Re: Driver station power
 

OK, brain-teaser for high school and college students:

The chemical reaction described above is

2H₂ + O₂ => 2H₂O

Notice there are three molecules on the left, and only two molecules on the right. So why is it an explosion? Why not an implosion?

Re: Driver station power
 

What about a simple small brushless fan to vent the hydrogen outside and allow the outside air inside? Probably no spark will exist in regular open space, unless the building is struck by lightning. So, after a while, the hydrogen would have diffused and possibly even turned into water. Also, how much H is even produced by a battery running at full capacity?

Re: Driver station power
 

What you didn't mention is that the process involves a significant amount of energy transfer.

In order to go from Hydrogen and Oxygen to H20, quite a bit of thermal energy is produced. Hydrogen and Oxygen, mixed with an ignition source like Al mentioned, would create a combustive reaction. An exothermic reaction, like this one, would be considered an explosion. :)

Do I get Ether points?:D

Re: Driver station power
 

Not quite yet...

A sealed steel tank contains a pure stoichiometric mixture of Hydrogen and Oxygen at ambient pressure and temperature. The tank is capable of sustaining very high pressure without damage or deformation. There is a spark plug protruding into the tank, as well as a high-pressure-fast-response pressure sensor.

The spark plug is ignited at t=0, and the pressure vs time is recorded. Assuming the steel tank does not burst or deform, and the pressure sensor accurately records the pressure, describe qualitatively what the pressure data looks like from t=0 to t=10 seconds.

Re: Driver station power
 

I remember this from 8th grade. Basically, there woll be a decent amount of potential energy that will be converted to heat. Basically, there is a sharp peak ad then the energy reduces down to zero. I believe that the deformation and pressure would be similar, as water as a liquid would probably have a lower pressure. Am I right?? :P

Re: Driver station power
 

My favorite answer to the question actually involves E=mc^2...

Re: Driver station power
 

There are only 2/3 as many molecules after the combustion as before, but they are *much* hotter. This increased temperature of the combustion product causes a large initial pressure spike¹, despite the reduced number of molecules.

However, even though the gas in the tank is momentarily very hot, its thermal mass is far smaller than the steel tank. The gas cools almost immediately, and since the number is molecules is less than it was before the combustion, the pressure drops below its initial value.

The gas will cool to ambient temperature very quickly. When it does, and assuming no condensation, the pressure in the tank would be 2/3 of what it was before the combustion.

However, because the gas is pure water vapor, the final pressure in the tank will not exceed the vapor pressure of water (at the temperature of the gas).

At ambient temperature (say 25C) the vapor pressure of water is only 0.48 PSI. This is much less than 2/3 of the initial pressure, so the pressure will cause some of the water vapor to quickly condense into liquid water until the remaining water vapor is just sufficient to create a pressure of 0.48 PSI.

¹which is why the gas would initially explode if not confined inside the sealed tank

Re: Driver station power
 

Isn't this equation just an approximation, not the exact calculation to less than a joule? Anyways, 1 kg of H fused together would probably cause ~9.0e16 J of work. However, as we know, most of this goes to heat, and that's why nuclear plants explode like atom bombs when you shut down their cooling system.

Re: Driver station power
 

No. The equation is an exact description of the equivalence of mass and energy.

Nuclear plants do not "explode like atom bombs". They melt down, which may or may not cause an explosion, but it is not a nuclear explosion. It could be a steam explosion, or combustion.

Re: Driver station power
 

If we have any need for batteries whatsoever outside of the robot itself, we always turn to the robot batteries themselves.

-We have our trailer rigged so we can power the internal lamps when we unload in the dark with no vehicle.

-Some charter buses don't have power, so we use the AndyMark inverter and 2 power strips on extention cords in the overhead bins to give everyone precious power during our rides to competition. Even at maximum inverter capacity, one battery lasts >6 hours.

-if we have to charge our driver station away from the plug, the robot battery/inverter combo is light enough (though inconveniently heavy) to tote around.

you already have the infrastructure to cycle through a battery every match and keep multiple on the charger. why not set one aside for other uses.
What advantage does a car battery have over the motorcycle battery you have plenty of?

Re: Driver station power
 

I agree, I was a bit sarcastic!

Re: Driver station power
 

There's much to appreciate in E = mc^2! Here's a link to a Wikipedia article that goes into more depth -- worth reading.

Re: Driver station power
 

I, myself, love e=mc^2, mostly because it defies physics and newton. Mass can be destroyed and energy can be fabricated. That leaves me to think, there are still some neutrons, protons,electrons, etc. Couldn't we use them to fabricate mass like gold?

Re: Driver station power
 

If you want to charge batteries on the go, I believe that a large lead acid would be much more beneficial. I do not think it would be wise to charge robot batteries with robot batteries

Re: Driver station power
 

Also, how did you get >6 hours of runtime on full load? The inverter is 200 watts continuous so 200/12=16 2/3 amps on full draw. At 17 amp capacity, you have roughly an hour of runtime. Also, that is under ideal efficiency. The inverter that I have at home requires 1 amp when powering nothing (except thin air).