Supersonic laser-propelled rockets: Hybrid approach may help power rockets, launch satellites, push future aircraft past Mach 10

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.
Credit: Y.Rezunkov/IOIE

Scientists and science fiction writers alike have dreamed of aircraft that are propelled by beams of light rather than conventional fuels. Now, a new method for improving the thrust generated by such laser-propulsion systems may bring them one step closer to practical use.

The method, developed by physicists Yuri Rezunkov of the Institute of Optoelectronic Instrument Engineering, Russia and Alexander Schmidt of the Ioffe Physical Technical Institute in Saint Petersburg, Russia is described today in The Optical Society's (OSA) journal Applied Optics.

Currently, the maximum speed of a spacecraft is limited by the amount of solid or liquid fuel that it can carry. Achieving higher speeds means that more fuel must be burned -- fuel that, inconveniently, has to be carried by the craft and hefted into space. These burdensome loads can be reduced, however, if a laser -- one located at a remote location, and not actually on the spacecraft -- were used to provide additional propulsive force.

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.

"Summarizing 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 aircraft to achieve Mach 10 and more," Rezunkov said.

Source: The Optical Society

From video camera to driverless shuttle vehicle

The EZ 10 shuttle vehicle. Credit: © EasyMile

A new type of driverless shuttle vehicle has been developed thanks to innovative computer vision guidance technology that enables the vehicle to locate itself on a roadway reliably and inexpensively. The technology, which is based on the use of simple video cameras, was developed by researchers at Institut Pascal (CNRS/Université Blaise Pascal de Clermont Ferrand/IFMA)[1]. It lies at the heart of the EZ-10 autonomous shuttle vehicle developed by Ligier Group[2], which will be unveiled at the Michelin Challenge Bibendum in Chengdu (China) from 11 to 14 November 2014.

Since the 2000s, a number of companies have sought to make cars autonomous using expensive and sometimes unreliable technologies[3]. In 2003, researchers at Institut Pascal decided to work on automated driving of urban electric vehicles using simple video cameras. 
The technology they developed is based on two stages. The aim of the first stage is to identify all the significant points in the immediate environment of the path followed, in a video recorded during an initial journey in which the vehicle is driven manually. The second stage corresponds to the automatic mode during which the vehicle continuously monitors its path, ensuring that the images provided by the on-board cameras correspond as far as possible to the sequence initially filmed. The initial video thus plays the role of a virtual track that the vehicle must follow when it travels in autonomous mode.

Since 2006, the researchers at Institut Pascal, in collaboration with Ligier Group, have been developing automatic driverless shuttle vehicles that can transport up to 10 people along short routes (in the region of one kilometer), rather like a horizontal elevator. The vehicles, which are designed to be used at specific sites such as industrial sites, airports and amusement parks, are able to deal with obstacles thanks to laser rangefinders fitted on all four sides of the vehicle. The shuttle vehicle can detect the presence of an obstacle at a distance of 50 meters and in this way modify its speed or even stop, depending on the potential danger. The researchers now intend to turn their attention to running a fleet of five vehicles at the Michelin Europe Technology Center at Ladoux. The aim is to deal with multiple and potentially simultaneous requests from call points or smartphones, in real time and on a large industrial site, rather like an automatic taxi service.

The localization technology, which is reliable and inexpensive, will be unveiled at the Michelin Challenge Bibendum in Chengdu (China) from 11 to 14 November 2014. Equipped with an access ramp for people with reduced mobility, the new EZ-10 shuttle vehicle will provide visitors with a completely automated transport service.

[1] Within the framework of the IMobS3 Laboratory of Excellence.

[2] It is marketed by the EasyMile company, a joint venture between Ligier and Robosoft Technology.

[3] For example: differential GPS (which is different from the GPS commonly used in cars) is not always reliable, especially in city centers, where the satellite signals can be reflected off the façades of buildings. This phenomenon can lead to erroneous location calculations.

Source: CNRS