The Hermes Spacecraft is "the most complex and expensive object ever built," astrophysicist Neil deGrasse Tyson says in a promotional video for the film and it is the result of a decade long collaboration between NASA, ESA, ROSCOSMOS, JAXA, ISRO. Hermes was also built using the SpaceX space station as a building platform.
Hermes 1

A picture from The Complete Ares III Mission Guide.

The Hermes is a spacecraft the crews of the Ares Missions used as a transportation system between Earth and Mars.

The Hermes was assembled in Low Earth Orbit with the new SpaceX Station serving as an assembly platform. Individual parts were transported to the station piece by piece. The process was tedious, but the results established a new era of space travel. Hermes was completed and flew its first mission in 2029, with the Ares I crew.

Crews take a transport shuttle to and from the ship. From there, the ship's revolutionary Nuclear-powered propulsion system utilises ion engines to churn out argon and propel the ship forward in a perfect controlled cruise. While aboard, the ship's rotating gravity drum generates enough artificial gravity to allow the astronauts ease of mobility while protecting them from the effects of long-term weightlessness. It also features state of the art plastic shielding to insulate the ship from cosmic radiation (which can cause cell damage and cancer). The ship features a powerful reactor that will power everything. It also offers an array of life support systems, such as its oxygenator and water reclamation processors.

Despite the innovations, the Hermes has a relatively short lifespan. It is currently commissioned for five missions to and from Mars, and the rigours of travel are expected to render the ship unsafe for additional interplanetary travel. Hermes was also re-proposed as a transport space craft for the Ares VI mission to put more satellites around Mars.

However, after the completion of Ares V, the Hermes is currently planned to be retooled and recommissioned as the new International Space Station open to astronauts from the world's established and emerging space programs. All this information is available in The Complete Ares III Mission Guide.

It will then by replaced by the Olympus spacecraft for further Ares Missions, such as Ares VII.

Hermes 2 Crop 2

A picture form the Ares III Mission Guide