On 5/29/2011 4:29 PM, Brian Thorn wrote:
On Sun, 29 May 2011 20:14:55 +0200 (CEST), "Anonymous Remailer
wrote:


http://www.spaceflightnow.com/news/n1105/29junosolar/

They should've powered it with an RTG, just like Cassini.

No RTGs available due to plutonium processing shut down in the 1990s
and Russia's refusal to sell any more of their's. This was the only
way to do the mission without waiting 10 more years.

The solar
cells on this billion dollar probe will only last three years at the
most,

Which is about the fuel limit anyway.

Juno OTOH will wear out its solar panels in
a couple of years.

Juno is more or less replacing the Jupiter observations lost by the
crippled Galileo, which failed to open its High Gain Antenna and spent
most of its limited bandwidth on the Galilean satellites instead. As
such, it doesn't need a 10-year mission.

All in all, a waste of time, money and effort in my opinion.

The price was right. An RTG would probably have doubled the cost.

They don't cost all that much, as they are pretty simple in design...
main cost is just the plutonium to power them:
http://en.wikipedia.org/wiki/Radiois...tric_generator
Plutonium goes for around 44,000 per gram, so it would take an awful lot
to double Juno's cost.
You want plutonium, go to the Japanese, who are burning it mixed with
U-235 as fuel in some of their reactors (that's also what we did with
the plutonium we got from Russia after the fall of the Soviet Union as
they destroyed a lot of their nuclear warheads).
The reactors GE sold the Japanese were a US design that produced
plutonium as part of normal operations that could be extracted from
their spent fuel rods, eliminating the US need for specialized breeder
reactors to make plutonium for our weapon's programs.
So unless they mixed it with U-235 and burned it in their reactors, to
the Japanese plutonium was simply a hazardous nuclear waste product that
had to be disposed of or stored somehow.
The whole "We're running out of plutonium for RTGs!" thing was BS by the
last Bush administration to try to restart US plutonium production for
new nuclear weapons.
Although space safety incidents with RTGs have been very few, the solar
power option removes the risk entirely, and with the continued
development of higher output solar arrays and lower power demand
electronics, the Juno approach becomes workable.

Pat