Monday, June 1, 2009

Airborne Infrared and Supersonic Stealth

Stratospheric Observatory for Infrared Astronomy

Stratospheric Observatory for Infrared Astronomy

Interestingly, an airborne ‘SOFIA-class” Infrared (IR) threat model against a supersonic stealth platform (for which the F-117 and B-2 are not) is totally absent from seemingly comprehensive analysis of F-22 Raptor capability?

When one moves the Infrared Search and Track (IRST) discussion out of military circles and into a different scientific discipline, in this case airborne infrared astronomy - then the entire subject matter shifts with respect to what is possible. If the Stratospheric Observatory For Infrared Astronomy, (SOFIA) is flown altitudes of over 41,000 feet, nearly the entire infrared spectrum will reach it’s telescope and measurement sensors.

Combat aircraft like Typhoon (PIRATE), Advanced Flanker Series, (OLS) and F-35, (DAS/ EOTS) infrared search and track (IRST) sensitivity will also be more akin to an airborne SOFIA.

The higher an IR sensor is flown, the lower transmittance %, (Y-axis) reaches the sensor.

The higher an IR sensor is flown, the more (lower) transmittance %, (Y-axis) can reach the sensor.

Stealthy F-22 may have little defense against detection (from a high altitude IRST) if she is flown at high speeds, and altitudes due to frictional heating of her airframe & jet exhaust plums in air temperatures of -30F, -40F, -50F, -60F degrees.

Some in the DoD would be quick to point out that the F-14A Tomcat IRST (the AN/ALR-23) was of limited range, limited quality and misidentified source of IR emissions. A much improved system was fitted to the USN F-14D, the Northrop AN/AXX-1 Television Camera Set (TCS). The TCS was “slaved” to the radar to follow whatever the radar was tracking, and the radar could be slaved to the TCS to track whatever the camera “sees.”

Typhoon (PIRATE),

Typhoon (PIRATE)

Keep in mind that fighters like Flanker could employ their IR-version of the R-77 ‘Adder’ medium range missile; regardless of what happening (or not happening) in the radio spectrum, read: with less regard to RCS.
Also Flanker does not use radar to track an aggressively maneuvering dogfight target for it’s gun firing solution. Only its IRST w/laser rangefinder is needed. So it’s a fair statement to say Flanker’s IRST has a robust air-to-air capability.

Some might argue that SOFIA looks-up into space while an IRST must look-out across the airspace for a stealth target in atmosphere. The problem is distance. SOFIA targets are celestial objects millions or more miles away, while IRST targets need only be 50-100mi away.

Whether supersonic Raptor can close and maneuver into firing position unseen by an IRST system will be a source of debate and secrecy for some time. Suffice it to say that IR sensor improvements & design-cycles will certainly - outpace - possible stealth airframe changes.

This discussion is in a way, a mute point. The Russians have already identified two main areas to exploit supersonic Raptor. They revolve around, and loop back into these two issues:

a) F-22 Primary weapon
b) F-22 Thermal signature

F-14 Tomcat Northrop AN/AXX-1-TCS.

F-14 Tomcat w/the Northrop AN/AXX-1-TCS.

The F-14 Tomcat had been slated to stay in service until 2008. However was retired from USN service in mid-2006 under former Defense Secretary Donald Rumsfeld. The Tomcat aircraft (and the manufacturing dies) were summarily shredded-destroyed for reasons allegedly involving Iran. However, the Iranians had already been producing their own F-14 spares & electronics for their F-14A-GR fleet, since the mid-1980s with US assistance via The Iran Contra Scandal.

The 1st Fighter Wing at Langley Virginia, declared their F-22 Raptors operational on 12-Dec, 2007.

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