Passive Sensors and Aerial Combat

An Anonymous reader (please, everyone, add a username to the end of your comments;  there are too many anonymous commenters to keep straight who’s who and to give proper credit for good comments, such as this;  no, it’s not a requirement, just a plea!)  posed the following question in a comment: 

“Will losses of high end radiating sensors or reluctance to use them bring us back to aircraft that fight primarily with passive E/O [electro-optical] sensors?”[1]

As the anonymous commenter noted, ComNavOps has often stated that ships in combat will not radiate (EMCON) until an attack is actually incoming.  To do otherwise betrays one’s own location and invites destruction.  We have passive electro-optical and infrared (EO/IR) sensors but we need to fully develop them into a complete, hemispherical sensor system (with extensive redundancy, of course!) that is fully integrated into the ship’s combat software system.  In other words, we need to be able to scan, detect, identify, track, and establish firing solutions/fire control using purely passive sensors just as we now do with radar [question: how will we provide guidance for missiles requiring illumination?].
 
The ability to fully engage using only passive sensors would be a significant advantage as it would eliminate the enemy’s ability to detect and target our radars – no more ‘free’ guidance for the enemy and no more concern about anti-radiation (ARM-type) missiles!  The enemy would have to earn his targeting and if he uses active radar, as most current missiles do, that would give us the ‘free’ detection and engagement.
 
Returning to the main topic … will/can aircraft fight primarily with passive sensors and, if so, what would that look like?  How would it differ from what we do now?  What new tactics would we need?
 
As you know, passive aerial sensors are nothing new.  WWII aircraft fought using optical sensors (Mk1 eyeball) almost exclusively.  In more modern times, the F-14 Tomcat had truly impressive EO/IR capabilities (see, “Tomcat Eyes”) although the Navy then promptly abandoned those capabilities with the advent of the F-18 Hornet and only now, weakly, is claiming to have developed a never before seen Infrared Search and Track (IRST) capability that the rest of the world has had for decades.
 
Before we can go any further in describing a passive-only aerial battle, it is necessary to recognize some characteristics of passive aircraft systems and operations.
 
Field of View – This is the soda straw issue.  Aircraft are limited to small sensors and, therefore, have limited fields of view as compared to radar.  Some aircraft, like the F-35, have attempted to address this with total spherical coverage but with only limited success.  As far as I know, the F-35 remains incapable of using its ‘see through’ sensors effectively in a combat scenario.  Of course, the AF sends me surprisingly little classified combat information on the F-35.  I have to get most of my detailed, classified information off video gamer’s websites!  (Couldn’t resist that one! LOL)
 
The salient point, here, is that an aircraft using passive sensors is not capable of ‘sweeping’ the sky like radar.  The aircraft can see a fairly limited section of sky at any given moment.  This greatly increases the likelihood that detection and encounters will occur at much close ranges than we anticipate and that impacts doctrine and tactics.  The F-35, for example, was never intended to be an up-close dogfighter but was, instead, intended to stand off and be an aerial sniper.  With limited sensing, this is likely to mean the F-35 will find itself engaged in visual range dogfights, all too often.
 
Stealth – Stealth is completely negated by passive optical sensors and significantly negated by infrared (IR) sensors.  Thus, in a pure passive environment, stealth aircraft will possess no advantage over non-stealth aircraft as regards detection, tracking, and targeting.
 
Concealment – With radar, the traditional tactics of hiding in the clouds, flying low, etc. are largely useless.  Radar is relatively unaffected by weather, clouds, or terrain (look-down radar is pretty much the standard, today).  However, with passive sensors many of those tactics are once again effective.  Optical sensors are significantly degraded by clouds, IR sensors are somewhat affected by clouds depending on density and moisture content, optical and IR sensors are affected by terrain, and so on.
 
What this is suggesting is that passive-only aerial combat is likely to be much closer range affair than current doctrine and tactics envision.
 
AEW Control – Aerial combat is generally controlled by ground and/or airborne radar systems and controllers.  This can still take place, however, AEW active control has become a major risk, with active emitting AEW aircraft being susceptible to very long range A2A missiles (see, “GoodbyePoseidon and Hawkeye”);  I’ve proposed passive AEW (see, “Passive Hawkeye”) but that has not yet been implemented.
 
The US Navy and Air Force rely heavily on AEW for detection and battle management and that will be significantly impacted if not nearly eliminated.  In fact, one could envision aerial combat devolving into back and forth attempts by both sides to alternately attack and defend their high value AEW and EW aircraft.  Whichever side can establish AEW control of the battle will have a significant advantage.
 
BVR (Beyond Visual Range) – BVR combat, the ideal of the US military and exactly what the F-35 was designed to do, becomes a difficult, if not impossible scenario in passive-only aerial combat.  Radar is the sensor of choice to implement BVR combat and passive sensors simply can’t provide reliable 50-100+ mile detection and targeting against fighter size aircraft – large bombers or support aircraft, yes … fighters, no.
 
 
Scenarios
 
With the above discussion in mind, one can envision various aerial combat scenarios:
 
1. Low altitude combat with aircraft trying to get lost in the visual and IR ‘clutter’ of the ground.
 
2. High altitude combat with aircraft making use of the clouds as cover to hide from optical sensors although IR sensors would mitigate some of that advantage.
 
3. Fighter sweeps wherein one accepts the lack of long range sensing and compensates with sheer numbers of aircraft.
 
4. Aircraft might not even carry long range missiles such as AMRAAM, preferring to carry a larger number of shorter range heat seeking missiles.
 
 
Caution
 
What’s disturbing about all this is that the US military does not appear to have given this even a moment’s thought.  We believe that aerial supremacy is our birthright and AWACS/AEW control of the skies is an article of faith.  What will we do when China starts routinely shooting down our AWACS/AEW and we lose control of the aerial battle?  Are we training for it?
 
What will happen when the Chinese conduct fighter sweeps against us and achieve aerial superiority?  Are we developing alternate doctrine and tactics?    
 
The enemy gets a vote and we may not like their vote.
 
 
Conclusion
 
The future aerial battle will be a battle for control of the long range sensing capability.  With long range sensing comes the prize of control of the battle by airborne combat controllers.  The side that can establish and maintain long range sensing and, thus, control of the aerial battle will, most likely, win that battle.
 
Both sides will attempt to remain silent by using passive sensors and this will result in close range encounters likely involving the scenarios described above.  The close ranges will shift the emphasis from long range, radar guided missiles to short range, heat seeking missiles.  Aerial combat will return to optically-based (EO or eyeball), close range dogfights.
 
The exception to this will be the specialized hunter-killer (H-K) aircraft that will be tasked with finding and destroying the other side’s AEW aircraft.  The H-K aircraft will be armed with the longest range, fastest, air-to-air missiles the enemy has.
 
 
 
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[1]Navy Matters blog, “More Incorrect Ukraine Lessons”, Anonymous, March 26, 2023 at 6:23 AM,
https://navy-matters.blogspot.com/2023/03/more-incorrect-ukraine-lessons.html?showComment=1679836994339#c418576362046182892