"I built the bus for two reasons. The first is to entertain people because, come on, it's a jet bus. The second is to keep kids off drugs. Jets are hot, drugs are not." [more inside]
Ultra-High Bypass (UHB) or "propfan" jet engines received attention in the late eighties as an economical and greener alternative to currrent GTF and ATF jet technologies. Adoption was partially prevented by industry fears that the external propellers would being seen as a step backwards. Evidently, General Electric and NASA are reinvesting in the technology.