The DEAN also uses a radial inflow plug nozzle primarily to enable the dual-expander cycle but also to allow a shorter, lighter engine.
Replacing the bell nozzle with the radial-inflow plug nozzle can expand the maximum diameter of the engine, but using a truncated aerospike allows a much shorter engine.
The engine's aft external expansion plug nozzle would serve as a heat shield during reentry.
Each of 12 secondary sets of optics condenses the reflected beam onto a tertiary set of optics, which in turn project a 2-centimeter laser beam across the plug nozzle surface.
For instance, it's easier to achieve a smaller adhesive bead width using low melts, because viscosity is more consistent and the lower temperatures don't produce char, which can plug nozzles
and lead to inconsistent application.