Talk:Lighter than air

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"gasses" ought to be "gases" in several places that show no edit buttons.

Perhaps brief mention should be made of why nitrogen has "negligible lift". Air is something like 75% nitrogen, so it makes sense that the molecular weight of air would be close to 28. thefamouseccles

Math markup[edit]

This page seriously needed to use math markup instead of those crazy blue rectangles used for preformatted text. MShonle 08:40, 4 Jun 2004 (UTC)

actual lift[edit]

Shouldn't the article include how much lift a cubic metre of He gives in air under specified conditions? WHich was what I was acctually looking up. Midgley 02:21, 12 January 2006 (UTC)

Well, we have a table of molecular/atomic masses, so it should be possible to work out for Standard conditions for temperature and pressure. -- ALoan (Talk) 10:58, 12 January 2006 (UTC)
I'll add some rough numbers. Blimpguy 17:01, 13 January 2006 (UTC)


this article talks about elements as if all atoms of those elements had the same mass. This is plainly not the case as the number of neutrons can vary. Does this open up any other possibilities? Plugwash 02:30, 12 March 2006 (UTC)

Elements have more or less the same average mass because of their naturally occurring proportions, which are valid all over the earth. —Preceding unsigned comment added by (talkcontribs)
Indeed, but the article does not currently say whether we are talking about the most common natural isotope, or the most common mix of isotopes. From the molecular masses given in the table, I would assume the former rather than the latter, actually. -- ALoan (Talk) 11:39, 13 March 2006 (UTC)
I'm not saying that isotope seperation is likely to be economically feasible but its still interesting to consider ;) Plugwash 00:34, 19 March 2006 (UTC)
More specifically silane made with silicon 22 (which according to our silicon article exists) would be lighter than air and a gas at room temperature. Plugwash 00:40, 19 March 2006 (UTC)
It is kind of cute to list all the possible LTA gases, but this level of detail (worrying about which isotope) is, I think, a bit over the top. Blimpguy 01:15, 19 March 2006 (UTC)

<--Back to left to avoid falling off page. Especially since Si-22 (and Si-23 and Si-24) have a half life of a fraction of a second. In fact the light elements all tend to be highly unstable when neutron poor; out of the first 16 elements, ( H, He, Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, and S) there are only five isotopes that are both lighter than the most common form, and have a half life of more than a few minutes. These are:

  • Al-26 : half life is 700,000 years. But that 1 amu doesn't make any difference to our list;
  • Na-22 : half life of 2.6 years is still highly unstable, and 1 amu fails to make any changes to our list;
  • F-18 : half life of 2 hours is extremely unstable, and the 1 amu doesn't make any changes to our list.
  • Be-7: half life of 53 days is extremely unstable, and the 2 amu don't make any changes to our list.
  • He-3 is stable (but extremely rare and expensive), however no changes to our list.

In short, if we exclude isotopes so extremely unstable that it is not possible to accumulate macroscopic quantities, light isotopes make no difference to our list anyway. -- Securiger 04:18, 2 August 2006 (UTC)

    • BTW I would have thought He3 could be easilly produced by bombarding lithium with neutrons to produce tritium and letting it decay, is there just a lack of demand for He3 or is there something else that prevents it being produced this way? Plugwash 17:34, 2 October 2006 (UTC)
Tritium is extremely expensive, so apparently not so easy to produce.--Roentgenium111 (talk) 20:48, 13 July 2012 (UTC)

Too Informal[edit]

The latest edits have created an article that is too informal and too conversational. Extraneous and misleading information has crept into the article.Anthony717 04:36, 27 September 2006 (UTC)

Please either say what the issues are so that others can consider them and act if necessary or edit the article yourself. I see you have but is that all there is? Paul Beardsell 13:43, 28 September 2006 (UTC)

Overwhelmingly comprehensive[edit]

Detailing a methodology for determining all possible lighter than air gases where we consider all isotopes of all atoms in all possible combinations forming molecules of dubious stability is ridiculous! For lessons in chemistry the reader will happily go elsewhere in Wikipedia. To be consistent we would have to also discuss in detail the properties of all possible balloon fabrics and their respective porosities and mean time to failure owing to UV induced decay. And all the physical properties of all 267 alloys of aluminium for the framwork and the costs of mining titanium in every South American country. Let's not forget to list the harshness of the various basket weaving materials on the bums of aspirant members of the Mile High Club (Ballooning Division). No! This peripheral detail goes elsewhere in Wikipedia and we then link to it. Not here! Paul Beardsell 22:18, 28 September 2006 (UTC)

on a large scale[edit]

"but no such device has ever been constructed on a large scale"

blimpguy, does this mean that there have been small scale models of this method that actually work? Plugwash 01:54, 30 September 2006 (UTC)

Will never work: I have edited article demonstrating why not even worth attempting. Paul Beardsell 08:20, 30 September 2006 (UTC)

revert revert[edit]

A recent edit has made stylistic and grammatical changes mostly to the good but material has also been removed because it is "repetitious". I'm not sure I agree but, if I did, sometimes a point can be made twice in an article for good reason. Certainly information has been lost so the deleted material could not have all been repetitive. I reverted to a version with more information albeit with stylistic flaws. It would have helped if I had explained here beforehand what I was doing. My revert has been reverted. Paul Beardsell 23:51, 14 November 2006 (UTC)

I have sent messages to Anthony717 and Psb777 asking them to come here and work out a consensus.Jonathan888 (talk) 00:06, 15 November 2006 (UTC)
Let the record show: I was here already. Paul Beardsell 00:32, 15 November 2006 (UTC)
Sorry, I was in a hurry and didn't realize Paul Beardsell was Psb777, it's all good, let's work it out, removing second copy of section revert revert that is same as first copy to reduce confusion.Jonathan888 (talk) 01:06, 15 November 2006 (UTC)

Editing for brevity and clarity[edit]

I edited article one year ago and again yesterday. To defend my side in a possible edit conflict, see the repetitive and overwrought text that needed help:

  • 1. "Low pressure buoyancy" ... "no such device has ever been constructed" ... "requirements are impossible to meet now and are unlikely ever to be met" ... "weight of the structure to prevent the collapse of the vacuum cannot be compensated for" ... "Furthermore, a perfect vacuum is impossible" ... "will almost certainly never be applied to ballooning" [It's very repetitive, and the word "furthermore" should be avoided.]
  • 2. "Unfortunately, silicon does not become a gas" ... "spare 1.8 units gives room for just one hydrogen atom" ... "Next would be magnesium" ... "Unfortunately, neither magnesium hydride nor magnesium are gases at reasonable temperatures" ... "isotopes are not considered in detail here but all are either too close to the common isotope to make a difference to the table or are radioactive with short half lives" ["Unfortunately", "gives room for", "next would be" and "reasonable" are unscientific. There's too much information here: "the lightest metals are not gases, except at very high temperatures" and "isotopes are not considered here" would suffice.]

Anthony717 00:32, 15 November 2006 (UTC) Note: Sorry for blanking others' content temporarily ... had browser trouble.Anthony717 00:32, 15 November 2006 (UTC)

OK: (2) first: I do not like the way the information about the metal gases and isotopes is presented. But I disagree that the information should be culled. Where else would this info be found? Better poorly presented information than information loss. Paul Beardsell 00:41, 15 November 2006 (UTC)
As for (1): Examples only: You have removed the reason why vacuums suck (pun!) when it comes to providing buoyancy. I disagree that "furthermore" is bad. Paul Beardsell 00:41, 15 November 2006 (UTC)
I am NOT saying all your changes are bad - very far from it - just that there are enough bad decisions sprinkled in with the good edits that reverting to a prior version and then you having another more careful attempt would be good for the article. Paul Beardsell 00:41, 15 November 2006 (UTC)


Yes, in truth it is density, but.. What is density if not weight/volume? So whatt calcutlation are we gona make to see if it 'flies'? Checking the same volume of it and air, who is LIGHTER will fly... So it's not really wrong to say lighter than air... If it was lighter than a book, would be wrong, because books have fixed volume... Air is not quantifiable as 'one air', two airs' so it must be quantified in volume or weight... It's only pseudo-intelligence to say: 'lighter-than-air' is wrong, the right is 'less-dense-than-air'... and if one is talking about 'less-dense-than-air', shouldn't one also mention hot air? as in hot air balloons? lift formulas for hot, less dense air should also be added, as I know many students in physics classes search for things of the sort. 21:35, 20 December 2006 (UTC)

Merge tag[edit]

I'm removing the merge tag, as it was inserted by an IP, had no discussion started, and no one's expressed any interest in it (for the record, I oppose the merge). Akradecki 18:25, 23 April 2007 (UTC)

The article should be merged with aerostats and molecular mass. A disambiguation page could link to the articles. Inwind (talk) 14:45, 21 August 2008 (UTC)
I have re-removed the merge tags, since, again, there has been no discussion since the tags were placed in August. At any rate, there seems to be enough information here to merit this article remaining independent of aerostat and molecular mass. Stebbins (talk) 05:06, 15 January 2009 (UTC)
I think that all articles are noteworthy in their own right. lighter than air relates to a number of subjects which should be clearly distinguished. Everything related to substances lighter than air belong to this articles. Where it refers to lighter than air craft the content should be included in aerostats. The gases which are used in aerostats should remain in lifting gases. Inwind (talk) 09:52, 21 January 2009 (UTC)


The ideal gas laws (Avogadro's law, Boyle's law, and Charles's law) are used to approximate gas density.

These three laws show that a gas with low density can be achieved by:

  • lowering the pressure (Boyle's law);
  • raising the temperature (Charles's law); or
  • reducing the molecular mass (Avogadro's law).

(number-crunching calculation desired....15 psi is unobtanium? Mass of container increases as surface area (square of dimensions). Displaced atmosphere, and hence lift, is proportional to the enclosed volume (cube of dimensions). Supporting its own mass is perhaps the shell's greater challenge). Also consider that the shell would not have to oppose 15 psi at ground level, only the differential needed for displace its weight of surrounding atmosphere. Greater pressure differential is only required for additional gain in altitude, and ambient atmospheric pressure decreases rapidly with altitude.

I think these notes need to be worked on before inclusion in the article. PV=nRT is a way better method to calculate gas density anyway.
density (ρ)=m/V; m=n*M (M is molar mass); ρ = PM/RT
Ewen 14:25, 7 November 2007 (UTC)

On the Vacuum Balloon[edit]

On the vacuum balloon part of the page the problem is surely one of scale. As we scale up the laws of physics effectively change* meaning that a vacuum balloon might be possible if it was built of a sufficiently large size. A sphere on the scale of several km in diameter built of a nano-molecular material like carbon-6 could possibly be self supporting - though I wouldn't want to be anywhere near it.

  • * Volume and mass are tied to a cube rule, while surface area is a square rule so-

Atm pressure ~= 10,000 kg / m^2, lift differential 1.7 kg / m^3,
Sphere - surface area = (SA = 4 x pi x r^2) lift volume = (V = 4/3 x pi x r^3)
At a radius of 1 km a sphere has a surface area of 12.5 M m^2 and a volume of 4.2 B m^3, so it has a lifting force of 7 M tons. We can see this is possibly getting somewhere near as it leaves a surface mass of 570 kg per square meter to achieve neutral buoyancy (Assuming an ultra rigid ultra strong carbon material). If you think these material constraints look insane I suggest you look at space tethers which must be self supporting and at least 46,000 km long (actually 10,000 or so longer!)
Vacuum balloons are very interesting because they have bizarre properties, built light enough and big enough vacuum balloons could almost reach space and could certainly serve to build a permanent high altitude platform. Looking at and researching future ways of reaching space these balloons looked almost sensible for a short while until I considered the effects of structural failure.
Lucien86 (talk) 02:08, 15 May 2008 (UTC)

I have tagged the vacuum balloon section with {{original research}} giving the following reason. Reliable sources needed for: "is perhaps", "could be used", "would be able to". -84user (talk) 16:20, 15 July 2010 (UTC)

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