Timeline for Why is tantalum being used for the Hayabusa bullets?
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| Jun 17, 2020 at 8:54 | history | edited | CommunityBot |
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| Jul 31, 2019 at 9:50 | comment | added | hdhondt | @Mark Even today, isotopic enrichment is probably more expensive than just using something like tantalum. Tantalum is about \$ 125/kg; heavy water (D2O) is over \$ 400/kg. | |
| Jul 31, 2019 at 9:46 | history | edited | hdhondt | CC BY-SA 4.0 |
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| Jul 31, 2019 at 2:54 | comment | added | Mason Wheeler | @Mark That's actually a very bad example because a huge amount of that expense was doing science research that had never been done before, creating plutonium at all which had never been done before, enriching uranium which had never been done before, building atomic bombs which had never been done before, etc. It's hard to say how much of that expense specifically was for plutonium enrichment. (And also hard to say how much it would cost today, about 80 years of scientific progress later!) | |
| Jul 31, 2019 at 0:00 | comment | added | IMil | @Mark you wouldn't need isotopically pure samples. If, say, you make bullets of 10% rare isotope and 90% common, then if you see 0.1g of the rare one in the sample, you may subtract 0.9 (adjusted for the mass difference?) from the common one. Assuming that the rare isotope isn't in fact more common in the asteroid than we thought. However, even if this assumption is justified, an iron bullet of non-standard isotope distribution might prove more expensive than a tantalum one. | |
| Jul 30, 2019 at 22:41 | comment | added | Mark | @Michael, isotopically-pure samples of elements are incredibly expensive. You might be familiar with the project to produce a sample of isotopically-pure plutonium-239. | |
| Jul 30, 2019 at 21:53 | comment | added | Schwern | @Michael While tantalum is expensive, they only needed 5 grams, and they can buy it on the open market. Compared to tainting the results of a $150 million six year project, that's peanuts. I don't know what 5 grams of ultra-pure tantalum costs, but to give an idea there are coins with 20 grams of tantalum selling for less than €200. Modern electronics have a few milligrams of tantalum. | |
| Jul 30, 2019 at 21:28 | comment | added | uhoh | @Michael that occurred to me to. If they used steel they'd have to isotopically enrich several chemical components, and then work much harder to defend their results because they still couldn't rule out the particular isotope profile they chose also occurring by coincidence on the asteroid perhaps. | |
| Jul 30, 2019 at 19:18 | comment | added | Michael | Why didn’t they use certain isotopes of an element which don’t/can’t occur naturally in the asteroid? | |
| Jul 30, 2019 at 13:02 | vote | accept | Mark Foskey | ||
| Jul 30, 2019 at 10:11 | history | edited | uhoh | CC BY-SA 4.0 |
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| Jul 30, 2019 at 5:23 | history | edited | hdhondt | CC BY-SA 4.0 |
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| Jul 30, 2019 at 5:02 | history | answered | hdhondt | CC BY-SA 4.0 |