What was a major historical factor that delayed the widespread adoption of liquid methane as a primary launch propellant?
Answer
Established infrastructure, legacy knowledge, and the significant capital investment required to switch from mature $ ext{RP-1}$ systems.
The aerospace industry had decades of experience and supply chains built around $ ext{RP-1}$. Transitioning to cryogenic methane involved significant development risk and capital investment, slowing its adoption until newer, complex engine technologies matured.

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