Quantifying Blasters

[Jake]

After looking around this site, I was kind of surprised that there is no real quantification of blaster power. The most I have seen is essentially comes down to, "well it can create a small explosion when it hits a wall of some unknown substance". I decided to do a little research myself and have, for a few days now, been trying to find the energy delivered by one blaster shot from scenes in the six star wars films. What I am attempting to find is a blaster bolt hitting a known substance and a scene that shows how much of that substance has been vaporized as a result of the blaster hit. As I said, the vast majority of gunfights in the films have blasters hitting unknown substances, but I have found two possibilities of blasters hitting semi known substances, and have attempted to interpret them.

The first occur during order 66. The scene is here: http://www.youtube.com/watch?v=09n0qd_n4c0. I noticed in these scenes that the blasters do not appear to travel through any of the jedi (we do not see bolts leaving their bodies). Now, some may argue that the jedi may be using force absorb or the like but if you look here (very depressing scene): http://www.youtube.com/watch?v=NAklFUImYhU at 1:35 the same thing happens to a youngling who can't be more than 11 and I highly doubt he would have learned that power. So, assuming the blaster gets all the way through the person but not quite far enough to leave (18cm for me), and leaves a maximum of a fist sized hole (5cm for my fist), and assuming a cylindrical hole, we have a volume of pi*.18*.025^2 = .000353m^3 of vaporized human. Since humans are about 70% water, I will approximate them as such. The density of water is .0997 kg/m^3 and the energy of vaporization of water is 2.26E6Joule/kg. So the energy to vaporize the given volume of water is (.000353m^3)*.0997kg/m^3*2.26E6Joule/kg = 79.54 joules. By comparison, a 5.56mm round fired from an M-16 weighs about .004565kg (http://en.wikipedia.org/wiki/5.56x45mm_NATO) and travels at 853m/s (http://www.globalsecurity.org/military/ ... -specs.htm). This gives it a kinetic energy of .5*.004565*853^2 = 1660.78 joules. Because of the extremely low energy delivered by the blaster rife compared to the M-16, this estimate seems far to low.

My second estimate comes from this scene: http://www.youtube.com/watch?v=QR3290xV ... re=related. Now I know that we do not know the material of the grate, but considering its primary purpose is to keep space idiots from falling into the garbage disposal, I'm going to guess it would be made out of some cheap star wars metal, so I will assume iron. Now, it has to be wide enough for Chewie to slide through, so I will assume he is 1.5X as wide as me (I'm pretty skinny) which is .45m. I will also assume its a cylinder with diameter .45m and length 1cm (.01m). The energy of vaporization for iron is 6.26E6Joules/kg and the density of iron is .787kg/m^3. So, the total energy is (pi*.225^2*.01)m^3*.787kg/m^3*6.26E6kj/kg = 7835.45. This estimate seems much more reasonable putting an e-11 blaster rifle at 4.72X the KE delivered by the M-16.

So, what do you think? Also, are there any other scenes in the movies (or books for that matter) that would be better for an analysis?

[Bottlestein]

So, assuming the blaster gets all the way through the person but not quite far enough to leave (18cm for me), and leaves a maximum of a fist sized hole (5cm for my fist), and assuming a cylindrical hole, we have a volume of pi*.18*.025^2 = .000353m^3 of vaporized human. Since humans are about 70% water, I will approximate them as such. The density of water is .0997 kg/m^3 and the energy of vaporization of water is 2.26E6Joule/kg. So the energy to vaporize the given volume of water is (.000353m^3)*.0997kg/m^3*2.26E6Joule/kg = 79.54 joules. By comparison, a 5.56mm round fired from an M-16 weighs about .004565kg (http://en.wikipedia.org/wiki/5.56x45mm_NATO) and travels at 853m/s (http://www.globalsecurity.org/military/ ... -specs.htm). This gives it a kinetic energy of .5*.004565*853^2 = 1660.78 joules. Because of the extremely low energy delivered by the blaster rife compared to the M-16, this estimate seems far to low.

My second estimate comes from this scene: http://www.youtube.com/watch?v=QR3290xV ... re=related. Now I know that we do not know the material of the grate, but considering its primary purpose is to keep space idiots from falling into the garbage disposal, I'm going to guess it would be made out of some cheap star wars metal, so I will assume iron. Now, it has to be wide enough for Chewie to slide through, so I will assume he is 1.5X as wide as me (I'm pretty skinny) which is .45m. I will also assume its a cylinder with diameter .45m and length 1cm (.01m). The energy of vaporization for iron is 6.26E6Joules/kg and the density of iron is .787kg/m^3. So, the total energy is (pi*.225^2*.01)m^3*.787kg/m^3*6.26E6kj/kg = 7835.45. This estimate seems much more reasonable putting an e-11 blaster rifle at 4.72X the KE delivered by the M-16.

I can't comment on the validity of assuming iron for the grate. However, with the body calculation:
1) Assuming "it's water", the first calculation still isn't correct. Its water at body temperature, 37 C. You have to have the energy to raise it to 100 C, then the energy to evaporate the water:
Blaster energy = mass of water * specific heat of water * (63 K) + mass of water * latent heat of vaporization
( temperature difference is the same whether calculated in Celsius or Kelvin )

2) The next objection is that it's not 70% distilled water. Molar concentration of solutes drives up the boiling point, as well as the specific heat.

As for other approximations - if one could find a good picture of stormtrooper armor blaster damage, that would be great. Plastics can have ridiculously high specific heats. Some more chemically well versed board member can comment on the melting point trends in plastics.

[Xess]

Also the density of water at about 30 degrees C is about 995 kg/m^3 not .0997 kg/m^3. Using that and your assumptions the mass of the water is .246 kg, the energy required to raise it to 100 degrees C is 64,800 Joules, the energy to vapourize it is 556,000 Joules. The total energy of the blaster bolt is then 620,800 Joules or pretty much 621 kiloJoules. or 374 times a 5.56mm bullet.

Edit: You're mistaking density units. You use the g/cm^3 value but work with kg and m^3 for your volume.

[Havok]

Hey did you quantify the scene where the Falcon's little belly blaster shot actual ice and did... no damage?

[Jake]

@Xess and Bottlestien: Thanks a lot guys, I knew I screwed up somewhere because my number was way too low. However, iron is now going to be very complicated because I think the specific heat of liquid iron is a function of temperature and pressure and I most certainly can not find it on the internet. Since the vaporization of iron involves going from solid to liquid to gas, I need the specific heat of liquid iron.

@Havok: I saw that you mentioned this scene in some other thread and I wanted to calculate this scene, but they never actually show a close up of how much ice is missing (although we do see mini explosions), so I can't really make any assumptions.

[adam_grif]

Hey did you quantify the scene where the Falcon's little belly blaster shot actual ice and did... no damage?

Hoth is obviously made out of duraice.

[Elfdart]

Hey did you quantify the scene where the Falcon's little belly blaster shot actual ice and did... no damage?

If there's no damage maybe the bolts just kept on truckin'.