Games like Terminal Closure
Games like Terminal Closure include Kerbal Space Program, Universe Sandbox, Hardspace: Shipbreaker, Reentry - A Space Flight Simulator, and Spaceflight Simulator. We matched them by the tags players give Terminal Closure on Steam (Simulation, Space, Space Sim, Realistic, and Military): closest matches first, and among equally close ones the better-known games.

Kerbal Space Program
Shared: Simulation · Space · Space Sim

Universe Sandbox
Shared: Simulation · Space · Space Sim

Hardspace: Shipbreaker
Shared: Space · Simulation · Sci-fi

Reentry - A Space Flight Simulator
Shared: Simulation · Space · Space Sim

Spaceflight Simulator
Shared: Space · Space Sim · Simulation

Kerbal Space Program 2
Shared: Space · Simulation · Space Sim

V: Rings of Saturn
Shared: Space · Space Sim · Sci-fi

Elite Dangerous
Shared: Space · Space Sim · Simulation

FTL: Faster Than Light
Shared: Space · Indie · Sci-fi

X4: Foundations
Shared: Simulation · Space · Space Sim

Children of a Dead Earth
Shared: Simulation · Space · Realistic

Tin Can
Shared: Simulation · Space · Realistic

Solar Expanse - Space Exploration Manager
Shared: Simulation · Space · Realistic

Stellaris
Shared: Space · Simulation · Sci-fi

Totally Accurate Battle Simulator
Shared: Simulation · Realistic · Physics

Cosmoteer: Starship Architect & Commander
Shared: Space · Sci-fi · Space Sim

Space Engineers
Shared: Space · Simulation · Physics

Empyrion - Galactic Survival
Shared: Simulation · Space · Space Sim

IRON NEST: Heavy Turret Simulator
Shared: Simulation · Military · Realistic

SpaceEngine
Shared: Space · Space Sim · Sci-fi

Arma Reforger
Shared: Simulation · Military · Realistic

Starpoint Gemini 2
Shared: Simulation · Space · Space Sim

Gunner, HEAT, PC!
Shared: Simulation · Realistic · Military

Starpoint Gemini Warlords
Shared: Space · Simulation · Space Sim