The Hermes from The Martian is a very big ship, this is a Kerbal stock parts only build of it, some in-space assembly required.
The Kermes 2 is assembled from seven modules, each includes a lifter to get it to assembly orbit (~150Km):
- Command & Lab Module
- Comms & Sensor Array
- Ring
- Hub & Docking
- Aft Panels
- Propellent Tanks
- Propulsion
The propulsion segment has 18 Ion engines which are sufficient to move the craft in Kerbal orbit, have not attempted a Duna transfer yet but there should be sufficient Xenon Gas on board to make the trip.
For Historical purposes here is the original Kermes which had some issues:
Included are several craft files, each with a launcher setup for assembly at about 150Km above Kerbin.
Lift and assembly in roughly this order:
- Command & Lab Module
- Forward Panels
- Docking Ports
- Hub
- Propulsion
- Spoke x 4
- Ring Braces
Some assembly required ;)