My latest creation is a rework of the Cityship Atlantis, a vehicle meant to carry 5000 colonists on a 40 year voyage to Alpha Centauri. I did a model of it five years ago, and now I've updated it based on some more realistic assumptions. For reference, the core vehicle (hab rings and tanks) is 250 meters in diameter and 1325 meters from pusher plate to engine nozzle. The wide thin rings are the basis of a magnetic sail used mainly for breaking at the destination. To the left of the image is a nozzle for a fusion drive, powered and fueled by liquid hydrogen in the big orange and white tank; it also acts the nozzle for the ramscoop drive. The original version of the Cityship just had a fusion drive, some spikes for a magnetic sail and a ramscoop for interstellar flight. I still like ramscoops, even though they might not be all Robert Bussard and Larry Niven hoped them to be. So to make it a little more realistic, I've added a hybridized Orion/Daedalus nuclear pulse drive to get the Cityship up to about 1.5% of light speed. By hybridized, I mean that instead of using left-over nukes, which tend to be in the hundreds of kiloton range, I've opted for a smaller explosion, one that uses tiny fusion bombs and iron propellant. Somebody more technical might call me on this idea, but here it is: Once a second, a conical canister shoots out the back -- it's mostly iron, but the pointy end has a set of focusing mirrors and a pellet of about a hundred milligrams of deuterium and tritium. Six of the 72 lasers at the edge of the plate fire at the canister, causing a small fusion explosion that vaporizes the iron and generates thrust. The segments of each rotating habitat ring are hinged, so that they can deal with acceleration from both spin and thrust and still leave the residents with a consistent direction of "up". I figure one pulse every second will generate between .03 and .07 gravities and propel the Cityship up to 1.5% light speed in about three or four months. Next, now that the ship has enough velocity to sweep up a decent amount of interstellar hydrogen every second, the ramscoop kicks in. The scoop itself is not deployed in this image. It would extend past the pusher plate on the right and it generates the field that collects hydrogen. For this, the Cityship turns around (again handy to have the hinged habitat segments). Now, the lasers that ignited the canisters are used to spray the area in front of the ship to ionize interstellar hydrogen. Four radar arrays scan ahead to look for larger obstacles that might require a laser zap or push. Also the mesh web segments on either side of the hab rings are there to intersect any debris that sneaks in from the side; acting as an external shield that takes the impact of a grain of interstellar dust and causes the explosion to occur away from the core vehicle. From the scoop, hydrogen ions flow into a central shaft, get seeded with tiny amounts of carbon, and fuse as they travel through the ship, generating the energy that expels them out the back at a higher velocity. After a couple of years, the Cityship reaches about 12% light speed. I figure for this first generation ramscoop, that's all it can manage. There are issues with absorbing the energy of the gathered hydrogen -- interstellar drag, if you will. Thanks for viewing and commenting and thanks if you're still reading at this point. A tiny story follows. --- The last view of Earth was of Antarctica. Two days after departing from Astra Station Atlantis passed eight hundred klicks over the South Pole, using the gravity well for maximum effect as we began the long hyperbolic fall towards the sun. At the time, I figured none of us would ever see that world again. --Alexander Tate, Remembrances of the Long Dark Night, Chiron Press 2210