BLISK (bladed disc) development

Air Force's long-running motivation for welded (vs. mechanically joined) bladed discs: lighter rim means smaller hub means cascading weight savings.

Because of that, the Air Force in particular has been looking at, for years, something called a bladed disc, or a BLISK. Right now you have a disc with these turbine blades essentially mechanically joined on the end, and that makes a big fat joint compared to if you could weld them together. That heavier section out at the rim means the hub has to be stronger because of the greater centrifugal force from the weight at the top of the rim. It's a great big flywheel, in a sense. So if you take the weight out up there, you can save weight here. There are follow-ons.