I really like the potential of this for military and especially space applications, but the usual civilian justification (Sydney to London in two hours?) makes no sense. How many people need to go that fast AND are willing to pay a premium for the privilege? And I'm talking development costs, too, not just operating costs. The SST lost money for the same reasons this will, unless they can bring prices way down and the operating characteristics like range and maintenance turn-around can be made comparable to conventional aircraft. I salute the technology, but spare me the marketing.