I lately got hung up on Aerospike nozzles. The concept has been around for decades in various toroidal or linear variants. The benefit lies in its altitude-compensating nature which allows the nozzle to achieve higher efficencies across the whole pressure regime when going from sea level up to the vacuum of space, while traditional bell nozzles are limited by their maximum expansion ratio.
However, no Aerosike nozzle has ever flown due to overheating and overweight issues. Modern 3D-printing technology could help to overcome these hurdles. Meanwhile the design process is not all too complex. The Aerospike mainly consists of a convergent nozzle and a spike geometry. The later one takes some careful design efforts in order to make the expansion work under the Prandtl-Meyer constraints.
I hope to share some more solid work soon, but for now a little fun teaser to demonstrate how the pressure compensation works. What do think about the future or Aerospike engines?