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Showing results for tags 'Radar'.
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Avoiding RADAR Though Jamming
pavelow posted a blog entry in Blog Having Nothing to do with PhysicsThere are two often used ways of avoiding RADAR (RAdio Detection And Ranging): Stealth and Jamming. My previous blog post covered stealth. This one will cover jamming. World War Two era planes weren't equipped with stealth technology to avoid radar, because it didn't exist yet. The air forces of the world had to figure out ways to avoid radar, and thus they figured out how to jam radar. World War Two era bombers were easily picked up by radar, so to confuse the towers, the planes released aluminum chaff. From the tower's point of view, all the signals from the chaff looked the same as the signals looked from a squadron of bombers. by jamming the tower with false signals, the airplane escaped without being tracked by the tower. Modern jammers work differently, but have the same purpose. modern radar jammers spam the radar source with false signals on the same frequency as the airplanes flying in the range of the radar. The towers still pick up the planes, but they can't distinguish the fake and real signals.
Avoiding RADAR with Stealth
pavelow posted a blog entry in Blog Having Nothing to do with PhysicsThere are two often used ways of avoiding RADAR (RAdio Detection And Ranging): Stealth and Jamming. This blog post will cover stealth. Radar can be rendered useless or less useful if the radio waves sent out by radio towers never return to the towers themselves. Airplanes today are equipped with more than one way to hide from radar. One way planes can avoid sending radio waves back to towers is by only allowing radio waves to reflect at one angle. The B2 bomber, as shown in the picture, was engineered to be as flat as possible, this causes radar waves to bounce off the plane as if it were a flat surface, and the waves never return to the tower they came from. Another way planes avoid sending radio waves back to towers is by using a stealth coating. Special versions of the F35 fighter jet are painted with a special stealth paint. When radio waves hit the surface of one of these planes, the paint traps the waves and absorbs a large amount of the energy from them. As a result, if radio waves do make it back to the tower of origin, they make it harder for the tower to distinguish the plane from something natural, like a bird, or even the environment itself.
RAdio Detection And Ranging (RADAR)
pavelow posted a blog entry in Blog Having Nothing to do with PhysicsRadar is used by militaries and civilians of the world for object detection. Radar works when a tower shoots a "beam" of radio waves in a direction. If an object is in this "beam" of radio waves, the waves will bounce back to the tower. The owner of the radar tower receives two very important types of data from the use of radar: Distance and velocity. Distance between the radar tower and object is determined by the time it takes the radio waves to return to the tower after they are initially shot. The radio waves travel at light speed. Therefore, it's pretty easy to determine the distance. Take light speed, multiply by the time for the round trip, and you get the distance. there is one twist, however. The total distance must be divided by two because the radio wave made a round trip, going to the object and back. The velocity of the object in the radar beam can be found using the Doppler effect. If the object is moving away from the tower, the frequency of the returning radio waves would drop. The opposite is also true. If the object is moving towards the tower, the frequency of the returning radio waves would go up. The extent to which the radio waves are shifted helps pinpoint the objects velocity.
The last manned combat aircraft?
bobbyburns posted a blog entry in RTB24's BlogThis March, the F-35 Lightning II made its first public demonstration at an air show. The U.S. Military is expected to purchase over a thousand of the new jets in total, eventually being put in service with the Navy, Air Force, and Marine Corps. The Air Force version, the F-35A, will be the lightest and most agile. The thrust to weight ratio is over one, meaning that the engine produces more thrust (191 kN!) than the weight of the aircraft. In other words, it is able to speed up while flying 90 degrees to the ground...straight up. The Marine Corps version, the F-35B, is the most powerful, in that it has a specialized engine. The thrust can be vectored down to "push" the aircraft off the ground, therefore allowing the aircraft to take off in ridiculously short distances (perfect for the Marines' shortened aircraft carriers) Lastly, the Naval version, the F-35C, has a larger wing area and strengthened landing gear for landing on an aircraft carrier. The wing area is increased simply because this version will have to fly very slow on final, meaning more lift is needed to keep the aircraft from entering an aerodynamic stall. The increased wing area provides more lifting surface area, so (by Bernoulli's principle), more air will flow over the airfoil, inducing a greater low pressure area over the wing. More lift is then created, allowing this model to control itself as very low airspeeds.