Advisers to the Nation on Science, Engineering, and Medicine

The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences.

The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Wm. A. Wulf is president of the National Academy of Engineering.

The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine.

The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Wm. A. Wulf are chair and vice chair, respectively, of the National Research Council.

www.national-academies.org

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NASA’s budget for fiscal year 2003 included funds to begin the Nuclear Systems Initiative focused on research into and development of enhanced capabilities in the general areas of spacecraft power and propulsion systems. The agency’s fiscal year 2004 budget request renamed the activity Project Prometheus and proposed substantial funding for research and development activities for the next 5 years in the following areas:

• Energy generation (including radioisotope systems for the near term and fission reactor systems for the longer term);

• Conversion to electricity (including both static and dynamic system design concepts); and

• Electricity utilization (for nuclear-electric propulsion, scientific instruments, and communications).

According to NASA, Project Prometheus was initiated in response to identified limitations in the current paradigm for solar system exploration. In particular, photovoltaic arrays restrict a spacecraft’s power budgets and are of limited use in the outer solar system. Similarly, chemical propulsion systems limit a spacecraft’s maneuverability and the number of solar system destinations that can be readily reached. In early 2003, NASA selected the Jupiter Icy Moons Orbiter (JIMO)—a mission to study three of the Galilean satellites of Jupiter—as the first mission to use the new nuclear propulsion capabilities. But in early 2005, JIMO was deferred until beyond 2017 in favor of a less complex, but as yet undefined, nuclear-electric propulsion (NEP) mission designated Prometheus 1.

In late 2003, Edward J. Weiler, then NASA’s associate administrator for space science, sought an independent assessment of whether, and if so, what, potentially highly meritorious space science missions beyond JIMO might be enabled if space nuclear power and propulsion systems could be developed and put into operation. In a letter dated October 14, 2003, Dr. Weiler requested that the Space Studies Board (SSB) and the Aeronautics and Space Engineering Board (ASEB) of the National Research Council (NRC) jointly organize a study to assist NASA in the following manner:

• Identify high-priority space science objectives that could be uniquely enabled or greatly enhanced by development of advanced nuclear power and propulsion systems for spacecraft; and

• Make recommendations for an advanced technology development program for long-term future space science mission nuclear power and propulsion capabilities.

In response to this request, the SSB and ASEB devised a plan to conduct a two-phase study sequentially addressing the two tasks identified in NASA’s letter. The Phase I report (i.e., this report) identifies space science objectives and possible missions that could be enabled beyond 2015 by development of advanced spacecraft nuclear power and propulsion systems, as well as by nuclear power systems that might be used on planetary surfaces. This report draws on the strategic goals and priorities outlined in the recent NRC decadal survey reports in astronomy and astrophysics, in solar system exploration, and in solar and space physics as its scientific starting point, and considers potential directions in each field which go beyond the time span of the current strategies. The authoring Committee on Priorities for Space Science Enabled by Nuclear Power and Propulsion strongly emphasizes that the purpose of its Phase I study is not to reprioritize the science goals and missions endorsed in the decadal surveys or to establish priorities beyond the nominal time frames of the existing survey reports. Rather, this study’s purpose is to define a series of unprioritized mission concepts to help identify where the availability of space nuclear power and propulsion systems can have a major impact. These conceptual missions can then be studied by NASA and the wider scientific community and, if found to have sufficient merit and potential, can be prioritized in the context of future decadal-survey activities.

Phase II of the study—originally scheduled to begin at a later date—will use the science mission concepts and associated mission requirements identified in this Phase I report as a set of reference missions enabled by nuclear systems. The Phase II study will consider the engineering requirements for such missions and make recommendations for an evolutionary technology development program for future space science missions utilizing nuclear power and propulsion capabilities.

In a subsequent letter, dated May 4, 2004, Dr. Weiler and Admiral Craig E. Steidel, the associate administrator of NASA’s newly established Office of Exploration Systems, modified the scope of the Phase II study to account for developments in the establishment of NASA’s new program of robotic and human exploration of the Moon and Mars. In particular, the committee was asked to address the following tasks during Phase II:

• Examine the gaps in technical capabilities needed to realize nuclear power systems for each of three classes—(1) instrumentation and propulsion for JIMO and follow-on science missions; (2) electrical power for spacecraft in transit or for operation on planetary surfaces; and (3) larger systems to energize thermal or electric propulsion systems for piloted spacecraft that would operate beyond the Earth-Moon system.

• Identify the major technology development areas where new work needs to be done to advance capabilities for each class.

• Compare the technical capabilities and development activities needed for each class, to identify common versus unique requirements.

Because of circumstances beyond the committee’s control, the Phase II study was postponed indefinitely in mid-2005.

The Phase I study was undertaken by the Steering Group of the Committee on Priorities for Space Science Enabled by Nuclear Power and Propulsion, supported by three panels focusing on science issues in solar and space physics, solar system exploration, and astronomy and astrophysics. The study was formally initiated when the Steering Group held its first meeting in Washington, D.C., April 7–9, 2004. Work continued at meetings held in Washington, D.C. (August 31–September 2, 2004), and in Irvine, California (November 15–16, 2004). In parallel with these meetings, the three science panels held their own information gathering and deliberative meetings: the Solar System Exploration Panel met in Washington, D.C. (May 5–7, 2004), and in Woods Hole, Massachusetts (June 21–23, 2004); the Solar and Space Physics Panel met in Washington, D.C. (August 9–11, 2004), and in Santa Fe, New Mexico (October 4–6, 2004); and the Astronomy and Astrophysics Panel met in Washington, D.C. (August 16–18, 2004), and in Pasadena, California (September 22–24, 2004). The three science panels completed drafts of their text in December 2004, and this material, suitably edited for consistent presentation, forms the basis of Chapters 3 through 8 of this Phase I report.

A fourth panel, focusing on engineering and technical issues, was supposed to have been appointed. Although intended to be active primarily in Phase II of this study, the fourth panel was to have supplied a limited amount of text relevant to this report. Due to the postponement of the Phase II study, this panel was not appointed and its role

in this report was played by those members of the Steering Group with engineering expertise. The text they drafted can be found in Chapter 2.

The Steering Group assembled the first draft of the full report in late January 2005. The final draft of this report was completed in early April and sent to external reviewers for comment in mid-April. The text was extensively revised in May and June and approved for release by the NRC on July 22, 2005. The executive summary along with the front matter of this report was released in an unedited, prepublication format on August 30, 2005. This, the edited text of the full report of the Committee on Priorities for Space Science Enabled by Nuclear Power and Propulsion, was prepared during the latter part of 2005 and finalized in January 2006. This version supersedes all other versions.

The Steering Group and its three supporting panels made a concerted effort to reach out to and engage the larger scientific and engineering community in this study. To this end, the following organizations were asked to make the study known to their respective constituencies: the International Astronautical Federation; the International Academy of Aeronautics and Astronautics; the American Institute of Aeronautics and Astronautics; the American Astronautical Society; the American Geophysical Union (the Planetary Sciences section and the Space Physics and Aeronomy section); and the American Astronomical Society (the Division for Planetary Sciences and the High-Energy Astrophysics Division). In addition, a Web site was established where material relevant to the study was posted. Although the committee did receive a small number of individual comments and suggestions via its Web site, the overall results of this outreach activity were mixed.

The work of the Steering Group and its panels was made easier thanks to the important help, advice, and comments provided by numerous individuals from a variety of public and private organizations. These include, in no particular order, the following: Marc Allen, Jay Bergstralh, Barry Geldzahler, Curt Niebur, John Rummel, and George Schmidt (NASA, Science Mission Directorate); Douglas Cooke, Leonard Dudzinski, Victoria Friedensen, Alan Newhouse, Raynor Taylor, and Carl Walz (NASA, Exploration Systems Mission Directorate); Keith Grogan, Torrence Johnson, Dayton Jones, and Robert Preston (NASA, Jet Propulsion Laboratory); Jason Dworkin, Sam Floyd, John Keller, and Robert MacDowall (NASA, Goddard Space Flight Center); Marianne Rudisill (NASA, Langley Research Center); Clark Chapman, Dan Durda, and S. Alan Stern (Southwest Research Institute); Francesco Bordi and Matt Hart (The Aerospace Corporation); Michael Brown and Richard Mewaldt (California Institute of Technology); J. Brad Dalton III (SETI Institute); Thomas K. Gaisser (Bartol Research Institute); Will Grundy (Lowell Observatory); Kevin Hurley (University of California, Berkeley); Edwin Kite (Massachusetts Institute of Technology); Jeffrey Linsky (University of Colorado); Michael Mendillo (Boston University); David Mildner (National Institute of Standards and Technology); Marcia Rieke (University of Arizona); Richard Rothschild (University of California, San Diego); Chris Shank (Committee on Science, U.S. House of Representatives); David A. Williams (Arizona State University); and Thomas Zurbuchen (University of Michigan).

This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the NRC’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the authors and the NRC in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process.

We wish to thank the following individuals for their participation in the review of this report: John F. Ahearne (Sigma Xi, The Scientific Research Society), Robert D. Braun (Georgia Institute of Technology), Jon H. Bryson (The Aerospace Corporation), Freeman Dyson (Institute for Advanced Study), Eugene H. Levy (Rice University), Bruce D. Marcus (TRW Inc., retired), Frank B. McDonald (University of Maryland), and Christopher F. McKee (University of California, Berkeley).

Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations, nor did they see the final draft of the report before its release. The review of this report was overseen by Louis J. Lanzerotti (New Jersey Institute of Technology). Appointed by the NRC, he was responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring committee and the institution.

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