Alan’s Landship Game is a set of free wargames rules that pits Victorians against Martians.
Majestic 12 Games has these demo rules for their Iron Stars miniatures wargame. I’ll let them explain:
Iron Stars is a game of space combat in an age of steam and steel. Set in a fictional universe based loosely on the writings of H. G. Wells and other fantasists, it provides a back story and ship designs from an alternate history in which the Martian Invasion actually happened, the ether is all?pervasive, and Cavorite is a reality. But, as with Starmada and other Majestic Twelve Games products, the focus is on players’ imaginations; a clear and concise ship construction system is provided so you can pit your own space dreadnoughts against the likes of the Royal Navy Ether Squadron or the German Aethermarine.
Royal Venusian Trading Company is a swords-and-planets exploration game with roleplaying elements based on old school D&D clones. From the author’s explanation:
In a fantasy Victorian Age universe, a team of ardent explorers are racing into unknown parts of the savage world of Venus in search of glory and riches beyond measure. Guided by hearsay, rumors, and third hand information, each Expedition will attempt to conquer the unyielding environment and plunge into the heart of the world of the cruel and fickle goddess of love.
The Game begins with the explorers outfitting their expedition. Then the team will move across the uncharted planet. Exploration, hunting, natives, natural, and other disasters will all have to be dealt with.
Matthew Hartley has a game called Kraken, inspired by the man against sea monster scene in Jules Verne’s 20,000 Leagues Beneath the Sea
Cloudships of Mars is a set of free wargames rules based on the excellent Space: 1889 universe. The Cloudships game features ships propelled by steam and sail gliding high above the plains of Mars thanks to the magic of “Liftwood.”