Earth-mounted lasers could be used to increase the speed of space rockets without the use of additional fuel, according to research by Russian scientists.

The researchers have conceived an approach that would integrate the spacecraft’s traditional fuel propulsion system with what is known as a laser-ablation propulsion system.

With this technique, lasers located outside of the spacecraft – probably on Earth – would be directed in a pulsed beam at the spacecraft. On contact, the laser beam would heat up the surface it makes contact with to create a plasma plume that in turn generates additional thrust.

By combining this system with the spacecraft’s nozzles – the conical exhausts that blast out gas to propel the craft – the researchers found that the gas flow could be increased to such a level that the craft could reach supersonic speeds, while simultaneously reducing the amount of fuel burned in the process.

“Summarising the data obtained, we can forecast the application of the supersonic laser propulsion techniques not only for launching small satellites to Earth orbits but also for additional acceleration of supersonic aircrafts to achieve Mach 10 and more,” said Yuri Rezunkov of the Institute of Optoelectronic Instrument Engineering, Russia.

The technique could provide a solution to the considerable challenge that is spacecraft fuel.

At present, all the fuel that is needed for a mission currently needs to be carried on the spacecraft at launch. This issue creates the frustrating situation where to carry 1kg of fuel into low-earth orbit (around 300km above Earth) requires a 50kg of fuel at launch.

Other solutions have been proposed, such as building refuelling stations in space, and mining asteroids for fuel that can be used without the need to escape Earth’s gravity well first.

However, these solutions are expensive to establish and are unlikely to be a practical solution for several decades at best.

By contrast, the laser system would be considerably easier to implement due to the level of infrastructure and the fact that the lasers could be located on Earth.

Other laser propulsion systems have been proposed previously, however their potential effectiveness has been limited, with issues such as potential instability of supersonic gases flowing through the nozzle and a choking effect caused by shock waves produced during the process.

However, in this system the plasma plume produced by the laser system would be guided to flow next to the interior walls of the nozzle, encircling the main jet propulsion. This would prevent these problems from occurring and allow the two forms of propulsion to work simultaneously.

If the system proved successful, it could even be furthered with lasers located in space, perhaps initially in orbit and, in the far longer term, on other planetary bodies to provide speed boosts to further long-term space travel.

Images courtesy of NASA.