Earlier this year famed Halo game creator Bungie announced the formation of Bungie Aerospace, a new venture aimed at publishing mobile games. The first fruit of that labor, Crimson: Steam Pirates, is now available for the iPad on the App Store. It’s free to download, with unlockable content available through a $1.99 in-app purchase.

Crimson: Steam Pirates is a steampunk take on a rollicking pirate adventure on (and above) the high seas of the Caribbean, as Thomas Blood’s pirate fleet attacks all comers. Ships armed to the teeth with swivel cannons and lightning guns cruise the waves, while zeppelins hunt above with incendiary bombs and submarines stalk from below with torpedoes.

The game features eight voyages, two “pass-and-play” multiplayer scenarios, more than a dozen different unit types, and more than 20 different crew members, each with special abilities. The game’s stats integrate with Bungie.net and Facebook.

Although there’s additional content for purchase, this isn’t a “freemium” game – Crimson: Steam Pirates comes with eight missions playable as soon as you download. A second “chapter” with mission packs costs you $1.99.

Crimson: Steam Pirates was made by Harebrained Schemes, a developer helmed by Jordan Weisman, creator of MechWarrior, Crimson Skies and Shadowrun.

[Updated 3:02PM PT with info about second chapter]