Nuclear thermal propulsion shapes the future of America’s dominance in space

OPINION:

The race to develop nuclear propulsion isn’t just about reaching Mars; it’s also an important next step in our battle for space dominance.

NASA is developing two options: nuclear thermal propulsion and nuclear electric propulsion. Although both hold important roles in the future of spaceflight, nuclear thermal propulsion has greater implications for our national security posture in space.

First, what is nuclear thermal propulsion? It’s a rocket engine that doesn’t burn its propellant. Chemical rockets burn a fuel, such as hydrogen, using an oxidizer, such as liquid oxygen. This generates hot gas that expands, not quite explosively, to be expelled out of the nozzle at extreme velocity, thus generating thrust.

A nuclear thermal propulsion engine does all that, but without the burning part. It turns out that if you just flow the fuel through the inside of a nuclear reactor, it will also heat up and expand, but even more violently, creating even more thrust. The lighter the fuel’s molecule, such as helium, the faster it goes. A nuclear thermal propulsion engine can generate thrust two to three times more efficiently than conventional chemical rockets. It’s perfect for in-space applications, where the radiation is easily managed.

That makes it great for traveling people to Mars, the travel time to which is an absolute tyrant. With chemical rockets, it takes nine months to get there and nine months to return. These trips must be 26 months apart because Earth and Mars are in different orbits and spend a lot of time on opposite sides of the sun. Consequently, a year and a half is spent just on travel, with precious little time, considering the cost and effort, actually being there and exploring.

Nuclear thermal propulsion could make the travel duration three times shorter. So, if we are going to routinely send people to Mars (and get them back), nuclear thermal propulsion is the way to do it.

This isn’t only about Mars; it’s also about maneuvering in orbit and the security demands we face today. There is a national security reason to want nuclear thermal propulsion. Right now, the Space Force is focused on disaggregating our small number of targets (I mean, military satellites) into many distributed satellites to get some resiliency if they are attacked. Still, it must move on very soon to establishing the ability to conduct “dynamic space operations,” or the ability to respond to an active and ongoing attack in space by China or Russia.

In other words, conduct space warfare just like naval or air war. We will have to reposition assets to hot spots, replenish satellites that have been destroyed, counterattack the threats, establish orbital security and control all this in real time.

It all requires the ability to maneuver through space, rapidly, at will and across vast distances, involving transits between different orbits and orbital altitudes. That takes a tremendous amount of thrust and copious quantities of energy (i.e., fuel). Today, that’s a big challenge. If only we had a much more efficient propulsion technology. Oh, yeah: nuclear thermal propulsion!

This technology was in hot pursuit in the 1970s and 1980s, but development abruptly stopped when the need for it seemed less acute, especially given that it was unsuitable for lifting rockets from Earth’s surface to space. Spewing radioactive exhaust and loose thermal neutrons out of the nozzle inside the atmosphere is somewhat undesirable.

For an in-space application, nuclear thermal propulsion is the ideal solution to many challenges in space exploration. Today, that need is urgent. With China and Russia developing new counter-space systems, the ability to move freely in orbit has become the new high ground of deterrence.

The good news is that the enabling technologies are catching up. Advances in high-temperature materials, autonomous control systems and compact reactor designs are bringing nuclear thermal propulsion from concept to capability. In September, Oak Ridge National Laboratory demonstrated new self-regulating control architectures, an important step toward making nuclear space propulsion safe, reliable and operationally independent.

Now is the time to kick nuclear thermal propulsion into high gear. We’ll plug the development time gap with novel chemical approaches, but the sooner nuclear thermal propulsion is ready, the faster we can get to Mars (pun intended), and the sooner we can guard the peace here to allow space for that to happen.

• Tory Bruno is CEO of United Launch Alliance. He is also a member of the National Academies, an honored fellow of the American Institute of Aeronautics and Astronautics and an academician of the International Academy of Astronautics.