Found this while trying to understand what state of tip jet development was:
http://www.fantastic-plastic.com/SikorskyXV-2Page.htm
Originally Posted by Site linked
By 1951, Sikorsky, the world's leading helicopter manufacturer, had fashioned a creative way to fuse the two concepts, the result being jet-powered aircraft with a single-bladed helicopter rotor that could be used for VTOL-style take-offs and landings, then collapsed stowed when the aircraft commenced horizontal flight.
Dubbed the XH-36, the plan was given the green light by a joint U.S. Army/Air Force development team charged with building a VTOL aircraft that could be used for difficult rescue operations. Unfortunately, the outbreak of the Korean War turned Sikorsky's attention and resources to more practical matters, and the XH-36 -- now known as the XV-2 -- remained a study project only until the entire project was cancelled in 1960.
Not sure how practical such a concept would be in the modern world:
Mart