Prevalant in the Mass Effect Universe are the kinetic shields. These are able to protect the wearer by absorbing the damage caused by high velocity particles from lets say, an assault rifle for a small number of hits before it overloads and enters the cooldown period.

My questions are :

1.Why cant this concept be used for melee attacks as well?

2.If velocity is the factor, how do the barriers trigger for assault rifles and shotguns which have broadly different fire rates?


I am also curious to know how these barriers trigger just before the impact?

3 Answers 3


The velocity of a melee hit is vastly slower than a bullet from an assault rifle.

Perhaps, in a similar manner to the shields in the Dune universe, the kinetic barriers only work with objects moving at a very fast speed, well above melee speed. In Dune, the speed at which an attack would work was very slow - sword fighters had to use guile rather than aggression to get through a shield - but it would appear that the speed that the ME Universe allows is faster than that.

So to speculate on your questions in turn (using the Dune shield as a reference):

  1. The concept could perhaps be used for melee, but maybe there are undesirable side effects to this. In Dune the shield can be tuned-down to repel even very slow attacks indeed, like 2-3 inches a second - but there are side effects of the shield, such as a poor exchange of air across the boundary. In the ME world the side effect of being able to repel relatively slow attacks like melee might also have side effects which outweigh the advantages such as the shield being very inflexible to the wearer, or the shield stopping the wearer interacting with equipment or touching things.

  2. As already discussed, the velocity of a punch (< 10 m/s) is a lot slower than any bullet or shotgun shell (> 300 m/s). It would be far easier to tell the difference between a punch and a bullet, than between a punch and adjusting something on your own equipment.

  3. Barrier Trigger. Who says that the barrier needs to trigger? Perhaps it is a feature of the shield technology that it reflects the energy of the projectile - so the higher energy the higher the barrier response. This is the impression the Dune shield gives, it is not something that triggers when a bullet hits it - it is a passive property of the shield. I see the Dune shield a bit like a non-newtonian fluid that allows a slow moving object, but resists a fast moving one.

  • Hmm.But how does one keep track of the velocity of bullet as it varies for different types of guns! Commented Mar 26, 2012 at 15:22
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    @AshwinGanesh It doesn't matter. A projectile shot from a shotgun is still substantially faster than a punch, even if it is considerably slower than a rifle's shot. Just set the activation threshold at speed X and everything at or above that mark will activate the barrier.
    – Xantec
    Commented Mar 26, 2012 at 15:30
  • I guess that means then that a barrier could be used to block melee attacks, but tuning the field to block the larger impact area of a fist or rifle butt may reduce or negate its effectiveness versus the smaller area of a bullet.
    – Xantec
    Commented Mar 26, 2012 at 15:34
  • @AshwinGanesh Its not the case of keeping track of the velocity, its just the case that any melee attack is vastly slower than the slowest bullet. If you said that the shield technology by its very nature would not resist a 'slow' object penetrating at 5 meters per second (or 16 ft/second which would allow any form of melee attack), but would deflect even the slowest bullet (over 300 meters per second / 1000 ft/second). There is a big range here. Commented Mar 26, 2012 at 15:37
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    Here's the relevant bit from Xantec's link re the goa'uld personal shields: The Goa'uld also possess personal shields, however their effectiveness is directly proportional to the amount of kinetic energy used, meaning it will stop energy weapons and high speed projectiles, but not slower moving projectiles such as knives or arrows.
    – eidylon
    Commented Mar 27, 2012 at 19:00

Barrier Deflection

According to the Codex entry for kinetic barriers:

Kinetic barriers are repulsive mass effect fields projected from tiny emitters. These shields safely deflect small objects traveling at rapid velocities. This affords protection from bullets and other dangerous projectiles, but still allows the user to sit down without knocking away their chair.

The first thing this does is explain that the barrier has a deflection effect on matter. Although I'm not a master of theoretical physics, this could be accomplished by using a mass effect field to give the wearer "negative" mass at a precisely calculated point during the projectile's flight. Such a negative mass would cause a negative gravitational effect (imagine if the sun's gravity (a product of its mass) repelled the Earth instead of attracting it).

Active Barriers

It would seem that the barriers are somehow active, not passive, since a simple mass effect field cannot differentiate between the mass of a chair and the mass of a bullet. The presence of multiple "tiny emitters", which would lead me to believe that the emitters are focusing and finely controlling the mass effect field's effects to specifically target and deflect small incoming projectiles (especially since the barrier doesn't "repel" the ground with its mass effect fields and cause the wearer to go flying up into the air every time they are shot).

Computerized Targeting and the "Reverse Firing Solution"

From the Codex entry for the M-622 Avalanche:

[It can cause] great damage to electronics like kinetic barrier emitters, which sometimes leads to total systems failure.

It would seem that the emitters are some sort of electronic (probably computerized) system, and it seems to work together as a unit (since "total systems failure" is an option). It's reasonable to assume that in a world where FTL jumps can be quickly and accurately plotted by computers, a computerized system should be able to detect incoming mass of whatever size is specified moving at whatever velocity is specified, and then calculate a "reverse firing solution" to deflect it before it can cause damage (yes, I made up that term just now).

Another thing that the codex entry for this weapon points out is that energy (such as that from a weaponized super-cooling effect) is likely unhindered by barriers, which makes sense logically, since energy has no mass for these systems to affect. But that is neither here nor there.

But what about…

The weapons in the series use mass effect fields to propel small chunks of metal to extremely high velocities, so how could even an awesome futuristic computer detect and calculate it that quickly? That I couldn't tell you. They have quantum entanglement communicators, so maybe they have extremely powerful quantum computing technology small enough to be outfitted to personal armor.

Melee Attacks

So assuming all that, my guess as to why melee attacks cannot be blocked by barrier shields is that the system is tuned that way on purpose. I.e.: Both the mass and velocity of the object must be within specified parameters in order for the system to activate the deflection effect. This would prevent the wearer's arm from getting ripped off if they stuck it through the barrier's "event horizon" of deflection (which is another indication that the system is active, not passive), as well as allow them to run/sprint without nearby objects being deflected randomly by the barrier.


First, this might be better in Gaming.

The shields in Mass Effect use repulsive mass effect fields. The fields use positive and negative current to increase or decrease mass.

I haven't seen these fields applied to any biological matter (although biotics can manipulate these fields). This also seems to go with the ability to use a shield without it harming the user. If that's the case, then the fields should only apply to inanimate objects, and melee attacks are usually thrown by a person. So if mass effect fields cannot influence biological matter, then melee attacks should usually be unaffected.

  • You are right. The previous answers and yours have explained the concept to a good degree. Now i'm just wondering how would it trigger just before impact? Commented Mar 27, 2012 at 3:54
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    I also want to point out that i am trying to understand the concept behind these shields and not interested in the gaming aspect. With a plethora of users who have read/played/watched sci-fi concepts related to this, i might be able to learn more here than at gaming. However, if the mods perceive this to be out of place, they can migrate this question. Commented Mar 27, 2012 at 3:59
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    Mass Effect fields must be able to affect biological matter, otherwise whenever a ship went FTL all the people on board would be turned into chunky salsa against the aft bulkheads.
    – Xantec
    Commented Mar 27, 2012 at 4:08
  • @Ashwin, there would be no trigger, the shield is always on. Commented Mar 27, 2012 at 13:32
  • @Xantec, I had the same thought, but wasn't sure. Again, it seems to selectively act on biological matter, and there are few in-game references. Commented Mar 27, 2012 at 13:32

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