High energy negative ion‐based neutral beam injection is a strong candidate for heating and non‐inductive current drive in tokamaks. Many of the equations related to the physics and engineering of this technique remain unanswered. In this paper, we consider the possibility of negative ion‐based neutral beam injection on DIII‐D. We establish the desired parameter space by examining physics trades. This is combined with potential design constraints and a survey of component technology options to establish an injector concept. Injector performance is estimated assuming particular component technologies, and concept flexibility with respect to incorporating alternate technologies is described.