Absolutely Rediculous Physics Question

[sareth]

Okay, so the other day I was mulling over the question of how to armor plate a lighter than air vessel. Which is, of course, patently ridiculous and pointless. Never-the-less, I would like to lay down a train of (il)logic here, then ask any of you physics/engineer types who read me to ponder something, and maybe even do some number crunching if

Comments

[kheldarthedwarf]

Here you go, check the subsection on vacuum balloons...
http://en.wikipedia.org/wiki/Lighter_than_air

Key point... "16% more efficient than helium and 7% more efficient than hydrogen"

[sareth]

Not particularly impressive improvement then...

^_^

[kheldarthedwarf]

Yeah, the density of hydrogen gas is already pretty low. Still, it's a cool idea, especially the comment in there about plasma windows. That just gives me a really great image in my head. Could make a neat steampunk-type setting...

[sareth]

*laughs*

Amusingly, it's a steampunk band that got me thinking about this...

http://www.youtube.com/watch?v=E-RCK1yXwHM

[coriakin]

Take a look at http://www.newton.dep.anl.gov/askasci/phy00/phy00844.htm

In my opinion, the amount of reinforcement a large vacuum container would require would prevent any reasonable amount of buoyancy from being obtained.

[sareth]

That's the conclusion I am coming to, yes.

Physicist Grad Student here!

[xepel]

Atmospheric pressure is 14.7 pounds per square inch at sea level

Re: Physicist Grad Student here!

[sareth]

I love you man... This is exactly what I was hoping for, even if half the math leaves me drooling and scratching myself as "Also Spracht Zaruthstra" plays in the background...

Heh. If you ever become a Physics Prof, you should use this on your students some time. *laughs*

Hmm... I *might* be able to use these numbers to swag whether or not you can make an armored Dirigible that uses Helium or (Oh, what a bad idea!) Hydrogen though... *ponderponderponder*

Re: Physicist Grad Student here!

[xepel]

Wait, wait! You've made a significant assumption that creates outrageous error!!!

We're talking 14.7 psid. A garden hose withstands 75 to 120 pounds water pressure. Our houses use thin copper piping. We don't need steel to withstand 14.7 psid. School children with bridges made from toothpicks are standing on them. You need a structure that will hold a film that will withstand 15 psid, not a solid inch thick piece of steel!

Won't this make a big difference?

Spenser

Re: Physicist Grad Student here!

[xepel]

True. A lot of problem is that even though the air isn't 'that' heavy - it's the structure and the self-support that gets to be a problem.

Hoses work just fine holding water in. But it's very easy to collapse them. Similarly, it's probably easier in general to have a material which is fine at containing yet is not that good at keeping stuff out.

I have a feeling that most materials you use for keeping a vacuum intact will either be too easy to collapse, or too heavy in general.

At this point we get more into structural engineering - we're not assuming one homogeneous substance. Maybe we can get some sort of very light but very strong substructure... but this is getting a little complex for me to go further on. Do we have an engineer in the audience? ;)

[xepel]

Aww, i took so long that other people got answers in before me. ;)

But that took a long time for me to calculate out!

[sareth]

It Is Awesome, though.

[meganeko_mausuu]

Those catgirls are hypnotic... especially when they seem to move in time with my music...
http://www.youtube.com/watch?v=tHbPD_bXaOA

[sareth]

Heh. Dancing catgirls...