No, but not because of the reaction time. Unfortunately jet engines are much less efficient at low speeds like this. They work best when accelerating a large volume of air a little bit, and that means they work poorly in the hover configuration required for an octocopter. Wiki link for the math: http://en.wikipedia.org/wiki/Propulsive_efficiency#Jet_engin...
Larger, slower props are required for maximum efficiency in a hover. The pressure above the prop is never more than one atmosphere, so "suction" is limited unlike when the airplane is flying at a high speed and air is continually forced into the inlet nozzles.
The 800N thrust of those engines is measured at cruising speed, when the only opposing force is drag and the intake and exhaust velocities are very similar. It produces much less thrust starting from zero velocity on the runway, when the opposing force is the inertia of the aircraft.
Jet airplanes, RC electric ducted fans, and jet ski watercraft have similar thrust-vs-velocity response, and are better for their intended purpose as a result - but that doesn't help for octocopters. However, tugboats use a ducted fan for the opposite effect. I am investigating the use of accelerating-configuration ducted fans or "Kort Nozzles" for octocopters.
And yes, the insane reaction time of miniature brushless electric motors is largely what allows these craft to function; you would want variable-pitch props or vectored thrust to make a turbine or internal-combustion craft work well, but that's not the reason they aren't used.
Larger, slower props are required for maximum efficiency in a hover. The pressure above the prop is never more than one atmosphere, so "suction" is limited unlike when the airplane is flying at a high speed and air is continually forced into the inlet nozzles.
The 800N thrust of those engines is measured at cruising speed, when the only opposing force is drag and the intake and exhaust velocities are very similar. It produces much less thrust starting from zero velocity on the runway, when the opposing force is the inertia of the aircraft.
Jet airplanes, RC electric ducted fans, and jet ski watercraft have similar thrust-vs-velocity response, and are better for their intended purpose as a result - but that doesn't help for octocopters. However, tugboats use a ducted fan for the opposite effect. I am investigating the use of accelerating-configuration ducted fans or "Kort Nozzles" for octocopters.
And yes, the insane reaction time of miniature brushless electric motors is largely what allows these craft to function; you would want variable-pitch props or vectored thrust to make a turbine or internal-combustion craft work well, but that's not the reason they aren't used.