The Myasishchev M-18 was a design for a Soviet supersonic bomber with a variable-geometry wing.
The project was dropped in favour of the Tupolev Tu-160 program. Although the design was the most successful when competing with the Tu-160 and Sukhoi T-4, it was dropped as Tupolev had the most potential to go ahead with the supersonic bomber project.
References
Myasishchev M-18 Wikipedia(Text) CC BY-SA