The Intricate Startup Sequence of the Apollo 11 Saturn 5 Rocket Engines

The startup sequence of the Apollo 11 Saturn 5 rocket engines is a complex process involving multiple moving parts and careful synchronization.

The engines start with a blocked propellant flow, which is later opened by valves, allowing fuel and oxidizer to flow into the engine.

Pyrotechnic devices are ignited to break metal wires, triggering the next steps in the ignition process.

The fuel and oxidizer valves leading to the gas generator are opened, initiating combustion and generating exhaust gases.

The thrust gradually builds up to 100% as the engine ramps up power, and a final signal triggers liftoff.

What is the purpose of the hypergolic cartridge in the startup sequence?

—The hypergolic cartridge contains starter fluid that, when exposed to oxygen, initiates the main combustion.

How are the engines ignited?

—Pyrotechnic devices are fired, breaking metal wires connected to a circuit, which signals the next steps in the ignition process.

Why are the engines lit in a staggered manner?

—To prevent excessive shock to the spacecraft, the engines are ignited one after another, allowing them to ramp up to full thrust gradually.

What is the role of the regenerative cooling system in the combustion chamber?

—The combustion chamber is regeneratively cooled by flowing fuel through the walls, which keeps the engine from overheating.

How much thrust does each Apollo 11 Saturn 5 engine generate?

—Each engine is capable of generating over 700 tons of thrust.

00:03The Apollo 11 Saturn 5 rocket engines are being celebrated on their 50th anniversary.

00:10Rocket engines don't simply go from zero to full thrust in an instant; there is a complex startup sequence involved.

01:43Pyrotechnic devices are fired to break metal wires and trigger the next steps in the ignition process.

03:55The fuel and oxidizer valves leading to the gas generator are opened, initiating combustion and generating exhaust gases.

05:36The engines gradually ramp up to full power, and a final signal triggers liftoff.

06:56To smoothen the engine thrust buildup, the combustion chamber is regeneratively cooled using ethyl glycol.

08:07Each engine is capable of generating over 700 tons of thrust, consuming more than two tons of propellant per second.