Dragon Ball GURPS: Calculating Force Field Kinetic Energy

[gibberingmouther]

So, I'm trying to figure out the math for my Dragon Ball GURPS-ification (GURPS is a tabletop system like Dungeons and Dragons).

I might have other questions, but first I was thinking about how the personal force field should work. This is made out of ki fused into one flexible sort of bubble that fits snugly to your body. It is supposed to be a single particle, but it doesn't make a huge difference if I understand correctly whether it's a bunch of individual ki particles fused together or just one "particle". Agh, excuse me if my writing isn't the best, but I just took my go-to-sleep meds and my brain is getting stupider...

Either way, you have a potential energy rating for the bubble based on the square cm of it. So, you could have 400 J/cm^2 which could deflect a bullet. But, based on this logic, it would be less effective against a knife or sword.

I think my reasoning about the potential energy being proportional to the surface area of ki bubble is correct, so my reasoning about the kinetic energy of the knife or sword must be wrong. If you thrust with a knife, does the full mass of it not come into play on determining the kinetic energy applied at the point? That's basically my question. Agh … my brain feels horrible now … ugh...

Again, copyright 12/11/2018 George Young. My avatar is my picture.

 

[PeterDonis]

you could have 400 J/cm^2 which could deflect a bullet. But, based on this logic, it would be less effective against a knife or sword

Why do you think so?

 

[gibberingmouther]

Why do you think so?

I think I've resolved this for myself for the most part, but I do have a question about one thing. Since the ki bubble is able to stretch, it's not just the tiny point of pressure of the knife that comes into the calculation. The area of the ki bubble around the point of the knife will stretch so you take the force rating of that into consideration as well. 80 kN/cm^2 is 400 J/cm^2 if the bubble has a give amount of .5 cm.

The warrior also has a denser body due to another ki based power, so that will also work to prevent penetration. A bullet from a typical handgun (I'm not a gun expert, but assuming a 20 g bullet with a 400 m/s speed, that's 1,600 J. If 4 cm^2 of force bubble resists the bullet, the kinetic energy could be reduced to 0 in .5 cm - actually less because of the "dense body" effect. In other words, a warrior at this level of power will only sustain bruises from small caliber handgun bullets.

Back to pointy things, there is a possibility of the force bubble being penetrated. With your 400 J/cm^2 force bubble, more give may increase bruising but it decreases the chance of the weapon penetrating the bubble. Less give means less bruising and possibly some of the bullet's KE being lost to deformation, but it increases the chance of the bubble being penetrated.

So, the question that remains for me concerns weapons like knives and swords. If you have a 3 lb sword, do I have to take all of that 3 lbs into consideration when calculating the Kinetic Energy at the point? Or would it possibly be more because of the person's weight behind a thrust?

Again, because I haven't published this yet officially, copyright 12/11/2018 George Young. My avatar is my picture.

 

[PeterDonis]

If you have a 3 lb sword, do I have to take all of that 3 lbs into consideration when calculating the Kinetic Energy at the point? Or would it possibly be more because of the person's weight behind a thrust?

The kinetic energy of the sword will take its mass into account, but not yours, since you're not moving with it. But the sword's cutting power depends on delivering force concentrated into a small area, not kinetic energy. Force per unit area is pressure or stress, so really the key property of the force field for resisting a sword thrust would be its tensile strength--how much stress it can withstand without breaking.

 

[Tiran]

Sounds like you are lifting the rules for how shields work in Dune.

 

[gibberingmouther]

Sounds like you are lifting the rules for how shields work in Dune.

"Armor of ki" is not like the personal force shields in Dune, which are in a bubble around the person's body and are based on some fictional physics which I just had to look up. The Holtzmann effect is a great literary device, but it's not really similar to how "armor of ki" works at all, besides that it's something invisible that works as armor.

I could give you a lot of info about how my game world works, but I'd rather save that for when I publish my stupid game manual.

 

[Tiran]

"Armor of ki" is not like the personal force shields in Dune, which are in a bubble around the person's body and are based on some fictional physics which I just had to look up. The Holtzmann effect is a great literary device, but it's not really similar to how "armor of ki" works at all, besides that it's something invisible that works as armor.

I could give you a lot of info about how my game world works, but I'd rather save that for when I publish my stupid game manual.

I was pointing out that Herbert's shields also stop bullets but not blades.

 

[gibberingmouther]

I was pointing out that Herbert's shields also stop bullets but not blades.

This is also a problem for real life ballistic armor (i.e. basic Kevlar), though they are now providing armor for police that can resist both stabbing weapons and bullets.

The ki armor should be able to resist both as well … but I'm trying to have some internal logic, and I thought pointy things (including pointy bullets or arrows) could be a problem for armor based on my very limited understanding of how armor physics works.

I thought at one point telekinesis could by itself work as armor, but that would require an insane amount of energy so that doesn't work.

Obviously, chainmail or steel plate can resist stabbing. I was just trying to get to a place where I understand some of the physics related to how armor works.

I think I'm good now though.

 

[Lren Zvsm]

In the novel, "Dune," personal force fields were invulnerable to bullets/projectiles, but could be defeated by slower moving knives or swords. Interesting that the "psychic force bubble" described here has similar properties.

 

[gibberingmouther]

In the novel, "Dune," personal force fields were invulnerable to bullets/projectiles, but could be defeated by slower moving knives or swords. Interesting that the "psychic force bubble" described here has similar properties.

But if you read what I had said, it does not have similar properties. I just wasn't sure about the physics of how materials for armor could resist a melee or ranged weapon whose kinetic energy was focused into a very small area.

Now I understand the related physics better and I have no problem with my "ki armor" being able to resist either melee or ranged weapons. Even with real armor, fast moving projectiles or pointy swords whose kinetic energy is focused into the pointy tip tend to be best at puncturing armor.

 

[Tiran]

But if you read what I had said, it does not have similar properties. I just wasn't sure about the physics of how materials for armor could resist a melee or ranged weapon whose kinetic energy was focused into a very small area.

Now I understand the related physics better and I have no problem with my "ki armor" being able to resist either melee or ranged weapons. Even with real armor, fast moving projectiles or pointy swords whose kinetic energy is focused into the pointy tip tend to be best at puncturing armor.

Your inquiry isn't about physics or armor - it is about a completely fictional notion that bears no relation to actual science except where you arbitrarily decide to apply it. Which is why people keep comparing your fictional idea with other fictional ideas that are effectively the same. The underlying hocus-pocus may matter a great deal to you, but your readers/gamers may not view the hand waving as important.

I'm sure a Gundam writer feels that Beam Saber is absolutely not a lightsaber, but most fans are unlikely to see the distinction.

 

[gibberingmouther]

Your inquiry isn't about physics or armor - it is about a completely fictional notion that bears no relation to actual science except where you arbitrarily decide to apply it. Which is why people keep comparing your fictional idea with other fictional ideas that are effectively the same. The underlying hocus-pocus may matter a great deal to you, but your readers/gamers may not view the hand waving as important.

I'm sure a Gundam writer feels that Beam Saber is absolutely not a lightsaber, but most fans are unlikely to see the distinction.

Well, I feel like my internal logic is pretty cool, for example how ki can enable the super strength and durability you see with characters in a lot of comics or manga. Without me talking more about it you're not going to be able to evaluate whether you agree with my opinion, but like I said I want to publish first. Almost there!

And the idea of armor as an invisible force field is hardly unique to Dune. For example, you have super man's invulnerability, which is much more like what my "armor of ki" is. Or magic armor that's a force field in D&D, or "psionic" armor in D&D and other games. Because it's shaped to the user's body, like super man's invulnerability, I think it's more like traditional comic book force fields than to the Holtzmann force field in Dune. Some people just latched on to the idea of "oh, it's supposed to protect against ranged but not melee attacks", which is not true.

 

[Tiran]

And the idea of armor as an invisible force field is hardly unique to Dune.

It isn't, but your specific qualities of deflecting bullets but not knives clearly reminds several of us the way Herbert's shields works, not the way Superman stops everything. Similarities with other fiction are fine, but don't be surprised if people keep pointing them out to you.

 

[gibberingmouther]

It isn't, but your specific qualities of deflecting bullets but not knives clearly reminds several of us the way Herbert's shields works, not the way Superman stops everything. Similarities with other fiction are fine, but don't be surprised if people keep pointing them out to you.

I think I'm just going to have this thread deleted because you guys aren't actually reading my posts before latching onto a few things I said - "force bubble", weak to stabby things - and then just going off about how it's similar to Dune.

 

[Lren Zvsm]

But if you read what I had said, it does not have similar properties. I just wasn't sure about the physics of how materials for armor could resist a melee or ranged weapon whose kinetic energy was focused into a very small area.

Now I understand the related physics better and I have no problem with my "ki armor" being able to resist either melee or ranged weapons. Even with real armor, fast moving projectiles or pointy swords whose kinetic energy is focused into the pointy tip tend to be best at puncturing armor.

I stand corrected. Thanks for some good posts.

 

[fresh_42]

I think I'm just going to have this thread deleted because you guys aren't actually reading my posts before latching onto a few things.

Threads which have received answers won't be deleted generally. We considered this rude to all those who took the effort to reply.
However, I can close it, as there is apparently nothing left to say.

Thread closed.