Helium And Hydrogen

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Helium and hydrogen

Hydrogen gas and helium has a lower density than air, it means that they weigh less than air. Therefore helium and hydrogen rise, and have lift force in air. Helium has a slightly lower lift force than hydrogen. Pure hydrogen has a lift force, that can lift 1,2 kg / m³. So that’s why, by mass, we say 75-76% was hydrogen and 24-25% was helium. But each helium nucleus is around four times the mass of a hydrogen nucleus, which means that, by number of atoms, the.

A lifting gas or lighter than air gas is a gas that has a lower density than normal atmospheric gases and rises above them as a result. It is required for aerostats to create buoyancy, particularly in lighter-than-air aircraft, which include free balloons, moored balloons, and airships. Only certain lighter than air gases are suitable as lifting gases. Dry air has a density of about 1.29 g/L (gram per liter) at standard conditions for temperature and pressure (STP) and an average molecular mass of 28.97 g/mol,[1] and so lighter than air gases have a density lower than this.

Helium And Hydrogen Gas

Gases theoretically suitable for lifting[edit]

Hot air[edit]

Heated atmospheric air is frequently used in recreational ballooning. According to the Ideal gas law, an amount of gas (and also a mixture of gases such as air) expands as it is heated. As a result, a certain volume of gas has a lower density as the temperature is higher. The average temperature of air in a hot air balloon is about 212 °F (100 °C).[citation needed]


Hydrogen, being the lightest existing gas (7% the density of air), seems to be the most appropriate gas for lifting. It can be easily produced in large quantities, for example with the water-gas shift reaction, but hydrogen has several disadvantages:

  • Hydrogen is extremely flammable. Some countries have banned the use of hydrogen as a lift gas for commercial vehicles but it is allowed for recreational free ballooning in the US, UK and Germany. The Hindenburg disaster is frequently cited as an example of the safety risks posed by hydrogen. The high cost of helium (compared to hydrogen) has led researchers to re-investigate the safety issues of using hydrogen as a lift gas; with good engineering and good handling practices, the risks can be significantly reduced.[citation needed]
  • Because the hydrogen molecule is very small, it can easily diffuse through many materials such as latex, so that the balloon will deflate quickly. This is one reason that many hydrogen or helium filled balloons are constructed out of Mylar/BoPET.[citation needed]


Helium is the second lightest gas. For that reason, it is an attractive gas for lifting as well.

A major advantage is that this gas is noncombustible. But the use of helium has some disadvantages, too:

Helium And Hydrogen Fusion

  • The diffusion issue shared with Hydrogen (though, as Helium's molecular radius is smaller, it diffuses through more materials than Hydrogen).
  • Helium is expensive.
  • Although abundant in the universe, helium is very scarce on Earth. The only commercially viable reserves are a few natural gas wells, mostly in the US, that trapped it from the slow alpha decay of radioactive materials within Earth. By human standards helium is a non-renewable resource that cannot be practically manufactured from other materials. When released into the atmosphere, e.g., when a helium-filled balloon leaks or bursts, helium eventually escapes into space and is lost.

Hydrogen and helium[edit]

Hydrogen (density 0.090 g/L at STP, average molecular mass 2.016 g/mol) and helium (density 0.179 g/L at STP, average molecular mass 4.003 g/mol) are the most commonly used lift gases. Although helium is twice as heavy as (diatomic) hydrogen, they are both so much lighter than air that this difference only results in hydrogen having 8% more buoyancy than helium.

In a practical dirigible design, the difference is significant, making a 50% difference in the fuel-carrying capacity of the dirigible and hence increasing its range significantly.[2] However, hydrogen is extremely flammable and its use as a lifting gas in dirigibles has decreased since the Hindenburg disaster. Helium is safer as a lifting gas because it is inert and does not undergo combustion.

Water vapour[edit]

The gaseous state of water is lighter than air (density 0.804 g/L at STP, average molecular mass 18.015 g/mol) due to water's low molar mass when compared with typical atmospheric gases such as nitrogen gas (N2). It is non-flammable and much cheaper than helium. The concept of using steam for lifting is therefore already 200 years old. The biggest challenge has always been to make a material that can resist it. In 2003, a university team in Berlin, Germany, has successfully made a 150 °C steam lifted balloon.[3] However, such a design is generally impractical due to high boiling point and condensation.


Ammonia is sometimes used to fill weather balloons.[4] Due to its high boiling point (compared to helium and hydrogen), ammonia could potentially be refrigerated and liquefied aboard an airship to reduce lift and add ballast (and returned to a gas to add lift and reduce ballast). Ammonia gas is relatively heavy (density 0.769 g/L at STP, average molecular mass 17.03 g/mol), poisonous, an irritant, and can damage many metals and plastics.


Methane (density 0.716 g/L at STP, average molecular mass 16.04 g/mol), the main component of natural gas, is sometimes used as a lift gas when hydrogen and helium are not available.[4] It has the advantage of not leaking through balloon walls as rapidly as the smaller molecules of hydrogen and helium. Many lighter-than-air balloons are made of aluminized plastic that limits such leakage; hydrogen and helium leak rapidly through latex balloons. However, methane is highly flammable and like hydrogen is not appropriate for use in passenger-carrying airships. It is also relatively dense and a potent greenhouse gas.

Hydrogen fluoride[edit]

Hydrogen fluoride is lighter than air and could theoretically be used as a lifting gas. However, it is extremely corrosive, highly toxic, expensive, is heavier than other lifting gases, and has a high boiling point of 19.5 °C. Its use would therefore be impractical.

Coal gas[edit]

In the past, coal gas, a mixture of hydrogen, carbon monoxide and other gases, was also used in balloons. It was widely available and cheap; the down side was a higher density (reducing lift) and the high toxicity of the carbon monoxide.


Acetylene is 10% lighter than air and could be used as a lifting gas. Its extreme flammability and low lifting power make it an unattractive choice.

Hydrogen cyanide[edit]

Hydrogen cyanide, which is 7% lighter than air, is technically capable of being used as a lifting gas at temperatures above its boiling point of 25.6 °C. Its extreme toxicity, low buoyancy, and high boiling point have precluded such a use.


Neon is lighter than air (density 0.900 g/L at STP, average atomic mass 20.17 g/mol) and could lift a balloon. Like helium, it is non-flammable. However, it is rare on Earth and expensive, and is among the heavier lifting gases.


Pure nitrogen has the advantage that it is inert and abundantly available, because it is the major component of air. However, because nitrogen is only 3% lighter than air, it is not an obvious choice for a lifting gas.

The de Lana-Terzi'svacuum airship (1670)


Theoretically, an aerostatic vehicle could be made to use a vacuum or partial vacuum. As early as 1670, over a century before the first manned hot-air balloon flight,[5] the Italian monk Francesco Lana de Terzi envisioned a ship with four vacuum spheres.

In a theoretically perfect situation with weightless spheres, a 'vacuum balloon' would have 7% more net lifting force than a hydrogen-filled balloon, and 16% more net lifting force than a helium-filled one. However, because the walls of the balloon must be able to remain rigid without imploding, the balloon is impractical to construct with all known materials. Despite that, sometimes there is discussion on the topic.[6]


Another medium that in theory could be used is a plasma: Ions repelling each other could give a pressure intermediate between vacuum and hydrogen and hence that counteracts the atmospheric pressure. The energy and the containment requirements are extremely impractical, so that it may only be interesting for science fiction.


It is also possible to combine some of the above solutions. A well-known example is the Rozière balloon which combines a core of helium with an outer shell of hot air.

Hydrogen versus helium[edit]

Hydrogen and helium are the most commonly used lift gases. Although helium is twice as heavy as (diatomic) hydrogen, they are both significantly lighter than air, making this difference negligible.

The lifting power in air of hydrogen and helium can be calculated using the theory of buoyancy as follows:

Thus helium is almost twice as dense as hydrogen. However, buoyancy depends upon the difference of the densities (ρgas) − (ρair) rather than upon their ratios. Thus the difference in buoyancies is about 8%, as seen from the buoyancy equation:

FB = (ρair - ρgas) × g × V

Where FB = Buoyant force (in Newton); g = gravitational acceleration = 9.8066 m/s2 = 9.8066 N/kg; V = volume (in m3).Therefore, the amount of mass that can be lifted by hydrogen in air at sea level, equal to the density difference between hydrogen and air, is:

(1.292 - 0.090) kg/m3 = 1.202 kg/m3

and the buoyant force for one m3 of hydrogen in air at sea level is:

1 m3 × 1.202 kg/m3 × 9.8 N/kg= 11.8 N

Therefore, the amount of mass that can be lifted by helium in air at sea level is:

(1.292 - 0.178) kg/m3 = 1.114 kg/m3

and the buoyant force for one m3 of helium in air at sea level is:

1 m3 × 1.114 kg/m3 × 9.8 N/kg= 10.9 N

Thus hydrogen's additional buoyancy compared to helium is:

Helium And Hydrogen Are Found Mostly In The

11.8 / 10.9 ≈ 1.08, or approximately 8.0%

This calculation is at sea level at 0 °C. For higher altitudes, or higher temperatures, the amount of lift will decrease proportionally to the air density, but the ratio of the lifting capability of hydrogen to that of helium will remain the same. This calculation does not include the mass of the envelope need to hold the lifting gas.

High-altitude ballooning[edit]

MAXIS: a balloon that has been able to reach a height of 36 km

At higher altitudes, the air pressure is lower and therefore the pressure inside the balloon is also lower. This means that while the mass of lifting gas and mass of displaced air for a given lift are the same as at lower altitude, the volume of the balloon is much greater at higher altitudes.

A balloon that is designed to lift to extreme heights (stratosphere), must be able to expand enormously in order to displace the required amount of air. That is why such balloons seem almost empty at launch, as can be seen in the photo.

A different approach for high altitude ballooning, especially used for long duration flights is the superpressure balloon. A superpressure balloon maintains a higher pressure inside the balloon than the external (ambient) pressure.


In 2002, aerogel held the Guinness World Record for the least dense (lightest) solid.[7] Aerogel is mostly air because its structure is like that of a highly vacuous sponge. The lightness and low density is due primarily to the large proportion of air within the solid and not the silicon construction materials.[8] Taking advantage of this, SEAgel, in the same family as aerogel but made from agar, can be filled with helium gas to create a solid which floats when placed in an open top container filled with a dense gas.[9]

Hydrogen And Helium Star

In 2012, discovery of aerographite was announced, breaking the record for the least dense material at only 0.2 mg/cm3 (0.2 kg/m3).[10][11] These solids do not float in air because the hollow spaces in them become filled with air. No lighter-than-air matrix or shell containing a hard vacuum has ever been constructed.

Submerged balloons[edit]

Because of the enormous density difference between water and gases (water is about 1,000 times more dense than most gases), the lifting power of underwater gases is very strong. The type of gas used is largely inconsequential because the relative differences between gases is negligible in relation to the density of water. However, some gases can liquefy under high pressure, leading to an abrupt loss of buoyancy.

A submerged balloon that rises will expand or even explode because of the strong pressure reduction, unless gas is able to escape continuously during the ascent or the balloon is strong enough to withstand the change in pressure.

Balloons on other celestial bodies[edit]

A balloon can only have buoyancy if there is a medium that has a higher average density than the balloon itself.

  • Balloons cannot work on the Moon because it has no atmosphere.
  • Mars has a very thin atmosphere – the pressure is only ​1160 of earth atmospheric pressure – so a huge balloon would be needed even for a tiny lifting effect. Overcoming the weight of such a balloon would be difficult, but several proposals to explore Mars with balloons have been made.[12]
  • Venus has a CO2 atmosphere. Because CO2 is about 50% more dense than Earth air, ordinary Earth air could be a lifting gas on Venus. This has led to proposals for a human habitat that would float in the atmosphere of Venus at an altitude where both the pressure and the temperature are Earth-like. Because the atmosphere of Venus contains no oxygen, hydrogen is not flammable there, and could be a good lifting gas as well. In 1985, the Soviet Vega program deployed two helium balloons in Venus's atmosphere at an altitude of 54 km (34 mi).
  • Titan, Saturn's largest moon, has a dense, very cold atmosphere of mostly nitrogen that is appropriate for ballooning. A use of Aerobots on Titan was proposed. The Titan Saturn System Mission proposal included a balloon to circumnavigate Titan.

See also[edit]


  1. ^'Air - Molecular Weight'. www.engineeringtoolbox.com. Retrieved 2018-01-16.
  2. ^'AERONAUTICS: Helium vs. Hydrogen'. TIME. 1924-03-10. Archived from the original on February 9, 2011. Retrieved 2013-11-24.
  3. ^'HeiDAS UH – Ein Heissdampfaerostat mit ultra-heiss-performance'(PDF). Aeroix.de. Archived from the original(PDF) on 2011-09-03. Retrieved 2012-10-21.
  4. ^ ab'Gases - Density'. www.engineeringtoolbox.com. Retrieved 2018-01-16.
  5. ^Tom D. Crouch (2009). Lighter Than Air
  6. ^Sean A. Barton (21 October 2009). 'Stability Analysis of an Inflatable Vacuum Chamber'. Journal of Applied Mechanics. 75 (4): 041010. arXiv:physics/0610222. Bibcode:2008JAM....75d1010B. doi:10.1115/1.2912742.
  7. ^Stenger, Richard (May 9, 2002). 'NASA's 'frozen smoke' named lightest solid'. edition.cnn.com. Retrieved 2018-01-16.
  8. ^Administrator, NASA Content (2015-04-15). 'Aerogels: Thinner, Lighter, Stronger'. NASA. Retrieved 2018-01-16.
  9. ^Grommo (2008-06-20), SEAgel Aerogel lighter than air solid. Not a UFO, retrieved 2018-01-16
  10. ^'New carbon nanotube struructure aerographite is lightest material champ'. Phys.org. doi:10.1002/adma.201200491. Retrieved 2013-11-24.
  11. ^'Aerographit: Leichtestes Material der Welt entwickelt - SPIEGEL ONLINE' (in German). Spiegel.de. 2012-07-11. Retrieved 2013-11-24.
  12. ^'Exploring Mars With Balloons'. Spacedaily.com. Retrieved 2012-10-21.

External links[edit]

Retrieved from 'https://en.wikipedia.org/w/index.php?title=Lifting_gas&oldid=1019423485'

Hydrogen and helium account for nearly all the nuclear matter in today's universe. This is consistent with the standard or 'big bang' model. The process of forming the hydrogen and helium and other trace constituents is often called 'big bang nucleosynthesis'. Schramm's figures for relative abundances indicate that helium is about 25% by mass and hydrogen about 73% with all other elements constituting less than 2%. Carroll & Ostlie give 23 to 24% helium. There is a window of uncertainty, but it is clear that hydrogen and helium make up 98% plus of the ordinary matter in the universe. This high percentage of helium argues strongly for the big bang model, since other models gave very small percentages of helium. Since there is no known process which significantly changes this H/He ratio, it is taken to be the ratio which existed at the time when the deuteron became stable in the expansion of the universe. This ratio is significant as a test of cosmological models since it will be affected by the time period from the time when the temperature dropped below that necessary to produce neutrons from protons to the time when the deuteron became stable, halting the decay of the free neutrons.

Basically , the hydrogen-helium abundance helps us to model the expansion rate of the early universe. If it had been faster, there would be more neutrons and more helium. If it had been slower, more of the free neutrons would have decayed before the deuterium stability point and there would be less helium.

The modeling of the production of helium and the hydrogen-helium ratio also makes predictions about other nuclear species, particularly 7Li, 2H(deuterium) and 3He. These observed abundances simultaneously fit the big bang model within a narrow range. The shaded areas represent measurements from regions which have a very small abundance of heavy elements, so that they seem to be good samples of primordial abundances. Besides being a sensitive test of the big bang model, the abundance of helium also correlates best with three types of neutrinos, rather than two or four. The presence of another neutrino species, and thus another round of leptons would give a higher helium abundance by about a percent.

The ratio of the number of baryons per photon was one of the contributions of the discovery of the 3K background radiation. Those measurements permitted a calculation of the photon energy density in the universe and the range of estimates for baryon density gave a baryon/photon ration of about 10-9.

Data from Boesgaard, A. M. and Steigman, G., 'Big Bang nucleasynthesis: Theories and Observations', Ann. Rev. Astron. and Astrophys. 23, 319 (1985).

Illustration of hydrogen-helium abundance