In the Federation, a jet is a grey plastic tube, about 6 centimetres in diameter and 8 centimetres long, open at both ends.  It has a two narrow metal bands round the outside, near one end.  When a power pack is connected to the metal bands, air rushes through the tube – a jet of air so fast that it can make the tube move, like a rocket.  Single jets are never used.  163 are fitted into a frame, making a bank of jets.

I learned about jets during my visit to the Zejets works on Obegon 4.  See Report H.