Cassini visits Earth

mwillis writes " Between 8:22 PM PDT and 8:51 PM PDT on August 17, Cassini swung by earth for a gravity assist, coming about 725 miles from the Earth's surface. It still needs a Jupiter flyby before reaching its target, Saturn. Video and mission status here " /sarcasm And, despite fears to the contrary, Cassini didn't smash into the planet and spread 75 pounds of Plutonium across the surface of the planet.

Comments

Re:that's very close!

[HeghmoH]

Contrary to popular belief, the craft is *not* carrying pure Plutonium. The Plutonium is actually in part of a salt/ceramic substance that you could grind very fin without any ill effects. Plutonium is very poisonous chemically, but not all that poisonous radioactively unless breathed in. 77 pounds of the stuff distributed through our atmosphere is nothing. When was the last time you had your place of living checked for Radon?

The worst danger from this was if it somehow lost control, plunged into the atmosphere, and clonked you on the head.

Re:Sociology Prof?

[cpt kangarooski]

Rockets in general are okay. The Air Force had developed a number of manned, piloted planes (as opposed to the NASA rockets, which were pretty much ballistic) with a combination of conventional jet engines and rocket engines.

They were reusable, achieved altitudes that were pretty close to the Mercury capsule altitudes and could land on the groud and be reused. Had the program continued they probably would have built a plane that could achieve LEO sometime in the 60's.

I don't mind using big rockets for heavy lifting, but I have always preferred the idea of establishing a space station in Earth orbit from which both small ferries to Earth and missions to the Moon (and other heavenly objects) could be launched. Von Braun also pushed for that idea, but as long as he was building big ass rockets anyway the Lunar Orbit Rendevous plan killed any chance for a permanent space station.

The International station and Mir are pipsqueaks comapred to Skylab, which rode up on one Saturn V and would still be operational today had they not put it in too low of an orbit. The thing was as big as a house.

Had things worked out differently, I think that we could have wound up with a fleet of LEO-capable space planes, a wicked huge space station and a large, permanent (or semi-permanent) base on the moon.

It's true though, that a lot of the Apollo program decisions were motivated by the political need to get to the moon by 1970 at the latest. And the rush to get there meant that no infrastructure was left to permit the space program to grow. It was a one time goal that accomplished very little in the end.

Conservation of energy

[HeghmoH]

The laws of orbital mechanics dictate that the Earth has to lose as much kinetic energy as Cassini gains during its gravity assist maneuver? Why hasn't anybody made a big deal about *this*? After all, having nuclear material spread througout the planet would be bad, but crashing into the sun because we had too many gravity-assisted spaceflights would be far, far worse.

Somebody should start a campaign to prevent NASA from using Earth for gravity assists. Our lives may depend on it!






For the humor impaired ;)

Re:If if if if if

[Fastolfe]

why would NASA go to the trouble to manufacture the safety mechanisms? I mean, if there is a ZERO percent chance of re-entry, then why bother with the extensive protection of the plutonium for the condition of re-entry?

The only time there was even a minutely significant chance of the probe re-entering the atmosphere was shortly after launch. The safeties were likely designed for that eventuality, not for the fly-by.

this is a "SAFE" operation to launch plutonium, then I am assuming that the craft is -not- going to be exploding!

There's no such thing as a 100% "SAFE" launch. There's always the possibility that the launch vehicle will explode on the pad, or shortly after lift-off, or perhaps later, when the probe is reaching earth orbit. Do you honestly think that such an explosion will cause a horrible radioactive dust cloud to settle down over half of the United States, killing thousands and giving cancer to countless millions? Not going to happen.

encouraging people to make light of the work of scientists by not questioning their methods is only helping the blissful ignorance campaign of the Con.

Who is encouraging this? This goes against the very foundations of science. By all means, question. But don't question US, question THEM. Read the press releases THEY'VE written, because those are the answers you're looking for, and you won't always find them here (though quite a lot of Slashdot regulars are qualified to respond).

Some people are indifferent to Cassini due to ignorance, I'll admit, but lots of us are indifferent to Cassini because we KNOW BETTER. You'll discover most all truely qualified astrophysicists and scientists were all TOTALLY comfortable with having Cassini make its pass. While they had to admit there was a slim chance of a collision (as they had to, since there's always a slim chance), that chance was somewhere in the neighborhood of 1 in several million, and getting more remote the closer Cassini came to earth.

If all of the people qualified to make decisions about something seem content that things are OK, perhaps you should give them the benefit of the doubt. NASA engineers are not stupid people. Ask your questions, sure, but don't turn a blind eye to the answers because of your own fears and doubts.

Re:Do you really believe a "safety report" from NA

[Fastolfe]

Really, we should be a little more critically-thinking than this.

Wow, you're ABSOLUTELY RIGHT. Why in the world did I ever put my trust in space flight with the DOZENS of experienced men holding PhD's in things like astrophysics and engineering when I can run around screaming with my arms up in the air with the rest of you uneducated Slashdot kiddies?

NASA isn't some sort of covert government agency bent on getting things into space no matter what the cost. The guys at NASA aren't stupid. Give the people with degrees the benefit of the doubt and leave your conspiracy theories at home.

Re:We'll always have Titan

[cpt kangarooski]

Well, one of the reasons for the selection of Cape Canaveral (or whatever they're calling it these days) as a launch site was that rockets which had problems shortly after launch would end up in the Atlantic Ocean. It's not as though that part of Florida is a particularly nice place to live. And I know, I'm from Florida.

However, given that the Pu is encased in an extremely durable salt/ceramic mix, it's not nearly so dangerous as a hunk of raw Pu would be.

Re:Sociology Prof?

[cpt kangarooski]

I concur. Although I wimped out and ended up in the English department, I was originally a Physics major (going from one of the hardest to one of the easiest majors, if you must know). I can't stand people disguising their opinions as fact.

I did very poorly in that class, primarily IMHO because I disagreed with him all the time, and on a number of occassions pointed out that he was provably wrong on something, and corrected him. It's all in the past now, so I don't really care much anymore, but he certainly made me realize that a lot of crap that I had tacitly supported or accepted was in fact, crap. That's good anyway.

Now, while I like the Cassini mission, and I'm willing to defend it from people with a science background of 'Plutonium is pure evil,' I don't really like NASA all that much.

I would have preferred that the USAF had been given more opportunities to research spaceflight. Between Von Braun's ultimately stupid utter reliance on rocketry and NASA's unwillingness to conduct the Apollo mission gradually (with a permanent Skylab-type installation in the mid-60's) we're really not at all as far ahead in space as we should be. About the only good thing there is regarding NASA, IMHO is that they are basically a civilian agency. It would have been crappy to let the military dominate space, but I could accept joint programs.

Couldn't have said it better myself

[Fastolfe]

Needs to be moderated up, IMO.

Please read before you post

[Fastolfe]

Reason #18 to post as an AC: Pulling "facts" out of your ass is encouraged.

The CERAMIC plutonium was divided up into small pieces encased in, I believe, uranium and graphite (or something), among other things. The idea is that, even if the probe were to have exploded or impacted the earth, the chunks of plutonium would not have burned up and neither would they have been in any way exposed in the end.

The chances of the Plutonium "catching fire and dispersing in the atmosphere" are nearly non-existant. Please do a little bit of research before you make assumptions like this and make AC's look worse than they already do.

72lbs of Plutonium isn't a lot.

You may think all scientists are arrogant, uncritical and blissfully ignorant when it comes to the things they do, but you should be willing to concede the possibility that the people with the PhD degrees in things like astrophysics and nuclear engineering might just know what they're doing. Mistakes happen, sure, but these guys are not stupid.

Re:Emotionalism and Information flow versus Scienc

[Fastolfe]

Agreed!

Why in the world did you post this as an AC? Post it as a user and be known. Let the credit flow to you. Let your comment's score be greater than zero.

Re:Titanic IV's

[Fastolfe]

So what do YOU think the conversation was like in that NASA conference room:

A:
"Since we're some kind of evil government agency, it's high time we started acting like one. We have all of this spare nuclear fuel around, let's see if we can trick congress out of some more money so we can build even MORE expensive space probes that can use some of this nuclear fuel. Oh, and don't bother trying to make it 'safe' or anything. We'll just tell everyone that we've got it safely in hand and there's no chance of any problems. Hah!"

B:
"OK, which energy source is going to work for us in this case? Solar? Let's see.. Hmm.. at this distance from the sun, we'll need X amount of power for the instruments.. which means we'd need solar panels that big.. hmm.. that's going to be expensive and heavy. Is there another power source that we can use that'll be lighter and more efficient for us? Ahh, that will work nicely."

C:
"OK, we have plans for the new probes all using solar panels, but you know, damn, we just have all of this extra money lying around. Let's outfit all of these babies with some NUCLEAR power! Yah, man!"

Concede the possibility that the men in white coats with PhD's in things like astrophysics and nuclear energy MIGHT just know what they're doing, whereas you do not.

Re:Beowolf

[Eccles]

I was stunned that no one mentioned Beowulf clustering on that recent Playstation 2 article. C'mon fellow smart alecks, we're letting the side down...

>Or better, a cluster made of people

A Soylent Green cluster?

Re:Agreed

[Detritus]

Plutonium is one of the most deadly substances around.

Please stop spreading this myth.

Plutonium is a mildly radioactive metal that is also chemically toxic. A short article can be found here. There are many chemicals that are far more toxic than plutonium.

Anti-nuclear activists would get more respect if they made scientifically sound arguments. Most of the anti-Cassini material appears to be written by people who flunked high school physics and chemistry.

plutonium isn't THAT toxic

[forii]

Okay, everyone here has heard how plutonium is "the most toxic substance known to man". That is utter and complete BS. (btw, you can thank Ralph Nader for that quote) Here's some perspective on plutonium.

Of course, No-one bothered with Galilleo

[EvilBastard]

Galilleo had two close passes with the Earth in '90 and '92 (the '90 was closer, 1000 km no ?) It was a lot sicker than Cassini, too, with the failure in the main antenna. Didn't hear a peep, then. Why ? Because no-one had an agenda to push back then. Now they do, and they go "Plutonium! Nasty! Be Scared! Cancer! They say it can't happen!!!!!!" and hope that no-one bothers checking up on the facts. (Oh, and the fact that most of the US was keeping an eye on that little tussle in Iraq.) Remember, the people who launch these things have friends and families here on earth, and, also, a mistake at this point means no more funding for the next 5 or 7 years.

Nuclear Whining - The New Olympic Sport

[Bowie J. Poag]

wildly_inflammatory_editorial_mode(on);
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Yeesh. All this whining makes me wonder why people aren't impressed with heavy-duty science anymore. Instead of the thrill of discovery, people would rather occupy their time panicking and whining about a 75 pound lump of "angry rock".

Reminds me of that episode in All In The Family where Gloria complains to Archie about how many people die every year by guns. Archie quips back, "Well little girl, would you be happier if they got pushed out of windows?"

Lets suppose for a moment that 75 pounds of plutonium *did* come hurtling through our atmosphere. First and foremost, it would probably be so badly degraded upon re-entry that it wouldnt matter *what* it was. You could send a damn dump truck full of boubonic plague through the Earth's atmosphere, it would probably disintegrate before ever reaching the ground. The earth is continually bombarbed by fairly large chucks of threatening debris 24 hours a day, 7 days a week, 365 days a year. Its been this way for millions, if not billions of years. There's a _reason_ why we arent living in a sea of craters, kids.

Besides.. Earth has already seen far worse man-made ecological disasters over the past 200 years than 75 pounds of plutonium could ever cause.

The Industrial Revolution, Hiroshima, Nagasaki, thousands of Cold War nuclear tests , Love Canal, Three Mile Island, Chernobyl, The Gulf War, just to name a few... I'd be willing to bet that if you took every single person who experienced irreversible physical illness as a result of these catastrophies, you could probably arrive at a figure of around 400,000 to 500,000 people grand total. And as tragic as those numbers are, they amount to less than one one-thousandth of a percent of Earth's human population. 75 pounds of plutonium, even *if* it came back to earth, would not reduce us to the level of a bunch of custard-eating Teletubbies living below ground for the next 10,000 years. Besides, i'd trust an engineer over a hippy, wouldnt you?

In other words, the 90's are over. We can all put down out guitars and quit whining now. Putting limits on what science can investigate is far more dangerous than sending a silly little spacecraft out for a spin.

}
wildly_inflammatory_editorial_mode(off);


Bowie J. Poag

Re:We'll always have Titan

[cpt kangarooski]

It's true though. And since we're talking about a planet-wide issue, should the US government have to get the permission of every one of the approx. 6 billion people that live here? Does this apply to private entities (individuals and corporations) which are conducting risky work?

The airplane argument I mentioned earlier is this: I hate to fly. I'm absolutely terrified of flying. Really. So I don't fly unless I absolutely have to; it's a stressful experience that I would be all too happy to not have to deal with. However, given that I am strongly concerned about planes dropping out of the sky on a more or less random basis, why should I be put at risk of having planes that I'm not even in falling on _me_? There's no reason for pilots et al to risk my safety by flying planes at all, even if I'm on the ground.

The answer of course, is that if something is not immediately dangerous and extremely risky, it can be done without having to get approval from the people who may be effected. The Cassini probe was determined to not be likely to endanger people, and thus, it was approved. Had it not been considered to be sufficiently safe, it would never have gone ahead at all.

We'll always have Titan

[cpt kangarooski]

I think I'll always have fond memories of the Cassini mission. Back a couple of years ago when debates were running rampant before NASA launched it, I got involved in a really enjoyable debate with some Sociology students at school.

The teacher in that class, who IMHO would ban himself if he realized that upon death he'll undergo radioactive decay, was always saying to his students 'Subvert the dominant paridigm.' And whenever he told his students to jump, every single one of the bozos asked how high.

I bashed through their anti-Cassini arguments like a knife through vaporized butter. My shining moment was when one of them complimented me for having subverted the dominant paridigm of the class. That was cool.

The moral is: stay far away from Gordy Fellman.

Re:We'll always have Titan

[cpt kangarooski]

Okay. How about (although we couldn't have known this for a fact then) that it really did work ;)

Most of my arguments for were rebuttals towards their arguments against.

People complained that NASA had no right to risk everyone. I replied that NASA does not really need to ask, that it is impractical at best to require everyone to ask for consent to risk (including the airplane thing, which I'll skip for brevity), and that the risk is quite low due to a number of factors. They include the precision of orbital mechanics, the success of previous RTG-equipped craft, the sturdiness of the RTG and the likely effects that the RTG could have in a worst case scenario.

Another person had asked why an alternative power source was not used (i.e. photovoltaic cells). I pointed out the low efficiency of said cells and that there is very little light from the Sun at the distance of Saturn's orbit and the dangers that the large number of objects in the Saturnian system pose to big ass solar panels.

Sadly, the class shifted to a mailing list, rather than continue to use the newsgroup (which was specific to that class!) for some reason after this whole thing wrapped up. Personally, I would have liked to rekindle it. ;) I'd like to say that you can go to dejanews and read through the posts, but since the group was specific to the school, it's not archived there, or anywhere in fact. Pity.