2010/12/03

Example: How to fool modern air power

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"All that glitters is not gold".

One of the favourite targets for air/ground attacks (next to  other high-value objects such airfields, command nodes, supply depots, air defence radars and tanks) these days is still the bridge. The destruction of bridges can stop or even entrap an enemy force or cut off its supply.
Well, that's the theory. In practice, this is a disruption and never complete. The right timing is most important for the operational level commander.

Back in WW2 bridges were quite easily destroyed in dive attacks (45-90°) with heavy (454-500 kg) bombs. A few hits did usually suffice for destruction, although some bridge constructions proved to be very resilient.

Guided munitions proved to be very useful against normal bridges, beginning with AZON bombs and even an active radar-guided glide bomb in WW2, later the very first laser guided bombs in Vietnam and finally GPS-guided bombs over Iraq.

There's a problem, though: Warfare is a contest against a thinking enemy who is often quite inventive.

Civilian bridges can easily be destroyed, and this is so utterly well-known and self-evident that armies prepare for this with military bridging. These military bridges are often segmented and can be repaired quickly. To cut such a lifeline reliably for more than an hour or two requires multiple attacks over time - something that doesn't exactly suit modern high-quality-but-low-quantity air forces well.

It's even worse: The enemy might be crafty.
The Chinese, for example, employed some underwater bridges when they endured total enemy air superiority.  Other armies (including the U.S.Army, which did not really need such a thing) did and do it as well.

ES91-56-6 (SC349005) 2 ½ ton trucks cross a river by underwater bridge, eight miles northwest of Taegu, Korea, on their way to the front line. 16 Sep 1950

Such underwater bridges have their tarmac a few centimetres below the waterline and alternatively it's also be imaginable to submerge a (pontoon) bridge like a submarine when an air attack is expected and to raise it again once the sky is clear again.

(Finally there's the possibility of using amphibious trucks as ferries, such as the M3 Amphibie in German service. This is a rather low capacity tool, though (few vehicles per hour).)

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Such bridges are difficult to find, but that's not the critical problem any more. Radars could very well detect the crossing movement of motor vehicles from very far away. The problem is rather in the attack. How do you aim a guided munition at such a target?
 
Infra-red sensors won't work - they "see" only the water surface!
Radar sensors won't work -  they "see" only the water surface!
Visual sensors or naked eye won't work, they "see only the water surface!
Laser illumination on water - not exactly promising!
GPS and INS (inertial navigation)?

GPS and INS can hit a target of known location, but that might be tricky as well. Military engineers could use a submersible pontoon bridge and move it by 20-100 m every hour. All it takes is a proper preparation of the riversides!


Now you're flying a 150 million bucks super stealth jet with some jam-proof high-tech guided bombs in your weapons bay - and you're still impotent against a crafty military engineering river crossing effort. That's certainly frustrating. Your only hope would be to remain entirely undetected and to catch the bridge while it's on the surface. You would probably have to do this twice a day and your whole squadron might be forced to do it a dozen times per day in order to reliably interrupt the bridge connection, though. You might think that they will eventually run out of pontoons, but how many pontoons can they buy for 150 million bucks !?


We can think of countermeasures against stealth, countermeasures against the guidance of stealth aircraft's air combat missiles - but the most important countermeasures to stealth aircraft might turn out to be completely unrelated to hard kills of flying objects (aircraft, munitions): 

Good old camouflage, concealment and deception plus a saturation with a low-quality-but-high-quantity approach are still valuable. Even bridges - once one of the easiest targets for bombers -  can be turned into impractical targets for modern bombers.

Sven Ortmann
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6 comments:

  1. Is this a case where dumb weapons would be better? For example, drop lots of mines (anti-personal and anti-vehicle) over both banks of the river and even mine the river bed itself[1]? My thinking here is that:
    * pontoons may be cheap but EOD teams are expensive and/or rare.
    * methods to rapidly clear mines from an area may themselves cause damage to the bridge infrastructure, while less damaging methods to clear the mines are slow.

    Of course, multiple sorties would still be required to re-generate the minefield to keep this crossing closed.

    [1] I guess a mine floating just below the surface tethered to the river bed would be best to deal with pontoons.

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  2. A floating mine is an alternative, but so is the attack on the vehicle stream instead of on the bridge.

    In the end, an air force needs also quantity, not just quality.

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  3. BK 37 on Ju87G ... sorry! 30mm on A-10 :-D

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  4. Oh, come one. An A-10 would be shred to pieces by VShorAD if it attempted to strafe such an important target.

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  5. The Soviets used IIRC underwater bridges/roads in their Crimean Offensive against the weak German forces on it, achieving almost complete operational surprise.

    The idea is a pretty neat one. ISTAR and effective field artillery with submunitions might be the proper answer in many cases, but the brige with no traffic on it might escape more then a passing glance, as such a bridge is outside of many an observers box.

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  6. I have to imagine that anything more than a minor current would produce a surface effect that could be observed from the air. Then hit the aimpoint with GPS/INS.

    If there is traffic on the bridge, then just use a vehicle as the target for a couple GBU-24s.

    Lastly, I wonder if you can get enough of a reflection off of the water for SALH to work? Maybe SALH combined with GPS/INS to get the seeker in the ballpark?

    Even a near miss from a large underwater detonation could produce significant damage from gas bubble expansion.

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