In a previous article, "Jay Honeck" said:
So there you have it. The Blackbird itself did not overfly Russia -- but
the D21 (that weird-looking probe that was mounted on top of the Blackbird,
between the two tails) did. It was not, however, a complete crossing.

The D21 wasn't a probe, it was an unmanned drone that was launched from
the SR-71. You probably mean the same thing, but when I see "probe" I
tend to think of something that stays attached.

BTW: Everything I've read suggests the D21 was spectacularly unsuccessful.
Besides killing a few SR-71 pilots in separation accidents, they also had
a couple that never returned from missions into China, and most of the
rest that did come back were found to have not collected any data due to
glitches.

--
Paul Tomblin http://xcski.com/blogs/pt/
"AOL would be a giant diesel-smoking bus with hundreds of ebola victims on
board throwing dead wombats and rotten cabbage at the other cars"
- a.s.r throws the Information Superhighway metaphor into reverse.