Juno sucks

On May 29, 11:14*am, "Anonymous Remailer (austria)"
wrote:
http://www.spaceflightnow.com/news/n1105/29junosolar/

They should've powered it with an RTG, just like Cassini. The solar
cells on this billion dollar probe will only last three years at the
most, and severly limiting the probe's effectiveness during the mission
when its solar panels aren't viewed towards the sun. NASA and the DOE
have failed to restart plutonium production for RTG's resulting in
maimed and demasculated probes like Juno.

Cassini has now operated for almost 15 years on its nuclear power
source, the Voyagers for almost 35 years. Due to its nuclear power the
craft will be safer since it won't have to rely on batteries during
swingbys behind Saturn. There's a good chance these probes will operate
for quite some time still. Juno OTOH will wear out its solar panels in
a couple of years.

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

Solar cells are actually considerably more efficient nowadays, and by
initially over-sizing should buy enough energy to last for 5+ years,
depending of battery cycle life more than anything else.

70+ m2 giving a conservative 450 watts is actually not an
insignificant amount of energy. 200 w/m2 for LEO application is well
above average for the rad-hard and more physically robust version of
PVs being utilized, so their off-sun hours should not be without
sufficient energy from battery banks that'll likely offer twice the
worse case demands.

http://www.nasa.gov/mission_pages/ju...o20110527.html

http://ntrs.nasa.gov/archive/nasa/ca...2007018845.pdf

There's actually no shortage of plutonium. If anything there's too
much plutonium that the public currently owns and gets to pay really
serious loot for its security, processing and holding onto for its
uses.

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On May 30, 11:30*am, Nomen Nescio wrote:
"Alan Erskine" wrote in message

ond.com...









On 30/05/2011 4:14 AM, Anonymous Remailer (austria) wrote:
http://www.spaceflightnow.com/news/n1105/29junosolar/

They should've powered it with an RTG, just like Cassini. The solar
cells on this billion dollar probe will only last three years at the
most, and severly limiting the probe's effectiveness during the
mission
when its solar panels aren't viewed towards the sun. NASA and the DOE
have failed to restart plutonium production for RTG's resulting in
maimed and demasculated probes like Juno.

Cassini has now operated for almost 15 years on its nuclear power
source, the Voyagers for almost 35 years. Due to its nuclear power
the
craft will be safer since it won't have to rely on batteries during
swingbys behind Saturn. There's a good chance these probes will
operate
for quite some time still. Juno OTOH will wear out its solar panels
in
a couple of years.

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

Well, Mr anonymous, the mission is only scheduled to last for three
years; where do you get the information that the PV arrays will "burn
out" in a couple of years? *The arrays on ISS (the space station) are
nothing special (just silicon) and will last for 10+ years and are
exposed to much more radiation than the Juno arrays.

I should rephrase that: the power systems on the probe will wear out,
mainly the batteries. RTG powered probes can keep working for decades
even though their design life was only a couple of years. Cassini's
main mission was projected to be a mere three years IIRC. It's still
going strong and still revealing mysteries about Jupiter and its moons.
Its longevity has been a real boon for planetary science.

Juno will probably work for the intended mission duration, but I doubt
it will last long after that. That makes it expensive IMHO.

There is no global shortage of plutonium, not that a few other
combinations of atomic fuel couldn't be utilized (especially for such
a short mission).

Most of our global plutonium is safely sequestered within in spent
reactor fuel that hasn't been reprocessed (except those tonnes of
plutonium in Japan that are just leaking out into the environment
pretty much everywhere). I bet North Korea if bribed at $50,000/gram
would gladly sell us their spare cache of plutonium (at least that
would be a hell of a lot cheaper than WW3).

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