Sail plane pilot reported partial power loss resulting in an immediate return to departure airport for a safe landing.

Narrative

At XA:38 local time; Pilot taxied his Stemme S10-VT Motorglider onto Runway XY at ZZZ; making appropriate radio calls on CTAF for departure on Runway XY. Listening on the frequency by the Pilot's hangar was his wife. Pilot started his takeoff roll with full power (115% turbo boost). After noting normal manifold pressure and airspeed coming alive; the plane lifted off the ground just short of mid field position. Per standard procedure; Pilot kept the Stemme 20 ft. off the ground to build speed to Vx at 60 kts. After Vx was reached; Pilot began a climb maintaining Vx speed; and activated the switch to begin to bring the gear up. At the threshold of the end of the runway (Runway XX threshold); the aircraft had gained altitude to 150 ft. AGL. At that point in the flight; Pilot sensed a significant drop in engine RPM; which was verified by the RPM gauge. Trying to immediately accessing the situation; Pilot traded airspeed to maintain altitude; dropping airspeed down to 48 kts. from 59 kts. After a few seconds of power loss; limited power came back. Pilot began a right turn back to the airport; with the intention to turn 180 degrees to make a downwind landing on Runway XX. On this turn; Pilot acknowledged RPM was in redline; around 6200-6300 rpm. Pilot suspected clutch failure at this point. Pilot throttled back to bring rpms in normal operation range. With limited power; Pilot was able to climb an additional 50 ft. to around 200 ft. AGL. Finishing the 180 turn; Pilot assessed that if power remained; he could initiate an abbreviated right downwind pattern to land on Runway XY. Pilot activated the switch to lower the landing gear. Pilot made a radio call on CTAF announcing that he was going to land immediately on Runway XY; which was acknowledged by his wife on the radio. At 200 ft. AGL abeam threshold of Runway XY; Pilot turned base and final; going through an abbreviated landing checklist acknowledging gear was down and flaps had been changed to 10 degrees positive. Pilot landed the Stemme safely on Runway XY; then back taxied to the end of Runway XY and exited the runway onto the east taxiway; and taxied to the hangar and shut off the engine. A neighbor of the Pilot; had witnessed the entire flight at the end of Runway XX; noting white smoke trailing the aircraft when the aircraft passed the end of Runway XX and was beginning to turn right. The smoke trail lasted about 10 seconds according to the neighbor. Pilot's wife also witnessed the flight from the north east end of the runway - she saw the smoke as well; as well as the low altitude of the aircraft returning to land on Runway XY.Later initial inspection by Pilot and A&P Mechanic found a badly damaged clutch; with significant burned residue and ash within the engine compartment. Pieces of clutch fell to the ground when the side and bottom cowls were removed for inspection.