Slashdot Mirror
Nuclear Powered Mission to Jovian Moons
Skyshadow writes "The San Francisco Chronicle has an article about NASA's new project, the JIMO (Jupiter Icy Moons Orbiter). The probe is designed specifically to search for liquid water and signs of life on Europa, as well as making detailed observations of Callisto and Ganymede. Planned for a 2010 liftoff, this new probe makes all previous interplanetary probes look wussy: it'll be 300 feet long and powered by a next-gen fission reactor (as opposed to nuclear batteries). Sure beats blowing money circling the earth over and over again..."
Or alternatively that nuclear material could be the neccesary kick that life there needs.
Personally I think we should drop a bunch of cheese and mayo sandwiches on the moon and see what happens.
Welll....not exactly. If the craft were to hit the surface of any Europa (wildly unlikely) and if Europa actually has liquid water oceans with ice-covered surfaces (not proven), then the reactor would melt through the ice, boil a large volume of water, and then sink to the bottom of the ocean, which would contaminate the deep structures of the moon more than the Jovian wind does.
However, (a) a reactor is a total nit on the scale of Europa, so the damage would be extremely localized, and (b) the moon itself is sufficiently tectonically active, due to tidal forces, that the reactor would be quickly swallowed up by the exolounar core, thus reducing its effects even more.
Bottom line: it'd be a catastrophe, but not one as large as it appears at first.
Your argument is a lot stronger when it comes to biological contamination, though. I haven't pushed the numbers, and I think that even a couple of hours in the Jovian magnetosphere ought to be sufficient to kill any unshielded terrestrial life forms which had contaminated the probe during assembly. I certainly hope so.
It is just tantilizing that out there, in our solar system, is another ocean.
One in which you could actually swim (lack of oxygen aside and all)! geniune water, at a comfortable temperature...well, at least in a thin layer (below which is seething boiling death and above, vacuum-of-space freezing).
The chances that this moon harbors life seem high. After all, we are all familiar with deep oceanic hydro-thermal vents and the bleached beasties that find the lightless life appealing.
It is my dearest hope that someday a probe will melt down a few miles, pop into this blackened world, and turn on it's lights to discover mile-long whale-like creatures.
Of course, it's most likely we will only find bacteria and other single celled dudes. But complex organisms are so much more cool...and kinda freaky.
But sadly, as it is with this universe, I have the sinking suspicion that europa will ultimately yield nothing more than the biggest cache of sterile water known to man.
Let us not also forget, intelligent life evolving in an environment where the outside universe is completely obscured by miles and miles of pitch-black ice might not be ready for the rest of the universe just yet.
This picture specifies a 20m boom, which appears to be over half the length of the spacecraft. I didn't find any reference to 300ft (or metric equivalent) at the JPL website (but feel free to correct me if it is there.) Eyeballing the picture, 20m for the boom implies about 35m total length. By comparison, 300ft is about 90m.
The 300ft figure is in the newspaper article. Possibly it is an error, possibly the reporter knows more than I do.
I am curious as to how they will launch something so long. Presumably it will be collapsed in some way, and expand after launch. Allowing the (presumed) heat-pipe connections between the reactor and the radiators in a collapsable configuration sounds like a challenging engineering problem.There is no indication of how it would collapse - telescoping and folding seem the most obvious.
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
I think it's just been done.
Although the Tuesday SF Chronicle article (referred to in this slashdot article) claims that Jimo will be up to 300 feet long, Both the astrobio.net article, (also referred to here) and a Monday SF Chronicle article (pointed to by today's SFC article) refer to Jimo being 60-100 feet long.
I'm thinking that somebody saw 100 feet, and thought metres. Hopefully they're not the engineers for the current mission.
Free Software: Like love, it grows best when given away.
Chemical engines are only capable of a theoretical max of ~400 seconds of specific impulse, with 175-300 seconds about as good as it gets for commonly-used propellants.
Ion engines in production easily achieve 3000+ seconds of impulse. So, once you're in orbit, ion engines are the way to go.
Cut your fuel mass by an order of magnitude, and enjoy. All you need is that handy nuclear reactor for power, and they build 'em pretty light nowadays.
"We have to go forth and crush every world view that doesn't believe in tolerance and free speech." - David Brin
What else can you do with a big highly powered probe like this?
Mmmmm - Pluto? Kuiper Belt? Oort Cloud?
My favorite:
A 500 AU Mission - using the Sun as a (gravitional) lens to look closely at other systems directly. Something 500 to 600 AUs is the Sun's focal length for the visible part of teh spectrum. High bandwidth real time images of other solar systems - any takers?
The Singularity is closer than you think
Quant
If you've read this you'll see some of the concept art for the Discovery before they settled on the final version. IIRC one looks exactly like this craft.
One good way to get from Europe to the US is to get in a row boat and start rowing.
Another is to go work someplace for a month and use the salary to buy a plane ticket.
NASA's rowing. I've taken the time to read the Space Elevator Phase II NIAC paper. For a good many years now, composite fabric with a higher and higher percentage of carbon nanotubes loading(hence a higher and higher tensile strength) is produced each year. Moreover, each year the scale of production jumps higher and in a very non-linear fasion. They were at 5% CN loading in March 2003 (as of the writing of the NIAC Phase II summary paper), promising 15% in a few months and techniques that will allow 25% and higher.
According to the current estimates, this will get us to elevator-worthy fiber in mid-2006.
If NASA really wanted to get to Europa, they'd funnel the 10 bil at CN research, building power-transmission lasers, hammering out the political hurdles and building a working elevator. Then they could send a manned boomer sub to Europa if they wanted, probbably for less money than this new idea of a white elephant.
For those too lazy to go read the paper, here's the piece that'll interest us:
"The University of Kentucky has published and patented on fibers 5 km long with 1% carbon
nanotube loading that achieved a tensile strength increase from 0.7 GPa to 1.1 GPa. Recent
results have included producing fibers with tensile strengths of 5GPa with ~5% CNT loading.
Steel has a strength of 3 GPa and Kevlar is at 3.7 GPa. This process used multi-walled carbon
nanotubes. This implies a roughly 100 GPa carbon nanotube strength or an interfacial adhesion
roughly 1/3 of theoretical. However, we must remember that in the current process only the
outer nanotubes are being functionalized and attached to, the inner tubes are not being fully
utilized. Understanding this implies that by finding a method to utilize the inner shells would
enable production of material performing close to theoretical maximum. A complimentary
technique now being developed at Rensealler Polytechnic Institute allows for the pinning of
the walls in the multi-walled tubes together so that all of the tubes can be used. Techniques at Foster
Miller will also allow for dispersion and implementation of the carbon nanotubes in the
composite at much higher loadings. Loadings over 25% have been demonstrated and higher
levels are possible. By combining these techniques the resulting material should have a tensile
strength near theory of 150 GPa for 50% loading. Material at 12 GPa (4 times stringer than
steel) is expected in the coming months and the full strength materials should be available within
two years at the current research rate."
"Hear that, NASA? That is the sound of inevitablity..."
-
Has everyone already forgotten about Cosmos 954?
At the time then President Carter called called for an agreement with the Soviets to prohibit earth-orbiting satellites with atomic radiation material in them. Unfortunately this was never enforced.And for a little history of Nukes in space.
- SR
Great idea. Go 500 AU away from the Sun, then take out your big telescope and ultra-sensitive visible/IR detectors and point them back at ...
the Sun. You'll see a blindingly bright object,
magnitude -13 or so. And your goal is to search
for planets around other stellar systems, which
might be, what, apparent magnitude 25 or so?
"But the gravitational lensing will amplify the light from those faint little planets!" you cry. Amplify by how much --- you need a factor of over one trillion in order to bring these planets up within one-millionth the apparent brightness of the Sun. Oh, and by the way, you'll be magnifying the STARS around which those planets circle by this same amount, which won't make the planets any easier to see.
Take a look at one of my course WWW pages describing the difficulties of direct detection of planets to get some idea of the practical difficulties. Using the Sun as a gravitational lens won't help at all.
Michael Richmond "This is the heart that broke my finger."
mwrsps@rit.edu http://stupendous.rit.edu