Can we play at designing weapons?

In the military context, designing weapons means creating equipment that is useful in combat. As this innovative work involves life- and-death issues, it is very particular in moral terms: ‘we innovate to kill’, said an officer interviewed during my inquiry. Based on an ethnographic study of a military hackathon – The 24h of Innovation, ‘Special Forces’ edition –, I describe the conditions under which it becomes possible to initiate engineering students, most of whom are civilians, in the creation of tools of war – an activity with potentially lethal implications. By describing the ‘framing’ and ‘coordination’ that support this innovation work carried out jointly by engineering students and Special Forces, I show that this 24-hour programme takes on a heterotopic form inwhich all participants can end up playing at making weapons without feeling any ethical qualms.