NASA Mulls Missions To Neptune and Uranus, Using the Space Launch System

MarkWhittington writes: According to a story in Astronomy Magazine, NASA is contemplating sending flagship sized space probes to the so-called "ice giants" of Uranus and Neptune. These probes would orbit the two outer planets, similar to how Galileo orbited Jupiter and how Cassini currently orbits Saturn. The only time NASA has previously had a close encounter with either of these worlds was when Voyager 2 flew by Uranus in 1986 and then Neptune in 1989. Each of these missions would happen after the Europa Clipper, a flagship-class mission scheduled for the mid-2020s.

Comments

Re:Flagship-sized probe to Uranus?

[Rei]

Herschel, its discoverer, wanted to name it "George". ;)

Really, Uranus was a naming mistake - in keeping with the names of the other planets, it should have been named Caelus.

Re:Use RTGs for ion propulsion then comm.

[Cassini2]

RTGs are being phased out because (a) the probes need more power than ever with modern computers, and (b) because of environmental concerns. Unfortunately, most of the environmental concerns revolve around the word "Plutonium" and the much more dangerous Plutonium-239.

The best RTGs use a chemically locked Plutonium-238 Oxide that is probably one of the safest fuel sources ever invented. The stuff is non-reactive ceramic that is almost indestructible, and is readily rejected by the human body if ingested. It's not even particularly radioactive, as radio-active isotopes go, because to make the RTG last for a long period of time, it is necessary to use an isotope with a sufficiently long-lived half-life characteristic. Plutonium-238 Oxide is the polar opposite of the more typical dangers from Plutonium-239 that everyone worries about.

See RTG generators and plutonium oxide for more information.

Re:Ehh

[Rei]

Flagship is a technical term. NASA missions are divided into categories: Discovery, New Frontiers, Explorer, and Flagship. Flagship are the most expensive, and most infrequently launched. Flagship missions cost over a billion dollars, usually $2-3B. Because they're so expensive and infrequently launched, one expects a huge scientific return out of them - for example, although Cassini-Huygens cost $3.26B, it's returned such a treasure trove of data and incredible discoveries about the Saturn system that I doubt anyone would say it's not worth it. Is Mars 2020 going to return anything that worthwhile? Not even close. The sort of scientific territory it's exploring is far too well tread already; it's exploring small details, not huge unanswered questions. The Uranus or Neptune probes may or may not prove to be worth their price tag, but at least they stand a better chance. I know a lot of people for example itching to find out more about Triton after Voyager's tease, which was conducted with 1970s tech.

Re:Use RTGs for ion propulsion then comm.

[Rei]

1) RTGs are not being "phased out". They're actually going to become more common in the coming years, now that 238Pu production has restarted.
2) Computer power consumption has dropped, not increased.
3) For outer planetary missions, there is literally no better solution to produce X number of watts, whatever number X may be (up until you get into the many-dozens-of-kilowatts range, where it probably pays to start developing an outright fission reactor)
4) Few people would consider 238Pu to have a "long half life". There are certainly things that it's long in comparison to, but as far as "long lived radioactive" products are considered, it's not even close to being considered one.
5) Plutonium is not "rejected by the human body", it's accumulated in the bones, and alpha radiation inside the body has 20 times the destructive power of beta and gamma per MeV (also, with beta decay, 2/3rds of the energy is usually lost as a muon antineutrino)

Note: Please don't misinterpret this, I'm pro-RTGs. I just wanted to correct the facts.