Nuclear Energy Preferred in Space Travel

Diego Valiente
February 19, 2015

Submitted as coursework for PH241, Stanford University, Winter 2015


Fig. 1: The Kiwi-A Prime nuclear rocket engine. (Courtesy of NASA. Source: Wikimedia Commons)

The human race has been enthralled by the exploration of space, but performing major long distance flights proved to be a major challenge since technology in the early stages of space exploration was limited. This frontier of space exploration was finally broken with the use and advancement of nuclear energy. [1] There are several means of creating enough energy to power a spacecraft; however, none are as reliable and as favored as nuclear power when it comes to exploring the solar system past the moon. Innately, space provides for extreme temperatures, dark environments, exposure to radiation, etc. These punishing conditions are not conducive to conventional energy sources. While regular means of power prove to be unsustainable in deep space, nuclear energy provides spacecraft with sufficient power to complete deep space flights.

This report will explore the various power sources that could be used in space travel and explain why nuclear systems are the most practical when performing space missions far from Earth.

Nuclear Energy Superiority Over Other Resources Used In Space Travel

Many are aware of the significant amount of power needed to launch spacecraft into space, but several people overlook the additional electrical power needed by the spacecraft to execute certain tasks, such as communicating back to the home base, managing technical apparatuses, and a variety of other functions. Spacecraft can be powered through a variety of different methods, each with its pros and cons; however, the preferred approach for longer space missions is nuclear energy. The following investigates the primary energy sources used for space travel and will highlight the superiority that nuclear power has in supporting spacecraft.

  1. Batteries - This was the first method used to power spacecraft into space. Batteries soon proved to have some major flaws. [2] Even though batteries gave sufficient power to launch for a short distance, they often lacked the overall power and wattage to support longer missions. Additionally, using batteries for long distance would be futile as those batteries would die well before the mission were to be accomplished.

  2. Fuel Cells - Fuel cells were developed in order to rectify some of the imperfections from batteries. [3] The fuel cell technology increased the wattage and therefore overall energy to power spacecraft. It also enhanced the overall longevity, but despite this improvement in technology fuel cells lacked the sufficient amount of lifetime to support long distance travel.

  3. Photovoltaic - Photovoltaic systems are more commonly used as they last much longer than batteries and fuel cells. [1] They rely heavily on the Sun's light to produce electricity to power spacecraft, which proves to be advantageous when making short missions. Once the missions extend past Mars, the Sun's rays are not as strong, and the solar cells are rendered inadequate.

  4. Nuclear - Nuclear energy proves to be the most effective when attempting to make long distance missions in space. [2] Nuclear energy not only provides way more power than batteries, fuel cells, and photovoltaic, but it also is an enduring source of energy as it has a much longer lifespan. Unlike solar energy, nuclear power is not dependent on the intensity of the Sun's rays, which makes it the optimal choice for traveling into deep space.

Nuclear Energy Efficiency and Sustainability Further Explained

The independence and longevity of nuclear energy makes it far more superior than any other power source currently used in space travel. Nuclear energy could be provided through several different methods such as through reactors, nuclear heaters, and generators. It is important to distinguish the two main types of nuclear energy methods that are utilized in space travel.

  1. RTGS - Radioisotope thermoelectric generators (RTGs) generate power to fuel spacecraft through the heat from the decay of Plutonium-238. [1] This method is essentially the most durable since Plutonium-238's half-life is multiple years, which proves to be an asset when exploring outer space. Despite its long lasting energy source, RTGs are not as efficient at converting this heat into electrical power. Nonetheless, RTGs have been proven to be well equipped to withstand the harsh conditions of deep space.

  2. Fission Reactors - These reactors release heat from nuclear fission and thereby create energy to power spacecraft. [3] Fission reactors are able to create much larger amounts of energy than RTGs, but require more maintenance with its control when launched into deep space.


After discussing the various different methods of supplying power to support spacecraft, and analyzing each method's strength and weaknesses, it should be evident that nuclear energy is the most practical and effective method. Nuclear energy not only has the durability to endure the extreme conditions of outer space, but it also provides spacecraft with long lasting power to make the lengthy trip within our solar system.

© Diego Valiente. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] G. L. Bennett, "Space Nuclear Power: Opening the Final Frontier", AIAA 2006-4191, 4th International Energy Conversion Engineering Conference and Exhibit, San Diego, CA, June 2006.

[2] R. D. Launius, "Powering Space Exploration: U.S. Space Nuclear Power, Public Perceptions, and Outer Planetary Probes," AIAA 2006-4191, 6th International Energy Conversion Engineering Conference, Cleveland, OH, July 2008.

[3] S. Copeland, "The Role of Nuclear Energy in the Future of Human Spaceflight," PH241, Stanford University, Winter 2012.