NASA spacecraft on journey to Jupiter hits halfway point

"NASA's Juno spacecraft is halfway to Jupiter. The
Jovian-system-bound spacecraft reached the milestone
today (8/12/13) at 5:25 a.m. PDT (8:25 a.m.
EDT/12:25 UTC).

"Juno's odometer just clicked over to 9.464
astronomical units," said Juno Principal Investigator
Scott Bolton, of the Southwest Research Institute in
San Antonio. "The team is looking forward, preparing
for the day we enter orbit around the most massive
planet in our solar system.""

See:

http://www.spacedaily.com/reports/NA...point_999.html


Interesting that a solar-powered spacecraft is being
sent as far out as Jupiter.

How far out can a probe be sent before solar becomes
impractical, and an RTG (Radioisotope Thermoelectric
Generator) becomes necessary?

After serious thinking wrote :

Interesting that a solar-powered spacecraft is being
sent as far out as Jupiter.

How far out can a probe be sent before solar becomes
impractical, and an RTG (Radioisotope Thermoelectric
Generator) becomes necessary?

I don't know the answer, but some of the thoughts on how to get to the
answer:

a) what is the mission? what instruments does that mission require?

b) does that mission require the instuments to be on for long
continuous periods?

c) what is the propulsion system used for mid-course corrections,
rendezvous, and station keeping? Does it require heaters for fuel
supplies, eletric pumps, or is it an electric drive (ion, plasma,
VASIMIR)?

d) what solar panels are you going to be able to qualify?

e) what batteries are you going to be able to qualify?

f) how much mass can you take for batteries?

g) revist b -- can the craft sleep for long periods of time?

I think that some of the spacecraft on quick design cycles could pick
batteries and solar panels that are only 5 years behind the bleeding
edge (at launch time), while other probes might need to stick with
previously qualified designs, which sounds more like 10 years behind
the launch-time bleeding edge.

I haven't tried to answer these questions, but you can probably find
ball park answers about the instruments and their power requirements by
looking at Sojourner, Spirit, Curiosity, Magellan, Cassini, Kepler,
.....

/dps

--
Killing a mouse was hardly a Nobel Prize-worthy exercise, and Lawrence
went apopleptic when he learned a lousy rodent had peed away all his
precious heavy water.
_The Disappearing Spoon_, Sam Kean

On 8/14/2013 2:24 AM, Snidely wrote:
After serious thinking wrote :

How far out can a probe be sent before solar becomes impractical, and
an RTG (Radioisotope Thermoelectric Generator) becomes necessary?

I don't know the answer, but some of the thoughts on how to get to the
answer:

[some good points]

I think that some of the spacecraft on quick design cycles could pick
batteries and solar panels that are only 5 years behind the bleeding
edge (at launch time), while other probes might need to stick with
previously qualified designs, which sounds more like 10 years behind the
launch-time bleeding edge.


I think this is a key point as well. That the technology timeline does
make a huge difference.

I would assume (having not done the research, but it would seem common
sense that) the solar cells on the Spirit/Opportunity rovers are quite a
bit different and far more efficient than say those used on the Mariner
space probes from the 1960s.

What would not have been possible without RTGs in the 60's is somewhat
more doable now with solar cells for craft designed in the 00's.

Dave

Dammit, it's 2013 already and we still don't have Back to the Future's
Mr Fusion portable power plant!

Did you know BTTF's original method of achieving time travel was to
have the car drive into an atomic bomb explosion test? From a science
point of view that's more realistic in terms of energy than reaching
88mph LOL.

--
T