A small turbojet of the type that the UK MoD wants to develop for one-way UAVs under its Project Callisto. (Janes/Patrick Allen) The UK Ministry of Defence (MoD) has launched a new effort to field an affordable engine for one-way unmanned aerial vehicles (UAVs). Dubbed Project Callisto, the effort launched on 6 July 2026 aims to bridge the performance gap between hobbyist, model aircraft engines and higher performance, long-life and more exquisite engines.