A pair of Russian scientists are proposing a radical new propulsion technique that would accelerate a rocket while in flight, by using a ground-based laser. Should it work, it could push aircraft to go beyond Mach 10.
Conventional rockets are limited by the amount of solid or liquid fuel they can carry. To achieve higher speeds, more fuel needs to be burned — fuel that has to be carried by the rocket and hefted into space. According to Yuri Rezunkov of the Institute of Optoelectronic Instrument Engineering and Alexander Schmidt of the Ioffe Physical Technical Institute in Saint Petersburg, these burdensome loads can be significantly reduced if a laser — one located on the ground — were used to provide additional propulsive force.
The effectiveness of current laser-propulsion techniques is limited by the instability of supersonic gas flow, caused by shock waves that "choke" the inlet of the nozzle, reducing thrust. Those effects can be reduced with the help of laser ablation, redirecting the plasma plume so that it flows close to the interior walls of a supersonic nozzle and significantly improving the overall thrust. (caption and image: Y.Rezunkov/IOIE)
A release from the Optical Society explains:
A number of systems have been proposed that can produce such laser propulsion. One of the most promising involves a process called laser ablation, in which a pulsed laser beam strikes a surface, heats it up, and burns off material to create what is known as a plasma plume—a column of charged particles that flow off the surface. The outflowing of that plasma plume—essentially, exhaust—generates additional thrust to propel the craft.
In their Applied Optics paper, Rezunkov and Schmidt describe a new system that integrates a laser-ablation propulsion system with the gas blasting nozzles of a spacecraft. Combining the two systems, the researchers found, can increase the speed of the gas flow out of the system to supersonic speeds while reducing the amount of burned fuel.
The researchers show that the effectiveness of current laser-propulsion techniques is limited by factors including the instability of supersonic gases as they flow through the gas nozzle, as well as the production of shock waves that "choke" the inlet of the nozzle, reducing thrust. But those effects can be reduced with the help of a laser-ablation plasma plume that is redirected so that it will flow close to the interior walls of the nozzle. Coupling the ablation jet with supersonic gas flow through the nozzle, they find, significantly improves the overall thrust generated by the nozzle.
The researchers say the proposed hybrid approach will help power rockets, launch satellites, and enable aircraft to exceed Mach 10.
Read the scientific paper at Applied Optics: "Supersonic Laser Propulsion."
[ h/t Gizmag ]