Early Sunday morning, SpaceX launched a Falcon 9 rocket carrying a Dragon spacecraft to the International Space Station. Among the footage of the mission launch was a view from inside one of the fuel tanks, and of course it has been turned into a GIF and is making its way around the Internet.
It’s totally mesmerizing, but doesn’t exactly come with a manual. So here’s the GIF, and what exactly you’re looking at.
The Falcon 9 rocket is SpaceX’s two-stage rocket. Both stages are powered by Merlin-class engines [Editor’s note: Wizard rocketssss] that burn traditional fuel: cryogenic liquid oxygen and rocket-grade kerosene. The Draco thrusters on the Dragon spacecraft — the one that will likely ferry US astronauts — uses different kinds of propellants. They use hypergols, fuels and oxidizers that ignite on contact without the need of an ignition source, which are chemicals with fancy names like nitrogen tetroxide and monomethylhydrazine. But it’s the cryogenic liquid oxygen that we’re interested in for the moment.
Any engine needs air for the fuel to burn. It’s the burning fuel that causes an explosive reaction, and when that reaction is directed through an engine bell it turns into the thrust a rocket needs to get off the ground. But because a rocket passes through the atmosphere so quickly, it can’t use atmospheric oxygen for this reaction. That’s why rockets carry their own oxidizer, but in a liquid rather than a gaseous form. Liquid oxygen, or LOX, is super-cooled oxygen that remains in a liquid state at temperatures below -298 degrees Fahrenheit (which is about -183 degrees Celsius).
The GIF shows the inside of a LOX tank, likely on the Falcon 9’s second stage.
The footage starts with the LOX resting at the base of its tank. That’s because the rocket’s second stage is firing. According to the launch video, the first shot of the LOX tank appears when the rocket is traveling at around 2.4 miles per second (or 4 km/s). With the rocket moving so fast and accelerating, it’s pulling enough g-forces to push the fuel against the bottom of the tank. It’s like standing in an elevator that suddenly shoots up really quickly — the g-forces would knock you to the floor. If you had a bottle of water in your hand, the water would also be forced to the base of the bottle.
Then we see a change in the fuel tank when the second stage shuts down. At this point in the flight, the remaining pieces of the rocket are in orbit, so the g-forces of launch have dropped off to nothing. With no g-forces keeping the fuel against the bottom of the tank, it starts to float. If the elevator you were in started suddenly falling, you and the water in your bottle would float upwards thanks to the sudden loss of g-forces. Of course, It probably wouldn’t look this dang cool, or spontaneously produce a Kurt Russel.
You can watch the whole video of SpaceX’s most recent Falcon 9 launch online, which includes shots from inside the LOX tank, here.