The Physics of Mandalorian Jetpacks
Happy Star Wars! And let the fourth be with you.
It has become a tradition for my physics bloggers to celebrate the day by posting stories like their analysis of Star Wars.
With season 3 of The Mandalorian now over, it seems fitting to take a look at the iconic “jetpack.” As a reminder, the Mandalorian are a group of people from the Star Wars universe, originally from the Mandalorian system. Known for their armor, many of them also use jetpacks. For those who haven’t seen the show, these are rear-mounted units with two rocket nozzles that shoot out exhaust. (A supercut of the jetpack scene from season 2 can be found here.)
Of course, the first time we saw one of these fighters in action was when Boba Fett used it in Episode VI: Return of the Jedi. We’ve seen a lot of Mandalorian flying since then. It is enough to get the data and understand how things work.
Jetpack vs. Rocket
Everyone calls these planes “planes”, but do they work as planes? Or does it work like a rocket?
To find the difference, start with rockets like the RS-25 engine used for NASA’s Space Launch System (SLS). All rockets are launched by launching the mass from the back of the engine. The RS-25 uses liquid oxygen and liquid hydrogen chemistry for propulsion. The combination of oxygen and hydrogen produces water vapor, all of which energy is used to atomize the water vapor into smoke.
What makes this move the rocket forward? Consider the change in water vapor momentum. Momentum is the product of mass and velocity. The water vapor produced by the reaction of oxygen and hydrogen first stops inside the rocket and returns to very high velocities. According to Newton’s third law, when a rocket engine propels water vapor, the water vapor propels the rocket. This creates a thrust that pushes water vapor out of the engine. (Or upward thrust for moon-bound rockets.)
Various types of rockets can use other liquid fuels and solid fuels, such as methane. (For example, the space shuttle’s solid rocket boosters use aluminum powder mixed with oxygen.) But the principle is the same.
Do you know what’s really great about rocket engines? Generates thrust without relying on nearby rockets. Rockets can be used in space or underwater without air.
However, there are also downsides. All fuel must go inside the rocket. It takes a lot of fuel to get enough engine power to lift a rocket off the ground. And if you want a lot of fuel, you need a bigger rocket. This will help identify any issues that arise. You need really big rockets to go into orbit or go to the moon. SLS is 212 feet tall. SpaceX’s Super Heavy rocket is 390 feet long. (At least that was until it exploded after it came out a few weeks ago.)