Watch this incredible slow-motion footage of a rocket engine test

The Slow Mo guys — aka Gavin Free and Daniel Gruchy — are back with another video that’s as fascinating as it is entertaining, this one showing a rocket engine test in astonishing, slowed down, detail.

The popular YouTubers traveled from the U.K. to Texas to point their slow-motion camera toward a test of Firefly Aerospace’s Reaver engine.

A video shared by the Slow Mo Guys starts by revealing the careful preparation that went into setting up the slow-motion camera. After all, too close to the action and it would’ve disintegrated, and too far and the footage would’ve lacked impact.

The biggest challenge was selecting the ideal camera exposure. Exposing to the natural light would’ve blown out all of the details in the extremely bright flames as they blasted out from the rocket engine. So, to capture detail in the flame while avoiding making everything around it completely dark, Free set the camera’s exposure at four stops under, making the image much darker from the outset. Afterward, after seeing the footage, he admits he probably should’ve stopped down even further.

The footage is still very impressive, showing the rocket engine firing at 80 times slower than real time. Such is the power of the rocket, which in a vacuum is capable of 45,000 pounds of thrust, the footage of the flames actually looks like it’s playing in real time.

This is noted by Free, who said in the video: “The most insane thing to me about this footage is that you could look at this and not necessarily know this was 2,000 frames a second; this is 80 times slower than real time, and the only indication is when these little pieces of debris are flying past the camera. The flame and the vibrations produced by the engine look so incredibly fast, it could almost be real time.”

Despite finding it a “pretty nerve-wracking experience,” Free was delighted with the footage they managed to get. Check it out in the video at the top.

The Slow Mo Guys have built a loyal following of 14.8 million subscribers since starting their YouTube channel 13 years ago. Their most popular video, showing the pair burst a giant water balloon, has picked up 198 million views to date. The channel’s content covers a huge variety of ideas, from the mundane (shattering glass), to the weird (spinning an apple until it explodes), to the wacky (diving on a paint-covered trampoline) … all captured in very slow motion.

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