K21 IFV (South Korea)

Westerners tend to be too Western-centric, looking mostly at what Europeans, North Americans, Israelis and to a lesser extent what the antagonists in Russia and mainland China produce as weapon systems.
There sure is more being written about the American taxpayer-rip off rackets (FCS, GCV) and the German IFV Puma than for example the South Korean K21 infantry fighting vehicle.

I wrote before about my scepticism about the IFV concept in general (1, 2), but this aside I'll have a look at the K21.

It sure does have a less unreasonable weapons layout and ammunition range than the Puma (which is really the limbo benchmark in this regard).

It goes against the trend and insists on amphibiousness - a characteristic which was given up during the 70's and 80's in many AFV programs because weight gains for additional protection, weapons and other equipment made amphibiousness impractical. The use of internal inflatable 'air bags'/pontoons for additional buoyancy may actually provide some extra protection: Rubber is a reactive material and quite weight-efficient as a defence against shaped charges' penetrating tips and the extra angling and spacing of the outer plate may add a lot to its protective value both against chemical and kinetic energy attacks. The system would need to use multiple isolated chambers, of course - or else a single AK bullet or sharp underwater obstacle could deflate one side. The safety of amphibious operation already requires such compartmentalization, though.

The quantity of mounted smoke dischargers is small as usually (I think too small), not reloadable from behind armour (a usual deficiency) and apparently not bulletproofed (this is going out of fashion, as bulletproofed discharger sets are becoming more common). They may also require extra attention when camouflage (nets, foliage) or add-on armour (ERA, NERA, cage) is applied, which wouldn't be so troublesome if they were mounted behind the turret, overshooting the turret (a still very rare location).

The front plate (trim vane) is apparently meant not only as bumper and helping critically during swimming (turned up), but also as spaced armour and probably of high hardness to help the poorly angled part of the front against 30mm shots.

The sights and sensors are probably a weak spot of this design, as known from so many others. Normal glass is not transparent to infrared wavelengths; that's why you can see with a thermal camera how much warmth escapes from a poorly insulated house through old-fashioned windows. You don't see the IR radiation that goes through windows, but rather the one emitted by the warmed-up windows. You need a special, rare kind of glass in front of a thermal (IR) sensor.
This in turn means that thermal sensors are natural magnets for bullets. You cannot use them much once they were shot out, so this is a major issue (comparable to the M1 Abrams deficiency revealed in Iraq; unprotected bore evacuators).
Such sights should not be vulnerable to bullets from many angles from beyond their own field of view. One of the K21's has a cover plate to protect it at times, but it's apparently still vulnerable from beyond its FOV when in use.

The primitive turret roof hatches are another weak spot. We've seen better designs for generations.

The official protection rating is strange. 30 mm APDS is hardly a relevant threat; the Russian 2A42 30 mm autocannon can fire more powerful APFSDS and both 23 mm AP-I and 67-85 mm HEAT warheads are much more common, much more troublesome threats. One shouldn't believe published figures, of course.
Quite notable is the use of a glass-fibre composite hull (first experiments with this during the 80's); this would no doubt be hyped up a lot as hyper modern leap-forward transformational if the K21 was American.

Some photos show external, possibly bulletproof, boxes instead of cage-like containers for rucksacks. This may be considered very important by the crews during weeks of campaigning, as unprotected individual items can easily be ruined by bullets and fragments.

Some components are identical to what the new South Korean MBT (K2) uses, which is a nice-to-have feature.

Remarkably, the dismount strength of nine men (of to me unknown size restrictions) is rather fine, albeit the presence of a missile armament may lead to a reduction to eight in practice (especially if the missiles are used as general direct fire support).

The most remarkable fact about the K21 is a different one, of course: It is a new tracked armoured fighting vehicle in production. That's rare in Western or Western-friendly countries nowadays.



  1. I remember you saying once that the GALIX smoke dispenser was the best design in NATO service. With AFVs, we constantly see people reinventing the wheel, rather than scouting out the market for what already exists. Its almost like they slap this equipment on as an afterthought. As for your stringent requirements, I think you'll have to go to the museum and steal a nahverteidigungswaffe :)

    Another thing that bugs me, what happened to the hull mounted machine gun?! Nobody puts them into tanks anymore, thats just stupid. A co-axial mg has a wider field of fire, but it can't utilise grazing fire.

    The k21 itself is a pretty mixed bag, poor ergonomics and suspension, but good weapons and armor. If it protects against 30mm APDS (as claimed by the manufacturer), they'll pose a major threat to the m2 bradley. I wonder if the iranians are going to want a shipment of k21s, after all, they are becoming quite antagonistic towards saudi arabia!

    1. The bow machine gun was of little use because its user lacked good optics. The users were typically first and foremost radio operators, and those became unnecessary as radios became better and to be operated by the turret crew directly.
      The bow machinegun also weakened the upper glacis plate and made production more expensive.
      Main gun stabilisation also allowed firing on the move tactics, in which a bow-mounted machinegun has no role to play (but it disappeared already in the T-44).

      Some upgrades (Abrams' TUSK, IIRC) include a RCWS on the turret with a quite freely-moving machinegun, similar to what the Marder had early on on its rear. A RCWS adds terribly much height and obstructs TC all-round view, but it's more powerful than a bow-mounted machinegun.

  2. Hey, I've done my research. After WW2, the west fielded two main battle tanks, the centurion and patton: Both had only a 4 man crew, and both ended up using the AN/VRC-12 radios. Are you suggesting a causal connection? If so, what made these radio sets so much better than their predecessors?

    As for the hull machine guns, maybe they wouldn't be of much use to a tank, but APCs and IFVs are another story. They actually have to deal with infantry on a regular basis, which requires grazing fire. By the way, what do you consider to be a good set of optics? The shermans hull mg used a panoramic sight with an exceptional field of view.

    1. I know too little about magnifying optics.

      The typical combat scenario includes hostile infantry that you don't see and the IFVs supposed to disembark the own infantrymen from a place where the volley of anti-tank munitions isn't too bad - and preferably behind smoke.
      A hull gunner couldn't easily dismount in the back (and IFV/APC usually have an engine or two next to the driver) and reduce the dismounts by one. He could still be employed as infantryman, but then he wouldn't use the machinegun most of the time.

      And then here's the thing about oblique angles. It's better to not point the hull directly towards a threat, but at an angle of 10-20° or so. This maximises the passive protection. Some 60° angled surfaces become >70° angled and will thus cause simple HEAT fuses to fail.
      This means the field of fire of a hull machinegun would largely point at a wrong direction.