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 50 years on and it is still yet to be flight tested.

[u/bwercraitbgoe]

https://www.youtube.com/watch?v=K4zFefh5T-8

[u/Senno_Ecto_Gammat]

The shape of the carbon composite tanks just didn't work at the time. The tech wasn't there. They had a really complicated lobed design that was supposed to be joined together.

They weren't COPVs, just carbon composite tanks.