scratch building locomotives

When tractors were first developed, they used enormous steam engines which were notoriously unreliable and challenging to maintain. These were phased out round the turn in the 20th century and substituted with internal combustion engines that have been more compact yet still powerful and ran on the variety of fuels including kerosene, ethanol and gasoline. By the 1960s many of these engines were phased out and only more effective internal combustion engines that ran on diesel and after this, biodiesel. However the humans living on the spaceship were different to the humans who will be living on earth now. They were so fat them to be struggling to walk. they travelled around in motorised chairs using a computer screen and cup & straw attached, chatting on phones and if they happened to fall out they only laid there until a robot arrived and picked them up. The adults were fat, your children were fat! They just laid around all day meals doing no exercise what so ever and to quote the captain, "Computer, define dancing".