Me 163 needs a smoke trail when the candle is lit, a la RATOs on Ar234's, as they (the RATO units) used the same rocket motor...
It wasn't the same rocket engine.
The RATO units used a Walter HWK 109-500, which used a "cold" Walter drive, there was no real combustion, only a chemical reaction by mixing T-Stoff and Z-Stoff.
The Walter HWK 109-509 however was a true "hot" rocket, producing thrust by a combustion of T-Stoff and C-Stoff.