APS is a compelling capability, but there are enduring concerns that as soon as a tank is fighting in real world conditions with friendly infantry and vehicles around it, the APS becomes a significant danger to everyone around it, automatically firing explosive projectiles or initiating explosive charges on the vehicle with zero warning. The following are some ideas that APS designers and users are looking at for technology to help mitigate the issues.
When a hard kill APS system goes off, things get a bit exciting for a moment. Whether a deployed system like Iron Fist (shown in the video below) or a distributed system like ADS, the broad approach is the same - an explosion is set off quite close to the vehicle, seeking to critically damage the threat projectile (which itself may ignite or detonate in some capacity, if only because it is itself a lump of energetic materials including HE and propellant).
All well and good - the system has done its job and stopped the missile or RPG from hitting it, and any armour present will soak up the blast and fragmentation that will ensue. But in real life a vehicle isn't alone on a test range, it is tightly integrated with infantry and other vehicles.
If those individuals are stood in the area of the defeat, they are clearly in for a relatively dramatic event in their life that could injure or kill them. In this hypothetical scenario, when reviewed later, the board of inquiry will likely find that they were killed by a friendly system (the APS) rather than hostile fire, and there will no doubt be a furore.
So the problem is to find a means to avoid hurting or killing friendlies around an APS-equipped vehicle, whilst trying to keep the system active and doing its important duty.
The simplistic solutions.
Before we get into the more complex technology enabled route, there are two obvious simple solutions - either just run it off, or just crack on and accept there is a risk.
Turn it off.
At the simplest level, you could just turn off the APS when dismounts are close by. This isn't especially useful, as the APS was added to the vehicles at significant weight and cost in order to mitigate a very real and dangerous risk, so turning it off simply adds the burden of those things with no benefit in kind. The only time an AFV will be totally alone is when it is not being used properly and is at significant risk - see evidence in the form of the many losses by Russian in Ukraine where tanks operated totally alone and unsupported, especially in urban environments.
We should therefore accept, at least for this discussion, that we want the APS to stay on all the time, and the objective is to maximise its coverage whilst trying to keep it safe for those nearby, so just turning it off becomes a non-starter.
Accept the risk and consequences.
Ultimately the risk of not having APS is arguably greater than of having it - if a missile does successfully hit a tank that has dismounted infantry nearby (and turning off the APS essentially assures that event should it be fired on) then the effect is likely to be much greater and more damaging than the more limited effects of an APS engaging on a restricted arc.
If either option leads to the injury or death of personnel in the path of the threat, is it not better to at least save the crew and not lose the significant asset that is a tank or other AFV in the fight they have found themselves in?
For illustration, contrast the overall effect of a successful kill of a tank...
...with the effect of a successful APS intercept, in this case a Trophy system fitted to a Bradley hull. The damage and secondary effects to materials and personnel around the vehicle are very different.
Caveat that the first video is a worst case scenario of a Russian tank suffering a catastrophic kill following detonation of the ammunition in the carousel (a consequence of the design and the lack of insensitive munitions compliant ammunition).
Not all tanks or AFV would explode this dramatically when hit, but the effect is still significant. The below video shows an M1 Abrams being hit and venting its ammunition racks through the blow-out panels. In either case the tank is eliminated from the battle and significant effect will be felt to those in close proximity to the vehicle.
So, it is reasonably safe to say that an APS is a lesser effect than an effective hit from an ATGM. With APS the damage is on a limited arc and in the case of deployed APS is pushed out from the vehicle by 10 to 30 metres, depending on the system.
The result is a very localised danger area, and when taken in the context of the whole vehicle, is very low - Rafael have claimed an unspecified (in terms of scenarios and data, which does render it a bit of a useless statistic admittedly) 1% risk of personnel being injured by a Trophy interception, owing to the low chance of the narrow danger area coinciding with a nearby individual, as well as the fact that the defeat event is largely blast and not a full HE/frag event that would happen when a warhead detonates.
In the case of distributed systems like StrikeShield, the danger is still isolated to a single arc around the vehicle, but rather than being pushed out from the vehicle, is located very close in to the vehicle, owing to the means by which such systems engage the threat.
StrikeShield as an example use non-fragmentary shaped charges with limited effect beyond a metre or two, and have been stated to present no greater blast effect than would be experienced from the detonation of an RPG, meaning there is no net increase in danger compared to if the system were not there.
In some ways this makes things easier - the tactics, techniques and procedures (TTPs) when operating with distributed APS vehicles is quite simple - don't get near them. So long as you are more than a few metres away, the effect is relatively (generalisation alert!) limited.
It's worth noting that good practice is to stay away from AFVs anyway, particularly in the urban fight. Heavy armoured vehicles are bullet magnets in urban terrain, owing to their being a very enticingly large and slow moving target, and occasional overconfidence that you can be the person to shoot out the optics at 250 m and blind the tank making it an enticing thing to have a crack at. Infantry bunched up in conga lines behind or beside tanks should be trained against - the tank will be attracting large volumes of fire, ricochets under and around the tank will be very high volume, and the tank itself is quite unpredictable (owing in part to most being relatively oblivious to their immediate surroundings, see my primer on AFV situational awareness for more) and may be a as much of a danger as a shield. The presence of a line of APS explosives looking directly down at you all around it may in fact be a handy reminder to stay away.
So in either case there is a reduced likelihood that a person will be in proximity to an intercept anyway, and if they are, the main effect will be a blast. In the modern battlefield most (generalisation alert, again!) dismounted infantry should be equipped with the baseline contemporary PPE, especially so if they are entering complex terrain alongside heavy armour, namely goggles or ballistic glasses, ballistic armoured helmets and vests, and earpro (either over ear or bespoke moulded inserts, in either case with integrated communications.
With this level of protective equipment on, an APS initiation within a few metres will not be significantly damaging, in fact it should leave little more than a momentary effect like a stun grenade. Systems like Rheinmetall's ADS are designed to be low collateral effect, and live fire tests with unprotected people and equipment in close proximity (albeit dummies) show there is a low level of danger.
The summary then, is that so long as basic rules are followed (don't be close to the vehicle) most risk is avoided, and the remaining risk is of a very low likelihood and so should be weighed and decided on. It is a risk, but is it sufficiently likely to override the benefits of the systems being employed? There is not a single right answer to that question.
Israel, ever the pioneer with APS, has already said they've experimented with the first layering of technology into the APS environment to reduce risk to dismounts, utilising blue force tracking (BFT), already being used to an individual level as part of whole force modernisation and integrated battle management systems.
The BFT lets the vehicle know soldiers are nearby, and their position (depending on the system the degree of fidelity of the position can vary, significantly). Integrating the BFT with onboard sensors to track specific solider positions, as well as digital communications and other networking elements, reasonably high fidelity positional tracking of the friendly forces around the vehicle can be defined, and then integrated with and overlaid on battlefield management systems (BMS) to begin to put together a clear understanding of the situation.
The reason for all this is to then allow the APS to intelligently track these individuals and produce no-fire or safe lanes around the vehicle, in terms of arcs, within which it will not activate APS and thereby avoid injuring or killing them.
It is not a perfect solution - this means there are areas where the vehicle now has no protection from the APS and so is likely to be destroyed if successfully fired on from that direction. But it is a radical step up versus simple turning it off, and is similarly more appealing to the dismounts than playing the odds game that they won't be in the area when the APS activates.
The real prize is in taking this a step further, and integrating vehicles with 'smart' APS into a broader network for much bigger picture intelligent function.
A note that the following line of development requires deployed APS like Trophy, as they need to be able to fire out at passing threat projectiles. Whilst such APS are designed to engage projectiles fired directly at the defended vehicle, further development has enabled the ability to engage crossing targets where they have requisite tracking data from their own or connected sensors. For distributed APS like ADS this would not be viable.
Once we know where everyone is relative to one another, we can begin to look at the bigger tactical picture in terms of APS coverage. If we continue the above example, we have identified there are two arcs around the vehicle (which we'll call vehicle A now) that are no longer protected in the event of an attack in order to protect the infantry near the vehicle.
However, there may well be another vehicle nearby that does have coverage that extends into the path leading down that arc. In the below image, you can see vehicle B, which is ahead of vehicle A and has a clear 'safe' firing lane through vehicle A's no-fire arc.
By networking the vehicles, you can ask the system to extend Vehicle B's engagement envelopes to include any threat that passes by it and into the no-fire arc of Vehicle A, thereby re-establishing coverage of that arc lost by the proximity of dismounts around Vehicle A.
This approach has been claimed to have been operationally proven by Trophy in IDF service on the Merkava, where a Trophy equipped Merkava protected another Merkava nearby and within the first vehicle's engagement envelope. This is not some specificity of the Israeli systems or scenario, and would be possible with any similar system and suitably equipped force - meaning an APS and networked BMS suite for all vehicles involved.
But why stop here - you can take this further as a concept. If we know the positioning of all friendly forces, we can be more proactive about warning and taking proactive mitigation of weaknesses.
In the example below, we have a group of vehicles that includes three tanks with APS (vehicles A, B and C) and a truck without it (vehicle D).
Via the same means as the prior example, the vehicles can be suitably networked to understand their relative positions and identify that vehicle D is unprotected across essentially all aspects. There is a modest area to its front and right where Vehicle A and B can protect it, but especially to the left and rear, it is very exposed.
The system can, at the least, warn both Vehicle D and the accompanying vehicles that it is exposed and at risk, and in a more proactive application can queue other vehicles to seek to manoeuvre to achieve complete coverage of all vehicles in the formation.
That would be achieved by symbology on BMS systems in the vehicles, and on any vehicles optics and augmented reality-type crew equipment. Again, this isn't actually a grand flight of fancy, the broad approach has been demonstrated with contemporary systems and is not an especially demanding task thanks to the myriad of radar and optical sensors already on the collection of vehicles in such a scenario.
This approach would allow a mixed formation of APS and non-APS systems to radically enhance their overall survivability, accommodate safety critical factors like the presence of soft skinned vehicles or dismounted personnel without losing all-aspect protection, and provide the crews and soldiers with a smarter suite of situational awareness and protective capabilities that extend beyond the vehicles equipped with them.
Recognise the enduring risk.
It is important to reiterate that nothing will remove risk from a combat environment, and APS both remove risk whilst adding a novel risk of their own.
The Israelis have demonstrated the value of APS, but also illustrate the need for a pragmatic view on their implementation. You cannot have APS providing effective coverage and simultaneously have them provide assurance that they will not cause fratricide issues. There is a risk, one to be considered and assessed.
There are many such risks already, and they are mitigated by training, by technology, and thereafter the remaining concerns have to be accepted as a tolerable risk versus their effect, or discard the APS system and save all the associated monetary and resource costs.
A tank firing its main gun in proximity to dismounts can very easily injure them severely. Someone in between a tank and its target is at risk of severe injury or death from things like sabot petals discarding. The crew will not have clarity of who is in proximity of the muzzle in complex terrain, and so it is a significant danger to those close by. Yet tank guns endure.
Anyone near an AFV fitted with ERA are at risk of injury or death if the ERA is hit and explodes (a primer on ERA is in the works). The big lump of metal, the front flyer plate, of an ERA cassette can be blasted well over 100 metres from the vehicle when the ERA initiates, and would be a fatally bad thing to get in the way of.
From a technology perspective, companies have spent significant effort trying to make low collateral ERA for this reason (systems like CLARA use materials that disintegrate rapidly, or systems like Rafael's Armour Shield KE seek to contain the plates and prevent them being projected away from the vehicle. But most ERA are quite dangerous, and consequently some users have avoided using them - note for example that British Challenger 2 in Iraq only had ERA on the lower front plate so that they would throw the flyer plate into the ground and minimise the risk.
So technology can help and do some really great things not just to reduce risk but radically enhance performance of the system at the same time, and training can help further.
But if users cannot tolerate the risk that an APS could realistically (even if a very low probability) be the primary cause of wounding or death for a friendly or civilian individual, then APS is fundamentally incompatible with their needs.