The Space Launch System (SLS) is an American heavy rocket. This rocket in real life is derived from, and is meant to replace, the space shuttle. This rocket includes one of the two most powerful boosters and one of the the most powerful first stage in the game, which comes in handy when you want to launch heavy payloads like the Station Refuel Silo. Also, it's a great help in sandbox.
To build a complete SLS rocket, these parts should be placed, in this order:
- SLS Core Stage
- SLS Solid Boosters or SLS Advanced Boosters
- SLS Payload Adapter
- Delta IV Second Stage or Saturn V Second Stage
- Orion tug module
- Any payloads you want
This rocket is designed to carry all sorts of heavy payloads into orbit and, in the future, carry the Orion spacecraft.
The Delta IV Upper Stage, or ICPS in real life, and the Saturn V Second Stage or EUS is to be used to boost Orion into orbit and beyond. It is listed as an optional part because of this. Afterwards, it will probably not be used as often.