The striking SNCASO Deltaviex; a dangerous compilation of ideas that nevertheless went on to be tested and explored successfully.
For example, most would agree that it would be a good idea to equip a single-engine, swept-wing jet designed to test new control concepts with an ejection seat. The Deltaviex, however, had none.
Similarly, most would probably also agree that an aircraft that requires compressed air from the engine to maintain control should probably have multiple engines for redundancy.
Not the Deltaviex.
The Deltaviex’s primary research goal was to explore “blown” control surfaces; the trailing edges of the wing and vertical stabilizer had a huge number of tiny holes (not unlike an air hockey table) through which compressed air would be blown for roll and yaw control.
So if the lone engine were to have failed, the Deltaviex would become an extraordinarily poor glider with little to no means of directional control and no way for the pilot to escape.
All turned out ok, though...no lives were lost to the Deltaviex.
And the story indeed has a happy ending...despite having wound up serving as a billboard by a garage owner, the aircraft was saved and restored by a wonderful aviation enthusiast group called Ailes Anciennes Toulouse, where it is now on display.