Transpiration cooling of rocket engines

A method of fabricating a rocket engine, the method comprising:

• vacuum plasma spraying a first metal onto a throat region of a mandrel to form a throat inner wall;
• vacuum plasma spraying the first metal onto a combustion chamber region of the mandrel to form a chamber inner wall;
• vacuum plasma spraying the first metal onto a nozzle region of the mandrel to form a nozzle inner wall;
• vacuum plasma spraying a second metal onto the throat inner wall, the chamber inner wall, and the nozzle inner wall to form an intermediate layer;
• forming a cooling channel in the intermediate layer;
• filling the cooling channel with a removable material;
• vacuum plasma spraying a third metal onto the intermediate layer and the removable material to form a closeout layer;
• and
• removing the removable material,
• wherein, a porosity of the first metal varies in an axial direction of the engine.

A method of cooling a rocket engine, the method comprising:

• passing a coolant through a cooling channel;
• passing the coolant from the cooling channel to a porous throat inner wall of the engine;
• and
• passing the coolant through the throat inner wall to a throat of the engine by transpiration,
• wherein, the coolant passing through the cooling channel cools a combustion chamber inner wall of the engine by convection,
• the coolant passing through the cooling channel cools a nozzle inner wall of the engine by convection,
• the coolant passing through the throat inner wall cools the throat by transpiration,
• the combustion chamber inner wall is formed by vacuum plasma spraying,
• the nozzle inner wall is formed by vacuum plasma spraying,
• the throat inner wall is formed by vacuum plasma spraying, and
• a porosity of the vacuum plasma sprayed metal varies in an axial direction of the engine.