Check this please (Mike, Connor, Ted, Surthle, etc)

[Ender]

Ok, I tried to make a spreadsheet to calculate how the energy a laser must have for its performance to match that of an given amount of explosive. Idea was if you saw something onscreen and could scale it, you could use nuclear effects scaling laws to determine yield and from that determine laser power and energy.

Well my results are way off from where I would expect them to be. As in, it takes 14 gigatons to match what a 1 kt nuclear device would do against dirt. (7 gt for 1 kt on iron) That gap shouldn't be that big, should it? I know that the ideal gas law breaks down at high pressures, but it wouldn't be off by that much. If this is right then the cannons on an Acclamator would only appear to do as much as 330 tons of TNT against ground targets. I figure I have to be off by at least 3 orders of magnitude somewhere in this.

Row 68 is missing a note, the 1/15th of a second is because that is the period in which a TL shot delivers its energy, per the measurements Mike has on his site.

The file is a spreadsheet is a .ods , it can be opened with Excel or Open office

link

If someone can help me figure out where I made an error, I would appreciate it.

[Themightytom]

wow i was going to post a question asking how to calculate that but I decided it was probably a question with an answer so simple I would look stupid.

but you went and made a spreadsheet so now I can see how its done assuming this gets resolved.

Yahtzee!

[EnsGabe]

The captcha for that site is a pain.

[Crayz9000]

The file is a spreadsheet is a .ods , it can be opened with Excel or Open office

Actually, as far as I'm aware, while Microsoft is working on direct ODF import/export from Office, they don't have it yet...

Anyway, if anyone wants to open it without installing anything, use Google Apps, which opens it just fine.

[Ender]

Ok, I realized that my last calculation with the specific heat of the ideal diatomic gas is a bit off because I used the derived temp as the change in temp instead of subtracting the boiling point from it to get the change in temp. But honestly, that is a pretty minor thing.

This isn't seeing much traffic, can I please get a mod to shift this to SLAM? Thanks.

[Teleros]

There is a conversion tool for .ODS to Excel format that works for Excel 2003 at least:

Link to website

Basically install and then open the spreadsheet as normal. Dunno what other versions it works with - I've got Office 2003 so didn't bother to check what it said for other versions .

[Vympel]

Moved to SLAM.

[Kuroneko]

I didn't take a look at your spreadsheet yet, but the ideal gas law is useless at the regimes you're trying to use it. The problem is more complicated by ionization of the particles involved, but even without taking that into account, you can at least get a better approximation via a van der Waals equation of state for non-interacting particles: P[V - nb] = nRT, where b = 4(N_A)[4/3πr³], r the van der Waals radius of your particles and N_A is Avogadro's constant. You may want to try to find the van der Waals parameters (a,b) for a better model.

[Ender]

I didn't take a look at your spreadsheet yet, but the ideal gas law is useless at the regimes you're trying to use it. The problem is more complicated by ionization of the particles involved, but even without taking that into account, you can at least get a better approximation via a van der Waals equation of state for non-interacting particles: P[V - nb] = nRT, where b = 4(N_A)[4/3πr³], r the van der Waals radius of your particles and N_A is Avogadro's constant. You may want to try to find the van der Waals parameters (a,b) for a better model.

Ok, I found a way to calculate out an approximate value of b (though when I'm off by an order of magnitude from the empirical measurement when I try it for water vapor), but how do I do it for a?