FACTOID # 29: 73.3% of America's gross operating surplus in motion picture and sound recording industries comes from California.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
RELATED ARTICLES
People who viewed "Lighter than air" also viewed:
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Lighter than air

Lighter than air gases are buoyant in air because they have a density that is less than the density of air. Lighter than air gases are used to fill balloons, airships, and aerostats. (Heavier than air aircraft include aeroplanes and helicopters.) In physics, buoyancy is an upward force on an object immersed in a fluid (i. ... Look up air in Wiktionary, the free dictionary. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... Balloons are a type of lighter than air aircraft that remain aloft due to their buoyancy. ... USS Akron (ZRS-4) in flight, 2 November 1931 An airship is a buoyant aircraft that can be steered and propelled through the air. ... Uncrewed aerostats can carry instruments and sensors for long durations that are impractical for humans and other aircraft. ... A Japan Airlines Boeing 747-400. ... This article refers to the tool of travel. ... The Bell 206 of Canadian Helicopters Robinson Helicopter Company (USA) R44, a four seat development of the R22 A helicopter is an aircraft which is lifted and propelled by one or more horizontal rotors (propellers). ...

Contents


Hot air

The density of a gas can be reduced by raising its temperature. Heated air is widely used as a lifting gas in hot-air balloons. (The gas in a hot-air balloon is not only heated air, but also includes the products of combustion from the balloon's burner.) Hot air balloons are the oldest successful human flight technology, dating back to the Montgolfier brothers invention in Annonay, France in 1783. ... This article is about the chemical process. ...


Hot air balloons have the advantage of straightforward lift control. To increase lift, more heat is applied. (Sometimes, to avoid collisions, sandbags are emptied to reduce ballast and gain lift rapidly.) To decrease lift slowly, the hot air is allowed to cool. To decrease lift quickly, hot air is released (vented). However, unlike balloons using low molecular mass gases (see below), hot air balloons require nearly continuous burning of fuel in order to remain aloft. (See Hot air balloon.) Hot air balloons are the oldest successful human flight technology, dating back to the Montgolfier brothers invention in Annonay, France in 1783. ...


Low molecular mass gases

Since the average molecular mass of air is 28.8, any gas with a lower molecular mass will be lighter than air (at the same temperature and pressure). A balloon containing lighter than air gas will expand as it rises. Weather balloons can be made with strong "envelopes" (buoyant containers) so that they maintain maximum height at maximum volume (instead of exploding). The molecular mass (abbreviated MM) of a substance, called molecular weight and abbreviated as MW, is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ... Rawinsonde weather balloon just after launch. ...


Determination of lighter than air gases is straightforward. These gases must have an atomic or molecular mass less than 28.8 and exist as a gas at room temperature. (This temperature requirement is based on our definition of a lighter than air gas; other definitions are possible.) Room temperature, in laboratory reports, is taken to be roughly 21–23 degrees Celsius (69-73 degrees Fahrenheit), or 294–296 kelvins. ...


The following elements with atomic masses below 28.8 have high boiling points: silicon, aluminum, magnesium, sodium, carbon, boron, beryllium and lithium. The hydrides, fluorides and oxides of aluminum, magnesium, sodium, beryllium and lithium are solids at room temperature and either decompose before boiling or have high boiling points. (See Ionic compound.) General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance dark gray, bluish tinge Atomic mass 28. ... Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Atomic mass 24. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... General Name, Symbol, Number boron, B, 5 Chemical series metalloids Group, Period, Block 13, 2, p Appearance black/brown Atomic mass 10. ... General Name, Symbol, Number beryllium, Be, 4 Chemical series alkaline earth metals Group, Period, Block 2, 2, s Appearance white-gray metallic Atomic mass 9. ... General Name, Symbol, Number lithium, Li, 3 Chemical series alkali metals Group, Period, Block 1, 2, s Appearance silvery white/gray Atomic mass 6. ... In chemistry, an ionic compound is a chemical compound in which ions are held together in a lattice structure by ionic bonds. ...


Water is a special case. Although water is not a gas at room temperature, steam has been used as a lighter than air gas. See discussion below. A girl in a swimming pool full of water Water (from the Old English waeter; c. ... In physical chemistry and in engineering, steam refers to vaporized water. ...

Lighter than air gases
Compound Formula Mass Comments
Nitrogen N2 28 Majority component of air (~78%)
Carbon monoxide CO 28 Toxic, flammable
Ethylene C2H4 28 Flammable, reactive
Diborane B2H6 27.6 Spontaneously flammable in air
Hydrogen cyanide HCN 27 Very toxic, flammable, water soluble
Acetylene C2H2 26 Very flammable, reactive
Methyllithium LiCH3 21.9 Very flammable, very reactive, explodes on contact with moisture
Neon Ne 20.2 Noble gas, similar price to helium with much less lift
Hydrogen fluoride HF 20 Very toxic, very corrosive, water soluble
Ammonia NH3 17 Toxic (at higher concentrations), slightly flammable, water soluble, easy to liquify
Methane CH4 16 Flammable, inexpensive, widely available
Helium He 4 Noble gas, expensive, very safe, small atomic size makes it prone to leakage
Hydrogen H2 2 Very flammable, inexpensive, prone to leakage

Many of these gases are not practical for use in balloons. The following combine poor lift with objectionable properties: carbon monoxide, hydrogen cyanide, hydrogen fluoride, methyllithium, diborane, ethylene and acetylene. Nitrogen has negligible lift. Neon is harmless and offers a modest degree of lift; however it costs roughly the same as helium, another noble gas with far superior lift. The four remaining gases (ammonia, methane, helium, and hydrogen) have been used as balloon gases. General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... Look up air in Wiktionary, the free dictionary. ... Carbon monoxide, chemical formula CO, is a colorless, odorless, tasteless, flammable and highly toxic gas. ... Toxic redirects here, but this is also the name of a song by Britney Spears; see Toxic (song) Look up toxic and toxicity in Wiktionary, the free dictionary. ... Flammable or Flammability refers to the ease at which a substance will ignite, causing fire or combustion. ... R-phrases R12, R67 S-phrases S2, S9, S16, S33, S46 Flash point Flammable gas Explosive limits 2. ... Diborane is a colorless gas at room temperature with a repulsive, sweet odor. ... Hydrogen cyanide is a chemical compound with chemical formula HCN. A solution of hydrogen cyanide in water is called hydrocyanic acid or prussic acid. ... It has been suggested that this article or section be merged with Solution. ... The chemical compound and unsaturated hydrocarbon acetylene, also known under IUPAC nomenclature (see IUPAC nomenclature of organic chemistry) as ethyne, was discovered in 1836 by Edmund Davy, in England. ... An organolithium reagent is an organometallic compound with a direct bond between a carbon and a lithium atom. ... General Name, Symbol, Number neon, Ne, 10 Chemical series noble gases Group, Period, Block 18, 2, p Appearance colorless Atomic mass 20. ... The noble gases are the chemical elements in group 18 (old-style Group 0) of the periodic table. ... Hydrofluoric acid is a highly corrosive solution of the chemical compound hydrogen fluoride in water. ... Corrosion is the destructive reaction of a metal with another material, e. ... Ammonia is a compound of nitrogen and hydrogen with the formula NH3. ... R-phrases S-phrases , , , Flash point −188 °C Autoignition temperature 537 °C Explosive limits 5–15% Supplementary data page Structure and properties Thermodynamic data Spectral data UV, IR, NMR, MS Related compounds Related alkanes Ethane Propane Related compounds Methanol Chloromethane Except where noted otherwise, data are given for materials in... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Atomic mass 4. ... Italic textLink titleLink titlelink titlelink titleBold text General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ...


Ammonia has sometimes been used to fill weather balloons. Due to its relatively high boiling point (compared to helium and hydrogen), ammonia could potentially be refrigerated and liquified aboard an airship to easily reduce lift and add ballast (and returned to a gas to add lift and reduce ballast). Rawinsonde weather balloon just after launch. ...


Methane (the chief component of natural gas) is sometimes used as a lift gas when hydrogen and helium are not available. It has the advantage of not leaking through balloon walls as rapidly as hydrogen and helium. (Most lighter than air balloons are made of aluminized plastic that limits such leakage; hydrogen and helium leak rapidly through latex balloons.)


Hydrogen and helium are the most commonly used lifting gases. Helium and hydrogen both provide about 1 kg of lift per cubic meter of gas at room temperature and sea level pressure. Although hydrogen is slightly more buoyant, helium is usually preferred because it is not flammable. For considerations of sea level change, in particular rise associated with possible global warming, see sea level rise. ...


Many countries have banned the use of hydrogen as a lifting gas for manned vehicles. The Hindenburg disaster is frequently cited as an example of the risks posed by hydrogen. The high cost of helium (compared to hydrogen) has led researchers to reinvestigate the safety issues of using hydrogen as a lifting gas: with good engineering and good handling practices, the risks can be significantly reduced. A sensible policy might allow hydrogen for cargo airships (both those unmanned and those manned only by pilots) and require helium for passenger airships. On May 6, 1937, at 1825 local time, the German zeppelin LZ 129 Hindenburg caught fire while approaching a mooring mast at Lakehurst Naval Air Station in New Jersey. ...


Steam

Although water is not a gas at room temperature and sea level pressure, water combines readily with dry air (until the partial pressure of water reaches its saturation vapor pressure). Moist air is lighter than dry air. Most hot air balloons burn propane to provide heat; the combustion products have an average molecular mass of 29.1; the "light" water vapor compensates for the "heavy" carbon dioxide. Pure water vapor (steam) could be used to lift balloons; however, the balloons would need to be double-walled to provide insulation, and condensation would be a serious problem. Nonetheless, two research efforts are currently underway to build steam-based aircraft. (See external links below.) The partial pressure of a gas in a mixture or solution is what the pressure of that gas would be if all other components of the mixture or solution suddenly vanished without its temperature changing. ... The vapor pressure is the pressure (if the vapor is mixed with other gases, the partial pressure) of a vapor (this vapour being formed from molecules/atoms escaping from a liquid/solid). ... Insulation must not be confused with insolation (the latter word has an o where the former has a u). Insulation is any material used to reduce or “slow down” or “resist” the flow of energy. ... Condensation is the change in matter of a substance to a denser phase, such as gas (or vapor) to a liquid. ...


Low pressure buoyancy

The average density of an aircraft can be reduced, at least in principle, by creating a partial vacuum. The concept of an airship supported by the buoyancy of a vacuum has been explored in science fiction. The envelope must be strong enough to resist crushing by external atmospheric pressure and light enough to be lighter than air. No such device has ever been constructed. Look up Vacuum in Wiktionary, the free dictionary For other uses, see vacuum (disambiguation) A vacuum is a volume of space that is empty of matter, including air, so that gaseous pressure is much less than standard atmospheric pressure. ... USS Akron (ZRS-4) in flight, 2 November 1931 An airship is a buoyant aircraft that can be steered and propelled through the air. ... Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ... diurnal (daily) rhythm of air pressure in northern Germany (black curve is air pressure) Atmospheric pressure is the pressure above any area in the Earths atmosphere caused by the weight of air. ...


Derivation

At low densities, the behaviour of gases is well approximated by the ideal gas law Isotherms of an ideal gas The ideal gas law is the equation of state of an ideal gas. ...

pV = nRT

where p is pressure, V is volume, n is the number of moles of gas, T is absolute temperature, and R is the universal gas constant. Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface. ... Volume, also called capacity, is a quantification of how much space an object occupies. ... The mole (symbol: mol) is one of the seven SI base units and is commonly used in chemistry. ... Absolute zero is the lowest temperature that can be obtained in any macroscopic system. ... Molar gas constant (also known as universal gas constant, usually denoted by symbol R) is the constant occurring in the universal gas equation, i. ...


Dividing both sides by V, R and T gives

p / RT = n / V.

Now multiply each side by A, the molecular mass of the gas in question: The molecular mass (abbreviated MM) of a substance, called molecular weight and abbreviated as MW, is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ...

pA / RT = nA / V

Notice that nA, the number of moles multiplied by the mass per mole, is simply the total mass of the gas. And mass divided by volume is density. So, Mass is a property of a physical object that quantifies the amount of matter it contains. ...

ρ = pA / RT

where ρ is the density of the gas. This equation shows that a gas with low density can be achieved by:

  • Lowering p, the pressure;
  • Lowering A, the molecular mass;
  • Raising T, the absolute temperature; or
  • Some combination of the above.

R is a physical constant and so cannot be changed. In science, a physical constant is a physical quantity whose numerical value does not change. ...


See also

Uncrewed aerostats can carry instruments and sensors for long durations that are impractical for humans and other aircraft. ... USS Akron (ZRS-4) in flight, 2 November 1931 An airship is a buoyant aircraft that can be steered and propelled through the air. ... Balloons are a type of lighter than air aircraft that remain aloft due to their buoyancy. ... In physics, buoyancy is an upward force on an object immersed in a fluid (i. ...

External links


  Results from FactBites:
 
Lighter than air - Wikipedia, the free encyclopedia (1013 words)
Lighter than air gases are buoyant in air because they have a density that is less than the density of air.
Lighter than air gases are used to fill balloons, airships, and aerostats.
Determination of lighter than air gases is straightforward.
Lighter than air - definition of Lighter than air in Encyclopedia (904 words)
The expression lighter than air refers to objects, usually aircraft, that are buoyant in air because they have an average density that is less than that of air (usually because they contain gases that have a density that is lower than that of air).
The opposite expression, heavier than air, refers to aircraft, such as aeroplanes and helicopters, that have a greater density than air.
Heated air is widely used in practice as a lifting gas in hot-air balloons (although, to be strictly accurate, the gas in a hot-air balloon is not just air, but also the products of combustion of the balloon's burner).
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m