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  • PAK-FA Secrets Via YouTube
    Posted by Bill Sweetman 10:37 AM on Mar 29, 2010

    Just popped up on YouTube, a couple of interesting T-50 videos. The first is an overview of some of the technologies involved in the aircraft.

    Noteworthy points: the video highlights a new honyecomb core material designed for high temperatures. It also states that the T-50 will have no fewer than five radar arrays:  the 1500-module forward active electronically scanned array (AESA), two side-facing X-band sub-arrays and two "decimetric" (L-band) arrays in the leading-edge root extensions. It also states that the goal is to fight the F-22 by closing within visual range.

    Another new video shows a novel inlet radar blocker. The compressor face of a jet engine is one of the least stealthy parts of an airplane. Not only will the whirling blades, at some point, reflect radar energy directly back at whoever is looking for you, but the shape and rotational rate will identify you, because computers can count very, very fast.

    Step 1 in dealing with this problem is to coat the inlet duct with radar absorbent material, because a lot of radar energy bounces off the duct wall several times on the way in and out again. High-level stealth, though, means physically blocking the line of sight with a "serpentine" duct (which is done on the F-22, JSF and Typhoon). But that can take up a lot of space, particularly with big engines, and isn't practical for a stealth retrofit or on some new designs.

    The Super Hornet, for example, has short inlet ducts so line-of-sight blockage by curvature isn't practical. The solution was to install a blocker in the inlet duct - looking down the duct, you see what looks like a compressor face, but isn't. It's a fixed composite structure, RAM-coated. And of course any stray electrons that do make it through the blocker and hit the compressor have to make it out through the blocker again. Problem: what bends electron flux also bends airflow, so you can get losses.

    Via Secret Projects comes an image of what is said to be the radar blocker for the Sukhoi T-50 PAK-FA, which looks solid if a bit lossy:

    blog post photo

    But the same thread also includes a Russian video of a more elegant solution:

    It uses flexible vanes with a rotating ring at the rear end:  in  the "stealth regime" it provides extensive blockage, but it clears the airflow when it doesn't matter or you need full speed or power. One challenge would be the structural design, because the last thing you want is a piece of RAM flaking off the moving surface and FODing out your motor. But it could be an interesting Su-35 modification.

    Tags: ar99, russia, stealth, T-50

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