The original concept, conceived by Bevin McKinney, was to have powerful rocket engines on the blade tips that would launch the vehicle into the atmosphere using aerodynamic lift from the rotors. At the same time, propellant would be delivered to the engines under high pressure generated by the centrifugal force.

When the atmosphere got too thin for the rotor blades to work, the tip engines would be angled to a vector that provided forward rocket thrust with enough angle to keep the blades spinning at high speed for the centrifugal pump action.

On reentry, the rotors would create a broader effective "base" that would slow the vehicle with less heating, and enough fuel would be kept on board so that the engines could be lit at low thrust during final descent and land the vehicle using rotor blade lift.

The design worked best on small vehicles, and we were targeting customers like Iridium who wanted to put many small satellites into low earth orbit.

There were other design hurdles that we never got around to studying in depth. Supersonic rotor shock effects on launch, edge heating issues on descent, and other things. There may very well be showstoppers out there.

But the real hurdle was when the small satellite companies basically went into hibernation for a time. We designed a larger vehicle (what you see in the ATV pictures) to try and capture larger payloads, but then the rotor takeoff concept became unworkable at that scale, and we had to put rocket engines in the base and just use folding rotors for the final landing. The larger concept never held together as well as the original.