Blimp lighter than hydrogen....?

[why06]

I was wondering the lightesest gas we have is hydrogen, but what if we simply created a vacum in the balloon wouldn't it float up near the exosphere. <font color="yellow"></font> <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>

 

[annodomini2]

If there was a vacuum, the pressure of the air outside would crush the balloon! <img src="/images/icons/rolleyes.gif" /> <div class="Discussion_UserSignature"> </div>

 

[tomnackid]

That idea was proposed as far back as the 14th century. One would be inventor designed an airship held up by four copper spheres from which all of the air was removed. But as the previous post pointed out if you remove the air the spheres will collapse due to outside atmospheric pressure. If you make the spheres thick and strong enough to resist the external pressure they will be too heavy to fly even though they will be lighter with the air removed. <br /><br />I suppose one could speculate on a "vacuum blimp" made from an airtight membrane evacuated and supported against external pressure by super-conducting wires embedded in the membrane carrying a powerful electrostatic or magnetic field. Hmmmm, sounds like something out of a 1930s Sci Fi magazine!

 

[yevaud]

Although this is quite dangerous to do, it has been successfully tried before: heat the Hydrogen. You gain extra lift that way. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[mlorrey]

yes, you'd need to develop some sort of super-buckyball: structurally strong enough to withstand an internal vacuum and external sea level pressure, large enough for the vacuum space to more than counterbalance the atomic mass of the carbon structure of the molecule.<br /><br />I believe I calculated once that a C-360 buckyball might be large and light enough to do slightly better than hydrogen. It was 6 or more years ago, so I don't remember the details.

 

[scottb50]

That's why you use Helium. A rigid center section with upper and lower gas bags that collapse to form a high-speed transport or expand to allow low speed operation and landing in confined areas. Use bleed-air heat exchangers to heat the Helium for lift and cooling turbines to cool it for storage. <div class="Discussion_UserSignature"> </div>

 

[yevaud]

Yep, and no chance of explosions either.<br /><br />There's also a hybrid lift system that I read about, using helium (which provide just neutral bouyancy) and several heated air chambers. You always have at least a tiny bit of lift, and then can control your ascent/descent with finess using the hot air. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[mlorrey]

Helium is four times heavier than Hydrogen, which means any given load requires more than twice the diamater envelope to be lifted with Helium than with Hydrogen (since the larger envelope is also going to be heavier, you need lift gas to lift that as well).<br /><br />Heating it up will only gain you so much, maybe half the diference.

 

[vogon13]

An atom of helium is not 4 times heavier than a molecule of H2.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[chriscdc]

You could use a powered system, where you use a light weight supporting structure with charged particles held in position. The charges push against each other providing support. Of course you would need a power source to replace the charge as it leaks away. <br /><br />You could try a lattice of metallic nanotubes. You would need someway of holding them apart as once they come into contact with each other, they will require lots of energy to separate (Van der Waals forces). If you can charge the system without it collapsing, you should be able to create a strong structure. <br />It would be like a colloidal system in that the particles are held apart by charge.<br /><br />You would need a way of keeping the charge localised, perhaps having the tubes connecting to a semiconducting material on which you could control the potential.

 

[scottb50]

Helium provides 93% of the lift provided by the same volume of Hydrogen. <div class="Discussion_UserSignature"> </div>

 

[why06]

I heard that a charge could becarried threw a pencil stripe... Is it possible that we could use nano cars to lay down a thin layer of grabhite only in speciffied location? I liked someone's idea about the bucky balls...<br /><br />....Maybe by combining both of these we can form a strong and light hybrid matterial and reduce on energy and weight.<font color="yellow"></font> <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>

 

[scottb50]

Sorry here's a good link:<br /><br />http://www.du.edu/~jcalvert/phys/helium.htm <div class="Discussion_UserSignature"> </div>

 

[why06]

That's true...<br />Hydrogen provides more lift, but is dangerous, a vacum would not carry any of these let downs.<font color="yellow"></font> <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>

 

[mlorrey]

You are right, it is an atom of Helium is twice as heavy as a molecule of H2. What, however, is the volumetric density? Hydrogen gas is .000089 g/ml, while Helium is .0001786 g/ml. This is at 0 deg C. Hydrogen slightly less than half as dense. However, various sources I've found claim that Helium provides over 95% of the lifting capability of Hydrogen, but do not explain why, given the significant density difference. <br /><br />Ah, I see, it is because the ratio of the displaced air to Hydrogen masses vs the same for Helium vs the displaced air is so close that there is less than 5% difference between the two. If this is indeed the case, then there really isn't much advantage to going with vacuum vs hydrogen, one would think.<br /><br />However, the original poster asked, I believe about improving performance at high altitudes, where the atmospheric pressure is much lower. The obvious answer is that since we are dealing with displacement ratios, it really doesn't matter, since ratios stay the same irrespective of the values they derive from. So long as the pressure inside the balloon remains the same as the outside, the density ratio is what does the lifting.<br /><br />However, this ignores one important factor: the makeup of the atmosphere changes with altitude. Firstly, moisture content of the atmosphere drops with altitude, which makes the air less dense. Ozone content goes up, which should make the air more dense, but it makes up such a smaller proportion than water that it doesn't make up the difference much. It isn't until we reach near the official boundaries of space that the atmosphere starts to gain significant proportions of hydrogen. It is at this point that balloon ships to orbit run into problems, as the gas inside has the same density as that outside, and no lift effect results (or, if helium is being used, you get negative lift and are stuck to strictly high density layers.) While the lower layers of the atmosphere are pretty well mixed (these are call

 

[propforce]

<font color="yellow">P1V1/T1 = P2V2/T2 </font><br /><br />Genius... just genius <img src="/images/icons/laugh.gif" /><br /><br />Have you thought about patent this idea? <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow">Hydrogen provides more lift, but is dangerous, ....</font><br /><br />A HOT hydrogen is only dangerous in the presence of spark and oxygen <img src="/images/icons/tongue.gif" /> <div class="Discussion_UserSignature"> </div>

 

[vogon13]

The Hindenberg (and other airships) was designed to work with either H or He.<br /><br />Additionally, IIRC, Hindenberg had another gas on board too. Something they called 'blaugas' and could be burned in the engines. Seems like it was a mixture of H and/or CH4 and/or CO.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[propforce]

I watched the documentary on Hindenberg on PBS as to why it burned.<br /><br />It turned out that the paint used on the blimp was very flammable and it was the paint that caused burning and not the hydrogen. <div class="Discussion_UserSignature"> </div>

 

[mikeemmert]

How about a steam balloon? Seriously! Steam is substantially less dense than air at the same temperature, and of course, hot air balloons work.

 

[nexium]

An extremely light envelope which can tolerate 1 milibarr over pressure or 5 millibarr under outside pressure can use hydrogen to reach the altitude where the pressure is about 10 millibarr. By pumping out some of the hydrogen, the balloon can rise higher, perhaps to the altitude of 2 millibar when the inside pressure is 1 millibar. that would give a 5 to 1 safety factor, which is marginal considering high speed ions will be hitting the envelope. The vacuum pump to get a better vacuum in a few days (than one mlilibarr) is likely too heavy. Sorry I don't know the altitude for two milibarrs. Neil

 

[scottb50]

It's a lot simpler to heat Helium, like the Rozier balloon. It would also be possible to cool it during high speed cruise to allow a more streamlined vehicle. You would heat the Helium, using bleed-air, making the vehicle light enough for the engines to lift it vertically and accererate it to a point aerodynamic lift starts to takeover. Pumps pull the Helium from the balloons and turbines cool it for storage in moderate pressure containers. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

another unobtainium.<br /><br />There are distinct physical limits that are possible with balloons. One of the problems is the lift gas, being of very small atoms or molecules, leak out through nanoscopic holes in the fabric, right between the molecules of the fabric material. While Helium is 65% more retainable than Hydrorgen, it is still a significant problem. The thinner your envelope material, the easier it is to leak through the material, so a higher leak rate results, thus a need to carry reserve lift gas, which counterbalances the weight savings of a lighter thinner envelope.

 

[scottb50]

Go into any grocery or card store and you can get a helium balloon. They stay up for quite a long time. I don't think the leakage would be an obstacle. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

Getting a balloon into orbit with a big ionic breeze machine is going to take months, not minutes or hours. Not to mention that the microwave beam from the ground hitting it are going to compromise the integrity of the envelope material.