The jury is still on for exotic propulsion schemes like EmDrive, Mach Effect Drive (MEGA) etc., but if they work they could open a cheap road to the planets and tomorrow the stars.
My last article about that published in Motherboard and CNET:
Especially relevant to Building Blocks:
"Some exotic propulsion research today is inexpensive "garage science" that doesn't require multi-billion dollar investment, and can even be self-funded. EmDrive enthusiasts can now 3D-print EmDrive parts and start doing independent experimental research."