I hate science reporting

[elfs]

Okay, so why is it that every report about Cassini starts with one of the following:

"The 3.3 billion dollar space probe Cassini..."

"About the size of a bus, the nuclear-powered space probe Cassini..."

Does it really matter, now, that Cassini cost that much money, or that it has a nuclear power source? I suppose it does, but it's not really the big first thing when talking about space probes now, is it? Why do they have to put that in the first paragraph, often the first sentence?

Is it that they're easy targets, simple fnords ("your tax money", "nuclear power") that the writer can hang a story off of, whereas details of the hydrocarbon-rich oceans and organic molecule-laden clouds don't resonate with a scientifically illiterate population?

Comments

[technoshaman.livejournal.com]

Is it that they're easy targets, simple fnords ("your tax money", "nuclear power") that the writer can hang a story off of, whereas details of the hydrocarbon-rich oceans and organic molecule-laden clouds don't resonate with a scientifically illiterate population?

Yes.

[poetpaladin.livejournal.com]

An accident during the launching of Cassini would have caused a hundred thousand extra cancer deaths a year for the next 20 years if the radioactive material scattered over the Earth. I dislike how NASA tries to play with peoples' lives.

[elfs.livejournal.com]

When a nuclear bomb explodes, only 8%-12% of the fissionable materials in the core actually fissions and is converted into energy; the rest is vaporized in the resulting explosion and cast as debris. Approximately half of this debris ends up in the atmosphere.

Between 1946 and 1962, the United States alone conducted dozens of above-ground nuclear test explosions, detonating approximately 22,000 pounds (11 tons) of plutonium along the way. One-half of 88% of 22,000 pounds comes out to about 9,680 pounds, or 4.84 tons of metallic plutonium dust in our atmosphere. We aren't dead yet. Another 72 pounds would have been insignificant.

The plutonium in Cassini was not metallic; it was a ceramic oxide of plutonium that does not-- and cannot-- cause the kind of cancer that everyone was worried about. Plutonium's primary radiant energy consists of alpha particles, which are blocked by a sheet of paper; in order to cause cancer, plutonium must be in a metallic state and it must be vaporized and it must then be inhaled, because only when lodged in the lungs can an alpha radiant source do enough damage to cause cancer. Plutonium oxide is not metallic and does not vaporize into dust efficiently under the kind of explosive pressures expected by a rocket failure; it absorbs the energy of impact and breaks into large chunks. The only way it could cause cancer is if someone deliberately ground it up and rammed it down your throat.

In May 1968, a Nimbus B weather satellite launch vehicle failed. The two SNAP 19B2 RTGs aboard landed intact in the Pacific Ocean and were recovered after 5 months. No release of plutonium occurred.

In April 1970, the Apollo 13 Lunar Lander burned up in our atmosphere. The SNAP 27 RTG on board landed intact into 20,000 feet of water in the Tonga Trench of the Pacific Ocean. The RTG is expected to successfully contain the plutonium for the duration of its half-life and even if it doesn't, plutonium oxide is not water soluble and will remain where it is. As an aside, during the cold war 7 nuclear reactors (5 Russian, 2 American) and over 50 nuclear warheads have also gone to the bottom of the Pacific and Atlantic oceans. No deleterious effects from the presence of any of these incidents has been recorded.

The 1961 re-entry of an unnamed navigational satellite dispersed 2.1 pounds of metallic plutonium into the atmosphere. Despite this apparently alarming amount of plutonium (according to some fearmongers, we should all have been killed twice over!) no deaths have been attributed to this incident. Since then, improvement in the quality and strength of RTG safety mechanisms have led to the above three catastrophic re-entries with the RTG unit landing intact.

Cassinni is flying a fourth-generation RTG, the GPHS, which uses far less plutonium than earlier RTGs and maintains the same standards of safety as earlier models. After the Soviet Cosmos 954 satellite (which carried a nuclear reactor) fell to Earth over Canada in 1978, the U.N. established a working group on the use of nuclear power sources in outer space which concluded that nuclear power sources "can be used safely in outer space provided that all necessary safety requirements are met." NASA has provided its safety research to all state, local, national, and international agencies possible.

NASA was hardly "playing". They take their work very seriously; most of them have families living in the area of the launch facility. The fact is RTGs are safe and reliable. The plutonium in them, if one should ever disintegrate, presents a greater chemical risk than it does a radiological risk-- it's effects on the human body are similar to that of an equivalent weight of lead.

I don't like fearmongering and scare tactics, so I went and read the literature, including the safety literature. The anti-Cassini side never once presented a peer-reviewed paper that cited the kinds of statisics commonly found in their literature. All of the claims of "hundreds of thousands of deaths" and "the end of all life on Earth" (as Helen Caldicott famously-- and ridiculously-- stated) were fraudulent from the beginning.

[fallenpegasus]

That's a very polite way of saying "You are lying, either out of spite or ignorance."

:)

[elfs.livejournal.com]

Heh. I attended the launch of Gallileo, and laughed at the people who opposed the "nuclearization" of space. Tell it to the sun.

I suspect most people who have an opinion about Cassini simply don't understand the science involved.

Not all plutonium is created equal

[neowolf2.livejournal.com]

Not to lend support to the radiophobes, but comparing plutonium by mass is not the correct thing to do here.

What matters for the radiological toxicity is activity (decays/time). The isotope in RTGs, 238Pu, has a much shorter halflife (87.7 years) than the main isotope used in fission bombs (24,100 years for 239Pu).(*) Short halflife means a proportionally greater activity. The energy of the alpha particles from 238Pu is also somewhat greater, but that's less important.

This is consistent with the observation that, unlike the oxide in RTGs, the cores in nuclear bombs do not visibly glow from the decay heat. The rate of production of decay energy per mass of Pu is much less in the bomb core.

You might argue that centuries in the future, the bomb plutonium will still be around radiating people, but by that time any remaining Pu will have been sequestered in sediments or soils, not suspended in the atmosphere as it was after it was released.

(*) 241Pu has a halflife of 14.4 years, but it's a beta emitter, and there's not much of it in weapons-grade Pu anyway.

Re: Not all plutonium is created equal

[elfs.livejournal.com]

True, but I think the point is still made. If we agree that 238PuO₂ is the nuclear ingredient in RTGs, then the chemical properties of 238PuO₂ make it a reasonably safe component to launch on a rocket. It is insoluble and its frangibility does not lend itself to easy vaporization or pulverization; a catastrophic launch event powerful enough to crack a case that survived head-on train collisions and drops from 10 kilometers onto a hard surface would most likely only kill someone if a chunk of it fell on them.

Re: Not all plutonium is created equal

[neowolf2.livejournal.com]

That's true, but remember Cassini also did a couple of flybys of Earth to pump up the orbit. If it had reentered due to malfunction/trajectory error, the RTGs would likely have burned up while reentering at above escape velocity (especially if the trajectory was near-vertical.)

What's really needed for outer planet missions are nuclear _reactor_ powered spacecraft, with 235U that is almost completely innocuous until after the reactor is turned on.