Boom Supersonic is completing construction of their Boom XB-1 one-third scale technology demonstrator, and has received orders for its Boom Overture supersonic passenger airliner from both United and American Airlines. But what it doesn’t seem to have is an engine. After conducting a joint study with Boom, Rolls-Royce announced it had no plans to develop a powerplant for the aircraft, joining the other big engine manufacturers in expressing a lack of interest in the market. Does this mean the end of Boom and its hopes to revive supersonic civil aviation?