Science Buddies: "Ask an Expert"

I have managed to produce hydrogen by electrolysis. My question is, is it possible to get a light-wieght object to propel or float due to the emission of hydrogen. What i have done is take hydrogen and get it to fill a pump that is located at the base of my hovercraft. i am not sure whether this is able to make it propel itself or the fact i am approaching this completely wrong. Thank you for taking the time to read this so far.

Yacub -- first things first. NEVER store hydrogen -- it is a very-easy-to-detonate explosive gas!

http://www.youtube.com/watch?v=lFptgQ8GA_U

Next, well now that I think more, there really is no next. On to some other good, but I hope less hazardous idea...

Thank you for the safety concerns, but do you mind taking in the actual questions and answering them?

No. I can't promote unsafe activities. Do it in a lab with supervision, if at all.

They project itself isnt a life size object, if thats what you were thinking. the hovercraft itself is 6 by 6 inches. To be honest I've seen the video and know the effects of un-safe use. The actual exposure of hydrogen shouldnt be more then 15 secs and below 10ml.

Hello yacub,

John Dreher is, of course, right about the hazards of hydrogen. It burns very hot, the flame is invisible in a normally lit room, and it is easy to ignite. On the other hand, I know that the web has hundreds of sites that tell you how to make hydrogen, so you don't need Science Buddies for that. I'll limit myself to discussing your questions about the hovercraft.

If you want to use the low density of hydrogen gas to lift the craft, that would be a blimp. The gas would need to be under just atmospheric pressure to be light. If you pumped it into a container at higher pressure, the gas would become denser, and the weight of the container would overcome the buoyant effect of the gas.

If you want to propel the craft by expelling the gas under pressure (like a rocket), hydrogen would be a very poor choice because it is so light. The propulsion force would be proportional to the density of the gas. Of course, you could burn the gas in a jet engine. At that idea, I join John Dreher in his safety concerns.

Good luck, WW

Hi,
I appreciate you taking the time to read this. But I have a few questions. Orginally, I wanted to propell the craft mainly using hydrogen but you said that it is much too light. So I've changed my idea to filling it in a balloon that is attached to the craft.
My question is, would that work and if so, could I tweak it and make it better. Seriously, any feedback is absolutley welcomed.

yacub,

In order to answer any question about using hydrogen to "propel" the craft is unanswerable without knowing how you would use the hydrogen. Just blow it out a pipe? Burn it in an engine? Something else? By "propel" do you mean lift it and push it horizontally or just push it horizontally? Please provide details.

WW

WW,
Thank you once again your time. I understand what you are coming from. My idea was to get to propel upwards off the floor. And Yes, i was to merely blow it out of a tube.

yacub,

yacub,

Okay, now I can answer. Plain air would be better than hydrogen if you are simply going to blow it out. The reason it's better is that air is denser than hydrogen.

The density of air at normal atmospheric pressure and 20 deg. C. is 1.2041 kg/cu m.

The density of hydrogen under the same pressure and temperature is 0.0899 kg/cu. m.

If you blow either hydrogen or air at the same pressure and speed, the air will give roughly 13 times as much force because it's that much denser.

You will need to blow a lot of either gas to lift even a model hovercraft. That's why hovercrafts have such big fans in them.

WW

ww,
Thank you for the comment. Another question, to lift something as light as a balloon approximately how much hydrogen would I need in comparison to plain air.
Yacub