Part of my Holt Industries personal project.
The HI_AJ-1 atmospheric propulsion unit. Structurally questionable, yet the first suitable candidate for mass production. It's cheap and intended for wide-scale industrial use. Modularity was always kept in mind, the ports on the back plate support a primary and quad-secondary feeds which split symmetrically across the combustion system. Extra holes are prepared for the potential introduction of other modified feeds.