I know people have different mental workflows for solving problems, but I never understood the concept of building software prototypes to see if something is possible, unless you're doing scientific research. I can understand building prototype for demo purposes (to avoid technical speak and to have a common reference for discussions).
Either something is possible or it is not. If you don't know, that just means you're lacking knowledge (and maybe it's never been done before). If it's possible, the only thing left to figure out is the cost of the solution (and if it's acceptable). The nice thing about software is that you don't have to commit everything at the beginning. You may build a working skeleton of the solution that you flesh out as the project goes, but I don't see that as a prototype.