dietz@SLB-DOLL.CSNET (Paul Dietz) (02/25/86)
Henry Spencer writes: >Timothy Wright writes, in part: > >> I read in the latest issue of The Nation that one of the shuttle's >> planned missions included the Galileo-Jupiter probe, which would have had on >> board about 46 pounds of Plutonium. A Challenger-type explosion would have >> either vaporized or finely distributed the stuff all over the greater Cape >> Canaveral area... > >Why? It didn't vaporize or pulverize the rest of the Challenger, just broke >it into small pieces for the most part. The interior of the cargo bay is >probably the best-protected area on the shuttle, too. The ET went off with the force of a small atomic bomb, but even an atom bomb doesn't necessarily destroy everything nearby. Graphite covered solid steel spheres have been suspended below A-bombs in above-ground tests and have suffered only slight ablation of the surface layer. The thermal pulse blows off a thin outer layer, but the heat takes too long to diffuse into the body and most radiates away. This phenomenon formed the basis for the Orion-style spaceship. The radioisotope thermal generators sound somewhat more fragile than solid steel spheres, though. Galileo and Ulysses are attached to Centaur upper stages. These high energy stages use a lot of LH/LOX fuel, and said fuel sits right next to the probe in the cargo bay. A Challenger-type explosion would certainly rupture and detonate the Centaur tanks. An aside: 46 pounds of Pu-238 is a lot more dangerous than a similar amount of Pu-239, since Pu-238 has a much shorter halflife (it has to to get respectable decay heat). A solution to the radiation problem might be to launch the radioisotope source separately and assemble in orbit (probably not feasible for current probes) or to design probes that use real nuclear reactors (certainly not possible for current probes). The latter solution could allow really high power transmitters (kilowatts at least) for high data rates from the outer solar system, and could even power ion engines.
henry@UTZOO.UUCP (03/01/86)
Paul Dietz writes, in part: > ... A solution to the radiation problem > might be to launch the radioisotope source separately and assemble in > orbit (probably not feasible for current probes) ... What probably would be feasible would be what was done for the isotope cartridges the later Apollo missions carried for their lunar-surface experiment packages: The isotope slug goes up as part of the same payload, but inside an armored cask. At deployment time, the astronauts transfer it from the cask to the generator. This would mean that NASA would have to get over some of its fetish about avoiding in-space assembly, though. Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry
carroll@uiucdcsb.CS.UIUC.EDU (03/02/86)
Didn't the above ground tests in the 50's and 60's release several tons of (obviously) vaporized plutonium into the atmostphere? Clearly, it killed millions of people off pretty quick.
carroll@uiucdcsb.CS.UIUC.EDU (03/06/86)
There is a big difference between "harmless", "dangerous", and "so deadly that it will kill off millions of people if any of it gets loose". The evidence I have seen indicates that plutonium goes in the second category, not the first or third. BTW, Mr. Pournelle is talking about plutonium OXIDE, the normal form it is found in. Metallic plutonium is quite a bit more toxic (as are all the heavy metals).