Lockheed Martin to Build Nuclear Powered Spacecraft 334
LouisvilleDebugger writes "The BBC reports that Lockheed Martin have received a $6M contract to develop the nuclear powered
JIMO, or Jupiter Icy Moons Orbiter. (According to the NASA project site, the first probes would not launch before 2011 due to development lead time.) On arrival at Jupiter, the extra power allows the probe to orbit each of three of the Galilean moons (Ganymede, Callisto, and most challenging from a radiation exposure standpoint, Europa) in turn, presumably helping to establish the possibility of liquid water and hence, life within the Jovian system. JIMO is a sub-project of Project Prometheus, initiated by NASA this year for the purpose of demonstrating that nuclear powered and propelled spacecraft may be safely designed and tested."
safe? (Score:3, Insightful)
Do they really think that it can be completely safe? What if it crashes onto earth just after launch? Or it blows up in the air, so radioactive particles get spread all around?
Re:safe? (Score:5, Informative)
Re:safe? (Score:3, Insightful)
Re:safe? (Score:5, Insightful)
Second, the chances of it blowing up in the air a la Challenger are slim. Granted it only takes once, but hey, there's no guarantee we'll all wake up tomorrow without some idiot gassing the planet.
The fact is that there are myriad possibilities for disaster in any big project, and the only thing any one person can do is to try to prepare for eventualities. Don't shoot down a project like this simply because it's nuclear. We all hear that word and think of Cherynobl (spelling?), Hiroshima and similar incedents. But just because it is nuclear powered doesn't mean that it's going to end like K-19: Widowmaker.
Think abou this: if we can do this it will forward research about our solar system by a long shot, which is something we must have if we ever hope to explore further out.
Re:safe? (Score:3, Insightful)
Is (probability of disaster)*(impact of disaster)(benefit of using nuclear power in this case)
It could well be, I can't say, or even predict from my standpoint. The risks may be high, but hell, we're far more likely to be computer simulations anyway, so go for it!
Re:safe? (Score:5, Insightful)
Re:safe? (Score:2)
There's no guarantee that it will blow up, but there is a pretty fair chance. 1 in 60? Would you buy a lottery ticket with 1 in 60 odds? People buy tickets for 1 in 1000000000 odds!
Technically, we could sit on our asses for 30 years until nanotech becomes more advanced, and use that to manufacture nuclear facilities on the moon. No more risky transporation from plan
Re:safe? (Score:3, Funny)
-aliens invade and destroy all of humanity
-or they dont
50/50 chance, you never know
What you don't realise... (Score:3, Informative)
A line from Cowboy Bebop comes to mind... (Score:2)
Eh, had to be there I suppose...
*honk*
Just thought of something... (Score:5, Funny)
Re:Just thought of something... (Score:2)
Re:Just thought of something... (Score:2)
2) Or they will have been liberated and won't complain.
3) Or they'll just use it as a cover-up for their own nuclear program.
4) Or they will just "strike back" without bothering with diplomacy.
5)
Space-based fission reactors (Score:5, Informative)
http://spacescience.nasa.gov/missions/prometheu
The reactor uses slightly enriched uranium, not plutonium, and is launched 'cold'. The uranium 'fuel' is much less toxic than plutonium. This type of fuel cannot be used to construct a fission bomb, as it contains far too low a concentration of U-235 to produce a nuclear explosion.
The reactor is launched 'cold', in a shut down state. That means that during launch, there will be no fission reaction products present. The reaction products are the biggest hazard with nuclear fuel, being both radioactive and chemically reactive, prone to dispersing throughout an environment if released. (Radioactive iodine and cesium isotopes being probably the best known examples.) The reactor is not started up until the spacecraft is on an interplanetary trajectory.
This is not a new technology. The SNAP-10A space reactor power system was launched in 1965. Methods for protecting and encapsulating the fuel elements to prevent dispersal or leakage are well known and tested. (These methods will survive explosions during the launch, as well as uncontrolled re-entry from orbit.)
Re:Space-based fission reactors (Score:4, Informative)
You are absolutely right. What many people fail to recognize is that there are different levels of radioactivity. If a radionuclide has a long half life it will be less radioactive in the short term. In particular, U-235 and 238 with hundreds of million year half lives (U-238 in the billions) will have very low radioactivity compared to a fission product which may have a fraction of a second half-life. If you don't start up the reactor until it is safely in orbit, then there will be no fission products, and even if it did burn up in the atmosphere, it would have too low radioactivity to even notice.
Re:safe? (Score:5, Informative)
I work with some of the folks who are responsible for safety matters regarding hazardous/radioactive material aboard spacecraft. Believe me when I tell you that the utmost importance is placed on the "what-if's" of any given launch failure mode. The containers that house the radioactive material are ridiculously well scrutinized and tested, the failure scenarios are taken into consideration, including atmospheric dispersion of debris from a launch failure.
We've used plutonium powered modules for years now as a source of long-lasting (30 years or so) electrical power. Those capsules are some of the toughest, most durable, explosion-proof, reentry-proof items ever created.
For example, for one space mission, 25 sample power capsules were made for testing by using them as artillery projectiles fired by a cannon into a solid concrete wall. This induced many times the stress these capsules would ever see in even the most horrific failure of the launch vehicle. Of the 25, only one showed any sign of a stress-related crack. This tiny crack set into motion a full review of the capsule manufacturing process, a study of the atmospheric effects of a failed launch vehicle, and other safety-related processes that delayed the launch for about a year.
Whereas these newer power sources are going to be a challenge, they'll be well thought out, or they won't go.
Re:safe? (Score:2)
credentials (Score:2)
Re:Past Failures? (Score:3, Informative)
Re:safe? (Score:3, Insightful)
The world is full of risk. The only way to avoid risk is to not be alive. Since we are alive, our role is to explore and learn and manage, not retreat to the cave in shame at our presence on the otherwise "pristine" earth.
Re:safe? (Score:5, Funny)
In Conneticut (Score:2)
Re:safe? (Score:2)
Hampton Roads was the place we used to go to for shopping and stuff. When I was growing up Gloucester had 2 stop lights in the entire county...which shows you how long ago I lived there.
But back to the subject. I remember growing up there and my dad working at the Shipyard...AND there's Surry Nuclear Power Plant nearby, plus the Naval Weapons Station there in Yorktown.
Not exactly the safest place to be for all the man-made horrors running around.
Re:safe? (Score:3, Informative)
Re:safe? (Score:4, Informative)
Yes (Score:5, Informative)
Oh, and for all those who believe that we should be designing a manned mission to Mars, let me be perfectly clear:
The only way we will get humans to Mars will be using nuclear propulsion and nuclear power sources(RTGs). Period.
And for those who question the safety of launching RTGs... this [nuclear.gov] link describes the cases where this has already happened. RTGs have survived abort detonations of REAL missions right after launch with no radiation leakage. They have also survived re-entry (Apollo 13) with no leakage. The safety technology is mature and works.
This is our only ticket for orbitter missions to the outer planets.
radioactive mineral deposits on mars? (Score:2)
That makes it pretty tough if you want to start a colony.
Re:radioactive mineral deposits on mars? (Score:2)
The Next Frontier (More on Nuclear Space) (Score:4, Informative)
Re:Yes (Score:3, Informative)
(Jupiter is about 5AU from the sun, and solar power drops off as 1/r^2, so you'd need 25 times the solar panel area as a spacecraft near Earth - and solar panels ALREADY dominate most spacecraft designs!).
Cassini was the last outer-planets launch, an
Re:safe? (Score:5, Insightful)
Radioactive material is toxic. So is rocket exhaust. So are zillions of other things in our environment, including all sorts of natural stuff in our food and our air. There is nothing magic or mysterious about radioactivity toxicity.
Your smoke detector contains a radioactive pellet. If you don't eat the thing, you are fine. Even if you do, you are probably okay (if a bit crazy). Dust contains radioactive materials. A large number of nuclear bombs have been exploded in the atmosphere, release lots of plutonium and other radioactive elements (the things are nowhere close to 100% efficient). We are still alive. Phosphorous products often have a raised level of radioactivity. If you are a camper with a Coleman lantern, the lantern mantles are radioactive. If you fly in an airplane or go to high altitudes (Denver, anyone), you are exposed to a lot of ionizing radiation (compared to sea level). Like getting a tan? You get it from ionizing radiation( UV rays).
Unless you are a fool, you wouldn't eat a gram of cyanide. Likewise, I wouldn't recommend eating a gram of a space probe's nuclear reactor. But that isn't going to happen!
Even if all the material were released into the environment (which is highly unlikely), the chances of harm to any one person are extremely low. You would experience far more danger driving to see the launch or just plugging in your computer!
Since the reactor is not activated until it is well away from earth, at launch it contains only uranium. Uranium is all over the place. Here in the Phoenix, AZ area there are significant concentrations in the soil in many areas where people live. My geiger counter gets 26 counts per minute in my driveway, but only 16 counts if it is sitting on top of the engine block of my car in the driveway. Wow! My driveway is radioactive. I guess I am doomed!
The uranium in a never fired nuclear reactor is no more dangerous than the uranium in soil - it is just more concentrated and has a different isotopic ratio (enriched reactor uranium is not more radioactive than unenriched - it just has a more U-235 (and less U-238). If it is dispersed in an explosion, it is no more dangerous than a dust storm here in this large metropolian area!
Anti-nuclear activists, a totally innumerate and scientifically ignorant press, the irrational conflation of nuclear weapons and nuclear power, and the unwillingness of people to look seriously at the issue have created a nuclear phobia in much of the western world.
Practicioners of "junk science" (Score:3, Insightful)
Let's take a look at Chernobyl, the anti-nuke crowd's favorite example of nuclear hazards. There were two major things about that disaster: 1) there was NO containment structure to keep the radioactive particle release to a reasonable level if something did go wrong, and 2) the reactor's design was an inherently unsafe design to start with. That ill-advised test caused the fissile material to overheat, and when they tri
For 6 Million? (Score:5, Interesting)
Re:For 6 Million? (Score:2)
Re:For 6 Million? (Score:4, Informative)
The pessimist in me says this one will be cancelled long before it ever launches
If they'd stop using the word nuclear... (Score:5, Insightful)
Re:If they'd stop using the word nuclear... (Score:2)
Re:If they'd stop using the word nuclear... (Score:2)
S
Re:If they'd stop using the word nuclear... (Score:2)
Its not just the pollution itself, its a question of risk/cost vs. gain, right now, we are taking much liberty with the natural world -- and for what reason? So people can buy their 15th pair of %big-brand-name% shoes this year? F that noise.
As for this projet, I wouldnt be against it. But I am a member of the Green Party. Environmentalists are not insane, m'kay? Powerfull peo
Re:If they'd stop using the word nuclear... (Score:5, Insightful)
The Bush administration and conservatives are terrified of the word "nuclear" as well--when it applies to any device not under US control.
The problem with nuclear power is not primarily the occasional accident, it's the deliberate use by nations and groups for war and terrorist acts. And, while it may not scare Americans to let the US military have access to fission and fusion devices in orbit, it should scare everybody else.
The Iraq war has proven that the US is unwilling to take into account the wishes of the international community and that the US will decide unilaterally global policy. It doesn't even matter whether the US decision was right in this case--monarchs and dictators also often make good decisions. All of that may seem fine to Americans, but the rest of the world wonders what is so democratic about having 300 million Americans make decisions for 6 billion non-Americans.
Re:If they'd stop using the word nuclear... (Score:3, Interesting)
So far as I know, the President has said little or nothing about anything "nuclear." "Nucular," on the other hand, scares the pretzels out of him.
This may explain why, after fulminating on national TV about the danger of "nucular" weapons in Iraq, he held his troops back for several weeks while looters plundered the largest nuclear materials depot in Iraq, which contai
Re:If they'd stop using the word nuclear... (Score:5, Interesting)
I for one do not want to sit in the dark ages and think that if NASA determines it best to use fission reactors to best perform deep space studies, so be it. Fanatics will fantasize about a cabal of technophiles, Illuminati and energy moguls and the x-files guys all hanging out in a dastardly plan to bring about Armageddon because you know, all these rich powerful people really want say, a nuclear war so they can live out their days in a bunker on a destroyed earth because that's the very definition of FUN! It's like people in a vocal minority to maraud around looking to bring Bush or the liberal establishment or [name your group to blame everything on here ]into every discussion.
All countries "are". They are not good. They are not evil. They are all unilateralist whenever they can afford to be. If you want others to believe in your morality, grab an orange robe and become a Buddhist monk. Otherwise, you're a money grubber just like the rest of us.
Those who bet on apocalypse the end of days, bet against a bright future basically always lose. It's not wise to sell short on the progressive countries of the world. Luddites who hearken back to the good ole days are essentially insane.
Now as far as nuclear devices with regards to the US - the US has been in possession of nuclear weapons the longest and has been able to refrain from using them the longest (Time since Nagasaki, as in, longest period of years since they were last used in war) despite the apparent efficacy of nuclear attack in bringing WW2 to a close.. They are staggeringly expensive and have little military value (until recently, the below ground penetrating missile/bomb design and nuclear torpedoes are also effective, both of these are tactical applications) they are essentially a threat over population centers. The US would not use strategic weapons unless they are used upon the US. Strategic weapons are essentially possessed only by France, Britain, Russia, China, US (and a lesser extent, India, Pakistan). They are effectively deterrence in that populations centers will be totally destroyed if the US is attacked. I don't foresee the preemptive use of strategic weapons nor is there any evidence of that in US nuclear posturing doctrine, which is publicly available:
FAS NPR [fas.org] , and Globalsecurity NPR [globalsecurity.org], and DefenseLINK NPR [defenselink.mil].
The new preemptive nuclear strike parts of the doctrine basically wants to make a case for the use of tactical nuclear weapons against well fortified targets. Given that a swift conventional campaign in Iraq was so politically painful for the US, I seriously doubt that the US will ever use tactical nukes, much less preemptively. I think the document says it best: It's a nuclear posturing document. Anyone can break their own doctrine or even a SALT treaty anytime they want (See DPRK for an example of violating agreements). You think "dismantled" warheads aren't ready to go at Pentax? The modification of the nuclear posturing to say we will consider the use of preemptive nuclear strike in response to threats from Nuclear/Chemical/Biological attack or threat is simply this: Terrorist of the world and Countries of the world: Think long and hard about turning a blind eye or abetting subversive organizations that place US citizens under a potential deadly threat.
Strategic Weapons and the Cuban Missile Crisis: On October 25, 1962, Castro begged in a letter to Khruschev to preemptively strike the US. Khruschev was essentially shocked that Castro didn't get it. The posturing wasn't designed to start a strategic nuclear war, which Khruschev made clear in a letter to Castro on October 27, 1962,
Re:If they'd stop using the word nuclear... (Score:2)
You want to see a space program that works, then it has to have nuclear aspects.
Besides, our reactors are designed to survive a re-entry without breaking open.
On balance I say exploration is worth the risk. (Score:5, Insightful)
Now according to the the National Human Radiobiology Tissue Repository [wsu.edu] who studied the Palomares incident as well as many other cases, a 78 year old person with elevated Pu in their bones will only have a 0.14285 probability of dying this year, whereas a normal american 78 year old will have an average probaility of dying this year of 0.12780.
We're already dropping nuclear material all over ourselves, and for the most part, you aren't going to hear about it until it's declassified.
Furthermore, have you been to Hiroshima and stood under the peace dome? Have you seen the children playing in the schools at Nagasaki?
The oppertunites for using peaceful nuclear power to explore space far outweigh the risks. Those accidents haven't degraded my environmental quality. I'm sure that a deliberate attack on myself would, but even that will heal with time.
We are talking about the power to reach out and travel the cosmos.
the chinese ming Emperor Zhu Di [berkeley.edu] built a massive navy which traded extensively in the pacific, reached africa and almost discovered america.
When Emperor Zhu died, his sucessor was advised to lessen the tax burden of the navy, and burned all the ships. Result? Other more outward looking seafaring nations whipped them. [serendipity.li]
If we don't have deep space capability, then we are dead meat when we come across those who do. Especially if they are ex-earth colonists who decide to return. No chance of benevolance through alien genetics there.
Re:On balance I say exploration is worth the risk. (Score:4, Insightful)
The health effects from plutonium, americium, and uranium intakes by humans, as determined with USTUR data can be summarized in two words, virtually none. A study of the causes of death of USTUR organ donors has been completed. The study showed that the vast majority of USTUR donors died from the same diseases that have caused the deaths of most of the U. S. population, heart disease, strokes, and cancers not necessarily associated with radiation exposure. This is in spite of the fact that the USTUR donors are a biased population in that a number of donors volunteered for the program after having been diagnosed with cancer. The average age at death of USTUR registrants is 63 years (range between 25 and 91 years). The average age of USTUR registrants who are still living is 73 years (range between 30 and 93 years).
[bold emphasis added]
That's not nuclear, THIS is nuclear! (Score:4, Informative)
Re:That's not nuclear, THIS is nuclear! (Score:2)
I think that Freeman Dyson worked out that if it was launched from the earth's surface, every time it launched between one and ten people would die, on average, from fallout. It got banned anyway (ironically, Freeman Dyson worked on the nuclear bomb treaty that ruled it out; and he did this, knowing that it would ban Orion.)
WMD (Score:2, Funny)
Re:WMD (Score:2)
according to the star trek timeline... (Score:4, Funny)
Khan!!!!!!
Re:according to the star trek timeline... (Score:4, Funny)
Europa? (Score:4, Funny)
Oh oh, aren't we suppost to leave Europa alone after 2010? The Monolith is going to be pissed!
Well hey... (Score:2)
Interesting (Score:3, Interesting)
Our thick atmosphere filters out so much radiation... I would have thought the vacuum of deep space would have allowed solar power to be more effective at a much greater distance than that.
Re:Interesting (Score:5, Funny)
Re:Interesting (Score:2)
Inverse square law (Score:2)
Re:Interesting (Score:2)
But wait, there's more (Score:4, Funny)
On arrival at Jupiter, the extra power allows the probe to orbit each of three of the Galilean moons (Ganymede, Callisto, and most challenging from a radiation exposure standpoint, Europa) in turn, presumably helping to establish the possibility of liquid water and hence, life within the Jovian system.
The probe will then dump its nuclear waste onto these moons, thereby killing that life.
Re:But wait, there's more (Score:2)
Re:But wait, there's more (Score:2)
Oh wait, Nasa already thought of that...
Bad Timing (Score:4, Insightful)
Re:Bad Timing (Score:2)
Or perhaps the Russians or the Chinese might be kind enough to at least lift NASA's fuel, so that NASA can launch an empty reactor.
Re:Bad Timing (Score:2)
And sticking out the back of the craft... (Score:5, Funny)
Spacecraft shape (Score:3, Funny)
Re:Spacecraft shape - there's a reason for that (Score:2, Insightful)
Cassini (the Saturn probe) was nuclear (Score:5, Informative)
According to JPL's Cassini "safety [nasa.gov]" page, they explain that the probe is powered by three radioisotope thermoelectric generators (RTGs) which provide energy by the natural radioactive decay of Pu-238. This isn't fission or fusion at work, but merely the harvesting of heat generated by the radioactive decay. The big question for environmentalists (and NASA) was whether these RTGs would remain contained in the event of a launch disaster.
The big difference between the RTGs of Cassini and the nuclear technology in JIMO [nasa.gov] is that JPL wants to have a full-fledged nuclear fission reactor this time around. This would obviously provide a lot more power for the mission, at the expense of extreme public scrutiny. It will be interesting to see how this situation pans out.
Cassini wasnt the only one (Score:3, Informative)
Re:Cassini (the Saturn probe) was nuclear (Score:5, Informative)
The real big difference is that they're now using nuclear to provide propulsion. The ion drive is really cool (but not because I wrote a little software for one of the early test satellites
To develop thrust in space, you basically have to eject some sort of particle with a given mass and speed. The traditional approach uses rocket fuel or hydrazine as the mass, and uses the potential energy of the chemical bonds to provide the velocity. Ion drives bring just the mass portion of the equation on the spacecraft (remember, it's insanely expensive to lift weight into space). To provide thrust, the ions are accelerated using electricity -- electricity is free near the earth, or in the case of deep space probes, can be generated by nuclear means far more efficiently than other means.
So, to summerize, in traditional systems, thruster mass and energy are closely coupled (i.e. chemical reaction), while in ion drives, the two are seperated so that the most efficient storage methods can be used.
Re:Cassini (the Saturn probe) was nuclear (Score:3)
Hence increased public scrutiny is silly, but of course the usually ignoramuses will raise all sorts of flack. To many, their god is the n
Nuclear Propelled, Not Powered, Is The Big Deal (Score:5, Informative)
Re:Nuclear Propelled, Not Powered, Is The Big Deal (Score:2)
Re:Nuclear Propelled, Not Powered, Is The Big Deal (Score:2)
First to combine nuclear+ion drive, yes. Cassini-Huygens [nasa.gov] used nuclear (Radioisotope Thermoelectric Generator) power for onboard systems, though, and Deep Space 1 [nasa.gov] used (solar-powered) ion drive.
Spacecraft aren't
Looking at the pictures (Score:2)
..on the JIMO site, I have one question:
Where the f*ck is HAL?!? We've go just about everything for the trip, and yet NO HAL!! His birthday came and went... Or is it the engineers said "Hey, we need an uber-intelligent AI to pilot this thing".. and everyone just started saying "Open the pod bay doors, Hal"
how does nuke==propulsion in space? (Score:2)
Re:how does nuke==propulsion in space? (Score:5, Informative)
Take Xenon or Krypton, use some electrical energy to ionize it, and use some more electrical energy to propel the ions out the back of your spacecraft much faster than you could ever propel the products of chemical combustion. Thus you get more momentum, gram for gram of propellant, than you would get from chemical propulsion.
Solar electric propulsion has been done before, such as Deep Space 1. But for going out to Jupiter with such a large payload, the Sun's energy is just not enough.
Re:how does nuke==propulsion in space? (Score:4, Informative)
The idea is to use something like hydrogen that when exposed to the reactor will couse great amounts of energy to be expeled useing a minimum amount of fuel
Re:how does nuke==propulsion in space? (Score:3, Informative)
Nuclear Thermal Propulsion (NTP) - Heat hydrogen and pass it by the reactor to heat it, then expel it.
Nuclear Electric Propulsion (NEP) - Ion propulsion, like Deep Space 1, except you have much more energy with a nuclear reactor than you would with solar arrays of a feasible size.
Both these methods are more efficient than chemical propulsion. NTP has much higher thrust than NEP, but NEP is much more efficient than NTP. So itll take longer to get
The only way to make space exploration practical (Score:4, Insightful)
The same is true with spacecraft. Rocket science IS hard. It will take a lot of trial and error effort before we really learn how to do it right. We are still barely past the equivalent of the Wright brothers era of space exploration.
UN Space Law (Score:4, Interesting)
THE LIABILITY TREATY
The Convention on International Liability for Damage Caused by Space Objects, the Liability Treaty, sets the minimum standards for establishing the liability for space faring nations for launch or spaceflight activities which could cause health, property, or environmental damage outside the launching state's borders.
The treaty, written in 1972, assigns the liability for a spacecraft causing damage to the Earth or to an airplane to the launching state regardless of fault. Damaged property must be restored to prior condition in accordance with international law and the principles of justice and equity. If a spacecraft collides with another spacecraft in space the liability is assigned based on the determination of negligence or malicious intent and the damages awarded as determined by international law.
If the launching state wishes to contest the damage award with the damaged state, the Liability Treaty states that both nations should go first through diplomatic channels and, if no satisfaction or resolution is achieved, a claims commission can be established. No case has ever gotten to this point. In fact, there has only been one case handled under the Liability Treaty: Cosmos 954.
Cosmos 954 was a Soviet Radar Ocean Reconnaissance Satellite (RORSAT) which was powered by a nuclear reactor. Previous Soviet missions using such technology would split the reactor from the parent body of the spacecraft and boost the radioactive material into a higher orbit where the reactor would remain for more than 600 years which was well beyond the life of the radioactive material. Cosmos 954 had a special problem; it went out of control and the technicians were unable to separate the reactor from the spacecraft's parent body.
In late January 1978, Cosmos 954 came crashing into the Great Slave Lake area of Canada spewing debris along a 500 mile footprint. As luck would have it the radioactive portion of the craft fell near a trapper's camp. The trapper looked at the unusual phenomenon and then left it alone. The Canadian Air Force later found the piece and the trapper and took both back to Yellowknife, N.T. where the trapper was found to be in good health and the reactor pieces were impounded. After the cleanup, the Canadian Government sent a $15 million bill to the Soviets. The Soviets paid less than half of this amount and agreed not to take back the spacecraft. The Canadians were happy with the amount they received and were happier still that the Soviets had acknowledged the spacecraft's existence. The Soviets had abided by the Liability Treaty.
Why go to Jupiters moons? (Score:5, Interesting)
For those who wonder why Jupiters moons are interesting, and worth visiting, I'll try to give a brief summary here. JIMO [nasa.gov] will be visiting Jupiters four Galilean moons, named after their initial discovery by Galileo Galilei (through his now-famous telescope). In order of distance from Jupiter, they are Io, Europa, Ganymede and Callisto.
Io is the only moon in the solar system to show volcanic activity; plumes of gas ejected from its volcanos, rising up to 250km above the surface, have been detected from Earth. The energy to keep the interior of Io molten comes from the tidal friction generated as the moon moves through Jupiter's strong gravitation field. Io is a great laboratory for understanding volcanic activity in general.
Europa, the next moon out, is one of the most likely places for life to exist in the Solar System (excepting, of course, Earth). Images of the moon reveal a very smooth surface (in fact, the smoothest in the Solar System), criss-crossed by long, narrow, straight features. These features appear to be fissures in the surface; combined with the fact that the surface is almost pure ice (which we know from spectroscopy studies), it appears that Europa may have a large sub-surface ocean of liquid water, covered by a crust of ice.
Support for the existence of this ocean comes from the discovery of ice rafts on the surface, much like found in polar regions on Earth, and from the detection of a weak magnetic field by the Galileo spacecraft. Europa is too small to have its own magnetic field, but if it contains a large quantity of conducting fluid (such as water with a high concentration of dissolved minerals), then its motion through Jupiters magnetic field will generate a field of its own.
The significance of the sub-surface water on Europa is that liquid water is one of the principal prerequesites for life (as we know it). Speculation as to whether life does indeed exist on Europa is ongoing; to find out, a cryobot/hydrobot mission to the moon is required. The cryobot would melt its way through the icy crust, and the hydrobot would descend through this hole and explore the oceans underneath. Interest incryobot/hydrobot technology was spurred on by the discovery of Lake Vostok in Antarctica, the world's fourth-largest freshwater lake, which is trapped under 2km of ice sheet, and may contain prehistoric lifeforms.
Ganymede is the largest moon in the Solar System, larger even than the planet Mercury. Both Ganymede and Callisto have heavily-cratered surfaces, indicative of millenia of meteorite bombardment. Both are a mixture of rock and ice, although the detection of a weak magnetic field around Callisto indicates that it may have a sub-surface ocean, like Europa. The existence of this ocean is puzzling, since Callisto is too far from Jupiter for tidal heating to be able to melt ice. Some have suggested that Calliso's ocean contains an antifreeze (maybe ammonia), which keeps the water liquid well below its normal solidification temperature.
IMHO, I think Europa is the jewel in the crown of the Galilean moons, due to the possibility that life may exist there. Unfortunately, as one can tell from JIMO's full name (Jupiter Icy Moons Orbiter), there are no plans to land on this fascinating world. In "2010: Odyssey Two", Arthur C. Clarke writes about a manned landing on Europa which discovers life; it would be great for me to see this happen in my lifetime, let alone by 2010.
Re:Why go to Jupiters moons? (Score:3, Funny)
Best we be a takin a shotgun or somethin wit us.
Clarifications (Score:4, Informative)
There are three types of nuclear "power" sources in space.
Radioisotope power- this generates electricity because the decay of the isotope heats a thermocouple junction that generates a voltage. I'll bet this is the kind they are using on the spacecraft in question, and it has been used on many other spacecraft, including the Voyager series. Not much isotope is needed, so even if the spacecraft crashes, minimal contamination would occur.
Nuclear reactor power- another way to generate electricity in space is to have a full fledged nuclear reactor onboard the spacecraft. These designs are *very* cool. Generally they use liquid sodium as the conduction medium. Remember, mass is the determining factor in the design. To my knowledge these have never been actually used in space.
Nuclear powered rocket- the most cool rocket ever. Uses a nuclear reactor, that has hydrogen gas "fuel" running through it, superheating that gas. The gas is then ejected out the nozzle at super high speed to provide thrust. There is no electricity generation involved. As mentioned earlier, these rockets are banned by a treaty. None have every launched to my knowledge.
Re:Io (Score:4, Informative)
Also, recent studies have indicated that Callisto and Ganymede might contain subterranean water, making the possibility of life greater there than at Io.
Don't we have a mining facility on Io? (Score:2)
It was a while back and it's pretty hazy to me now...
Re:Io (Score:2)
Io is certainly a geologist's wet dream ... (Score:3, Interesting)
Re:One more distaster waiting to happen... (Score:2, Insightful)
I suppose telecommunications sattelites are a waste of money too?
Re:Possibilities for reuse? (Score:2)
It would be better just to spend $200M per mission and save the rest of the money.
Re:Possibilities for reuse? (Score:2)
Re:Risky (Score:2)
Re:Risky (Score:3, Informative)
Space (i.e., all that exists) is full of radiation. That's how the stars work. Some of the radiation happens to kills humans, some of it happens to keep us warm. The universe doesn't care one way or the other.
Altough a private venture says they will launch a very small sail into orbit this year, they remain untested. We have no hard proof tha
Re:Risky (Score:2)
First, the amount of radioactive material we're talking about is miniscule compared to what's here on the ground anyway (and I'm talking natural sources).
Second, Nasa shields the hell out of any reactor it launches. It's designed to survive an explosion and re-entry intact . They blow them up and fire projectiles at the shields to prove they're safe.
I live in Hampton Roads, Virginia.
Re:Liquid water, and hence, life. (Score:5, Insightful)
If we found liquid water on Europa and there was no life, an excellent research question would be, "why not? why is Earth special?". So either way, interesting results would be returned.
Re:Water needed for life? What about deep and hot? (Score:2)
Not to mention, having water there is the only way that it will ever be possible for us to pay Jupiter a visit...
Re:Only 6M??? (Score:2)
Re:Does anyone know anything about this? (Score:2)
In explanation, some early designs suggested that you could build a big shield and explode a bomb behind it. The force created against the shield would push you forward... This isn't a design taken seriously by anyone any more.
Re:Military application? (Score:4, Funny)
Now the army reactor....it was a spectacular failure (ie, it failed spectacularly). One poor guy got pinned to the roof by a control rod! (They had been doing some repairs, and some genius decided to raise a control rod...startup rate went ballistic, water (I believe it was a water reactor) flashed to steam, and other very very bad things. When I was going through power school, it used to be the running joke as to why the army shouldn't run reactors. Anyway, their reactors were intended to power a forward deployed base. They'd just fly in the parts and flip the switch.
SL-1 (army) link: http://www.radiationworks.com/sl1reactor.htm
The reason these reactors are feasible for space i due to the fact that...it's space. There won't be any people around, so you only need to shield the instruments. Between that and the small size of the reactor (in terms of power), very little shielding is required.
--Jubedgy
Re:ehmmm! ...NERVA?...anybody? (Score:3, Informative)
It's currently thought that electric propulsion will be more efficient than thermal propulsion. The thermal drives produce more thrust than a similar power ion drive, but the ion drive has a far higher specific impulse. Eventually, io