Aerospike engines. Why aren’t we using them now?
Over 50 years ago an engine was designed that overcame the inherent design inefficiencies of bell-shaped rocket nozzles, but despite much research in the 60’s, 70’s and 90’s and was to power the replacement for the Space Shuttle. But 50 years on and it still yet to be flight tested. So why aren’t we using Aerospike rocket engines?