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Stealth Technology: Planes Moving Unseen

Vishwas Purohit
With the advent of the radar in WW2, detection of planes and missiles became uncannily easy. How was one to avoid this type of electromagnetic detection? Motion in stealth means avoiding all conventional means of detection.
The term RADAR is common in today's everyday language. It is used when referring to a technique of recording the speed of a moving object. The term is an acronym made up of the words radio detection and ranging.
It is used to refer to electronic equipment that detects the presence, direction, height, and distance of objects, by using reflected electromagnetic energy.
Electromagnetic energy of the frequency used for radar is unaffected by darkness, and also penetrates weather to some degree, depending on frequency. It permits radar systems to determine the position of ships, planes, and land masses, that are invisible to the naked eye because of distance, darkness, or weather.
The development of radar into the highly complex systems in use today represents the accumulated developments of many people and nations. The general principles of radar have been known for a long time, but many electronic discoveries were necessary before a useful system could be developed.
World War II provided a strong incentive to develop practical radar, and early versions were in use soon after the war began. Radar technology has improved in the decades since the war. We now have systems that are smaller, more efficient, and better than those early versions.
Modern radar systems are used for early detection of surface or air objects, and provide extremely accurate information on distance, direction, height, and speed. They are also used to guide missiles to targets, and direct the firing of gun systems. Other types of radar provide long-distance surveillance and navigation information.
The electronics principle on which radars operate is very similar to the principle of sound-wave reflection. If you shout in the direction of a sound-reflecting object, you will hear an echo. As you know, the speed of sound in air is 340 m/s. You can estimate the distance and direction of the object quite accurately.
The time required for a return echo can be roughly converted to distance if the speed of sound is known. A radar uses electromagnetic energy pulses in much the same way. The radio-frequency (RF) energy is transmitted to and reflects from the reflecting object.
A small portion of the energy is reflected and returns to the radar set. This new returned energy is called an ECHO, just as it is in sound terminology. Radar sets use the echo to determine the direction and distance of the reflecting object/planes/missiles.
The major parts involved in radiowave reflections are:
  1. Gaps and Breaks in the surface
  2. Unshielded cockpits
  3. External weapons
  4. Exposed Engines
  5. Large right angled tail surfaces
  6. Right Angle wing design
Reflecting radiowaves! These two words are the crux of the whole stealth system. What would supposedly happen if the radiowaves were absorbed on the surface of the incoming missile or plane? We would get no reflection or ECHO whatsoever. The plane would be invisible to the radar system.
To make stealth technology successful, the plane would need to be of special design, and have no surfaces that would reflect the radio waves. However, complete absorption of radio waves would not be possible by changes in the mechanical structure alone. This is completed with the help of a special coating on the plane.
This coating is made from a partially conductive polymers, that gives a conducting path to the radiowaves coming at it, and emits the same frequency from the other end of the plane, thereby, not reflecting or absorbing any of the oncoming waves, and rendering the object invisible to radar.
Other mechanical designs involved in rendering the plane invisible to radars are:
  • Shielded cockpits
  • No seams or gaps in the skin of the ship
  • No right angles on the tail surfaces
  • Having angled wings that direct the radar waves away from the surface rather than reflecting them
  • Having its design by angular plates that reduce specular reflections and diffract radar waves into space
  • Screens cover engine ducts to prevent radar waves from entering, amplifying, reflecting and going back. These screens are similar to the screens used in your microwave ovens
  • Serrated waves diffract radar waves away from the radar antenna.
Stealth fighters like the F-117 have smaller signatures than their earlier counterparts, as they are designed to absorb radiowaves or divert them away from the radar antenna. As stealth technologies advance further, so will the detection techniques. And the hide and seek game will go on forever.