@msh210 That would be awesome to behold. Maybe it could be done with sustained negative air pressure below them to counteract the tendency of the flames to rise.
@msh210 Internet seems to say that the main problem with upside-down candles is that they melt the wax off quickly, and it drips down and puts out the flame. I wonder if a device could be engineered to partially isolate the unburnt candle from the burning wick and allow just enough melting to provide fuel for the flame. Internet also seems to say that upside-down candles are a symbol in some sort of unsavory worship, so perhaps best avoided in chanukiyot.
@IsaacMoses To isolate the fuel, use liquid fuel in a container with a hole at the bottom only barely wide enough for the wick (thick fuel better than thin, perhaps). Maybe.