British military aerospace corporation BAE Systems has developed a fundamentally new device for measuring the speed of a flying aircraft. Until now, the main instrument has been air sensors in the form of small tubes, better known as pitot tubes.
The principle of their work is well known. It is based on measuring the difference between static and counter pressure. During flight, the counterflow of air through the holes in the pitot tubes creates a certain pressure, which is directly dependent on the speed of the aircraft. The speed is calculated from the difference between static and counter pressure.
However, pitot tubes have several disadvantages. So at high speed and at high altitudes, they can become covered with ice. Also, the option of a collision with birds is not excluded.
BAE Systems specialists have proposed a fundamentally new system called the Air Laser Velocity Sensing Device - LASSI, which uses a new technology using an ultraviolet laser instead of air pressure.
A laser is used to reflect light from surrounding air molecules, and the color change of the reflected beam is caused by the Doppler effect, which can be measured.
A good example is the amplification of the sound of the siren of an approaching police car. The reason for this is the change in the frequency of the sound wave. Roughly the same thing happens with an invisible ultraviolet ray. Reflected from molecules in the process of movement, it constantly changes color, which is immediately fixed by the detector. The higher the aircraft speed, the faster the color change occurs.