Because it's basically a design project, very little new research is going to be needed - we already know HOW to build an SST, even most of the information about how to build a reasonably quiet one is in the public domain.
That's a bold statement, to say the least.
Was chatting with a SNECMA engineer about this very subject and his view was that current propulsion technology was not capable of producing an engine for an SST that could meet current noise and emissions standard, and that he would not envision any such thing before at least 20 more year...
FWIW