True bliss is being able to live the serenity prayer (at least stripped of the religious aspects): the courage to change the things you can, the serenity to accept the things you can't, and the wisdom to know the difference.
People who feel burdened by knowledge tend to be bad at separating the concept of things that are bad and things that you should actually worry about.
Ignorance of danger might be good for happiness if you're powerless to stop it. But it might be bad for happiness if you suffer harm that you didn't have to, just because of your own ignorance. People who live like that sometimes feel like they're just tossed around by the world, powerless against the forces that affect their lives.
Boom Supersonic is a private company working on it, with an eye towards better fuel efficiency than the Concorde. They're still in the early stages, though, so who knows if they'll actually be able to finish a design, much less manufacture a working model.
And NASA has been doing some research on sonic boom characteristics, to see if a plane can be designed to fly faster than the speed of sound without causing a sonic boom.