Smoother Flying with Laser Technology

For all the abstract beauty of white lines slicing through picture book blue skies, the vapor trails which aircraft leave in their wake as they blast through the air are a warning for anything which moves too close. Planes, particularly after take-off, whip up micro-cosmic storms which are powerful enough to throw any unsuspecting aircraft off course, with potentially devastating consequences.

As things stand, the world of commercial aviation is governed by a rule which dictates a minimum distance between aircraft of 11.1 kilometers. But this gap has now been deemed significant enough to merit a solution.

With a reduced distance, more planes could take to the skies, which would mean more money for the industry, and take-off and landing delays could be minimized, thus heightening overall airport efficiency. At least that is how the argument goes. And based upon it, the Fraunhofer Institute for Applied Optics and Precision Engineering (IOF) in the German city of Jena, has come up with a pocket-sized problem-solver.

"If it were possible to measure the position and actual extent of the contrail, the actual safe distance could be adjusted to the actual conditions, which would increase take-off and landing frequency at airports," said Thomas Peschel of the IOF.

Smart sensor

Project I-Wake -- short for Instrumentation Wake -- is a joint effort between Thomas Peschel and eight teams from four different countries. Together, the scientists have developed a smart sensor which can tell when the air is calm enough for a safe take-off regardless of the current 11.1 mile restriction. Ultimately the idea is to make the optical scanner a standard fixture, ensuring a fast and accurate way of assessing dangerous levels of turbulence prior to take-off. A prototype is currently being tested on board a Cessna.

For all the apparent complexity of the innovation, Peschel stresses the simplicity of the technology behind it. "A laser sends pulses into the air space just ahead of the plane, the light is dispersed on aerosols or dust particles and registered by a detector," Peschel explains. The effect is that the frequency of the laser pulse changes according to whether the particles of dust are moving towards or away from the beam. By adjusting the wave lengths of the dispersed laser light, it is possible to tell within fractions of a second whether the air is still turbulent following take-off, or whether it is calm enough for the next plane to hit the skies.

"The challenge in developing the device was to be able to use the laser beam to scan the area in front of the plane at a relatively high frequency," Peschel recalls. In order to achieve this, the team of scientists came up with a small, high-precision mirror which moves back and forth seven and a half times a second, taking the measurements, and consequently the first steps towards filling the skies with yet more traffic.