Starcraft vs Halo

[Agent Sorchus]

Isn't there a latent heat missing? Starting from a solid you'd need mass times specific heat times change in temperature + mass times heat of fusion + mass times heat of vaporization.

And while it is reasonable not to set the starting temperature at one degree above absolute zero, why would you see the need to devote space to saying that isn't what you're doing?

While you are correct, in that latent heat is needed for perfect accuracy, all my calculations are simplifications to determine the Order of Magnitude. I only went for the OoM calc because I don't think that the pixel count is accurate enough for any more accuracy or effort than that.

To within an OoM is good enough for our purposes, because if it is close enough between SC and Halo that someone might claim that it matters we will know that the battles would be close enough that tactics and other unsubstantiated things will matter more.

[Sapper007]

You NEVER multiply energy units.

if you cant multiply them then you cant divide them either, right?

[Formless]

You NEVER multiply energy units.

if you cant multiply them then you cant divide them either, right?

Actually, yes, because when you divide units you get non-dimensional numbers. Again, if you had taken a basic physics or chemistry class you would know this because stoichiometry is one of the most basic things you need to know to do coherent calculations.

Lets put it in geometric terms: what is a meter divided by a meter? Hint: you get a number, but the number corresponds to no real world value. Multiplying units or dividing units changes the units. Multiplying joules by kilograms or joules by joules changes the units into units you cannot use.

[Sapper007]

I guess MIT is wrong about how to calculate energy for vaporization and latent heat...
because they have you multiplying the mass and joules...
maybe i should have used your formula instead theirs...


http://web.mit.edu/kei1/www/THERMO5D/sol4.pdf

[Raxmei]

Woah, wait. Is the problem that you don't know the difference between energy needed to raise to boiling point and energy of vaporization?

edit: You're seriously posting a 14 page homework assignment as a cite. It would be considerate to quote the relevant part or at least point out which question you're talking about.

[Xess]

I guess MIT is wrong about how to calculate energy for vaporization and latent heat...
because they have you multiplying the mass and joules...
maybe i should have used your formula instead theirs...


http://web.mit.edu/kei1/www/THERMO5D/sol4.pdf

Where does that link tell you to multiply mass by energy? The only times I see them multiply mass by anything is when the multiply mass by the latent heat of fusion/vapourization and when finding the heat capacity of water where they multiply mass by the specific heat of water. The units of which J/kg and J/degrees Celsius, ie NOT a unit of energy but a unit of how much energy per kilogram is needed to overcome the latent heat of fusion/vapourization and how much heat is required to raise a certain mass of water by 1 degree celsius.

So MIT isn't wrong, you however read their assignment wrong.

Woah, wait. Is the problem that you don't know the difference between energy needed to raise to boiling point and energy of vaporization?

That seems to be his problem exactly. Sapper, the heat of vapourization is the energy need to vapourize a substance after you have already raised the temperature to the boiling point. The energy needed to raise a substance to the boiling point is not the same as the heat of vapourization. The heat of vapourization is a separate property of the substance.

[Imperial528]

I had orginially done this for the Species 8472 v. Protoss thread, but it applies here better:

A calculation of Dragoon firepower, done using the cinematic "The Ambush" from the Protoss campaign in the Original StarCraft.

In the cinematic, a terran outpost is ambushed by a cloaked/teleported force of Dragoons. Notable during the cinematic, is that there are two scenes which show Dragoon firepower quite nicely:

Scene 1:

A terran atop a watch tower, celebrating the recent kill of a crippled Dragoon.

Impact of a Dragoon phase disruptor.

Directly after the impact.

Fireball resulting from impact, note what appears to be pieces of steel flying outward, most appear molten while some do not. Note that the terran appears to have been completely vaporized. (In another scene one is.)

To calculate the energy required to heat a human body to the temperature of spontaneous combustion (around 1500, also near the melting point of most steel) I found the specific heat capacity of the human body, which averages out to 3470 j/kgC, and used an average weight of 87.6 kilograms for an adult male. I estimated that the event occurred in 250 milliseconds (1/4 of a second). My calculations indicated that about 444Mj of energy would be required, and that the energy released would be around 1.7 gigawatts. In this scene I did not include the mass of the watch tower or the terran's metal armor, as the remains of it are not shown. However, Scene 2 gives me good reason to believe that the terran was more or less vaporized.

Scene 2:

The Sergeant before being hit.

During impact.

Immediately after impact.

Resulting fireball. A few frames after this one show the skeleton crumpling to the ground, but it is hard to tell if it is intact or if smaller bones are missing.

I used the same method and data for this scene, with the exception of time. Since I was able to see the scene in more detail, I estimated that it occurred in slightly less time, at 150-200 milliseconds. This gave me a power output for the phase disruptor of the Dragoon to be around 2.2-2.9 gigawatts. As you can see, the skeleton seems to remain intact, other than being charred and crumpling to the burning ground as nothing is keeping the bones together anymore.

I haven't done this in awhile, so I may be a bit off (or completely), but after putting the equations in "reverse" (to find every number I started with) it seemed to be done correctly. If I am in error, feel free to call it out.

[Sapper007]

Okay then help me figure this out....

ergy can be added to a system either by doing work (W)on it or by adding heat (Q)to it. Energy transfer by work requires aforce to act through some distance. Energy transfer in the form of heat occurs between objects that are at different temperatures,with energy spontaneously traveling from the higher-temperature object to the lower-temperature one. When energy is added toan isolated system in the form of heat, either the temperature (T) of the system will increase or the system will undergo a phasechange at a fixed temperature.
The specific heat (c) of a sample characterizes the rate at which it changes temperature per unit mass when it receives energy inthe form of heat. The relationship between the energy input in the form of heat (Q) and the resulting temperature change (T2-T1) is:
Q=mc(T2-T1)

where is the mass(m) of the sample and (c) is its specific heat, which depends on its phase. For this problem, assume that specific
heat values are a constant for all temperatures within a given phase, which is a good approximation.
The latent heat (L)of a sample characterizes how much energy is required per unit mass to force the system to undergo a phase change at a fixed temperature. The amount of energy input in the form of heat (Q) required to completely change the phase of a sample with mass(m) is
Q=mL
.
Phase changes between solid and liquid phases are characterized by a latent heat of fusion . Phase changes between liquid andgas phases are characterized by a latent heat of vaporization .
In general, every phase (solid, liquid, or gas) has its own specific heat value and every phase change has its own latent heatvalue.


Doesnt that multiply Mass by Joules/kilogram?

[Lancer]

In a word, yes. The standard unit for mass is the kilogram, so in the expression Q = mL, the kg units cancel out, and you're left with just some scalar quantity times energy.

[Sapper007]

In a word, yes. The standard unit for mass is the kilogram, so in the expression Q = mL, the kg units cancel out, and you're left with just some scalar quantity times energy.

so what your saying is that L is a set joule number to vaporize or fuse 1kg of material at a defined mass... so you have to multiply the energy and the mass to find out how much energy is required to complete the phase that material at a defined mass, right?

[Xess]

In a word, yes. The standard unit for mass is the kilogram, so in the expression Q = mL, the kg units cancel out, and you're left with just some scalar quantity times energy.

so what your saying is that L is a set joule number to vaporize or fuse 1kg of material at a defined mass... so you have to multiply the energy and the mass to find out how much energy is required to complete the phase that material at a defined mass, right?

Yes, L has units J/kg while mass has units of kg. We get kg * J/kg so the kgs cancel out and leave you with Joules.

[Sapper007]

okay...

so when i found the latent heat of vaporization with the first equation... and then used the J/kg i found from that in the vaporization formula... i got my numbers...

so again where did i go wrong with the calculations?

PS There is no solid "proof" that complete vaporization happened... but given the nature of the blast and and the complete pass through of the beam prior to fragmentation of the ship its a reasonable assumption...

[Xess]

okay...

so when i found the latent heat of vaporization with the first equation... and then used the J/kg i found from that in the vaporization formula... i got my numbers...

so again where did i go wrong with the calculations?

PS There is no solid "proof" that complete vaporization happened... but given the nature of the blast and and the complete pass through of the beam prior to fragmentation of the ship its a reasonable assumption...

You didn't find the latent heat of vapourization with your first equation, you found the energy required to raise the mass to the boiling point which is completely different from the latent heat of vapourization. The latent heat value is the energy required to change the phase of the material once it is already at the melting/boiling point and is a property of the material like the specific heat capacity.

First you find the energy required to raise the mass to the boiling point, which you did correctly. Then you multiply that mass by the L value which is a property of the material and not the same as the energy required to raise the temperature to boiling. You then add those two values together to get the total energy required to vapourize the material.

[Sapper007]

You didn't find the latent heat of vapourization with your first equation, you found the energy required to raise the mass to the boiling point which is completely different from the latent heat of vapourization. The latent heat value is the energy required to change the phase of the material once it is already at the melting/boiling point and is a property of the material like the specific heat capacity.

First you find the energy required to raise the mass to the boiling point, which you did correctly. Then you multiply that mass by the L value which is a property of the material and not the same as the energy required to raise the temperature to boiling. You then add those two values together to get the total energy required to vapourize the material.

okay got it... my mistake(its been a long time since my last Physics class)... so... whats the latent heat of steel?
and after that calc we add the the energy to raise to boiling, the heat of fusion and the heat of vaporization then use those numbers times 3(1/3 of second to blow through the ship) to find the output per second, right?

[Xess]

okay got it... my mistake(its been a long time since my last Physics class)... so... whats the latent heat of steel?
and after that calc we add the the energy to raise to boiling, the heat of fusion and the heat of vaporization then use those numbers times 3(1/3 of second to blow through the ship) to find the output per second, right?

I don't know the Lv of steel, but iron's is 6088 kJ/kg which is good enough for an order of magnitude. I did the calcs for that last page and it takes about 2.25 megatons to vapourize the steel, so 6.75 megatons/second.

[Imperial528]

Since I did not include latent heat of vaporization in my original equation for the Dragoon (been awhile since I've done this), I redid them and I resulted with a total of ~1.58 Gigawatts. This time I also calculated the energy required to make the initial blue-white fireball, assuming a radius of 2 meters. For the person I got an energy requirement of 757 megawatts, and for the air I got an energy requirement of 825 megawatts.

[Sapper007]

I found a formulat for finding the latent heat of vaporization for 4340 steel... so give me a few days and i will come back with more refined numbers... and I will calculate for the entire ship... now that i know what i'm doing...

[Raxmei]

It isn't quite right to apply the time the impact takes as the per second firepower of the weapon. If the weapon is capable of firing continuously and the result seen is the result of a 1/3 second burst then that works. If it fires discrete shots then the length of time between shots is what matters.

[Sapper007]

what do you all make of the 5 minute day night cycle in the infested colony mission?

[Imperial528]

Game mechanics.

PS: Upon taking time out of the equation, I get 395 megawatts per shot.

[Imperial528]

I just got the time between shots, the Dragoon that killed the terran Sergeant fires at around 2:00, and then fires again at around 2:05 or 2:06, giving a recharge time of 4-6 seconds.

[Xenophon13]

I just noticed that in the cinematic after the supernova mission in SCII when valerian mengsk's battle cruisers are approaching the Hyperion mat says that "their shields are down" so they have some sort of shield...

[Imperial528]

It may be a physical-contact shield, which would repel boarders. Or nav shielding, which depending on what it is supposed to block, could make a difference in battle. Either that or an upgrade given to the Hercules and Minotaur classes when they were put into production.

Although, (and this is just speculation), in the campaign battlecruisers can be given defense matrix generators, so perhaps it was referring to those?

[Xenophon13]

They also supposedly have cold fusion according to the Battle of the Amerigo cinematic.

But maybe thats just the name of the drink