Steam User Rating: 98% Positive
Wishlist It: Steam Store
I can't talk about the latest simulation games without bringing up Kerbal Space Program. This ambitious project aims to realistically recreate space physics for space craft.
You can build and rebuild your space craft, watch it crash fifty times before it breaks the atmosphere and watch it explode when attempting re-entry.
There is a steep learning curve to be had in Kerbal Space Program, but if you are as dedicated to astronomy as these adorable little Kerbals, than you will be making supply trips to space stations you placed among the stars in no time.
Couple it all together with a lovely community and some great mods, and you have a must-watch for the Steam Summer Sale.