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New Frontiers 4: Argo?
Mongo
post Aug 21 2008, 01:36 AM
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There does not appear to be a thread about this proposed New Frontiers mission, so I am starting this one. If there is an existing thread that I am unaware of, then by all means merge them.

Argo is a proposed outer solar system multiple flyby mission, rather like an updated Voyager mission, but based on the New Horizons bus, and using a similar instrument suite. It would launch between 2017 and 2019, with either a Jupiter / Neptune / KBO or a Trojan / Saturn / Neptune / KBO trajectory. Even a combined Jupiter / Saturn / Neptune / KBO trajectory is possible.

Neptune would present a much different system than in 1989, as telescopic observations show a more dynamic Neptune atmosphere, due to the change in season, and much more of Triton and the other Neptune satellites would be visible (most of Triton's northern hemisphere was in darkness in 1989, but will be well lit in 2030).

The second big payoff would be the vastly greater access to KBOs (~4000 times the accessable volume of New Horizons), with several already-known large KBOs (400km diameter or larger) within reach. The objects reachable with Argo are expected to include:

18 cold classical KBOs (interesting because they apparently formed in situ beyond Neptune's orbit, rather than further inward)
40 KBOs with diameters between 200km and 400km
9 KBOs with diameters greater than 400km
several binary KBOs

plus the possible Jupiter Trojan early in the mission. The wide expected range of choices allows for the selected KBO to be of very high scientific interest (and naturally, follow-on KBO targets could be selected after the primary KBO target has been selected).

Typical flight times from launch to the Neptune flyby are about 10 years (Jupiter gravity assist) or 13 years (Jupiter Trojan flyby), with the large KBO flyby 2 or 3 years later.

Expected cost including launch vehicle (according to the linked pdf): under $800M with the following strawman instrument package:

High resolution visible camera: New Horizons (NH) or reduced Cassini heritage
Near-IR spectrometer: NH heritage
UV solar & stellar occ. spectrometer: reduced Cassini heritage
Far-IR linear radiometer: Diviner heritage
Magnetometer: replaces NH dust instrument
Charged particle spectrometer: NH heritage
Gimballed high-gain antenna: heritage radio science instrument

The big uncertainty at this point seems to be the availability of plutonium-powered RTGs by the time of launch.
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mchan
post Nov 6 2008, 05:00 AM
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QUOTE (infocat13 @ Nov 2 2008, 12:54 PM) *
Weapons grade plutonium and uranium can not be used in RTG's as those compounds are to "hot" and the radiation would interfere with spacecraft science instruments. The thought that occurred to me is could an RTG have a say 10 to 15 percent mix of the weapons grade material with the existing supply and/or could the weapons grade material pellets be in the interior of the RTG canister as to be shielded by the surrounding material.


Pu-239 and U-235 (whether weapons-grade or not) has far less heat output per unit mass than Pu-238. Pu-238 has a relatively high heat output due to relatively short half-life (80-something years) vs Pu-239 or U-235 (24K or 700M years). In this sense, Pu-238 is "hotter" than Pu-239 or U-235. A piece of Pu-238 will probably be glowing hot depending on what it is alloyed with while you can hold a piece of Pu-239 in your hands without discomfort (it will still feel warm from alpha decay of other isotopes mixed in).

In the sense of penetrating radiation, the main decay mechanism of Pu-238 is spontaneous alpha decay which is stopped by several feet of air at standard atmospheric pressure. This vs the highly penetrating gamma rays from the fission reactions which are the main decay mechanism for Pu-239 or U-235, so Pu-238 may be thought of as less "hot" with less penetrating radiation. In order to get a high heat output from Pu-239 or U-235, you'd need a near-critical mass and some moderating material to produced a sustained chain reaction, i.e., a nuclear reactor. Then you'd have to worry about shielding against the gamma radiation and neutrons from the fission reactions.

In short, Pu-238 has an entirely different means of heat production and shielding requirements than Pu-239 or U-235. One does not mix with the other.

The "weapons-grade" part comes into play in reducing the overall mass of plutonium or uranium required to sustain a chain reaction, and allows for much more compact reactor designs. Reactors on naval ships and for space applications use "weapons-grade" material.

QUOTE (jgoldader @ Nov 5 2008, 05:52 PM) *
NASA has to get its plutonium from the Department of Energy, which maintains the only facility(ies) for processing the proper isotope of plutonium.


For a while, NASA also purchased Pu-238 from Russia, but even that source is dwindling. As pointed out, the facilities for Pu-238 production were shutdown. It is expensive to produce Pu-238.
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- Mongo   New Frontiers 4: Argo?   Aug 21 2008, 01:36 AM
- - vjkane   This is my favorite mission option for the 2nd New...   Aug 21 2008, 04:56 AM
|- - tedstryk   QUOTE (vjkane @ Aug 21 2008, 04:56 AM) Th...   Aug 21 2008, 11:43 AM
- - Greg Hullender   In one of the backup slides, they noted that they ...   Aug 21 2008, 03:43 PM
- - Mongo   New Horizons masses 478 kg. I assume that Argo wo...   Aug 21 2008, 04:08 PM
|- - ugordan   QUOTE (Mongo @ Aug 21 2008, 06:08 PM) Is ...   Aug 21 2008, 04:20 PM
- - Greg Hullender   The Galileo atmospheric probe weighed 339 kg, of w...   Aug 21 2008, 04:29 PM
|- - vjkane   QUOTE (Greg Hullender @ Aug 21 2008, 05:2...   Aug 21 2008, 04:48 PM
- - Ken90000   Actually, the Pioneer Venus sent their data direct...   Aug 21 2008, 04:32 PM
|- - Greg Hullender   QUOTE (Ken90000 @ Aug 21 2008, 09:32 AM) ...   Aug 21 2008, 07:07 PM
|- - vjkane   QUOTE (Greg Hullender @ Aug 21 2008, 08:0...   Aug 21 2008, 08:03 PM
- - mchan   A steerable antenna would add complexity and cost....   Aug 21 2008, 06:32 PM
- - Mongo   It is interesting that from what I read here at Un...   Aug 22 2008, 01:34 AM
|- - vjkane   QUOTE (Mongo @ Aug 22 2008, 02:34 AM) Tha...   Aug 22 2008, 03:40 AM
- - Mongo   According to this report entitled Radioisotope Pow...   Aug 22 2008, 05:05 AM
|- - vjkane   QUOTE (Mongo @ Aug 22 2008, 06:05 AM) ...   Aug 22 2008, 02:42 PM
|- - Greg Hullender   QUOTE (vjkane @ Aug 22 2008, 07:42 AM) Ju...   Aug 22 2008, 03:55 PM
|- - infocat13   QUOTE (Greg Hullender @ Aug 22 2008, 11:5...   Nov 2 2008, 08:54 PM
- - Vultur   I kind of hope New Frontiers #3 is a Venus lander ...   Nov 3 2008, 12:11 AM
- - Enceladus75   Yes, I would love to see another landing on Venus ...   Nov 6 2008, 01:08 AM
|- - jgoldader   QUOTE (Enceladus75 @ Nov 5 2008, 08:08 PM...   Nov 6 2008, 01:52 AM
- - mchan   QUOTE (infocat13 @ Nov 2 2008, 12:54 PM) ...   Nov 6 2008, 05:00 AM
|- - Mark6   QUOTE (mchan @ Nov 6 2008, 05:00 AM) For ...   Nov 12 2008, 10:10 PM
- - elakdawalla   What makes me think that is that clearly Hansen an...   Nov 12 2008, 11:14 PM
|- - vjkane   Both outer planet flagship proposals include the o...   Nov 13 2008, 12:17 AM
||- - Mark6   QUOTE (vjkane @ Nov 13 2008, 01:17 AM) Fr...   Nov 13 2008, 03:46 AM
||- - vjkane   QUOTE (Mark6 @ Nov 13 2008, 03:46 AM) I h...   Nov 13 2008, 06:34 AM
|- - mchan   QUOTE (elakdawalla @ Nov 12 2008, 03:14 P...   Nov 13 2008, 07:13 AM
- - infocat13   Mango and Emily and our other posters................   Nov 13 2008, 08:10 AM
- - Mark6   Yet it is still the case of squeezing as much as p...   Nov 13 2008, 04:58 PM
|- - mchan   QUOTE (Mark6 @ Nov 13 2008, 08:58 AM) ......   Nov 14 2008, 11:33 AM
- - dvandorn   I know where you can find a few pounds of Pu-238. ...   Nov 14 2008, 07:29 AM
|- - infocat13   QUOTE (dvandorn @ Nov 14 2008, 02:29 AM) ...   Nov 14 2008, 08:24 AM
- - dvandorn   Oh, this isn't a bomb, it's not weapons-gr...   Nov 14 2008, 08:55 AM
- - stevesliva   Thought you meant Mars 96 for a bit. And yeah, I ...   Nov 14 2008, 06:38 PM
|- - infocat13   QUOTE (stevesliva @ Nov 14 2008, 02:38 PM...   Nov 15 2008, 04:53 AM
- - Ken90000   Apollo 13's ALSEP?   Nov 14 2008, 07:17 PM
- - imipak   ISTR reading about RTG powered cable taps*, but ...   Nov 14 2008, 10:17 PM
- - dvandorn   Give Ken the Kewpie doll, we have a winner! ...   Nov 14 2008, 10:41 PM
- - dvandorn   Actually, while I was mostly kidding about any att...   Nov 15 2008, 06:09 AM
- - mchan   With a radioactive half-life of 87.7 years, you...   Nov 15 2008, 07:47 AM
- - sci44   I wonder how far you can go by just reducing the s...   Nov 20 2008, 09:14 PM
|- - vjkane   QUOTE (sci44 @ Nov 20 2008, 09:14 PM) I w...   Nov 21 2008, 12:52 AM
|- - sci44   QUOTE (vjkane @ Nov 21 2008, 12:52 AM) Ur...   Dec 1 2008, 10:33 PM
|- - infocat13   http://www.lpi.usra.edu/opag/nov2008Meetin...ation...   Dec 9 2008, 01:26 AM
- - mchan   The slides in the March OPAG presentation showed M...   Nov 21 2008, 07:24 AM


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