Space flight software is no longer a closely guarded secret for space vehicle developers, owners and operators - it is open-sourced and available as a commercial-off-the-shelf module. Despite its wide availability, limited security research has been conducted on flight software in an unclassified environment. This paper proposes a research agenda that outlines critical challenges for space flight software and proposes a series of research and development efforts that could ultimately aid in developing inherently secure space vehicles.