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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..."
The mission site has much more detailed interesting information.
- "Hear that?! The percolations are imminent! Cease your ingress!"
They ARE planning a lander, JIMO can carry a probe, which can determine the water abundance, deep winds, and thermal structure to 100 bars.
Unless I'm mistaken, landing on Europa could be a very bad thing, since it's quite possible that the lander could contaminate the environment there. After all, it's been proven that some bacteria is capable of surviving in space. I don't think anyone will want to take chances like this. Not quite yet at least.
Europa is already under extreme radiation. The speculation is that if life existed, it would live under the hundreds of miles of ice which cover the planet. Water blocks electromagnetic radiation extremely well (for example, visible light can't penetrate more than a few hundred feet -- ask any SCUBA diver), so it seems like it would absorb electrons and alpha particles pretty well too. NASA does need to be careful, but not with regard to Europa. If this probe blew up on launch it would be bad.
In the 1970s, the Soviet Union launched several dozen fission reactors on naval radar satellites, most of which are still whizzing over our heads. (These orbits are expected to decay within the next couple of centuries.)
Actually, a new fission reactor loaded with fresh fuel would be no big deal if it blew up. Uranium isn't all that radioactive before you start splitting it. With just a little bit of depletion, it's regarded as safe enough to spew liberally over battlefields (for some definition of safe). If you don't switch the reactor on until you're safely in orbit, you won't have much to worry about.
The radioisotope thermal generators (RTGs) that many of our current probes use are far more dangerous. They carry a considerable amount of a highly radioactive isotope of plutonium that has a half life of a few decades. The decay (not fission) of this isotope generates the heat to generate electricity with a thermocouple.
A fission reactor starts out with almost no radiation, and it builds up as the fuel burns. An RTG starts out with maximum radiation, and it slowly decays over time. Clearly, the first choice would be better to strap into a rocket.
Probably. However, for a probe that large, it was really a necessity.
The reactor will be providing 10+ times as much power as a battery-operated probe. This means more power to instrumentation, allowing for active devices like laser rangers, radars, and the like. It also means more power for propulsion (I didn't notice any mention of propulsion in the article, but flying about in Jupiter's strong magnetosphere probably means a lot of fine tuning can be done magnetically). And perhaps most importantly it means more power to send homeward, ferrying those oh-so-important bits. All these sensors are going to generate a lot of data, and the probe needs to be able to send it back at the rate it is generated.
High-speed Road Trip (18.000KPH)
BU's Center for Space Physics had a seminar speaker talking about this a month or so ago. So, to answer questions:
-The reactor will be started up in orbit and, like all missions carrying nuclear material, it's well-shielded and, even if it weren't, basically huggable without detrimental effects
-The goal here is to provide a deep-space probe with a much larger energy budget than possible with RTG's. It's not really a LOT of power; just that RTG's are very little power. One interesting consequence of this design is the propulsion: ion drive, as tested on Deep Space 1.
-Instrument package is by no means finalized yet; it's basically pie in the sky. That includes what exactly will happen with a lander
-"What if something goes wrong" scenarios tend to be based on the idea that stuff can "fall out of the sky." It can't. The people running the mission know where things are going
-To the poster who said "small cheap missions are better": the manned program tends to be the money sink (as were all the examples you quoted). The really small cheap unmanned missions have a sadly high failure rate. This is more like Galileo or Cassini or Magellan: big, expensive, and incredibly valuable in scientific return. There's a place for small and cheap, but outer planets missions are expensive no matter what. You can't afford two baskets, so you make a *really good* one.
In short, this is a chance to do a pure science probe the likes of which we haven't seen before. It's incredibly exciting and pushes our true exploration of the solar system further.
Here's a nice drawing of the design. Anyone know why the reactor is all the way at the front and the thrusters are at the back??
They also mention on the JPL site that the propulsion system (and I guess much of the rest of the proposed design) was vetted on the Deep Space 1 mission. Some interesting reports on the technology here.
Soylent Green is peoplicious!
That nuclear material could have an unmeasureable detrimental effect on any life there is there, so NASA needs to be damn certain that this baby will not contaminate the surface even if the worst case scenario was to occur.
The possibility of contamination is precisely why the Galileo satellite was purposefully crashed into Jupiter. It was to prevent earth-based microbes (not nuclear material) from contaminating Europa, in the chance that it would eventually crash there after loosing power. Preventing biological contamination of enviroments in which life may have independently originated is of prime importance.
Concerns of biological contamination could be addressed in future missions via proper sterilization of the spacecraft. This was not done with Galileo because there was no reason to do so at the time. It may have been sterile, but had not been checked as such.
Though nuclear contamination was not the issue, Galileo did have nuclear material onboard for power (but not a fission reactor). This led to some folks speculate that NASA was trying to detonate Jupiter, which is nicely debunked here.
Europa's oceans are thought to be at least 2 times as voluminous as all of Earth's oceans combined
One of the main points of the mission is to confirm the existence of these oceans. The oceans are only inferred: we believe that there is a large liquid water ocean because of Europa's magnetic moment. The salt-water is conductive, and as Jupiter's magnetic fied varies, it induces a field in Europa. As Europa moves through various parts of Jupiter's field, the orientation varies. We detect this field and its variations, and deduce a large ocean. More information is here.
While looking up the previous USA space fission reactor, I came across this interesting site: Nuclear Powered Space Missions - Past and Future.
The most interesting information here is about the accidents - which there have been a surprisingly large number of, including an incident in 1978 where a 20-25% of a Soviet fission reactor re-entered and was scattered across Canada.
In the Book 2001 the NSA (or whatever 3-letter agency) did not lie to HAL-9000. HAL was the only crew-member that was fully informed about the nature of the mission (studying the monolith in orbit around Jupiter). It was the instructions not to inform the human crewmembers that led to HAL's nervous breakdown and erratic behaviour.
the chemical term 'organic' doesn't have much to do with life.
Organic chemistry: [n] the chemistry of compounds containing carbon (originally defined as the chemistry of substances produced by living organisms but now extended to substances synthesized artificially)
a silicon-based lifeform would not be 'organic' in chemical terms.
No one can understand the truth until he drinks of coffee's frothy goodness.
--Sheikh Abd-Al-Kadir, 1587
Those aren't solar panels. They're radiators for the heat generated by the reactor.
{nitpick}
When a solid becomes a gas directly, without first becoming a liquid, it sublimates. When a liquid becomes a gas, as you're describing, it evaporates.
{/nitpick}
One of the "Making of 2001" type books describes the design process for the Discovery.
At one point it had a nuclear pulse ("Orion") drive.
There was serious thought to giving it whopping big radiators, which would make it look even more like this probe . . . but they didn't want people thinking they were wings!
The design of this probe is a "classic," in the sense that it looks a lot like design proposals for nuclear-ion rockets circa 1960. One of the science encyclopedias I had when I was a kid had nifty pictures of 'em.
Stefan
Not that it would matter, even if it did work as you suggest. Without a magnetosphere like earth's to protect it, any atmosphere would soon be stripped away by the solar winds.
"Lord, grant that I may always be right, for Thou knowest that I am hard to turn" -- A Scots-Irish prayer