I was watching a program on
TLC about
space junk. Apparently
radioactive payloads have been going into space at least some 26 years before the
shuttle explosion. And it's also reentered the
atmosphere a couple times.
A
Russian craft used
plutonium to keep its
avionics warm. Bound for
Mars, it
fumbled on takeoff and wound up stuck in
low earth orbit. It circled Earth a few times and reentered the
atmosphere. The Russians claim it landed (
harmlessly...) in the
pacific ocean.
A
Pu laden
US experiment from the 60's called SNAP 9A was part of a
malfunctioning Navy spacecraft that said
oops and sprayed itself throughout the atmosphere. It was said that everyone now carries a small quantity of plutonium in them due to this event.
Which was interesting but a bit
weird. I can think of a couple ways Pu can bridge a
generation, but the show didn't go into it.
NASA claims SNAP burnt up in the upper atmosphere, "as designed", and said nothing about mass plutonium
poisoning.
Intriguing!
NASA has launched 38 of these RTG's (
radioisotope thermoelectric generators) so far. Here's another one:
"An
experimental nuclear reactor power system, the SNAP 10A which used
thermoelectric power conversion, was launched by the
United States in 1965 and worked satisfactorily for 43 days until shut down. It is now in a very high orbit
where it will remain for hundreds of years." ---nasa.gov
Neat. I hope they put a "Plutonium On Board!!!" placard in it's rear window, to warn off
future space travelers from Earth or otherwise.
The modern US probe
Cassini carries around 72 pounds of plutonium. In August of 1999 it performed a
gravity assist swingby in order to speed it's quest to
Saturn. It flew within 725 miles of Earth, and (according to
NASA) would have vaporized 32-34% of the Pu into the atmosphere if it accidentally reentered. That's around 25 pounds of plutonium. Originally it was to fly within 312 miles of Earth, but the figure quickly grew due to
public outcry.
Sources:
A space show on
TLC (Didn't get the title, clicked in halfway through)
http://www.animatedsoftware.com/cassini/
www.nasa.gov