spaceship earth

a peaceful spaceship.

land ecosystem:

both plants and humans need light.
they also both need water.
an atmosphere is required:
 plants inhale CO2 and exhale O2.
 animals exhale CO2 and inhale O2.
animals require vast area's of plant life (forest).
humans and animals eat animals and plants.

water ecosystem:

waterplants and algae produce O2 (from light).
fish breath that O2 directly from the water.

Both plants and animals require relative long undisturbed timeframes... years, typically.

This spaceship needs a big, slow-starting, but ultimatly fast going engine: the ion drive.

The spaceship
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The purpose of the spaceship is to have planet-independent interplanetary space traffic.

The spaceship a flat cicle, is tilted towards the star, and its radius is as big as is required for reasonably sized ecosystems. No solar panels are needed for the electronic systems, that energy is provided for by the engine, as is the H2O is split in the engine into H2 and O2. The iondrive allows arbitrary changes in orbit, but slowly. When the star distance increases, the temperature gets lower and the amount of light received gets lower. The disk is livable on both sides, ot rotates around an axis in the star- surface area plane in 12 hours. Tho there is zero-gravity in space, sandwiched between the two biocicles is a 1g gravity engine.

The iondrive engine
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The engine is a cylinder, normally positioned exactly on the spaceship axis, is able to 'rotate' around the origin for 20 degrees. The exhaust is long enough to shield all ecosystems from the mile long, intense blue light of the engine. A big engine.