Originally Posted by
WHBM
Doesn't that describe almost every military aircraft programme. And a fair few civil ones as well. Even the Boeing 707 would not have got going were it not for it's military-funded predecessor KC-135.
I'm not trying to make some anti-concorde point, I'm just observing that no one has ever succeeded in designingv & developing a supersonic airliner as a viable commercial proposition. Plenty of airliners have been designed and developed and have recovered their investment from sales, and military aircraft are commercial proposition almost by definoition (because it's almost universally true that the intended customer pays up-front for the development).
But the original question was looking for tgings which have been developed and then discovered to have no commercial application. I would suggest that the inability to recover development costs from sales (historic and future, IMHO) puts the concept of supersonic airliners firmly in this category.
PDR