The Delta-K is an American rocket stage, used as the second stage of several variants of the Delta rocket. As of 25 May 2008, 138 have been launched, and excluding one which was destroyed by the explosion of a lower stage, none have failed. It is propelled by a single AJ-10-118K rocket engine, fueled by Aerozine 50 and dinitrogen tetroxide, which are hypergolic.
The Delta-K is still in use, currently as the second stage of the Delta II rocket.