Falcon 9· guided tour

Merlin Vacuum Engine

the big bell

Look how huge this engine's bell is compared to the nine at the bottom. That is not for show — in space there is no air squeezing the flames, so the exhaust is allowed to spread out really wide. A wider bell in space means more push.

Push

934 kN

Efficiency

348 s

Nozzle ratio

165:1

How it works

Down at the ground, a bell this big would not work: the air outside would squash the flame and shake the engine apart. That is why the bottom engines have small bells and this one has an enormous one. Each engine is shaped for the place it works in.

For the grown-up

The niobium-alloy nozzle extension is radiatively cooled and glows orange in flight. Isp of 348 s is the highest of any flown US hydrocarbon engine. It throttles down to 360 kN for fine terminal guidance.

Merlin rocket engine family