Complex sentence: In his small laboratory in Worcester, Massachusetts, Goddard worked with liquid oxygen and gasoline to propel rockets into the atmosphere, and in 1926 he successfully fired the world's first liquid-fuel rocket which reached a height of 12.5 meters.
Split into simpler sentences: In his small laboratory in Worcester, Massachusetts, Goddard worked with liquid oxygen and gasoline to propel rockets into the atmosphere. In 1926 he successfully fired the world's first liquid-fuel rocket, which reached a height of 12.5 meters.