The Tri-Dart is an elegant ship used to courier royalty in and around the galaxy. Sleekly designed to slip through air during launch and landing, it also has no problem navigating the space lanes. Powered by the powerful Vera-Thrust engine system, the ship can travel almost as fast as the fastest intra-galactic military rocketship. It is also available to discerning clientele for commissioned private cruises. See our brochure.

This is how I describe this rocket on Thingiverse.

I wanted to play with simple spherical shapes using similar spherical shapes to boolean-subtract to see how the vaulted arches could form a working rocket ship.

I think the results are interesting at least:

The engine is booleaned out of the groined vault formed when three tall spheroids were cut away from the main body: