What command is responsible for the development of shipboard weapons systems?

Naval Sea Systems Command (NAVSEA) is primarily responsible for the development of shipboard weapons systems. This command oversees the design, construction, and maintenance of naval ships and submarines, as well as their associated weapon systems. NAVSEA plays a crucial role in ensuring that the Navy’s fleet is equipped with advanced technology and capabilities to meet operational needs.

Specifically, NAVSEA manages a wide array of systems related to surface naval ships and submarines, including systems for combat, weaponry, and support logistics. Therefore, the focus on shipboard weapons systems aligns closely with NAVSEA's responsibilities, making it the correct answer for this question.