|Engine Restart Capability||No|
|Can Attach Payloads||Yes|
|Can Attach Boosters||No|
The Proton First Stage is a medium-sized first stage , unlocked after the completion of Mission 11. It is used to make the Russian Proton rocket.This part is similar to the Soyuz First Stage in that it has pre attached boosters.It costs 15,000,000$ in Career Mode .