A bit of both.
In August 1957, a steel plate was blasted to well over escape velocity
by a nuclear experiment. Nobody claimed it made it to space, since
there's that minor matter of the atmosphere.
A few years ago the story appeared in New Scientist (formerly a
quality magazine, become a vehicle for putting the usual ecologist
spin on all happenings scientific). The plate had become a manhole
cover, and needless to say it was launched by accident (those evil
nuclear scientists are always messing about blowing things up by
accident you see). According to this version: if it could have made
it out of the atmosphere it would have escaped from Earth's gravity.
Well duh. Like what does "escape velocity" mean?
Now the meme seems to have mutated into: it escaped the Earth, the
Solar System and who knows what else. This strain of the meme will
probably catch on because Americans would love to believe that they
actually beat those darn Russkies into space after all.
The entire claim seems pretty dubious to me. Most of the explosion's
energy would be released as radiation which would melt the plate (at
least) immediately. The shock wave would hit it after a fraction of a
second and send globs of molten steel flying. There would be no
intact plate to be "watched leaving the area" on camera.
The speed claim also seems dubious, even applied to globs of molten
steel. I wonder is it legend too, proceeding from the popular belief
that nuclear explosions can do just anything because they're
infinitely powerful. I could be wrong on this though.
In any case, in the atmosphere the globs would be broken down into
ever smaller drops with ever larger surface area per unit momentum,
getting heated up and slowed down immensely for a second or more
(that's a hell of a long time!)
That thing came down in a fine rain of liquid steel spread all over
the Nevada desert, if you ask me.
Rob.