Popular Mechanics (South Africa)
The Pentagon wants to launch a nuclear thermal rocket in 4 years
PICTURE THIS: WORLD WAR III IS JUST hours away. In the cold vastness of space, enemy robotic spacecraft are slowly adjusting their orbits and preparing to launch a surprise attack on the US’s fleet of satellites. The uncrewed craft, with robotic arms strong enough to disable a satellite, are creeping up on American spacecraft, about to deal a knockout blow to the US military. But down on Earth, US Space Force guardians have been keeping track of the assassin craft, knowing that in order to present as low a profile target as possible, they have just enough fuel for one attack. At the last minute, after the enemy satellites have committed to attack, the command activates the nuclear thermal propulsion (NTP) engines on the American satellites, quickly boosting them into a higher orbit and safely out of range. Later, as the enemy satellites careen unpowered into the infinite void of space, the same engines, powered by uranium, will safely return the American sats to their positions in lowEarth orbit.
This capability could arrive sooner than you think. In April 2021, the Pentagon’s Defense Advanced Research Projects Agency (DARPA) announced that it commissioned General Atomics, Blue Origin, and Lockheed Martin to build the Demonstration Rocket for Agile Cislunar Operations (DRACO): the world’s first NTP system for spacecraft.
Cislunar, the region between Earth and the Moon, covers a much more expansive area than the simple Earth orbits followed by satellites. A cislunar spacecraft would need powerful and efficient engines that maximise the ship’s fuel-carrying capacity. Enter NTP, which works by pushing a liquid propellant such as hydrogen through a working nuclear reactor core. As the reactor splits the atoms of the uranium fuel, it generates heat. The heat then transforms the hydrogen into a gas that squirts out of the rocket exhaust nozzle at high pressure, creating thrust.
The US Department of Energy believes NTP will be twice as efficient as chemical rockets, which produce relatively heavy water vapour as a waste by-product. Hydrogen gases, on the other hand, are lighter and thus easier to accelerate, generating greater thrust.
‘DRACO is developing NTP propulsion technology that will enable the rapid manoeuvre needed to enable a wide variety of missions in the future,’ says the programme’s manager, US Air Force Major Nathan Greiner. These would include conducting space domain awareness missions – detecting, tracking, and identifying objects in Earth’s orbit – within the cislunar domain, Greiner says.
NTP provides a specific impulse, such as fuel consumption rate, that’s much greater than existing chemical propulsion systems, ‘with a thrust-to-weight that’s far higher than existing electric propulsion systems,’ Greiner explains. This unique combination allows NTP to quickly execute large delta-V manoeuvres – a spacecraft’s ability to change velocity – and enable rapid transits across long distances, he says.
The goal is to send a DRACO-powered, proof-of-concept spacecraft above low-Earth orbit in 2025. If the Pentagon prioritises NTP, it ‘could likely be deployed as an operational system by the early 2030s,’ Greiner says.
Successful military operations, from air-to-air combat to campaigns, are often determined by one side’s ability to outmanoeuvre adversaries. Once spacecraft have weapons, the race will be on to build increasingly faster armed spaceships. Just as the steam engine trumped the sail at sea, NTP could improve upon chemical rockets in space.
On Earth, humans have seized control of the domains of air, land, and sea with military vehicles. If history is any guide, the Space Force and the military space arms of other countries will likely need an entire ecosystem of armed craft to conquer the next domain.
Space warfare may mimic the evolution of war at sea, only across much greater distances. Small drone ‘spacefighters’ could be launched from larger craft to destroy enemy vehicles, similar to today’s aircraft carriers. These new carriers could be guarded by defence ships, such as the guided missile cruisers that protect naval task forces at sea.
This might sound like science fiction, but it follows a well-trodden path through human history – and NTP could make it a reality.