The theory behind EmDrive is based on his quantized inertia theory. I was under the impression he was the original proposer of the idea. It looks like it was instead proposed by someone else in 2006; however McCulloch submitted a paper in 2013 supporting it (https://arxiv.org/abs/1302.2775) and publically advertises about how his theory allows for "an electric rocket" on his twitter https://twitter.com/memcculloch