That "Galileo thing"

They’ll probably get a laugh out of it - they’re rather a Jovial group.

This is written by an aerospace engineer with a limited understanding of nuclear physics, but this is my shot at it. Also, I didn’t read the linked site, because that would just lead to a Pit thread. Galileo has RTG’s (radioisotope thermoelectric generators - had to look that up), which means they give off a lot of heat, which is used to power the spacecraft. It does not have a nuclear reactor. From my understanding, the RTG’s are just passively giving off heat, whereas fission or fusion is actively continuing the reaction - the difference between hot charcoal and a raging fire.

In order for a nuclear reaction to be sustained, you need a whole bunch of factors to be just right, such as the right kind of fuel in the right amount, in close proximity. If Jupiter had those conditions, it would have gone off long ago. The type of energy put into the system doesn’t necessarily matter, so Shoemaker-Levy 9 would do the trick.

In other words, alarmist is understating it.

An RTG is just an example of a subcritical reactor. It’s much simpler than a critical reactor, and doesn’t have a potential for thermal runaway (meltdown). It’s still a nuclear reactor, though.

I first heard this drivel a dozen years ago when a friend gave me a tape recording of Bill “NO REALLY!” Cooper giving his pan-conspiracy rant.

Bill, who’s currently spending his time in the 24/7 anal probe level of hell, claimed that the “baby star” that is Jupiter was to be ignited by this very event.

Jupiter is a big object, spectacular even, but hardly stellar. I think it misses the star-club grade by a factor of about 200. If I’m way off there I’m sure Chronos, Q.E.D. or some other physics übermensch will be along to correct.

If I can manage it I’m going out to Jupiter to watch the atmospheric entry, though… :wink:

I’m reminded of Arthur C. Clarke’s book 2010: Odyssey Two, the sequel to 2001. In it the super advanced aliens from the first book/movie turn Jupiter into a small sun. Even in the book, though, it took some pretty serious effort on their part.

Paging Bad Astronomer…No one debunks quite like Phil.

Good job to cerberus1949 on keeping a skeptical, scientific mind rather than swallowing this stuff up.

from here:

Jupiter is about 80 times shy of the 0.08 solar mass limit needed to sustain a hydrogen fusing core. Any fusion reaction would just blow itself out and Jupiter would go right on spinning.

Look, the entire freakin’ Earth is about half the size of The Great Red Spot. The Galileo probe is, at best, the size of a car. For the probe to have any signifcant impact on Jupiter’s make up, it would have to have an incredible power source. If it had such a power source, we wouldn’t need oil.

No, Galileo will not turn Jupiter into a star. Why not?

  1. The plutonium onboard cannot undergo fission like a bomb. It’s the wrong kind (isotope) of plutonium. You need Pu239 or Pu241 for a fission bomb, and Galileo has Pu238 (cite). There isn’t any way I know of to get 239 from 238, despite the claims of the alarmists.

  2. If you did drop a fission bomb into Jupiter, not much would happen. Getting a fission bomb to ignite fusion is not like throwing a match into a bucket of gasoline. You need very specific engineering to confine the explosion so that the hydrogen gets compressed. Even if Galileo had weapons-grade fissionable Pu on it, it would have to be designed specifically to ignite fusion. The design won’t do that (cite).

  3. Even if you had the engineering right to ignite fusion, it still won’t work. Jupiter doesn’t have the right kind of composition to fuse. You need deuterium or tritium (isotopes of hydrogen with extra neutrons), not just plain old hydrogen (cite).

  4. Even if you had the correctly engineered bomb to ignite fusion, and a source for the fusion, not much would happen except you’d get a regular H-bomb bang. Fusion is not a self-sustained process except in the core of a star. Jupiter’s atmosphere is too rarified, even deep down, to get a sustained fusion reaction. You would need a mass 80x that of Jupiter (0.077 times the Sun 's mass) to sustain fusion (cite).

OPINION ALERT: 5) Any claim made on the YOWUSA or TMGNOW site is probably wrong. It’s the way to bet. Those guys couldn’t get something right if they quoted the dictionary. I’ve dealt with them before. Someday I’ll write it up, but it’s too tiring to think about right now.

For more info, we are discussing this on my own Bad Astronomy bulletin board. Lots more details are there.

Actually, its about 20’ long, so its about the size of a small bus.

Maybe that’ll make a difference???


bernse, I had a 1971 Chrysler Newport that was 22 ft long. A Tucker 48 comes in at about the same length.

You know better than that, BA. the sun and other stars are composed of primarily ordinary protium (hydrogen with no neutrons in the nucleus), yet they fuse just fine. We need deuterium in hydrogen bomb cores, because the energy needed to cause fusion is lower. Of course Jupiter can’t fuse anyway, because of the other points you raised.

It looks like NASA is more concerned about possibility of Galileo accidentally hitting Jupiter’s moon Europa than they are about it igniting the planet itself: NASA to Crash Galileo Probe Into Jupiter

[bolding mine]

Sounds like one day we’re moving to Europa! All right! I can’t wait to see Jupiter looming up in the sky above me.

I’m packing my 1920’s style Death Rays as we speak.

Wait! It is coming from the void, from the great beyond, from the realms into which no human consciousness has yet passed!

It is a message, a prediction, a forecast of the future in terms so specific, so scientific, so epistemological that no one could ever possibly doubt that it is true!

The message states:

They have spoken. Loudly. I have a headache and am going off to take a nap.

Suppose we set off a nuclear bomb on Jupiter. Why wouldn’t the hydrogen in Jupiter’s atmosphere undergo fusion?

Well, some of it probably could. The energy released by the bomb might be enough to fuse some hydrogen. But that would create an explosion…the extremely hot material from the bomb would be ejected outward. As the explosion expands, the temperature very quickly falls below the temperature needed for nuclear fusion.

On the Sun gravity keeps the hydrogen compressed enough to continue the fusion reaction. But Jupiter’s gravity is much much much smaller than the Sun’s gravity. The fusing hydrogen would expand quickly, and the fusion reaction would stop. Without that compression you can’t get a self sustaining reaction.

This is the same reason that nuclear bombs don’t start self-sustaining fusion reactions in the Earth’s atmosphere. Nitrogen can be fused…except any fusion reaction would be so energetic that it would destroy the conditions needed for continued fusion.

Like I said, about the size of a small bus!


And you know better than that, QED. The Sun has 1000 times the mass of Jupiter, giving it the confinement it needs to create the proton-proton chain of fusion. Jupiter is 1/80th the mass it needs to do that. Perhaps I should have said, “Jupiter doesn’t have the right composition to fuse for its mass”. Remember, we are talking about fission implosion triggering, not mass-constrained fusion.

Even a fission implosion trigger won’t get plain old protons to fuse together, from what I have read. If someone knows more, please say so!

Yeah, but how many buses do you know of that could cruise at 120 MPH and feel like they were doing 40 MPH? :wink:

My Suburban is about 18.25 feet long. The Chrysler Newport was 22 feet!? Wow.

However, consider that the space probe weighs about 747 pounds. This is less mass than any car I know of here in Atlanta, even the aluminum electric jobs. On the other hand, it will be traveling at 106,000 MPH, very much like most small cars in Atlanta… which is why I drive the aforementioned Suburban.

Regarding the reactor… I was recently castigated by a stranger (with PETA stickers all over his car) for driving a “fuel-wasting road-hogging view-blocking behemoth”. I figured that if I am going to annoy the eco-people, I should at least do a good job of it. I printed a nice green bumper sticker that reads “EARTH FRIENDLY – This vehicle NEVER needs refueling!” It’s on the left side of the rear bumper. On the right is a white sticker with the words “Experimental” and a small radiation trifoil.
I discovered that there are an amazing number of very gullible and extremely excitable people on the road.

That’s better. The way your post was worded, it seemed to imply that only deuterium and tritium can fuse under any circumstances.

As to whether a normal nuclear detonation can ignite proton-proton fusion, I don’t think so. There just isn’t enough heat and pressure. So I think it’s safe to say no matter what we throw at Jupiter, it’s not going to ignite.