Complex sentence: The air is then used for combustion much like in a conventional jet and once the helium has left the pre-cooler is further heated in by the products of the pre-burner to give it enough energy to drive the turbine and the liquid hydrogen pump.
Split into simpler sentences: The air is then used for combustion much like in a conventional jet. Once it has left the pre-cooler the helium is further heated in by the products of the pre-burner to give it enough energy to drive the turbine and the liquid hydrogen pump.