Complex sentence: Proceedings of the 6th Australian Space Science Conference, p.186-211,2006, where Mars Direct and the DRMs used nuclear reactors for surface power and, in the case of the DRMs for propulsion as well.
Split into simpler sentences: Proceedings of the 6th Australian Space Science Conference, p.186-211,2006. This is in contrast to Mars Direct and the DRMs, which used nuclear reactors for surface power and, in the case of the DRMs for propulsion as well.