What key features in George Stephenson's *Rocket* proved the viability of smooth-railed railways?

Answer

A multi-tubular boiler and a blast pipe

Stephenson’s *Rocket* incorporated advanced features like a multi-tubular boiler and a blast pipe, which together improved fire efficiency and increased the engine's power output.

What key features in George Stephenson's *Rocket* proved the viability of smooth-railed railways?
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