Sunday, July 18, 2010
Cruising at 45,000 feet and at mach 1.7, a Lockheed Martin F-22A prowls the skies over Northern Alaska. It's powerful AN/APG-77 AESA radar is the most advanced fighter radar in the world. Suddenly the pilot hears a faint warning noise. He turns and looks at his liquid crystal display to find that a faint radar contact is approaching from 40 nautical miles away. AWACS confirms the identity of the aircraft is an enemy PAK FA. The PAK FA is stealthy with an frontal rcs around .01m^2 but, it's not stealthy enough to evade the Raptor's radar. The raptor pilot selects his AIM-120D missile gains lock and fires. The AIM-120D closes the distance of 40 nautical miles in 60 seconds at 4,000 feet per second. The AIM-120D slams into the PAK FA utterly destroying it. The difference between the Pak Fa's rcs .01m^2 and the Raptor's rcs of .0001m^2 is the difference between life and death. Whoever can evade being detected and achieve missile lock first wins in this new era of 5th generation technology. This is the future of stealth combat.
The term stealth is complicated. It generally means the aircraft can operate without giving enemy forces signs of its presence. Stealth is achieved through a variety of factors. Basically, the goal is to reflect as few radar waves back to the source as possible. This is achieved through an aircraft's shape and materials used in its construction. The stealth technique used to cloak 5th generation stealth fighters is called planform alignment. Planform alignment is a technique where the flight surfaces of an aircraft have identical angles that reflect the radar waves away from the source. This allows for aerodynamically viable airframes that are able to maneuver as well as reflect radar waves. Different planes have different degrees of stealth. Depending on which surfaces of the airplane are facing the radar, the smaller or larger the plane's rcs will be. Most stealth aircraft maintain the smallest rcs from the front view; side and rear rcs sizes tend to be larger. Thus, in a dogfight pilots will face the enemy with the front of their aircraft in order to lower their chances of detection.
The following figures are taken from Global Security & Air Power Australia
RCS signatures for X band radars
F-22A Raptor: front aspect rcs .0001m^2, side & back rear rcs .01-.001m^2
F-35 Lightening II: front aspect rcs .0015m^2, side & rear rcs .01m^2
PAK FA: all around rcs .01m^2 (estimated)
Stealth aircraft can still be detected (given a REALLY powerful radar); its a matter of who can detect who first. The stealthier an aircraft is the longer it takes to detect. For example, the AN/APG-77 AESA radar can detect an aircraft with an rcs of 1m^2 from 150 miles away and a target with an rcs of .01m^2 from around 46 miles (40 nautical miles) away. Once the enemy is detected, missile lock is not an issue. Today's air to air missiles are incredibly lethal. If the target can be found then achieve missile lock can be achieved on fairly stealthy targets. The main problem for one who wishes to shoot down stealth aircraft is that they would have to track every insect, bird, and flying animal in the vicinity. Stealth aircraft have such small radar signatures they are automatically disregarded as a threat. The F-22A has a radar signature comparable to that of a honey bee. A system that can quickly determine the difference between a bird and a stealth fighter is needed. Such a task is not easy. At the speeds in which most stealth fighters fly, by the time you detect them (and assuming they have not already killed you) you only have seconds to shoot it down before it slips out of your radar.
Currently, the United States possesses the best AESA radars and aircraft avionics. Israel is not far behind the U.S and the Russian Federation behind Israel. One of the factors in determining how powerful a radar is how many transmit/reviver (tr) nodes a radar has. The AN/APG-77 has about 1,500 tr modules (F-35 uses an upgraded version of AN/APG-77 called AN/APG-81 which has increased ground attack capabilities). The PAK FA uses an upgraded form of the Irbis-E radar system which will feature 1,500 tr nodes.
Detection ranges for X band radars (front aspect)
F-22A and F-35 can detect PAK FA 40 and 30 nautical miles away respectively
PAK FA can detect F-22A 15 nautical miles away
PAK FA can detect F-35 28 nautical miles away
The potential for stealth fighters to achieve beyond visual range kills exists. The technology just needs to be refined. Stealth fighters will be engaging each other at much shorter distances than 4.5 generation fighters, as detection will take longer.