The United States seeks to deploy nuclear fission engines in its military satellites, making them more maneuverable, speedier and able to evade anti-satellite weapons.
Nuclear propulsion would give satellites effective maneuver warfare capabilities in space, increasing their flexibility for both offensive and defensive operations, and increasing their survivability against Chinese or Russian anti-satellite weapons.
US military satellites are used for intelligence, surveillance, reconnaissance, targeting, missile defense and navigation, and thus are crucial for military operations. They are currently deployed in satellite constellations that can be easily tracked and destroyed by potential adversaries, namely China and Russia, with satellite tracking capabilities and anti-satellite weapons.
The US Defense Advanced Research Projects Agency (DARPA) has awarded multiple contracts to General Atomics, Lockheed Martin and Blue Origin to develop a satellite nuclear propulsion system for low-Earth orbit demonstrations in 2025 as part of its Demonstration Rocket for Agile Cislunar Operations (DRACO) program.
Nuclear thermal propulsion works by harnessing the heat generated from nuclear fission to accelerate propellants such as hydrogen to tremendous speeds. The technology has significant advantages over traditional chemical propulsion, including longer endurance, the ability to carry heavier payloads and double the fuel efficiency.
In contrast, traditional satellite chemical propulsion uses liquid fuel that requires very complicated systems, with tanks, pipes, valves and very delicate control mechanisms. In addition, hydrazine fuel is highly toxic, volatile and explosive, thus requiring special precautions to handle.
To be sure, nuclear thermal propulsion also has its drawbacks.
These include radiation effects by the nuclear reactor and the hefty weight of the engine assembly. Other disadvantages include the high costs of satellite nuclear reactors, low technology maturity, heavy radiation shielding requirements and social issues regarding the use of nuclear energy.
Critics also argue that a potentially better defense would be simply to substantially increase the number of military satellites, to the point that shooting them down would be unfeasible due to their sheer numbers.
The US developed satellite nuclear propulsion from the 1960s to the 1980s but never operationalized the technology, as then there was no capability requirement for satellites to outmaneuver anti-satellite weapons. However, the development of anti-satellite weapons by near-peer adversaries such as China and Russia later prompted the US to restart the development of satellite nuclear propulsion.
China, for one, has been working on anti-satellite weapons since the 1960s. Under its Program 640, China has explored multiple anti-satellite technologies such as missiles, kinetic kill vehicles, lasers, space early warning and target discrimination components. However, the program was abandoned in the 1980s.
In 1986, China initiated its Project 863 program, which aims to overcome its technological limitations in areas critical to its national security. Under the project, China may have developed lasers that can blind the optical equipment of reconnaissance satellites and laid the groundwork for laser-based anti-satellite weapons that can physically destroy military satellites.
In 2006, China reportedly illuminated a US satellite with a ground-based laser in an apparent anti-satellite weapon test. The ground-based laser was reportedly designed to damage or blind reconnaissance satellites and could also be used to guide kinetic weapons against the targeted satellite. China followed up the test in 2007 when it destroyed one of its non-operational weather satellites using a ballistic missile.
Since then, China has developed multiple anti-satellite technologies such as kinetic-kill missiles, ground-based lasers, orbiting space robots, space surveillance, satellite jammers, cyber capabilities and directed-energy weapons.
Russia’s anti-satellite weapons program began in the 1950s, with the proposal to use Moscow’s nuclear-tipped interceptor missiles against satellites. However, this was recognized as a poor option as the nuclear blast would also destroy all nearby friendly satellites.
In the 1960s, Russia tested a co-orbital anti-satellite weapon, in which the weapon was launched into the same orbit as the target satellite and moved close enough to destroy it with fragmentation. To date, this system remains Russia’s only dedicated anti-satellite weapon.
Russia also explored other anti-satellite weapons concepts in the 1970s and 1980s, such as autocannon-armed space stations and aircraft-mounted lasers.
In 2021, Russia successfully tested its Nudol PL-19 anti-ballistic missile against one of its inactive satellites. The test created a huge cloud of space debris, which forced personnel aboard the International Space Station (ISS) to take shelter on multiple occasions and raised concerns about the growing militarization of outer space.