Node 4, also known as the Docking Hub System (DHS), is a proposed module of the International Space Station

International Space Station

The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...

 (ISS). NASA

NASA

The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 is considering a 40-month design and development effort for Node 4 that would result in its launch in late 2013.

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).

Since Space Shuttle program

Space Shuttle program

NASA's Space Shuttle program, officially called Space Transportation System , was the United States government's manned launch vehicle program from 1981 to 2011...

 has been terminated, should a decision to build and launch Node 4 be taken, it could be launched by an Atlas V

Atlas V

Atlas V is an active expendable launch system in the Atlas rocket family. Atlas V was formerly operated by Lockheed Martin, and is now operated by the Lockheed Martin-Boeing joint venture United Launch Alliance...

 or Delta IV rocket.