Gas balloon
The gas balloon is a balloon that consists of a thin, gas-tight envelope such as latex or silk fabric with a rubber skin . It is filled with a gas that has a lower density than the surrounding air and thus leads to static buoyancy . For this so-called lifting gas , hydrogen (H 2 ) and helium (He) are mainly used , but in the past also luminescent gas or town gas . The world's first unmanned flight with a gas balloon was carried out on August 27, 1783 in Paris by Jacques Charles and the brothers Anne-Jean Robert and Nicolas-Louis Robert. This was followed by the first manned flight by Charles and Nicolas-Louis Robert on December 1, 1783. The flight led from the Tuileries Palace over a distance of 36 km to Nesles-la-Vallée .
As a non-flammable noble gas, only helium offers the advantage of safe handling; For safety reasons, hydrogen is uncommon for small balloons in people's hands.
Gas filling
Hydrogen gas is only half as dense as helium gas and therefore gives (in dry air) around eight percent more buoyancy. A hydrogen-filled balloon can therefore carry a little more payload than a helium-filled balloon of the same size. The big disadvantage of hydrogen, however, is that it is flammable , which has led to serious fires several times in the history of aviation - the best-known example is the disaster of the Hindenburg airship .
For the safety of the non-flammable helium, one accepts three disadvantages: high price, high leakage rate, because helium is only present as a single-atom noble gas (does not form a molecule, such as H 2 ) and therefore diffuses through latex, membranes on textile balloon covers and small leaks , as well as the slightly lower lift.
Most of the unmanned balloons, such as the many daily weather balloons , are operated with H 2 as the lifting gas under strict safety precautions in Germany ; the problem of flammability is assessed as a manageable risk given the quantities required. Gas balloon launch sites are usually located where there is sufficient hydrogen available and the balloons can be filled inexpensively. These include above all chemical plants such as in Gersthofen near Augsburg , Bitterfeld , Burgkirchen an der Alz , Ibbenbüren and Marl . The launch site in Düsseldorf-Eller is also one of them, due to a hydrogen pipeline that runs from Marl to Düsseldorf, in order to provide the companies located there with an inexpensive supply of hydrogen. Since September 2006 there has been a new launch site for gas balloons with a hydrogen pipeline in Gladbeck . The place is connected to the main line of the chemical park in Marl. The starting point is in the Wittringen Castle Park . In the meantime (September 2016) the "Willi Eimers Airport", as this balloon launch site has been called since September 15, 2016, is one of the most active launch sites in Europe. On the night of September 18-19, 2016 alone, 32 manned gas balloons took off from here within 90 minutes.
Small balloons ( advertising and toy balloons ) are filled with a balloon filling valve from helium pressurized gas cylinders of the appropriate size. The largest standard, 50 liter, with a mass of 49 to 68 kg, 1.60 m high steel cylinder contains ideally 10 m³ at a filling pressure of 200 bar , but in reality only 9.1 m³ of helium, a quantity that has a mass of only 1, 5 kg and is sufficient for 600 balloons with a diameter of 30 cm and a volume of 15 liters each. In the past, combustible city gas or lighting gas was also used for this. If a balloon is only filled with air (equal to or less (colder) than the ambient temperature), it does not develop any buoyancy and essentially sinks to the ground under the weight of the balloon membrane. Because of the risk of burns to hair, skin and clothing, it is no longer permissible to fill balloons for children or adults with flammable gas. So-called "balloon gas helium" is often used, or helium of untested purity and therefore less expensive.
Size, load capacity and climbing height
The carrying capacity of a gas balloon depends primarily on its volume and take-off weight (balloon envelope plus payload ). The covers of small research balloons and radiosondes weigh 100 g to a few kilograms, and the payloads start at around 0.2 kg. With a weightless shell, the buoyancy would only depend on the difference in gas density outside / inside. For air under atmospheric pressure it is about 1.16 to 1.34 kg / m³ (at +30 or −10 ° C air temperature ), for the lifting gas it is about 0.08 to 0.20 kg / m³ (H 2 or He in the same temperature range). This means that each cubic meter of balloon could lift up to 1 kg - and the faster ( rate of climb ) the lower the payload.
Since the air pressure decreases with increasing altitude, the filling gas expands when a balloon ascends. Ideally, the buoyancy force remains the same, since the pressure and density and thus the load-bearing capacity of the surrounding air decrease, but the balloon gas volume increases proportionally to the same extent due to the reduced pressure.
The maximum height of rise of a gas balloon in the atmosphere depends above all on the ability of its envelope to expand with as little resistance as possible in accordance with the expansion of the filling gas, which increases with height. The elastic tension of the envelope increases the further it is stretched. This leads to an increasing pressure difference to the environment, and the lift force decreases. The ascent stops at a certain height as soon as the load capacity and weight of the device are in equilibrium.
If the envelope is closed and cannot withstand the expansion before this equilibrium can be established, the balloon bursts. When climbing a weather probe, this can be desirable in order to end the ascent at a roughly predefined height and to enable the probe to return by parachute. A good 800 gram balloon only bursts at an altitude of around 33 km , where the air pressure is only about one percent of the ground pressure. It has expanded to four to five times its diameter (around 10 m) and is visible for dozens of kilometers. Illuminated by evening sunlight , such missiles are sometimes the cause of UFO reports. A meteorological balloon carries a capsule with the measuring instruments and the telemetry transmitter and mostly also reflectors for optical measurements from the ground; Small GPS receivers are also increasingly being used. In order to achieve a good rate of climb , the ratio of payload to balloon size or filling must be optimized. A lifting force of 5 N (approx. 0.5 kp ) results in rates of climb of 150 to 300 meters per minute.
The shells of large balloons are usually made of non-elastic material. These cases have an opening on their underside. Since the gas is not under excess pressure and accumulates in the upper area of the envelope, it does not flow outwards. The opening compensates for the expansion of the filling gas during the ascent. If a certain height is exceeded, gas escapes from the opening and the buoyancy decreases until the ascent stops, as the volume of the filling gas in the envelope can no longer increase. If such a balloon is to reach the greatest possible height, the envelope is only filled to a small part of its maximum volume when it takes off. This allows the expansion of the filling gas to be absorbed up to very great heights. The manned American high altitude research balloon Explorer-2 (1935) was filled with only 6370 m³ of helium when it took off, with a total capacity of 104,774 m³. In order to save weight, the shells of modern large stratospheric balloons are made of plastic film (e.g. polyethylene ) only a few hundredths of a millimeter thick .
Balloon types and range of uses
Large gas balloons are mainly used as weather balloons , sometimes also in photogrammetry and archeology for the production of aerial photographs from low altitude. In both areas of application, balloon sizes of 1 m and up are common. Smaller balloons are a common toy for children (see balloon ).
In Switzerland, a gas balloon was used to position a mobile phone antenna about 1000 m (next destination 5 km, finally 21 km) above Switzerland. Google has a similar goal with its Loon project (an independent company since July 2018), NASA lists the spin-off "GATR" for military applications or civil defense.
Unmanned gas balloons have also been used to transport remote-controlled astronomical telescopes to the edge of the earth's atmosphere in order to carry out observations outside the earth's atmosphere. Gas balloons have also been used on other planets: for example, the landers of the Russian Venus probes VEGA-1 and VEGA-2 released gas balloons in the high atmosphere of Venus in order to study the currents there. There are e.g. B. also since 2011 the company Stratoflights, which u. a. markets gas balloons for advertising, events or private purposes and provides information (e.g. under tutorial - legal).
There have also been attempts to use balloons as a means of transport or a crane . Thus, the built CargoLifter the crane balloon CL75 AirCrane for loads up to 75 tons. However, there are also tethered balloons that are used for tourist purposes, such as the HiFlyer in Berlin above Potsdamer Platz ("Die-Welt-Ballon").
For reasons of cost, however, they are inferior to hot air balloons for passenger transport . In order to be allowed to transport passengers with gas balloons for commercial purposes, expensive helium would have to be used as the carrier gas because of the flammability of hydrogen . Even the cost of filling a gas balloon with cheaper hydrogen would cost more than the relatively small amount of propane gas that is needed to heat the air in a hot air balloon for a good one-hour journey. However, gas balloons can be in the air for up to four days without interruption, but common hot air balloons only for a maximum of a few hours, depending on the fuel supply. Gas balloons are also completely silent. The gondola for passengers is suspended from a network of ropes. If the balloon is to sink, some gas is allowed to escape; if it is to rise, ballast in the form of sand is thrown off with the help of a small shovel. Gas balloons can easily be distinguished from hot air balloons by their spherical shape.
An airship is an elongated gas balloon with a drive and control surfaces. Other airships often have additional support structures and / or several gas cells (see rigid airship ).
The overpressure balloon does not blow off any gas when the rebound height is exceeded , but keeps it in the envelope, whereby the internal overpressure towards the outside increases by 1 hPa every 8 m. Therefore, the material has a higher strength and also a higher weight. The safety valve blows off at around 50 hPa (400 m). This balloon has the advantage that it swings around the equilibrium height without loss of gas or ballast .
control
The height of the balloon is controlled either by reducing the ballast or by reducing the buoyancy gas. Ballast is carried along in the form of sand or water and thrown off if necessary, which initiates an increase. If the height is to be reduced, gas can be released via the travel valve.
Balloon sport
As with hot air balloons, there are competitions in gas ballooning up to the world championship. It is mostly about achieving goals with the greatest possible accuracy. Due to the longer journey time, however, the distances are much greater than in corresponding hot air balloon competitions and can be several hundred kilometers. A completely different type of competition is the Gordon Bennett race , which is about covering the greatest possible distance. The participants in this race are usually in the air for several days and often cover distances of well over a thousand kilometers.
Cluster ballooning
On July 2, 1982 in Los Angeles, truck driver Larry Walters tied 42 helium balloons to a garden chair. It rose to 16,500 feet (about 5,000 meters); his flight ended two meters above the ground in power lines. Walters became known nationwide as "Lawn Chair Larry". He achieved an altitude record in clustered balloon flight , flying with bundles of balloons. The record was never officially recognized as it was flown with an unauthorized aircraft.
See also
Web links
- The world's most modern gas balloon launch site in Gladbeck
- German Free Ballooning Association V.
- German Federal Aviation Office
- Gersthofen balloon museum
swell
- ↑ Gottfried kurz: Lighter than air. 2nd Edition. Urania, Leipzig 1980, p. 52 ff.
- ↑ http://stratxx.com/blog/ with the “X-Tower” project on February 20, 2014 - according to its own information, STRATXX is a company for telecommunications and security equipment. For an older contribution to the "X-Tower" project see https://www.blick.ch/news/schweiz/ostschweiz/kamal-alavi-62-wollte-handy-antennen-durch-luftschiffe-im-all-ersetzen-der- tiefe-fall-des-zeppelin-fuersten-id3698298.html , according to the current status (June 21, 2018) the bankruptcy of StraxXX Holding AG has been lifted: https://handelsregister.help.ch/aktiengesellschaft.cfm?nr=CH- 170.3.028.753-0 & name = StratXX_Holding_AG
- ↑ Inflatable Antennas Support Emergency Communication. Retrieved October 6, 2018 .
- ↑ Interactive weather balloon tutorial . In: Stratoflights . ( stratoflights.com [accessed October 6, 2018]).
- ↑ Click on Flying Times of Winners ( Memento from January 25, 2016 in the Internet Archive )
- ↑ spiegel.de: Flying high in the garden chair , March 14, 2011.