English: Space Tug Missions Managed by Marshall Space Flight Center, the Space Tug concept was intended to be a reusable multipurpose space vehicle designed to transport payloads to different orbital inclinations. Utilizing mission-specific combinations of its three primary modules (crew, propulsion, and cargo) and a variety of supplementary kits, the Space Tug was capable of numerous space applications. This 1970 artist's concept illustrates the crew module concept. The Space Tug program was cancelled and did not become a reality.