HI All
<See Part I in the ships locker.>
My discussion in Part I was on the setting effects and game mechanics, this is intended to be a more technical look at how they might work, and the implications, from a counter-measures and limitations viewpoint.
Disclaimers - I am not a Physicist (IANAP). YMMV, May not be suitable for YTU, May contain nuts. Any allowable rights reserved.
----
Personal Point Defense Lasers Part II
Technical details:
The PDL system has several key components - a central module with logic and power supply connecting to sensor head (passive optics and lidar) and emitter head aka battle mirror. Larger 'hydra' battlefield systems often have multiple heads of both types to allow for the loss of some heads in counter-strikes. [Some systems will have a built-in counter-battery radar, while others will use a separate airborne or spaceborne wide-area radar platform, with hand-off to the PDL for incoming threats.]
A PDL works on a 4-step cycle of detection, targeting(with target acquisition, identification,sorting/prioritization & tracking), target engagement and damage assessment (and re-engagement if necessary).
Detection can be based on active or passive sensors. Seismic and acoustic passive sensors can detect the sound and vibration signature of a distant ballistic launch, e.g. the distant 'crump' of mortars and tube artillary or the roar of rockets, with seismics working even without atmosphere.
[Sidebar: Counter-sniper - In atmospheric environments, PDL acoustic sensors will approximately triangulate the sound of small arms fire to a 10m area, with more accuracy if multiple sensors share data. Once localised, the PDL goes Active in counter-sniper mode, making a second shot from the same area very hazardous and the PDL is often being able to dazzle or blind the shooter or destroy the scope even if only 1 shot is fired with the sniper doing post shot hit assessment. If the PDL is already Active, even the first shot will be accurately back-tracked and the firing point engaged before the first shot hits. Some advanced PDL's may even attempt to lase the bullet if it is slow enough, attempting to damage the bullet'streamlining and AP potential by asymmetrically melting or dehardening the bullet tip. It might just throw off the aim an inch or two at longer ranges and turn a kill shot into a survivable wound. It will certainly detonate an explosive bullet. Gauss projectiles are usually too fast to target unless at extreme ranges.
In the Imperium it is well-known that pointing an optical sight at alert Imperial ground forces is a good way to earn an eye-patch if you're lucky, abrupt head vaporisation by PGMP burst if less so..]
Passive thermal and optical sensors can spot a launch plume, smoke/vapour trail or muzzle flash. After a passive detection, the PDL will alert it's operator if in passive mode, or go active if in passive-active mode.
The primary active sensor is the Lidar aka laser radar. This is usually based on a low-power tuneable pulse laser which sweeps very short laser pulses through the scan area. Early models use a spinning mirror to direct the beam like a lighthouse, but solid state multi-laser arrays can be more efficient with shorter gaps between sweeps.The laser light is usually invisible to the eye, to avoid illuminating the surroundings (this is known as laser illuminator mode), varying from lowest resolution far-infrared(quite stealthy, undetectable to IR goggles/NVG, and able to penetrate some soft covers) to green-blue for penetrating water (to about 50m - shallow water is a favourite hiding place for battle dress and drones) to higher power UV for burning through IR smoke and light rain, or spotting simple optical camoflage). The laser frequency is also tuned to maximise or minimise atmospheric penetration depending whether range or stealth is most important.
When Active the lidar sweeps a wide area in Scan Mode, e.g. 360 degrees and a wide vertical range, 0-80 degrees elevation is typical, some even providing a full hemispherical dome coverage. (The operator sets sensitivity and scan limits if less coverage is desired.)
[Lidar can be amazingly sensitive, and if fine-tuned they can detect the puff of air from a blowpipe launch, capture speech vibrations off a window, measure the alcohol on a miltiaman's breath or determine the sex of a mosquito. This can lead to lots of false alarms if the sensitivity is set too high. This is also why they are useful remote sensors for lots of civilian applications from weather control to archeological mapping, atmospheric analysis from orbit and pest control]
Once a threat is detected, either by the Active lidar detecting small rapidly moving objects inbound, or a cue from a passive or remote sensor(radar or orbital optics), the lidar goes into Targeting Mode.
In this mode, the lidar switches from wide scan to tight focus once the target is acquired. The target is tracked for a few milliseconds to determine the trajectory and whether it is manuevering. Likely origin and destination points are extrapolated.
While tracking continues, the target identification phase begins - the shape is mapped in 3D (many projectiles are spin-stabilised so most sides can be seen) and imaged in several frequencies - (thermal,visible light, UV), so the projectile can be identified in the system's database. OCR routines can even read any surface markings or barcodes to aid identification. IFF challenges may be exchanged if it is possibly friendly or neutral fire just passing through. Countermeasures like reflec or ablat coatings are noted and factored into the engagement plan, and decoys are identified and ignored. Completely unknown projectiles may even receive additional probing to estimate density and composition - with several laser pulses of increasing power to spectroscopically sample the surface layers. (Stealthy recon drones often self-destruct during this phase when they detect the laser targeting focus, rather than being clearly identified)
Once identification is complete, a target prioritization and sorting step occurs, where the PDL's battle logic module decides which objects to shoot and in which order. If the warhead type and yield can be determined an optimal safe expected detonation point can be chosen. Careful detonation point selection can lead to neutralisation of the attacking launcher or allied hostiles(detonating the grenade as it leaves the enemies hand/barrel) or controlled fraticide of other projectiles in the salvo.
[If dangerous detonation seems unavoidable the PDL can send a warning flash alert to friendly units in the target area, with info of the weapon type, expected danger area, target point/CEP, current trajectory, etc. Depending on the time available they can take evasive or damage limitation actions. Battle Dress for example will usually bound up(TDX), curl into a ball (frag airburst or building collapse) or drop prone (ground burst or energy weapons fire). The Battle Dress operator can allow the armour to react automatically to their personal PDL alerts to save time, but false alarms are tiresome.]
Once the target is identified and being tracked, and the battle logic has decided when to fire, the engagement begins. Most systems use a second more powerful laser to hit the target, so the lidar can continue scanning and tracking other targets. The laser shot may be a number of short high-power pulses to cause a shattering effect. or a continous beam that heats and melts the target point. Depending on the target projectile and amount of available data on it, engagement objectives may be: to blind terminal guidance/homing sensors; degrade flight surfaces and streamlining to disturb the aim; trigger detonators if a full premature detonation is desired, disrupt detonators if a misfire/squib/dud is desired; shatter, melt or spot-weld the fragmentation casing, ignite the explosive fill or fuel in burning conflagration not detonation; reduce Armour-piercing capability through annealing or melting the kinetic penetrator tip or simply vapourise the whole projectile.
There is a cycle of shots and post-engagement reimaging for damage assessment to determine if additional shots are required. This cycle is a frequent attack surface for countermeasure designers, who can do tricks
like making the first projectile salvo solid duds filled with concrete instead of explosives, to force the PDL to make repeated shots trying to detonate them, while letting through more of the follow-up salvo to do the damage. To avoid this, at some point the PDL logic may have to abandon a targeted projectile to engage others, and fine tuning that cut-off is a key decision of the operator, as they have to live or die by the results of their decision.
[Sidebar: PDL Safety and legality
Most PDL engagements occur too fast for human involvement, and thus like their close cousins sentry guns & other automated weapons, they have extensive safety measures and restrictions on where and by whom they can be used. Most polities treat personal PDL as a battle dress component and react accordingly.
IMTU the Imperial Rules of War restrict fully-autonomous weapons systems thusly: lethal, mobile, autonomous - pick 2. Thus fixed sentry guns, unpowered smart-mines and 'defensive' PDL are permitted as weapons of war provided visual and audio warnings are posted. Traditionally sentry guns and PDL have a revolving red light warning beacon that switches on when active. A warning siren at start-up is also required when in areas that may have non-combatants. The weapons systems also have build in IFF checks to avoid engaging friendly units <and these are what T5 datacaster attacks engage>]
---
Corrections, suggestions and comments encouraged.
<Part III PDL Countermeasures to follow, if anyone is still reading
>
DX
----
Aslan in my party: "Thanks for the forty acres, and the mule was delicious!"
<See Part I in the ships locker.>
My discussion in Part I was on the setting effects and game mechanics, this is intended to be a more technical look at how they might work, and the implications, from a counter-measures and limitations viewpoint.
Disclaimers - I am not a Physicist (IANAP). YMMV, May not be suitable for YTU, May contain nuts. Any allowable rights reserved.
----
Personal Point Defense Lasers Part II
Technical details:
The PDL system has several key components - a central module with logic and power supply connecting to sensor head (passive optics and lidar) and emitter head aka battle mirror. Larger 'hydra' battlefield systems often have multiple heads of both types to allow for the loss of some heads in counter-strikes. [Some systems will have a built-in counter-battery radar, while others will use a separate airborne or spaceborne wide-area radar platform, with hand-off to the PDL for incoming threats.]
A PDL works on a 4-step cycle of detection, targeting(with target acquisition, identification,sorting/prioritization & tracking), target engagement and damage assessment (and re-engagement if necessary).
Detection can be based on active or passive sensors. Seismic and acoustic passive sensors can detect the sound and vibration signature of a distant ballistic launch, e.g. the distant 'crump' of mortars and tube artillary or the roar of rockets, with seismics working even without atmosphere.
[Sidebar: Counter-sniper - In atmospheric environments, PDL acoustic sensors will approximately triangulate the sound of small arms fire to a 10m area, with more accuracy if multiple sensors share data. Once localised, the PDL goes Active in counter-sniper mode, making a second shot from the same area very hazardous and the PDL is often being able to dazzle or blind the shooter or destroy the scope even if only 1 shot is fired with the sniper doing post shot hit assessment. If the PDL is already Active, even the first shot will be accurately back-tracked and the firing point engaged before the first shot hits. Some advanced PDL's may even attempt to lase the bullet if it is slow enough, attempting to damage the bullet'streamlining and AP potential by asymmetrically melting or dehardening the bullet tip. It might just throw off the aim an inch or two at longer ranges and turn a kill shot into a survivable wound. It will certainly detonate an explosive bullet. Gauss projectiles are usually too fast to target unless at extreme ranges.
In the Imperium it is well-known that pointing an optical sight at alert Imperial ground forces is a good way to earn an eye-patch if you're lucky, abrupt head vaporisation by PGMP burst if less so..]
Passive thermal and optical sensors can spot a launch plume, smoke/vapour trail or muzzle flash. After a passive detection, the PDL will alert it's operator if in passive mode, or go active if in passive-active mode.
The primary active sensor is the Lidar aka laser radar. This is usually based on a low-power tuneable pulse laser which sweeps very short laser pulses through the scan area. Early models use a spinning mirror to direct the beam like a lighthouse, but solid state multi-laser arrays can be more efficient with shorter gaps between sweeps.The laser light is usually invisible to the eye, to avoid illuminating the surroundings (this is known as laser illuminator mode), varying from lowest resolution far-infrared(quite stealthy, undetectable to IR goggles/NVG, and able to penetrate some soft covers) to green-blue for penetrating water (to about 50m - shallow water is a favourite hiding place for battle dress and drones) to higher power UV for burning through IR smoke and light rain, or spotting simple optical camoflage). The laser frequency is also tuned to maximise or minimise atmospheric penetration depending whether range or stealth is most important.
When Active the lidar sweeps a wide area in Scan Mode, e.g. 360 degrees and a wide vertical range, 0-80 degrees elevation is typical, some even providing a full hemispherical dome coverage. (The operator sets sensitivity and scan limits if less coverage is desired.)
[Lidar can be amazingly sensitive, and if fine-tuned they can detect the puff of air from a blowpipe launch, capture speech vibrations off a window, measure the alcohol on a miltiaman's breath or determine the sex of a mosquito. This can lead to lots of false alarms if the sensitivity is set too high. This is also why they are useful remote sensors for lots of civilian applications from weather control to archeological mapping, atmospheric analysis from orbit and pest control]
Once a threat is detected, either by the Active lidar detecting small rapidly moving objects inbound, or a cue from a passive or remote sensor(radar or orbital optics), the lidar goes into Targeting Mode.
In this mode, the lidar switches from wide scan to tight focus once the target is acquired. The target is tracked for a few milliseconds to determine the trajectory and whether it is manuevering. Likely origin and destination points are extrapolated.
While tracking continues, the target identification phase begins - the shape is mapped in 3D (many projectiles are spin-stabilised so most sides can be seen) and imaged in several frequencies - (thermal,visible light, UV), so the projectile can be identified in the system's database. OCR routines can even read any surface markings or barcodes to aid identification. IFF challenges may be exchanged if it is possibly friendly or neutral fire just passing through. Countermeasures like reflec or ablat coatings are noted and factored into the engagement plan, and decoys are identified and ignored. Completely unknown projectiles may even receive additional probing to estimate density and composition - with several laser pulses of increasing power to spectroscopically sample the surface layers. (Stealthy recon drones often self-destruct during this phase when they detect the laser targeting focus, rather than being clearly identified)
Once identification is complete, a target prioritization and sorting step occurs, where the PDL's battle logic module decides which objects to shoot and in which order. If the warhead type and yield can be determined an optimal safe expected detonation point can be chosen. Careful detonation point selection can lead to neutralisation of the attacking launcher or allied hostiles(detonating the grenade as it leaves the enemies hand/barrel) or controlled fraticide of other projectiles in the salvo.
[If dangerous detonation seems unavoidable the PDL can send a warning flash alert to friendly units in the target area, with info of the weapon type, expected danger area, target point/CEP, current trajectory, etc. Depending on the time available they can take evasive or damage limitation actions. Battle Dress for example will usually bound up(TDX), curl into a ball (frag airburst or building collapse) or drop prone (ground burst or energy weapons fire). The Battle Dress operator can allow the armour to react automatically to their personal PDL alerts to save time, but false alarms are tiresome.]
Once the target is identified and being tracked, and the battle logic has decided when to fire, the engagement begins. Most systems use a second more powerful laser to hit the target, so the lidar can continue scanning and tracking other targets. The laser shot may be a number of short high-power pulses to cause a shattering effect. or a continous beam that heats and melts the target point. Depending on the target projectile and amount of available data on it, engagement objectives may be: to blind terminal guidance/homing sensors; degrade flight surfaces and streamlining to disturb the aim; trigger detonators if a full premature detonation is desired, disrupt detonators if a misfire/squib/dud is desired; shatter, melt or spot-weld the fragmentation casing, ignite the explosive fill or fuel in burning conflagration not detonation; reduce Armour-piercing capability through annealing or melting the kinetic penetrator tip or simply vapourise the whole projectile.
There is a cycle of shots and post-engagement reimaging for damage assessment to determine if additional shots are required. This cycle is a frequent attack surface for countermeasure designers, who can do tricks
like making the first projectile salvo solid duds filled with concrete instead of explosives, to force the PDL to make repeated shots trying to detonate them, while letting through more of the follow-up salvo to do the damage. To avoid this, at some point the PDL logic may have to abandon a targeted projectile to engage others, and fine tuning that cut-off is a key decision of the operator, as they have to live or die by the results of their decision.
[Sidebar: PDL Safety and legality
Most PDL engagements occur too fast for human involvement, and thus like their close cousins sentry guns & other automated weapons, they have extensive safety measures and restrictions on where and by whom they can be used. Most polities treat personal PDL as a battle dress component and react accordingly.
IMTU the Imperial Rules of War restrict fully-autonomous weapons systems thusly: lethal, mobile, autonomous - pick 2. Thus fixed sentry guns, unpowered smart-mines and 'defensive' PDL are permitted as weapons of war provided visual and audio warnings are posted. Traditionally sentry guns and PDL have a revolving red light warning beacon that switches on when active. A warning siren at start-up is also required when in areas that may have non-combatants. The weapons systems also have build in IFF checks to avoid engaging friendly units <and these are what T5 datacaster attacks engage>]
---
Corrections, suggestions and comments encouraged.
<Part III PDL Countermeasures to follow, if anyone is still reading
>DX
----
Aslan in my party: "Thanks for the forty acres, and the mule was delicious!"
