The correct answer is option 1, which states that only the first statement is correct. Let`s dissect both statements for better understanding:

Statement 1 - The usage of aluminium powder as a solid fuel for rocket engines is indeed accurate. The reason for its use is its high energy content. When aluminium is burned, it creates extreme heat, resulting in a substantial amount of energy. Therefore, it acts as an efficient fuel for rocket engines.

Statement 2 - Contrary to the given statement, the thrust per amount of fuel burned is actually lower in solid fuel propelled rocket engines compared to liquid fuel propelled engines. A key advantage of liquid fuels over solid fuels is that they can be regulated and shut down mid-flight, allowing for more control. On the other hand, once solid fuel is ignited, it continues to burn until all the fuel is expended, which gives less control over the thrust. Therefore, statement 2 is incorrect.