Imagine this scenario: World War III is imminent. In the vast emptiness of space, robotic enemy spacecrafts are gradually altering their paths and getting ready to launch an unexpected assault on the United States’ fleet of satellites. These unmanned vessels, equipped with powerful robotic arms capable of disabling a satellite, are silently approaching American spacecrafts, poised to deliver a devastating blow to the country’s military.
However, back on Earth, the guardians of the U.S. Space Force have been monitoring the assassin spacecraft, understanding that in order to minimize their vulnerability, they only have enough fuel for one strike. Right before the rival satellites launch their attack, the command triggers the nuclear thermal propulsion (NTP) engines on the American satellites, promptly propelling them to a higher orbit and beyond the reach of danger. Subsequently, as the enemy satellites drift aimlessly into the vast emptiness of space, the same uranium-fueled engines will safely return the American satellites to their original positions in low-Earth orbit.
The prototype vector of the EmDrive, also known as the electromagnetic engine or the impossible engine, is still being defended by its inventor despite failed tests. This engine is believed to be a potential interstellar space engine of the future. The image shows the prototype in question.
The space between Earth and the moon, known as cislunar, encompasses a larger expanse than the typical orbits of satellites around Earth. A spacecraft navigating this region would require highly efficient engines that can hold a large amount of fuel. This is where NTP comes in – it utilizes a liquid propellant, such as hydrogen, to power a nuclear reactor core. As the uranium fuel is split by the reactor, heat is generated and used to convert the hydrogen into a gas that is then released through the rocket’s exhaust nozzle, resulting in thrust.
According to the Department of Energy, NTP is predicted to have twice the efficiency of chemical rockets. This is because chemical rockets produce heavy water vapor as a byproduct, whereas hydrogen gases, being lighter, can be accelerated more easily, resulting in higher thrust.
According to Greiner, NTP offers a specific impulse comparable to gas mileage, which is significantly higher than current chemical propulsion systems. He also notes that NTP has a higher thrust-to-weight ratio compared to existing electric propulsion systems. This unique feature allows NTP to efficiently perform large delta-V maneuvers, which is crucial for spacecrafts to change velocity, and enables fast travel over vast distances.
In 2025, the aim is to launch a proof-of-concept spacecraft using DRACO technology beyond low-Earth orbit. According to Greiner, if the Pentagon gives priority to NTP, it could potentially become an operational system by the early 2030s.
The success of military engagements, whether in aerial combat or larger-scale campaigns, often relies on the ability of one side to outmaneuver their opponents. With the incorporation of weapons into spacecraft, the competition to construct faster and more heavily armed spaceships will begin. Similar to how the steam engine surpassed the use of sails at sea, the implementation of nuclear thermal propulsion (NTP) could potentially improve upon the capabilities of chemical rockets in space.
An Overview of NTP Programs’ Origins
NERVA: In 1961, the possibility of using Nuclear Thermal Propulsion (NTP) was explored by a joint effort between NASA and the Atomic Energy Commission through the Nuclear Engine for Rocket Vehicle Application (NERVA) program. Similar to DRACO, NERVA utilized a nuclear reactor to heat hydrogen and produce thrust. NASA’s plan was to incorporate an NTP engine as the last stage of a chemical rocket. However, due to insufficient funding, NASA made the decision to terminate the program in 1973, despite its potential.
Project Orion: During the 1960s, Project Orion had the goal of launching a spacecraft into orbit and beyond using a series of nuclear bombs detonated below it. This concept relied on protecting the spacecraft and its crew with a massive graphite plate. The plan was for the spacecraft to ride the shockwave created by the explosions and enter the atmosphere. Unfortunately, the Partial Nuclear-Test Ban Treaty of 1963 prohibited nuclear explosions in space and above ground, ultimately bringing an end to the Orion project.
Project Timber Wind: During the 1980s, the Pentagon initiated the Strategic Defense Initiative with the goal of constructing a defense system capable of intercepting nuclear attacks from air, land, and space. This endeavor involved the launch of extensive payloads into outer space. Timber Wind was introduced as a project to investigate the use of nuclear thermal propulsion (NTP) for intercepting intercontinental ballistic missiles. However, with the end of the Cold War and the decline of the Soviet Union as a major threat, the need for a space-based defense system diminished and Timber Wind was ultimately abandoned.