Back to the Future — NASA Renews Interest in Nuclear Space Propulsion

Nuclear space propulsion can offer much higher thrust with less weight than chemical rockets.  The BWXT project is part of NASA’s “Game Changing Development Program,” and has the potential to significantly alter space travel.  Although the exact design of any nuclear space propulsion system to result from this effort is unclear, it is clear that any design would be a novel, next-generation reactor concept.

Nuclear power has been long embraced by NASA.  For example, the Voyager spacecraft, the farthest man-made objects in space, use nuclear batteries.  NASA’s Orion and NERVA projects directly experimented with nuclear propulsion, although those programs were terminated.  But as NASA has more closely looked at travel to Mars, nuclear propulsion has reentered the fray as a potentially suitable means of travel.

The legal questions that arise from the use of nuclear power in space are varied.  There are treaty issues.  Five treaties and five declarations of legal principles govern many aspects of the exploration and use of outer space, and these and other legal documents would touch on increased reliance on nuclear power.  The Orion project, which essentially sought to use nuclear explosions to drive spacecraft, was cut off by a treaty, the Nuclear Test Ban Treaty.  There are also commercial issues, such as a shortage of plutonium for nuclear space batteries (radioisotope generators).

Moreover, the current legal regime focuses on the government’s use of nuclear power for peaceful purposes in space.  DOE has extensive experience with radioisotope generators, and most if not all U.S. nuclear power systems launched to date, including for both security and NASA missions, have been provided under the NASA/DOE Radioisotope Power Systems Program. Space, however, is quickly being privatized, with independent companies aiming to get to Mars far earlier than NASA is planning.  The entry of private companies into space may call for an increased role for the government to take on a role as a regulator of private nuclear spacecraft efforts.

Jurisdictional oversight would need to be addressed for commercial projects that do not fall under the authority of the Department of Energy.  For example, in the U.S., the nuclear regulator for civilian nuclear projects—the Nuclear Regulatory Commission—has its oversight limited to the jurisdictional boundaries of the U.S.  Other issues that would need to be addressed include fuel sources.  The United Nations Principles Relevant to the Use of Nuclear Power Sources in Outer Space provide a requirement that nuclear reactors in space use highly enriched uranium, not plutonium, which has historically been used in radioisotope generators.  Highly enriched uranium can be hard to procure in the commercial sector.  Pursuant to presidential directives, nuclear power sources in space may also need Presidential approval before launch.  Other issues that would need to be addressed include nuclear insurance and nuclear liability for third party damages.

Nonetheless, the use of nuclear power in space is not a new frontier for NASA, and the agency’s renewed interest presents a promising use of this powerful technology.  Moreover, the legal and commercial issues associated with any potential civilian use of nuclear technology in space do not appear to be insurmountable.  With the amount of energy nuclear power can provide, for long duration, while using small amounts of material, this technology makes sense for space travel and exploration.

Authored by Amy Roma and Sachin Desai.