenance.
Chris G – NSF, Assistant managing editor, journalist, and writer for @NASASpaceflight tweeted out a photo of the first Block 5 Falcon 9.
— Chris G – NSF (@ChrisG_NSF) February 27, 2018
In the past, SpaceX has used high-quality cork as a quasi-ablative thermal protection system for those same components, including the payload fairing. A major downside of cork, however, is that it is very ablative and tends to come off rather haphazardly in large chunks, all of which must either be spot-fixed or replaced entirely before a booster reflight. By replacing that cork with Pyron or a similar internally-developed material, those sensitive Falcon components may be almost totally insulated from and resistant to temperatures as high as 2300 °F (1200 °C)
Titanium grid fins are another central feature of Block 5, acting as a near-indefinitely reusable replacement for the aluminum grid fins SpaceX has traditionally used.
Finally and perhaps most importantly, is the octaweb – the assembly at the base of Falcon 9 responsible for safely transmitting nearly two million pounds of thrust from its nine Merlin 1Ds to the rest of the rocket’s structure, while also taking the brunt of the heat of reentry. Before Block 5, the octaweb was protected from that heating with an ablative thermal protection system, likely around 80% cork and 20% PICA-X, the same material used on Cargo Dragon’s heat shield. Based on comments made privately by individuals familiar with SpaceX, that ablative shielding is to be replaced by a highly heat-resistant metal alloy known as inconel. By ridding Block 5 of ablative heat shielding, SpaceX will no longer have to carefully examine and replace those materials after each launch, removing one of the biggest refurbishment time-sinks.
With the block 5 Falcon 9, including the reusable fairing debuted on the launch of PAZ, SpaceX may well be able to achieve Elon Musk’s famous goal of lowering the cost of launch by nearly an order of magnitude. While SpaceX will likely use that cost reduction to first recoup its considerable investments in reusability and Falcon Heavy, major price drops may reach customers soon after.