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..."
The mission site has much more detailed interesting information.
- "Hear that?! The percolations are imminent! Cease your ingress!"
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.
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.
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.
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.