DOC: tutorials for orbit generation

**Is your feature request related to a problem? Please describe.**
The documentation is bare bones.  Creating new spacecraft can be inferred from the docstrings, but this is not the most user-friendly version.

**Describe the solution you'd like**
Needs a tutorial that specifies what is inferred from docstrings.

**Describe alternatives you've considered**
😿 

**Additional context**
n/a
