There is the Lapcat http://www.reactionengines.co.uk/lapcat.html http://www.reactionengines.co.uk/lapcat.html which would be comparable to Concorde and uses a S

There is the Lapcat http://www.reactionengines.co.uk/lapcat.html http://www.reactionengines.co.uk/lapcat.html which would be comparable to Concorde and uses a Sabre variant called Scimitar, however the article never mentions it. Personally I think whoever wrote the article did almost no research and just conflated the Skylon and Concorde in their heads, then just wrote down why what they had imagined did not make any sense without realising that it was not in fact what was being proposed. edit - thinking about it, they also only used the mach 5 number in the article. The Skylon is designed to go five times that fast to get to low earth orbit, the mach 5 figure is just the speed while air breathing.