To give US satellites a chance against rivals, pursue safe nuclear propulsion

An artist’s illustration of a nuclear-powered rocket. (DARPA)

As orbits around Earth become increasingly crowded and contested by terrestrial rivals, it’s highlighted the vulnerability of satellites to ground-based or space-based attacks. In the following op-ed, the Mitchell Institute’s Christopher Stone argues it’s time to upgrade US satellite defenses through maneuverability and longevity using nuclear propulsion, an idea he says is much safer than critics contend.

In recent years China has been deploying multiple offensive anti-satellite weapons, according to US intelligence, in support of its military strategy to challenge American dominance in space. They seek to target undefended US satellite constellations locked into highly predictable orbits that essentially turn vital space assets into sitting ducks.

American leaders have long sought to maintain space as a peaceful domain, but given these actions, they must respond with a new generation of satellites able to maneuver for defensive and offensive purposes. Would we ever send a soldier, ship, or aircraft into harm’s way without the ability to maneuver to evade a threat? Of course not. The same must hold true in space – and nuclear-propulsion offers the agility and longevity satellites will require in a future conflict.

Current satellite constellations are controlled by either chemical or electric propulsion and are analogous to the lumbering airships of last century. Electric propulsion, while very efficient is very slow. Chemical propellant, while very powerful with thrust, is not fuel efficient and as such only provides limited maneuver options in a dynamic, warfighting domain such as space.

Most satellites can use chemical propellant-powered thrusters to maintain their desired orbit, execute limited maneuvers like adjusting their position to perform a specific tasking, or deorbit after mission completion. Given the cost and other challenges associated with launching mass into space, satellites typically carry small amounts of chemical propellant. Expending this limited store of propellant to avoid rapidly moving threats would reduce a satellite’s operational lifespan, which would prematurely end its mission life and require an early replacement.

Space nuclear thermal propulsion engines (SNTP), on the other hand, are incredibly efficient and powerful, and could provide the agility and maneuverability of modern fighter planes in space. SNTP systems are not like nuclear weapons or legacy nuclear power reactors that many of us think of when we hear the term “nuclear.” Instead, SNTP uses fission energy to heat and expand hydrogen propellant which then flows through a nozzle to create thrust. This does not involve a combustion process or a nuclear explosion, but it does mean they have long service lives and can provide rapid results when circumstances require. Current forms of propulsion simply cannot match those performance attributes.

This will require space new force designs that leverage nuclear thermal propulsion (SNTP). While many have understandably cited safety concerns regarding this technology, such as radiation hazards to humans during storage, launch, or accidental re-entry, the reality is that modern developments mean these systems can be fielded responsibly and reliably.

If a rocket carrying an SNTP engine were to fail at launch, there is no danger of a radioactive spill. The rocket itself would be powered by a traditional chemical rocket using launch and resulting trajectories over water or other uninhabited areas. There would be no radioactivity generated during storage or launch because the system is not activated until the satellite reaches orbit. Risk is further reduced by designing SNTP engines so nuclear fission chain reactions and inadvertent criticality events cannot occur.

Once on orbit, the US would only operate SNTP systems in what are called “nuclear safe orbits” that are above 700 miles in altitude. This means SNTP-powered satellites would remain in space for several hundred years. This holds true even if guidance and control of the spacecraft is lost. Added to this, the system only runs for short periods of time. Any radiation released as part of its operational use would radiate out into space, already a radiation heavy environment due to space weather such as coronal mass ejections.

When it comes time for an SNTP system to re-enter the atmosphere after decades in space, the small amount of radioactivity it generated over its operational lifespan would dissipate substantially. Any materials surviving re-entry would not be radioactive hazards to human health.

This contrasts substantially with older designs, like that seen with the Soviet Union’s Cosmos-954 satellite incident in the late 1970s. This older, primitive design crashed into an uninhabited part of Canada and spread limited radioactive debris. No one wants that to happen again. Years of advances in materials, nuclear technology, and procedures have produced systems far safer than legacy systems.

Moreover, it is also important to recognize that current satellites, almost all of which are powered by chemical propellants, are not risk free. These materials are incredibly toxic and present major health risks if humans are exposed to them in the event of a launch or reentry accident. Any form of space propulsion presents levels of risk, however modern SNTP is a safe option thanks to decades’ worth of development.

While safety must always drive decision-making when it comes to our activities on orbit, it is also crucial to recognize overarching security concerns. The connection between security and safety is undeniable. Adversary actions demand the US gain the ability to maneuver assets on orbit. SNTP is a key technology necessary to realize that objective. Surrendering the initiative on orbit to concerted, determined adversaries like China poses a far greater risk.

We have already fallen behind in other critical military technologies, like hypersonic weapons. We cannot risk additional failings. It is also important to recognize that China is also developing SNTP engines to power their military space vehicles, so this technology will be on orbit in the near term whether the US chooses to adopt it or not.

Our military should seize the opportunity to leap ahead of our adversaries by fielding SNTP-powered spacecraft as soon as possible. The technology is mature, the demand pronounced. It is possible to pursue safety and security, and it should be pursued as soon as possible.

Christopher Stone is Senior Fellow for Space Studies at the Mitchell Institute’s Spacepower Advantage Center of Excellence. He is also the former Special Assistant to the Deputy Assistant Secretary of Defense for Space Policy in the Pentagon.