A Nuclear-Powered Space Oddity

February 10, 2021

This Critical Questions expands on an article originally published in Lawfare on February 3, 2021.

The United States is considering becoming the first state to launch a space nuclear propulsion system under the new national strategy for space nuclear power. According to Space Policy Directive-6, signed by President Donald Trump on December 16, these systems are necessary for exploration because they will help shorten travel time, which helps protect crewed and robotic spacecraft from prolonged exposure to harsh radiation. Although the directive’s space exploration goals are admirable, it unfortunately gives too little attention to crucial safety considerations.

Q1: Hasn’t the United States already been leveraging nuclear energy technology in space?

A1: Yes. Since the late 1960s, the United States has leveraged nuclear energy technology to help power spacecraft. Recent examples include the ongoing New Horizons mission, the Cassini mission to Saturn, and the Voyager 1 mission to reach interstellar space for the first time in history. These missions used radioisotope power systems—nuclear energy technology that converts heat into energy by harnessing the natural radioactive decay of plutonium-238. According to the Trump White House’s directive, although “no space nuclear propulsion systems have been launched to-date,” these systems are necessary for space exploration because they will shorten travel time to Mars.

Q2: So what’s new?

A2: At its core, Space Policy Directive-6 is an ode to exploring Mars. The directive is unique because it prioritizes developing more advanced radioisotope power systems capabilities and nuclear propulsion systems to support robotic and human exploration of Mars and the Moon. For example, it calls for developing new uranium fuel processing capabilities by the mid-2020s to “enable production of fuel that is suitable for lunar and planetary surface and in-space power,” including nuclear electric propulsion, and nuclear thermal propulsion functions. Additionally, by 2027, NASA expects to “initiate a fission surface power project for lunar surface demonstration . . . with scalability to Mars exploration.” Overall, developing advanced radioisotope power system capabilities will provide spacecraft with a greater source of energy for deep-space missions, and as NASA explains, “better fuel efficiency versus solar energy in darker and colder locations.” On that point, the directive reinforces the centrality of the 2019 National Security Presidential Memorandum-20, which discusses the process for launching spacecraft containing space nuclear systems, as well as Executive Order 13803 to revive the National Space Council.

Q3: Where does the strategy need additional improvement?

A3: As written, Space Policy Directive-6 provides greater guidance on leveraging advanced nuclear power systems to explore Mars than it does on promulgating security principles for criticality accident planning and launch safety. Criticality assessment—that is, evaluating each system function for potential points of failure and evaluating how to minimize loss of life or damage to the system in the event of an accident—is essential for many reasons. For example, it could help quickly determine a course of action if a nuclear-powered satellite were to malfunction and accidentally reenter the Earth’s atmosphere, contaminating Earth surfaces. Despite these concerns about accidental reentry from Earth orbit or during an Earth flyby, the directive is surprisingly silent on criticality assessment standards; instead, it briefly mentions that a “highly reliable operational system” is needed for spacecraft operating fission reactors in low Earth orbit.

To be clear, developing space nuclear propulsion systems is both an admirable goal and an opportunity to signal the United States’ strategic resolve and intentions in space. For developing space doctrine, however, failing to articulate “principles of safety, security, and sustainability” with granularity is a missed opportunity in international relations to shape the behavior of other spacefaring nations as well as aspiring spacefaring nations.

Both groups look to the United States as a model to follow—so if the United States cuts any safety corners for the operation and disposition of these advanced systems, other states may view that as something to emulate. For example, as Cort Thompson points out in Lawfare about anti-satellite weapons testing, “Where the United States has left a vacuum of inaction, Russia and China have taken the lead on shaping the ASAT [anti-satellite] conversation with their own proposals to the international community, the ‘Treaty on the Prevention of the Placement of Weapons in Outer Space, the Threat or Use of Force Against Outer Space Objects.’”

Q4: What should the Biden administration do?

A4: Although the Biden administration “has yet to indicate what it plans to do with President Donald J. Trump’s legacy in this area” of space initiatives, as the New York Times reports, on February 3, White House spokesperson Jen Psaki stated that President Biden “fully supports” the U.S. Space Force and the administration looks forward to continuing the work of the Space Force. That said, despite the uncertainty about the Biden administration’s posture on deep space exploration, a recommended first step is to encourage collaboration between the U.S. government and the commercial space sector to advance the country’s strategic capabilities and signal what it means to be a good steward of space. As noted in the Department of Defense’s 2020 Defense Space Strategy, communicating with allies and other partners is necessary for ensuring space stability. The cost of failing to do so calls to mind the haunting parable by Danish philosopher Søren Kierkegaard: “A fire broke out backstage in a theatre. The clown came out to warn the public; they thought it was a joke and applauded. He repeated it; the acclaim was even greater. I think that’s just how the world will come to an end.” Thus, to advance U.S. strategic leadership in space, the Biden administration should ensure our space exploration goals are pursued in equal measure with safely harnessing advanced nuclear power systems.

Zhanna Malekos Smith, J.D., is a senior associate (non-resident) with the Strategic Technologies Program at the Center for Strategic and International Studies in Washington, D.C., and a professor of cyber warfare studies with the Air War College. The views expressed are those of the authors and do not necessarily reflect the official policy or position of the Department of Defense or the U.S. government.

Critical Questions is produced by the Center for Strategic and International Studies (CSIS), a private, tax-exempt institution focusing on international public policy issues. Its research is nonpartisan and nonproprietary. CSIS does not take specific policy positions. Accordingly, all views, positions, and conclusions expressed in this publication should be understood to be solely those of the author(s).

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