For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
The Gun Club—famed purveyors of massive cannons since the Civil War—is bummed out because their country is (sadly) mired in peace. Yuck. Luckily, club president Impey Barbicane has a plan: They will build a giant cannon, not to kill people, but to launch a shot all the way to the moon. Assisted by his faithful sidekick J.T. Maston, Barbicane leads the Gun Club to Tampa, Florida, where they will begin construction for launch.
Act II
An unexpected telegram arrives from Michel Ardan, a French adventurer, asking if he can ride inside the cannonball. Le what? Charmed by this one-of-a-kind Frenchman, Barbicane agrees and modifies his design to include a passenger. Meanwhile, Barbicane's arch-nemesis Captain Nicholl (a world-renowned armor-plate designer) is publicly attacking the project, finally demanding a duel to the death with Barbicane. Luckily, Ardan arrives at the nick of time with an enticing counter-proposal: The three of them should go to the moon together. Good times.
Act III
Surprisingly, everybody's gung-ho about the idea. After completing construction, our intrepid heroes set up the cannon for launch. And guess what? It works. That said, there are some unforeseen side-effects—natural disasters, earthquakes, and ominous clouds that cover the sky for weeks. The clouds are so thick that they can't even track the capsule. When the clouds finally break and Maston spots the capsule, he sees it has missed its mark and is currently orbiting the moon.
And that's it. Nobody knows what will happen to the capsule—at least, until they read the sequel.