will it take off?

[turnkey4099]

Maybe they just left the parking brake on.

But given a power plant with enough thrust to overcome the drag it would still take off with thebrakes locked.

Harry K

 

[Andre']

The greatest effect on the candle flame is not the oxygen concentration difference between Earth and the shuttle but the microgravity which does not support convection. If there were no ventilation fans running and everyone stayed still untill the air motion ceased then a candle flame might self extinguish by depleting the oxygen adjacent to the flame.

If the crew stayed still with no fans going they would also deplete the O2 in the vicinity of their noses and so would also self extinguish.

The question then becomes which lasts longer?

 

[patrick_g]

If the crew stayed still with no fans going they would also deplete the O2 in the vicinity of their noses and so would also self extinguish.

The question then becomes which lasts longer?

Uh, I think the crew, like us on Earth, inhale and exhale. When exhaling the stale air would be propelled away from the breathing person and mixed with the ambient air. Although inhalation currents are diffuse and more localized than exhalation currents the only way to get static air in the vicinity of the astronaut's noses would be if they held their breath which would result in passing out and having their autonomic system start them breathing again.

If there is no fan assisted air circulation there are bigger problems than how well the air is mixed by exhaling. It takes circulation through the atmosphere controlling system to scrub the CO2 out of the air supply and to distribute the replenishment O2.

Pat

 

[MossRoad]

We work on the assumption that all the survivors will age and pass on.

So the bottom line is... there are no survivors. Ever.

 

[MossRoad]

I tried to eat 10 soda crackers in one minute tonight. It cannot be done, here on earth, or on the space shuttle.

 

[Egon]

That's right Moss.

You need smaller crackers.

 

[TomOfTarsus]

The greatest effect on the candle flame is not the oxygen concentration difference between Earth and the shuttle but the microgravity which does not support convection. If there were no ventilation fans running and everyone stayed still untill the air motion ceased then a candle flame might self extinguish by depleting the oxygen adjacent to the flame.

Since the air is not static, due to crew motion and ventilation systems, the candle would probably burn (some) but erratically without the nice flame shape we are so accustomed to seeing. As previously correctly mentioned the capillarity of the wax in the wick will supply fuel to the end of the wick. Depending on several factors, including the melting point of the candle, in the absence of a molten pool of wax (held in place on Earth by gravity) the candle flame will NOT be fed at so nearly a constant rate as if it were on Earth.

Pat

Pat,

You were correct about the microgravity & convection, which completely escaped me. I'm wondering if some sort of pattern would be set up anyway based on gas expansion and mass flow stuff, but like you said, without gravity it's hard to say what would happen.

But I think you missed on the molten pool of wax, which would likely stay where it belongs simply by mutual attraction and surface tension. I'd thought of that aspect but didn't say anything in my post.

Great brain exercise, and neat how we can "enlighten" one another.

We need more smilies, like one throwing up after a bad pun!

Later,

Tom

 

[daTeacha]

Which brings us to the question of what happens if one of shuttle or space station crew should happen to suddenly become sick to his/her stomach while sleeping on board the orbiting station, literally waking in the midst of puking their guts out, followed by an episode of the dry heaves. Whither goest the ejecta, and whither goest the astronaut if overcome with retching while trying to get to the head in a weightless evironment?

Does the action of retching act to propel them about the cabin or not since they are more or less freefloating across the cabin when it starts?

BTW, for those somehow offended or upset by the question about reverse peristalsis, I'm eating lunch as I write this.

 

[patrick_g]

But I think you missed on the molten pool of wax, which would likely stay where it belongs simply by mutual attraction and surface tension. I'd thought of that aspect but didn't say anything in my post.

Later,

Tom

Without gravity the molten wax will probably be pulled into a globular shape by surface tension which will expose its bottom surface (assuming the candle stick to "define" up and down) to cooling air instead of insulating wax. Exactly what effect this more available pool of fuel with a cooler bottom would have on the flame (if there is one since a flame is a shape generated by the effect of gravity) is not so simply inferred.

Gas (CO2, H2O, unburned and partially burned fractions of wax, and such) expanding into 4 pi steradians (minus the solid angle subtended by the candle) would not have any mechanism for drawing in more air to support combustion. Without gravity, no convection.

Say you ignite the end of the candle wick with a laser to avoid disturbing the air any more than absolutely necessary. The wax and (whatever material is in the wick) is heated above the flame point for the wax and it starts to have an exothermic reaction between the wax and oxygen in the air in contact with the wick. The products of combustion slowly move radially outward away from the wick due to expansion. The only thing working to get more air in contact with fuel (assuming no drafts when the candle experiment started) is Brownian motion which is not sufficient to keep the fire hot enough to keep melting fuel for capillary action to work and the fire goes quietly goes out from lack of oxygen without the typical little smoke whisp floating up wistfully since that is not possible in micro gravity.

There may be a few minor variations but I think I described pretty much what would be observed. If the candle was kept moving then it might stay lit.

Pat

 

[TomOfTarsus]

You sound like a CFD guy! It's a good analysis and I see what you mean, but I wonder if the "affinity" (for lack of a better term) of the wax pool for the candlestick would prevent it from going completely globular. Not that said affinity would help the combustion to continue (it would, of course, if the flame could continue).

It's amazing how much we take gravity for granted. But in an effort to wildly flog the deceased equine, I'm wondering if there would be any other transport phenomena set up just from said reaction that would not be gravity dependant. It's a stretch, I'll admit. But f'rinstance, since the reaction cannot proceed in a purely spherical manner, would a thrust be set up, and even this slight movement allow the flame to get more O2?

Ok, I'll quit. I should be doing other things anyway.

Good chatting with you.

Tom