Elon Musk had an interview with the Everyday Astronaut.
Elon reiterated that he changed to steel construction for the rocket when carbon fiber was taking too long. Carbon fiber was a standard in the rocket industry.
SpaceX Falcon Heavy use of composites for the fairing (payload nosecone cover). The interstage, which connects the upper and lower stages of the rockets, is a composite structure with an aluminum honeycomb core and carbon fiber face sheets.
In December 2018, nine months after starting construction of some parts of the first test article carbon composite Starship low-altitude test vehicle, SpaceX CEO Musk announced a “counterintuitive new design approach” would be taken by the company. SpaceX switched to stainless steel construction.
All engineers at SpaceX need to have some perspective of a chief engineer. Everyone in engineering at SpaceX needs to understand all of the parts of the whole system they are building. They need avoid having engineers optimizing just one part. The engineers need to question the contraints that they are being given. This can only be done if they understand the whole system.
One of the most common mistakes of smart engineers is to optimize on a part or process that does not need to be present. If the whole system is understood and the purpose of processes and parts is understood then it is possible to eliminate parts and processes.
There is a final discussion of the aerospike engine. The aerospike has greater theoretical efficiency. Elon indicates that with their two-stage rocket, they can optimize the booster with sea-level optimized engines and the upper stage can have vacuum optimized engines. This reduces the practical need for an aerospike.
SOURCES – Everyday Astronaut, Elon Musk, SpaceX
Written By Brian Wang, Nextbigfuture.com