The Fall of the Angels

It has been said that these "ships" are rather grown than made.

David's ship does 'emit' some kind of blue light when it sets off on its journey.

As to how they are constructed, the distinction between 'grown' and 'made' gets rather blurred in an advanced technological civilisation. There may be a time, perhaps in a hundred years even on Earth, when you can buy a dehydrated packet of vacuum cleaner nano particles, add water, a few kilos of powdered rock and – presto – you've got a new vacuum cleaner.

At any rate, energy has to somehow be consumed and depending on efficiency, a certain amount is expelled in the form of unusable energy such as exhaust. 

I think they have to use some kind of slave labor to build their ships and lv223 facilities. My guess their jockey suits are grown or the shell of some engineered creature. Thought Ridley said the ships used magnetic fields but also the exhaust about blows Noomi out of the hangar. Geiger really had a unique mind, so glad he got to share with us.