Project Orion! My favorite of the bunch, just because it’s so typically human. Throw boom boom out ship, big explosion make ship go. It’s so insane given how dangerous nukes are but of course the math works out, and the universe doesn’t care what seems insane, only what abides by the laws of physics.
I wrote my own article on Project Orion some time ago: https://steemit.com/space/@alexbeyman/project-orion-the-starship-propelled-by-nuclear-bombs
I don’t suppose you’re looking for new writers? If you check out my articles so far, you’ll notice I just finished a series on manned undersea habitats, past present and future. It’s a topic I don’t see anybody covering on Futuresin.
There’s a lot of focus on space, but little to none on the 75% of our own planet covered in ocean. Mastering and inhabiting the ocean is a critical step for our species on the road to Kardashev level 1.