Can loosely remember seeing a film made in the last 2-10 years of a young person building a space ship. At some point the ship comes to life and an element that it fills with a liquid of sorts to protect from effects of force for space travel? Beyond that can’t remember anything.
Could this be Explorers?
Ben Crandall is a young teenage boy living in the suburbs of Washington, D.C., who experiences vivid dreams about flying through clouds and over a vast, city-like circuit board, usually after falling asleep watching old sci-fi films (The War of the Worlds is a favorite). Every night, upon waking from the dream, he draws the circuit board. Ben shows the sketches to his friend, child prodigy Wolfgang Muller. At school, Ben develops a crush on Lori Swenson, but he isn't sure whether it's mutual. Both boys meet punkish-but-likable Darren Woods, with whom they share their circuit-board concepts. Wolfgang builds an actual microchip based on Ben's drawings. The chip enables the generation of an electromagnetic bubble which surrounds a pre-determined area. As the boys discover, the bubble is capable of moving at near-limitless distances and speeds without the usual ill effects from inertia. They construct a rudimentary spacecraft out of an abandoned Tilt-A-Whirl car; they name their ship the Thunder Road, after Bruce Springsteen's song of the same title. Their experiments with the Thunder Road draw attention from the United States government, which sends agents to scout the area for UFOs.
After Ben receives more dreams about the circuit board, Wolfgang discovers a means of producing unlimited sustainable oxygen; this means longer flights, whereas previously they were limited to whatever a typical oxygen tank could hold. They finalize their plan to explore the galaxy in search of alien life. The boys complete lift-off, despite interference from the authorities (one of whom silently wishes them well). Shortly after breaking Earth's orbit, something overrides the boys' personal computer-controls. The Thunder Road is tractor-beamed aboard a much larger spaceship. The boys venture out to meet their "captors", Wak and Neek: two green-skinned aliens whose knowledge of Earth comes almost entirely from junk culture, particularly television reruns. The young explorers hit it off with their extraterrestrial hosts, but then the alien ship is suddenly intercepted by a larger-still alien vessel. Feigning an attack by space-pirates, Wak urges the boys to leave. They are in the process of doing so when they're interrupted by a gigantic brown extraterrestrial, this one bearing a close resemblance to the other two, who gestures furiously while grinding out barely-comprehensible alien language. As it turns out, Wak and Neek are brother and sister; they've taken their father's ship out for a "joy ride", sending the dreams to the boys in the hopes of meeting humans. Transmissions of old black-and-white movies have kept the extraterrestrial populace at a distance – except for the curious Wak and Neek – due to the way humans generally depict violence toward alien life.
Wak and Neek's father allows the Thunder Road and its crew to depart, after Wak and Neek give the boys a parting gift: an amulet which, according to the extraterrestrials, is "the stuff dreams are made of". The boys make it safely back to Earth, but a malfunction results in them crashing the Thunder Road into their neighborhood lake. Now they're back to square one... or so they think. A week later, Ben has a dream at school in which he envisions another vast circuit board while flying through more clouds overhead. This time – thanks to Wak and Neek's amulet – Ben is joined in the dream by Wolfgang, Darren and Lori. They proclaim that the circuitry is "really complicated", and wonder where this one will take them once they've constructed it. Lori smiles at Ben while holding his hand.
It's a kid (three kids) building an alien spaceship. It's not a fluid inside the ship, but it is a way of protecting themselves from inertia.