Soyuz-5, also named Irtysh is a planned Russian rocket that is being developed by JSC SRC Progress, formerly within "Project Feniks." It will replace the capability of Zenit-2 and Proton Medium. It will initially be a two-stage rocket, but Soyuz 5 can be enhanced with an optional Blok DM-03 upper stage for geostationary missions. The rocket is loosely based on the Zenit launch vehicle with a RD-171MV engine on the 1st stage, enlarged to 4.1 m in diameter, while the 2nd stage is powered by 2 RD-0124MS engines derived from engines used on the 3rd stage of the Soyuz-2.1b. The Soyuz-5 can lift 17 tonnes to a Low Earth orbit.