Node 4
Node 4, also known as the Docking Hub System (DHS), is a proposed module of the International Space Station (ISS). NASA is considering a 40-month design and development effort for Node 4 that would result in its launch in late 2013.[1]
Node 4 would be built using the Node Structural Test Article (STA) and docked to the forward port of the Harmony module. The Structural Test Article was built to facilitate testing of ISS hardware and was intended to become Node 1. However, during construction, structural design flaws were discovered. The under-construction Node 2 was renamed Node 1 and the STA (ex-Node 1) was put into storage at the Kennedy Space Center (KSC).[2]
Since Node 4 would not be completed until after the end of the Space Shuttle program, it would be launched by an Atlas V or Delta IV rocket.[3]