It used to be that the government would explicitly solicit for somebody to build them a particle disintegrator. If that was your business, you could then apply for a grant based on that solicitation. Recently, they have added something called “open topic”, which is basically for anything that the government would find useful but isn’t smart enough to ask for, from ray guns to open source cybersecurity projects. I think if it’s related to either blowing things up, or preventing things from getting blown up, uncle sam wants to talk to you!