The difference is in where the torque is generated. In a traditional helicopter, the engines (mounted to the main body) generate torque to spin the main rotor. Since the body spins the rotor, by Newton's third law, the body and the rotor spin in opposite directions. Therefore, you need a tail rotor to counteract that.
With this design, the torque to spin the rotor is generated on the rotor itself, so there is no torque effect on the airframe. Note that there is still a (rotorless) tail with fins, probably to stabilize the aircraft in forward flight.
If you want to attach a spinning object to a stationary one you need bearings, which means friction, which means torque. Nowhere near the torque of a normal helicopter, but something. I take it the double fins in the back (at the end of a long lever) can more than handle that. Or at least, as long as the bearings don’t fail.
Gyroscopic precession, though... Is that enough tail or do you have to be gentle changing directions in this thing?
> Or at least, as long as the bearings don’t fail.
If the bearings fail, counteracting torque is the least of your worries - you should land immediately before the rotor shits itself and you turn into a flaming lawn dart. From the UH-60 operator's manual:
> 9.22.10 Main Transmission Failure.
> WARNING
> If % RPM R decreases from 100% to below 96% with an increase in torque during steady flight with no engine malfunction, the main transmission planetary carrier may have failed. During a main transmission planetary carrier failure, it may be impossible to maintain % RPM R at 100%.
> NOTE
> Decreasing % RPM R may be accompanied by a drop in transmission oil pressure of 10 psi or more, and possible unusual helicopter vibrations.
> PROCEDURE
> 1. Collective - Adjust only enough to begin a descent with power remaining applied to the main transmission throughout the descent and landing.
I like to keep people guessing by alternating between ironic understatement and hyperbole. Too much BBC perhaps.
I know in low rpm devices, especially with radial forces (wheels) a bearing or race can start to go without destroying the whole assembly. To the point that bicyclists can bring in a wheel that's so far gone that the labor to fix it is twice the cost of a new wheel (I can fix this or we can get you a new pair of wheels for the same price, installed). How long do you have between the first chip and game over on a rotor?
Some how, even though "LAND AS SOON AS POSSIBLE" is in all caps, I doubt it entirely captures the urgency. If anything involved with keeping the blades attached fails, sounds like a case of any other plans you had are over and you need to be on the ground RFN while it's still a choice.
With this design, the torque to spin the rotor is generated on the rotor itself, so there is no torque effect on the airframe. Note that there is still a (rotorless) tail with fins, probably to stabilize the aircraft in forward flight.
For more on this design, see https://en.wikipedia.org/wiki/Tip_jet