In 2001, the Volvo Technology Award went to a group of engineers who had developed a completely new form of nozzle cooling known as film cooling.
It was designed for the Vulcain propulsion unit for the Ariane space launch rockets, and reduced the nozzle production cost by 40%.
Sprayed at supersonic speed
Film cooling means that gases are sprayed at supersonic velocity along the inside wall of the nozzle to cool the wall and improve its strength.
In the Vulcain 2 nozzle, the upper half is cooled by liquid nitrogen pumped through the tubes that comprise the wall.
Exhaust gases used
The lower half is film-cooled using the exhaust gases from the two turbines that drive the fuel and oxygen pumps, together with the hydrogen already used to cool the upper half of the nozzle.
The film follows the entire wall as far as the nozzle outlet, protecting it from the extremely high flame temperature of 3,100°C.