Vision and Voyages for Planetary Science in the - Solar System ...

The projected need decreased from 2008 to 2010 largely due to dropping the lunar rovers
associated with the Constellation program (56 kg of plutonium), but also due to a better understanding of
requirements. The current plan assumes an additional 10 kg of plutonium-238 will be purchased from
Russia, and that an average of 1.5 kg/year of new domestic production can begin, but no earlier than
2015. The Russian purchase is subject to ongoing negotiations, and monies for startup of domestic
production were rejected in 2010 by the Congress. Hence, neither of these sources is assured at this time,
and without at least 5 kg of new material from Russia as well as renewed production, NASA’s current
plans for future planetary missions cannot be carried out.
This decadal survey recommends a variety of missions and mission candidates (under the New
Frontiers program) that require RPSs. As such, these recommendations would modify NASA’s 2010
requirements to some degree. The current supply of plutonium-238 is sufficient to fuel four MMRTGs
plus three ASRGs, or 19 ASRGs, or cases in between.
TABLE 9.5 Comparison of NASA Requirements for Plutonium-238 as Reported to DOE in 2008 and
2010
Mission
Projected
Launch
NASA Administrator Letter
of 29 Apr 2008
Power
(We)
Pu-238
Usage (kg)
NASA Administrator Letter
of 25 Mar 2010
Projected
Launch
Power
(We)
Mars Science Lab 2009 100 3.5 2011 100 3.5
Lunar Precursor Not in plan 2015 280 1.8
Mars (RPS and Heater Units) Not in plan 2018 280 1.8
Outer Planets Flagship 1 2017 700-850 24.6 2020 612 21.3
Discovery 12 2014 250 1.8 2015 280 1.8
Discovery 14 2020 500 3.5 2021 280 1.8
New Frontiers 4 2021 800 5.3 2022 280 1.8
New Frontiers 5 2026 250-800 1.8-5.3 2027 280 1.8
Discovery 16 2026 500 3.5 2027 280 1.8
Outer Planets Flagship 2 2027 600-1000 5.3-6.2 Deleted from plan
Pressurized Rover #1 2022 2000 14
ATHLETE Rover 2024 2000 14
Pressurized Rover #2 2026 2000 14
Pressurized Rover #3 2028 2000 14
Pu-238
Usage
(kg)
Projected ESMD requirements deleted
for human missions
The largest user of plutonium-238 is any mission that baselines MMRTGs rather than ASRGs.
Currently this only applies to JEO, for which five MMRTGs are baselined—i.e., one more than can be
supported by the current supply of Pu-238. The Titan Saturn System Mission is the only other mission
that baselines MMRTG use, and it is deferred until the decade subsequent to this study.
None of the recommended Mars missions use an RPS. Of the potential New Frontiers missions
requiring RPSs, Io Observer requires two ASRGs, LGN four, Saturn Probe two, and Trojan Tour and
Rendezvous two. Hence, a maximum of six ASRGs for two New Frontiers missions brackets potential
requirements. The Uranus Orbiter and Probe and the Enceladus Orbiter each require three ASRGs, and
cannot be carried out with MMRTGs due to the latter’s prohibitive mass. Discovery 12 is needed to
qualify ASRGs, and Discovery 14 and 16 could potentially use these as well—each is currently baselined
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