Thanks for the link, this clears up a lot: http://www.reactionengines.co.uk/images/sabre/sabre_cycle_1024.jpg http://www.reactionengines.co.uk/images/sabre/sabr

Thanks for the link, this clears up a lot: http://www.reactionengines.co.uk/images/sabre/sabre_cycle_1024.jpg http://www.reactionengines.co.uk/images/sabre/sabre_cycle_10... There is no nitrogen in the system (not as consumable, anyway). Shoddy BBC reporting, as usual. The heat exchangers use chilled hydrogen fuel they have to take up anyway, before it is burned in the rocket motor. That makes a ton more sense.