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:Use RTGs for ion propulsion then comm.

[Rei]

Why all spacecraft don't utilize the extremely high energy/weight RTGs for deep space PROPULSION is beyond me

First off, even with the little we use today, we already have a serious shortage of it. At least funding has been reestablished to produce more. But production rates are going to be very slow and expensive, and this means that the fuel will continue to be expensive. Unfortunately, 238Pu needs to be thought of as a manufactured product, not a waste product. It's impractical to extract from nuclear waste - you have to first separate out neptunium (which isn't too common to begin with, which means lots of reprocessing, which is expensive), and then you have to bombard it with a lot of neutron flux for a long time (neutron flux being very valuable, as it's what you can use to make power (by bombarding a fissile target) or medical/ industrial isotopes). And you need a lot of plutonium to be useful for space probes (kilograms), not the sort of ng/ug/mg quantities usually used in medicine and industry.

The net result is that RTGs are almost always the best option from Saturn on out, usually the best option for Jupiter, sometimes the best option for Mars and the asteroid belt, and seldom for Earth on inwards.