Comment

Comment by Less Prone on January 22, 2017 at 1:09pm

I'm sorry if you felt my comment was personal, that was not my intention at all. I get your point about expressing your opinion in the introduction. I found this site where you can make the above calculation in Imperial units.
http://www.engineersedge.com/calculators/pipe_bust_calc.htm

Inserting the numbers of the first calculation in Imperial units gives this

Pipe Working Pressure Calculation

Variable Description Units Input

Outside Diameter (OD) = 2.360 inches = 60mm

Wall Thickness (T) = 0.004 inches = 0.1mm

Allowable Stress (S) = 1450psi = 10Mpa

Safety Factor (SF) = 2.00

Results

2.458psi Working Pressure 0.0169MPa = 0.169atm (safety factor of 2)

4.915psi Bursting Pressure = 0.338atm

I have used the inside diameter in my calculation because that is normally used when the formula is proved in physics. That explains a slight difference in the results. Outside diameter is more of an engineering point of view, and more practical to measure. I guess this proves it is correct.

Comment by Anti Everything on January 22, 2017 at 11:20am

The guy that might take your comment personally is the guy that made the video. As for me - I believe nothing, am loyal to me and people near me (I have little or know influence over people outside my community that I cannot see and touch). I have been lied to and manipulated from birth, and I know it. Aside from getting all personal your comment was exactly what I expect when I post a thing. It was intelligent, thoughtful and thorough. You certainly give me something (else) to think about.

I cannot prove out your math so I have to 'assume' you are correct, or...?

'Deep Space' has the idea here - talk shit and mock all of it, get serious if necessary, and only for a moment.

As for muddying the water with my opinion on things I post - I choose not to do that as a habit. How do we form our "natural conclusions", and why would we need an 'auto-pilot' for important thinking?I would rather REACH a conclusion then 'assume' one.

Maybe one should not assume on the outset that because one posts something they buy it hook line and sinker. Many articles and videos posted I surely don't believe the people posting them believe all of any of it,... At least I hope I'm correct in my guess. A great deal of the 'stuff' posted on this site is no different then the stuff posted on many,many,many other sites. Gossip, half truths, speculations, ideologies that agree with some sort of personal bias, whether beneficial or harmful. The rare postings are the 'from the heart' or solution oriented, at least those are the hardest to see right off because they don't hit the 'TOP TEN LIST' often. Look at that list right now! Number 10 is the only thing worth looking at (imo), and this article I posted is AT # 3! Just by commenting I 'trolled' my way to the list. Hardly seems honest to me.

Anyway, I appreciate many of the things you post and the fact you reply to comments. These things help make some sort of relationship between strangers.

Comment by Less Prone on January 22, 2017 at 9:37am

AE, You have every right to publish that video and I did not prohibit you in any way. A natural conclusion of you posting it, is that you support what it says. That's why I made my comments. How are we going to exchange different ideas if we are not supposed to criticize what we see wrong. You can criticize my postings also. Only personal attacks are off limits. You could have done well if you had included your ideas of the video when you posted it. Don't take a critique of your posting personally, I appreciate your input.

Comment by Anti Everything on January 22, 2017 at 8:33am

How could I be serious? I didn't make the video. I simply found parts of it interesting. Should I fall in line to some rules of this web site? Surely I must not know the rule of posting or I would never post inappropriate material that offends people, no no can't have that. All the same I appreciate the math on pressure/vacuum.

Comment by Less Prone on January 22, 2017 at 7:43am

You can't be serious. The space is filled with water? They are talking about vacuum as if it were something extraordinary while it in fact is a physical state of zero pressure. Air pressure at sea level is one atmosphere that roughly equals 1 bar, 100kPa, 15psi or ten meters of water column (see the link for the exact figures). Pressure holding capacity of an internally pressurized vessel (cylinder,  pipe, sphere, or other) is the difference of its internal pressure compared to the external pressure, where the internal pressure is higher than the external pressure. If the internal pressure is one atmosphere and the external pressure is vacuum, the pressure difference is one atmosphere.

The following equation, pd = 2sδ, is used to calculate piping, where;

p = pressure difference (internal pressure > external pressure)

d = internal diameter of the pipe

s = thickness of the pipe wall

δ = yield strenght of the pipe wall material

Let's consider sending a Coke can into space. Now how much pressure can we hold inside the can in an absolute vacuum?

According to the equation above we have

p = 2sδ/d

Can diameter d = 60mm

Wall thickness s = 0.1mm

Pure aluminum yield strength = 10Mpa (10N/mm2)

p = (2 x 0.1mm x 10N/mm2) / 60mm = 0.033Mpa = 33kPa = 0.33atm, the can would burst with one atmospheric pressure inside it.

Now yield strength of pure Aluminum is a fraction of the strength of high strength Aluminum alloys ranging from 200 MPa to 600 MPa

Therefore using the best available alloy, we repeat the above calculation and get the following

p = (2 x 0.1mm x 600N/mm2) / 60mm = 2MPa = 2000kPa = 20atm, the can will hold one atmosphere with a safety factor of twenty!

Now if we scale up the Coke can to a space vessel of 4m (13 feet) in diameter we'll have to increase the wall thickness also by multiplying it with a factor 4000mm/60mm = 66 to maintain that same safety factor of 20. That means 66 times 0.1mm = 6.6mm. If we reduce the safety factor  to 5 we are still very much on the safe side and the required wall thickness would be 1.7mm. A 0.7 mm wall would still work with a safety factor of two.

So much of the vacuum mystery. Any space suits or vessels have to be airtight, of course.