Artist concept of the S-IVB firing to send the crew to the Moon, aka the translunar injection burn. It fired in a vacuum. For real. NASA.
“Rockets can’t fly in space! There’s no air for the engine to burn in space! And there’s no air for the rocket to push against in space! WE’VE NEVER LEFT EARTH!”
So goes the cry of people who don’t believe we landed on the Moon — at least, this is one of their claims. But it’s wrong. In spite of what they think, rockets can and do fly in a vacuum. Fuel and oxidizer mix and ignite in a combustion chamber causing a controlled explosion that is directed out through the engine bell. This forceful expulsion of hot gas is thrust, and when that thrust is powerful enough to overcome the mass of the rocket, it lifts (ideally) smoothly off the ground.
So where does this misconception come from? Most likely, from cars.
Most of us interact with a car engine in our daily lives, so that’s the familiar benchmark. A car engine isn’t the same as a rocket engine (if they were identical our morning commutes would be much faster!) but the general ...